Simple DIY FM antennas: Building a Folded Dipole Pt.1

Overview

These simple antenna construction projects are primarily designed to be fun to encourage more interest in long distance FM reception, DAB+, digital television or the two metre band amateur radio. Once again, the additional criteria (or criterion) are that an antenna design should offer simplicity in construction & measurable performance.

Copper pieces © 2006 FreshElectrons

Copper pieces © 2006 FreshElectrons

Building a folded dipole antenna is only marginally more difficult to construct than the popular DIY circular FM loop project. Again it’s an all copper affair! Annealed copper tubing was chosen as antenna material for the earlier project.

For construction of the folded dipole, inflexible copper pipe is used. 90 degree ‘elbows’ are chosen for the joins which means no special tools are required to bend the copper.

To aid readability, this construction article is published in two parts. The focus in this article is on getting everything ready for the build. The second part is the ‘home stretch’, the fun part with a step-by-step guide to building the antenna.

Why build a folded dipole?

Unlike a multiple element yagi antenna, a folded dipole may perform satisfactorily under challenging indoor reception scenarios where multiple metal signal reflections often exist.

Copper tubing prior to construction  © 2014 FM DXing at WordPress

Copper tubing prior to construction © 2014 FM DXing at WordPress

The straight copper pipe must be cut into five pieces. The final step is to glue the antenna together so it does not fall apart. Antennas don’t perform well in pieces! Although gluing may not be considered mandatory it is recommended, especially if the antenna will be mounted vertically. Otherwise, the heavy pieces of copper pipe may fall to the floor.

The most important part of the construction is getting the dimensions reasonably accurate for the required frequency. Once that step is complete, then one proceeds with the fun ‘hands on’ part, which is cutting the copper pipes and gluing the folded dipole together!

Project cost

The author spent $45.50 to build this project. This figure might be considered an indicative minimum cost.

For the apartment dweller whose tool shed is likely to be entirely bare, the maximum cost of the entire project is $86. Perhaps that maximum cost might seem expensive? But another way of looking at it is to consider that many of the materials (such as a quality tube cutter, Wire Glue adhesive, tape measure, surplus ‘off-cuts’ of copper tubing, PVC pipe & marker pen) can be used for years to come in future projects.

Metal pipe cutter 6-35 mm © 2012 Robert & Mihaela Vico

Metal pipe cutter 6-35 mm © 2012 Robert & Mihaela Vico

Copper elbows © 2012 Robert & Mihaela Vico

Copper elbows © 2012 Robert & Mihaela Vico

Cost projections exclude discretionary items such as mounting tripods & masthead preamplifiers. Buying copper tube in 1.5 metre / 59 inch increments (the shortest lengths the author has seen at the retail level) may increase the tabulated representative price of tubing by as much as 23%. To minimize cost, it is recommended to purchase the longest piece of ¾ inch copper pipe one can reasonably transport home and then cut it into the lengths required.

Feedline is a mandatory additional cost. Its cost is likely to be insignificant. Obviously, cost will vary with the length and type of feedline required. For detailed discussion, please refer to the feedline section in part two of this publication.

ESSENTIAL MATERIALS COST PLACE OF PURCHASE (PICKUP)
¾ in diameter straight copper tube x 3 m OR $25 OR Discount hardware retailer
¾ in diameter straight copper tube x 4 m $33 Discount hardware retailer
Store brand tube cutter OR $8 OR Discount hardware retailer
Brand name tube cutter (recommended) $17.50 Discount hardware retailer
Copper elbows to suit ¾ in tube x 4 pcs $10 Discount hardware retailer
Alligator clips with 12mm jaw x 2 pcs $2.50 Electronics retailer
OPTIONAL MATERIALS COST PLACE OF PURCHASE (PICKUP)
Wire Glue $10 Electronics retailer
Permanent ink marker pen $1.50 Discount hardware retailer, supermarket or newsagent
F-type outdoor balun $5 Electronics retailer or Discount hardware retailer
Store brand tape measure $3 Discount hardware retailer
Highest pressure grading (thickness) PVC pipe x 2 m $3.80 Discount hardware retailer

Before building, one must ascertain the dimensions

According to Martin E. Meserve K7MEM, the most important measurement for the folded dipole is its total length, measured tip to tip.

The recommended dimensions for a folded dipole can be calculated using simple software or by using raw calculations. A useful rule of thumb is that a folded dipole is typically 2% longer than a single dipole.

There are at least four ways of obtaining the measurements. One recommended way is to use software calculations. This software provides precise measurements for constructing a folded dipole. The only input required is the resonant frequency of the antenna & the diameter of the tubing. The software is simple to use.

Option 1. Download VK5DJ’s Yagi Calculator software. Use the Design Yagi function.

The software will enable one to manipulate the antenna design with MANA-GAL Basic antenna modelling software to allow further analysis or optimization.

Option 2. Download Al Legary VE3SQB’s software Yagi-Uda Antennas.

Option 3. Use the on-line Folded Dipole antenna calculator. Unfortunately this calculator only allows the calculation of dimensions for tubing diameters of 10.2 mm, but its calculations may be considered a useful rule of thumb.

Software calculations  © 2014 FM DXing at WordPress

Software calculations © 2014 FM DXing at WordPress

Option 4. The lazy way! An alternative route is to copy. That’s right, simply copy the dimensions of a commercially made aluminium folded dipole from an FM yagi. As always, it is recommended not to deviate from the dimensions, including the use of an identical thickness of tubing.

A commercial design made from aluminium

The following dimensions were taken from commercial folded dipole found in a 5-element FM yagi.

ANTENNA CHARACTERISTIC SPECIFICATION
Material Aluminium tubing
Theoretical Gain 2.14 dBi
Aluminium Length – Longest piece 1.455 metres (57.3 inches)
Total Length – measured tip-to-tip 1.54 metres (60.6 inches)
Straight Tubing Diameter Approximately 13 mm (more likely 12.7 mm)
Spacing Gap between the dipole ends – ‘Feed Gap’ in centre of antenna 25 mm
Spacing Gap between the tubing – Horizontal section separation 50 mm

An example construction made from copper

Using software calculations, the author constructed the following dipole. She appears in the photographs in this series.

ANTENNA CHARACTERISTIC SPECIFICATION
Material Copper tubing
Gain (theoretical) 2.14 dBi
Maximum Gain (theoretical modeling in free space) 0.32 dBd (2.47 dBi)
Copper Length – Longest piece 1.5 metres (59 inches)
Bandwidth (theoretical modeling in free space, SWR < 1.5) 85.9 – 98.7 MHz (12.7 MHz)
Total Length – measured tip-to-tip 1.54 metres (60.6 inches)
Straight Tubing Diameter 19 mm
Bend Diameter 20 mm
Spacing Gap between the dipole ends – ‘Feed Gap’ in centre of antenna 50 mm
Spacing Gap between the tubing – Horizontal section separation 50 mm

Terminology

What was that? Did I hear you ask what the #$%^ is the ‘feed gap’? What on earth is ‘tip-to-tip length’? Relax, in his introduction, Martin K7MEM offers a thorough explanation of the terminology used. Antenna gain is often quoted with reference to the half wavelength dipole, that is dBd.

Folded dipole terminology © 2014 FM DXing at WordPress

Folded dipole terminology © 2014 FM DXing at WordPress

Modelling

For those who enjoy software modelling, Graham Daubney F5VHX cautions that the folded dipole may be difficult to model accurately in software. David Jefferies PhD suggests, ‘Any modelling process needs careful validation by measurements’.

Build a copper folded dipole antenna easily without soldering © 2015 FM DXing at WordPress

Build a copper folded dipole antenna easily without soldering © 2015 FM DXing at WordPress

Indicative specifications

For comparative purposes, the author examined the on-line specifications of eight aluminium or stainless steel folded dipoles marketed for FM broadcast applications. In these models for sale, maximum forward gain figures were 0, 1 or 2 dBd & front to back ratios were 4-7 dB. Those manufacturers purporting to offer the highest specifications typically took into account overall performance when the antenna was mounted vertically on a horizontal conductive pole. There was some standardization and simplicity to be found in the crude analysis nonetheless; a typical element diameter was 19 mm & maximum bandwidth 10% of the centre frequency!

Bandwidth is typically measured using VSWR (Voltage Standing Wave Ratio). Rescue Electronics tested the bandwidth of their FM folded dipole designed for FM reception. The SWR was measured at less than 2 (a mismatch loss of only 0.51 dB, calculated at Antenna Theory) between approximately 80-110 MHz.

Holl_Ands has provided SWR modelling plots for his folded dipole (which includes FM coverage) which are invaluable for comparisons between copper tubing diameters.

Stay tuned for part two… it is expected to be published shortly… but the author is too distracted, ‘at the trough’ trying to emulate the DX pig!!!

Further reading

Bandwidth of the Folded Dipole by Natalia K. Nikolova PhD

Bandwidth Explained at Antenna Theory.com

Copper FM J-pole Antennas by Michael Martens, KB9VBR

Simple FM antennas: Introducing the Half Wave Folded Dipole

Cost:  From $ 45-75

Length: Approximately 137 cm (54″)

The Half Wave Folded Dipole comprises two elements of typically Aluminum Alloy construction. The Folded Dipole forms the active (or driven) element in a Yagi-Udi array.

Folded dipole for DAB+ bands © 2013 Digitek

Folded dipole for DAB+ bands © 2013 Digitek

How is it used?

This directional antenna is typically mounted ‘broadside’ to the desired transmitter. Experimenters may choose to add additional dipole elements or incorporate reflectors and directors.

How do I buy one?

If looking to purchase one, there are several options:

  • Remove this element from an inexpensive FM yagi. Before purchasing a yagi to ‘harvest’, please check with the retailer or manufacturer to ensure that the element can be removed; on some retail FM antennas (including the Matchmaster & Hills three element FM yagis) the folded dipole can NOT be physically detached.
  • Rescue Electronics Surplus of Connecticut custom manufactures a ceiling-mounted folded dipole. This antenna is ideal for bedrooms; cost is from $99 with worldwide shipping possible.
  • D-lenp of China manufacturers a two element FM yagi with detachable folded dipole. Cost is $25 plus shipping. Five element varieties are also available.

How do I make one?

At the end of this article there are links to Do It Yourself (DIY) antennas that enthusiasts or radio amateurs have constructed with copper tubing for FM broadcast, digital television & even 850 MHz wireless internet reception!

A folded dipole for FM may be constructed with 19 mm (0.75″) square tube aluminium extrusions or even 6, 8 or 10 mm round tube extrusions.  The choice of round tubing is recommended. Although one metre (3.3 ft) long extrusions (at several of these diameters) are widely advertised for a few dollars each from a major hardware retailer, it is usually necessary to make a custom cut of the appropriate length.

To determine the required lengths for each of the three sections of the folded dipole, please consult an on-line dipole antenna calculator or a step-by-step guide to FM yagi construction. During October*, a step-by-step DIY project will be published on this blog as part of this series on simple FM antenna building. Readers can easily and inexpensively make their own folded dipole for FM reception from copper tubing.

A potentially easier solution than the use of aluminium or copper tubing is to construct a folded dipole (or a standard single dipole) from copper or aluminium foil tape attached to a round tube PVC pipe. And better still; the total cost is far less than a round of drinks with a few lads at The Local.

Is it suitable for field trips?

Absolutely! (Most antennas are, of course but the lighter and smaller to carry the better!)

Half Wave Folded Dipole & suppression choke in sedan © 2013 FM DXing at WordPress

Half Wave Folded Dipole & suppression choke in sedan © 2013 FM DXing

How does it perform in the field?

Whenever this writer ventures into the mountains, this antenna is employed since it outperforms the factory monopole in the car. Whilst this antenna design has long been studied using computer modelling by researchers, empirical observations in the field are (hopefully) a bit more colourful for readers!

Redcliffe foreshore © 2014 Andrew Sutherland

Redcliffe foreshore © 2014 Andrew Sutherland

One of the most rewarding mobile reception achieved with this antenna (above) was rare tropospheric ducting from Nouvelle Caledonie during September of 2013, whilst parked on an unobstructed peninsula (left). Granted, even with a 19 decibel masthead signal amplifier employed in this scenario, these signals were extremely weak! Nonetheless, the bottom line is that the folded dipole antenna offers an enormous potential for any receiving application.  (If reading about mobile mountain DX fun previously published on this blog, please remember that the half wave folded dipole antenna was employed on these ‘day trips’ without exception).

Harry's Hut © 2006 Rae Allen

Harry’s Hut (3.7 mi / 6 km W of ocean) © 2006 Rae Allen

Typical DX application with the folded dipole & Degen DE1121 at Harry's Hut © 2014 FM DXing

Typical DX application with the folded dipole & Degen DE1121 at Harry’s Hut (36 ft / 11 m ASL) © 2014 FM DXing

Harry's Hut © 2014 FM DXing

Harry’s Hut © 2014 FM DXing

In September of 2014, this antenna was used at the insect-ridden Harry’s Hut day-use area (above) situated on the western bank of the upper Noosa River. The folded dipole was hand held vertically by the ‘old man’ (dutifully assisting) a few metres above a park bench (inset, right) a short walk from the jetty and canoe landing facilities (below). As a contrast to the peninsula trip recounted above, nothing is notable about this stop! It is included merely as a typical illustration of mobile FM reception that may be ordinarily expected with this antenna (using a narrow filter modified Degen DE-1121 portable recording receiver).

Harry's Hut jetty © 2006 Rae Allen

Harry’s Hut jetty © 2006 Rae Allen

On this evening (during a ‘quick and dirty’ 15 minute listening window available) there was enjoyable jet-reflected scatter from community radio in Byron Bay (coastal S) to public radio in Rockhampton (inland NW) during flat spring conditions (zero ‘tropo’) comprising a scatter range of 390 mi / 627 km. Even the terrific country narrow caster from Bundaberg was audible.

These signals were NOT audible on the Toyota Prado factory double DIN CD/cassette radio, a quality Japanese DSP receiver. Due to superior design, any contemporary car radio typically exhibits greater sensitivity than its portable radio counterpart. For a portable radio to exhibit such out-performance in the field can be attributed to the use of the folded dipole antenna. Such a comparison seemed fair, since both the vehicular antenna and the portable antenna were operated at the equivalent height above ground. Adjacent channel interference was NOT a determining factor in reception.

Any inexpensive portable receiver that features an external FM antenna jack will accommodate a folded dipole (or loop) FM antenna. These radios include the CR-1100, DE-1103 (KA-1103), DE-1121 (KA-1121), PL-660, PL-606 or PL-310ET from the Tecsun manufacturing parent company. Others include the Digitech AR-1748 (bloggers suggest this may be manufactured by Redsun) or the Sangean ATS-505P, to mention a few current models. An antenna adapter (typically a 3.5 mm audio plug to PAL socket) is required. These are available from $4 from electronics retailers. Make no mistake… this writer believes that purchasing a portable receiver which accommodates an external antenna (and the use of a ‘homebrewed’ or commercially-made external antenna) is worth the extra effort!

What about a wire folded dipole?

Wire Dipole inside window © 2013 FM DXing

Wire Dipole inside window © 2013 FM DXing

The above observations are limited to the ‘metal version’ of the half wave folded dipole. It should be acknowledged that a twin lead wire version of this design is widely available. Whilst physically similar to the wire dipole (left) it differs from that ‘pure’ dipole design by having joined conductors and a 300 ohm impedance. Detailed information on the limitations of wire-based antennas appears in the table and references below.

Terk offer three amplified indoor antennas designed solely for FM reception. Amongst these models, the FMPro is based on a folded dipole design. It is weather proofed for use outside. Rival manufacturer Magnum Dynalab offer the SR-100 Silver Ribbon Tunable antenna.

ADVANTAGES DISADVANTAGES
Improved Voltage Standing Wave Ratio (VSWR) measurements at the terminals suggest best efficiency over most other simple antennas, including twin lead (ribbon cable) antennas. More expensive to buy than other simple antennas such as a wire antenna or Rabbit Ears.
Wider bandwidth than a single element dipole. (David Jefferies PhD suggests a sensible single dipole may exhibit a 15% fractional bandwidth). Although the folded dipole is still often classified as a narrowband antenna, the wider bandwidth may be considered a favourable attribute for reception on the FM or digital television bands. May be considered unsightly; beauty is in the eye of the beholder (or ‘beer holder’) of course!
Higher directivity than a single element dipole. Because of its directional characteristics, ideal for mobile reception to null strong, unwanted local stations. Due to higher impedance over a single dipole, requires a balun (usually supplied) if connected to a tuner with a 75 ohm coaxial input only.
Ideal for ‘mating’ with a quality masthead pre-amplifier if using a car receiver or component tuner. Unsuitable for air travel because does NOT fit in standard ports (suitcases).
Easily fits in the cabin of the average sedans (including in the boot). Depending on the size (a function of the wavelength) the copper version may be quite heavy (but effective exercise) if transporting to a summit or forest clearing.
Extremely durable; it will probably outlast one’s portable receiver! Significantly better durability than telescoping rod antennas such as Rabbit Ears.
Easily fits in a bedroom for indoor reception near a window.

As always, the writer has no affiliation with any retail merchant or product manufacturer mentioned. This entry is NOT intended to be construed as an endorsement of any particular product. Prospective buyers should carefully make their own enquiries according to their particular needs and circumstances.

The author wishes to acknowledge the valuable assistance of David in providing his feedback and personal observations of earlier drafts.

Altitude measurements performed with Celestron altimeter calibrated on-site. Calculations performed with Google Earth using ACMA KMZ data.

* Due to abnormally hot & active tropospheric ducting experienced during October & November, the aforementioned copper folded dipole DIY project will now be published (later than originally scheduled) during December in two parts. The writer apologies for the delay in publication. 


ANTENNA SUPPLIERS

D-lemp Communications Limited

Magnum Dynalab

Rescue Electronics Surplus

Terk Antenna Range


ANTENNA TUBING V WIRE EFFICIENCY

Holl_Ands

Rescue Electronics Folded Dipole


ANTENNA MATERIALS

Building antennas from everyday materials

Spark Fun United States

Tapes Online Australia


DIY DESIGNS TO BUILD WITH ALUMINIUM TUBING

Copper or aluminium foil tape dipole

Copper foil tape antenna

Stealth antennas made from conductive foil


DIY DESIGNS TO BUILD WITH ALUMINIUM TUBING

Folded Dipoles

Element diameter considerations


DIY DIPOLES TO BUILD WITH COPPER TUBING

Bruce’s dipole for FM band

Dave’s off-centre single dipole

850 MHz dipole for Wireless Internet

Nepaeric’s dipole for FM band

Single dipole for two metre band amateur radio 

VHF high band dipole for Digital TV

VHF high band & UHF dipoles for Digital TV


DIY ANTENNAS TO BUILD WITH COPPER TUBING

189 MHz yagi for Digital Television (includes dipole)

P2P micro-powered FM broadcast antennas used by uni students in Melbourne (2009)

Have loop, will travel: out in the field with a $20 FM antenna

Beachfront © 2014 FM DXing

Beachfront © 2014 FM DXing

It’s not much fun going to the trouble of building any antenna without taking it out for a play, right?

Beachfront © 2014 FM DXing

Beachfront loopy style © 2014 FM DXing

The FM loop antenna may offer satisfactory reception whilst travelling on vacation (above) or on a field trip. Under these situations, a small FM yagi antenna may be considered too obtrusive or unwieldy. The loop offers a compromise. Surely, that is an incentive to get out the city into some fresh air!

Example #1: Beachfront resort

On the small balcony of a 2nd floor beachside apartment, permanent tropospheric scatter reception from 80 kW public services northwest was possible at 354 km / 220 mi with this loop antenna.

Beachfront loopy style © 2014 FM DXing

Beachfront loopy style © 2014 FM DXing

‘Dead of winter’ conditions prevailed, which were typical for mid July. However, these signals were comfortably audible (e.g. strong enough to trigger Yamaha’s CSL) over five consecutive nights.

Beachfront loopy style (MTV Unplugged!) © 2014 FM DXing

Beachfront loopy style (MTV Unplugged!) © 2014 FM DXing

Fading occurred only very briefly. The maximum elevation on the balcony was 22 m / 72 ft ASL.

Beachfront listening © 2014 FM DXing

Beachfront listening © 2014 FM DXing

A component FM tuner was used at this apartment with the loop.

Beachfront listening, local reception © 2014 FM DXing

Beachfront listening, local reception © 2014 FM DXing

Example #2: D’aguilar Range portable field trip

At a secluded spot on the D’aguilar Range, the loop was mounted in the carpark on a three metre PVC mast. The circular antenna can be accommodated in a sedan by collapsing the rear seat.

Mountains loopy style © 2014 FM DXing

Mountains loopy style © 2014 FM DXing

Upon arrival on-site, the loop took less than five minutes to erect by moonlight (if one is lucky!) or torchlight. OK, so she ‘looks a bit worse for wear’ on this occasion, but nonetheless performs!

Mountains loopy style © 2014 FM DXing

Mountains loopy style © 2014 FM DXing

At this location, the lowest figures from the altimeter (taken between 10-10:30 pm) indicated an elevation of 468 m / 1,535 ft ASL with a warm ambient temperature of 10.8 degrees C / 51 F.

Mt Samson © 2013 Berknot

Mt Samson © 2013 Berknot

The spot was located between the SOTA (Summits On The Air) mountains of Sim Jue and Samson.

Mt Samson © 2013 Berknot

Mt Samson © 2013 Berknot

The date of the trip was early August at 10:30 pm. Despite a very congested FM dial, the following services listed below were heard in flat conditions with a tropospheric index of nil. These stations are never heard permanently at home during winter, apart from some of the northern reception. An obstructed southern path (which includes the McPherson range topping 1,359 m /4,459 ft ASL) may be the likely explanation.

Rebel logo © 2014 Rebel Radio Network

Hitz FM logo © 2014 Bundaberg Broadcasters

North

  • 3 kW commercial services at 274 km / 170 mi
  • 1 kW commercial service at 217 km / 135 mi

4DDD logo © 2014 Dalby Broadcasting

West

  • 2 kW community service at 145 km / 90 mi

Now FM logo © 2014 Moree Broadcasting

South West

  • 100 kW commercial service at 416 km / 258 mi

Ten FM logo © 2014 Ten FM Community Radio

Life logo © 2014 Life FM Community Radio

South

  • 15 kW commercial services at 331 km / 206 mi
  • 1 kW community service at 272 km / 169 mi
  • 100 watt commercial services at 169 km / 105 mi
  • 50 watt public translator at 163 km / 101 mi
Recording at mountains in car, loopy style! © 2014 FM DXing

Recording at mountains in car, loopy style! © 2014 FM DXing

A brief check with the car radio indicated that the majority of these stations were not audible with the car radio antennae. This suggests that the loop was performing as it should. In fact, one of the 5 kW commercial services located 77 km / 48 mi south was audible as an image on the receiver. Simply, there were no obstructions in the site’s path.

Live in the city? A field trip can be rewarding fun with any tuner or antenna!

JamesMP has some taken some interesting photos of the aforementioned Dundas mountainous region. Previously, reception at this region has been discussed in this series.

Example #3: Beachfront apartments

These photographs illustrate the ease of assembling the FM loop antenna at two contrasting beachside apartment complexes, located just 900 m / 0.6 mi apart.

Beachfront loopy style at a favourable location © 2014 FM DXing

Beachfront loopy style at a favourable location © 2014 FM DXing

On the balcony of a 14nd floor beachside apartment, permanent tropospheric scatter reception from 80 kW public services northwest was possible at 578 km / 359 mi with this loop antenna in mid October. Signals were audible every evening during the stay. The maximum elevation on the balcony was estimated to be 60 m / 197 ft ASL.

Beachfront loopy style in tough conditions © 2014 FM DXing

Beachfront loopy style in a ‘shocker’ of a location © 2014 FM DXing

Contrast the observations directly above to those in a complex above a popular entertainment precinct! On this particular 15nd floor balcony, all modes of long distance FM reception were affected by enormous levels of electrical interference. In addition, dozens of high rise apartment towers in close proximity attenuated signals. These observations may reflect a worst-case scenario.

Despite this apartment building being a ‘shocker’ of a location, FM signals received with the loop were more distant than results using the vertical telescopic antenna on the Silabs’ portable receiver. (The portable receiver exhibited images across the FM band. This symptom ‘masked’ weak signals, of course).

At this location, the antenna could not be left outside overnight or positioned at the top of the PVC mast, both of which are normally undertaken. Why not? The antenna was readily visible from neighbouring balconies and possibly from the busy tourist strip below.

The maximum distance at this location was 402 km / 250 mi from 100 kW public services. This reception was only possible during enhanced conditions; those stations were not permanently receivable each night. The antenna was moved inside the apartment after 9 pm nightly which may have limited opportunities for more distant signals.

Distances & azimuths of FM broadcasts are calculated with FM Scan. Station logos are solely provided for the purposes of research & education under the Fair Use provisions of the Copyright Act in this jurisdiction. This article will be continuously updated, it is a work in progress.

Reflections at Lake Poona, Great Sandy National Pk & Rainbow Beach

Lake Poona bush walking (sans 4WD)

Lake Poona is accessible from Freshwater Road just west of Rainbow Beach. The lake comprises part of the Great Sandy National Park (NP). The park comprises some 220,000 hectares according to Bonzle and is tentatively World Heritage listed. The colourful Great Sandy NP (below) is sandwiched between Fraser Island & Tewantin – Noosa.

4WD vehicle driving south of Rainbow Beach © 2014 FM DXing

4WD vehicle driving south of Rainbow Beach © 2014 FM DXing

The Lake Poona walking track starts at the Bymien picnic area (map). This area is accessible via a loosely graded dirt road which is officially deemed suitable for 2WD vehicles.

To access the lake, a challenging walk (4.2 km / 2.6 mi return) is required. There is no direct vehicular access to Lake Poona. With a couple of short breaks, the walk took 43 minutes for its first half. Based on alitmeter readings, the elevation rises from 183 m (600 ft) to well over 240 m (787 ft) through the mid-point of the walk. Because of small rocks that are loose underfoot on the track, undertaking the walk is particularly challenging in the dark, even by torch light! It is therefore recommended to leave the lake and commence the return half of the walk at least half an hour prior to sunset.

Who is this tool at Lake Poona? © 2014 FM DXing

Who is this tool at Lake Poona? © 2014 FM DXing

The colour of the water in Poona Lake (above) is distinctive. It forms as a result of tea tree leaves that fall into the water. The pristine lake tastes good; the home brewed ale afterwards in the apartment… even better! This blogger roughly estimates that the lake is at least 226 m (741 ft) wide and 574 m (1,883 ft) long…  assuming seasonal rainfall maintains its capacity! The expansive lake can be easily seen from an aircraft. Fishing enthusiasts should be aware that reports suggest that fishing in Poona Lake is unlikely to be a fruitful endeavour!

4WD driving permitted on Rainbow Beach © 2014 FM DXing

4WD driving permitted on Rainbow Beach © 2014 FM DXing

The walk, which culminates at the south east corner of the lake, seems to be surprisingly unpopular. Even on a busy summer Sunday, with the Rainbow Beach patrolled surf beach ‘pumping’ nearby (above), only two thirty-something walkers were seen during the course of the walk.

Expansive Lake Poona © 2014 FM DXing

Expansive Lake Poona © 2014 FM DXing

Despite the obvious potential (above), there was no swimming undertaken on this occasion due to lack of time. The time of arrival was 5:30 pm. About three minutes were spent on a brief survey of FM radio reception. This act of madness was done discreetly, when nobody else was around.

Only very rudimentary portable radio equipment (below) was able to be taken on the bushwalks. Frozen water bottles, insect repellent, a ‘smart’ phone (apparently?), torches & two video cameras take precedence!

Tree hugging radio at Lake Poona © 2014 FM DXing

Tree hugging radio at Lake Poona © 2014 FM DXing

At the lake, signals from Bundaberg (93.9 MHz, N), the Darling Downs (100.7 MHz, SW) & the Gold Coast (89.3 MHz, S) at a distance of 224 km (139 mi) were clearly audible on the Tecsun PL-300WT (below). The 80 kW FM western ‘beasts’ broadcasting from Biggenden (116 km / 72 mi) were so strong the signals were bleeding onto adjacent channels such as 99.5 MHz. Jet-scattered transient signals from Coffs Harbour were NOT receivable at the lake. Tropospheric Index: light blue.

The highest point of the walk is roughly about one kilometre from the lake. At this point is a grassy clearing of about 25 square metres (269 square ft) with a basic selection of log ‘seating’ to recharge one’s depleted physical ‘batteries’. Unfortunately, the towering trees nearby attenuated FM signals at this area. This seemed to negate the benefit of the higher altitude, as signals listed above that were clear at the lake were noticeably absent.

Tecsun PL-300WT radio at Lake Poona © 2014 FM DXing

Tecsun PL-300WT radio at Lake Poona © 2014 FM DXing

Great Sandy NP radio observations

In contrast to Lake Poona, at two locations a short drive away, Coffs Harbour’s RN on 99.5 MHz would ‘boom in’ via jet reflection at this time of day. These were accompanied by daily late afternoon showers which were likely indicative of flat atmospheric conditions. These two trips are detailed below:

A third of the way (3 km / 1.9 mi) to Neeb’s Waterhole (map), the tour was forced to stop on a hill (where the road parts in two directions) that is roughly estimated to be 50 m (164 ft) ASL using Google Earth. Access to the waterhole was previously possible via Mullin’s carpark through Cooloola Way with a 4WD vehicle (that is, four-wheel drive or SUV, sport utility vehicle) but is now closed for repair to all traffic due to severe flood damage, which necessitated turning the vehicle back.

On this hill in Cooloola Way, the extensive 4WD metal body (below) was used as a highly effective ground plane. The radio was placed on the high roof of the vehicle. The Tecsun radio battery ground was connected to the roof and the telescopic antenna fully extended vertically. The base of the telescopic antenna is NOT touching the metal roof, only the ground wire does.

4WD beach route between Middle Rocks & Double Island Pt © 2014 FM DXing

4WD beach route between Middle Rocks & Double Island Pt © 2014 FM DXing

This yielded far better results than the 4WD factory radio. As seems to be commonplace, the Toyota’s telescopic antenna was too short. The FM telescopic wasn’t captured on film, but is probably only two-thirds of the length of the portable receiver’s telescopic antenna. Worse, the factory receiver did not feature sufficient selectivity for the modern congested FM band.

Although worthwhile for long distance FM reception, this ‘portable on the roof’ approach unfortunately yielded this crazed enthusiast dozens of insect bites that affected ‘sleep quality’ for the remainder of the vacation!

The highlights were Stanthorpe (103.3 MHz, SW) & Coffs Harbour (99.5 MHz, S) at distances of 302 km & 476 km (286 mi) respectively. A ‘rebelliously-strong’ signal from Beaudesert (90.5 MHz, S) was a pleasant surprise at 210 km (130 mi). It’s hard to maintain interest when insects are feasting on the back of one’s knees, but signals towards the north & west seemed lacklustre with nothing obvious further than moderate strength Bundaberg, 146 km (91 mi)! Tropospheric Index: unknown.

At the Tin Can Bay Volunteer Coast Guard (map), a simpler arrangement was used since a conventional vehicle was able to be used. Obviously this is more convenient (translation: ‘bite free’ comfort) & yields superior results to a portable receiver sited in the ‘middle of nowhere’, although perhaps it does not offer as much ‘quirky’ enjoyment. Again, a Blaupunkt ‘Sharx’-enabled radio with an amplified Shark Fin (an appropriate match for pun enthusiasts?) was effective, as is regularly used.

Overlooking Tin Can Inlet west of Rainbow Beach © 2014 FM DXing

Overlooking Tin Can Inlet west of Rainbow Beach © 2014 FM DXing

The car was driven to a parking space overlooking Snapper Creek near the Coast Guard’s antenna arrays (above). At this spot, Bundaberg (93.9 MHz, N) & Brisbane (104.5 MHz, S) were strong. Satisfactory reception was possible from Redland Bay (100.3 MHz, S), Ipswich (94.9 MHz, S), the southern Gold Coast (95.7 MHz, S), Beaudesert (89.7 MHz, S), Cherbourg (94.1 MHz, W) & Coffs Harbour (99.5 MHz, S) at a distance of 491 km (305 mi). North-western signals from Gladstone (93.5 MHz) & Rocky (103.1 MHz) at respective distances of 287 km & 348 km (216 mi) were weak. Tropospheric Index: dark blue.

Great & Sandy but dense terrain

The Great Sandy NP comprises many ranges of dense rainforest. Not only does this result in exhausting 4WD driving for relatively inexperienced drivers (like this long-suffering writer) but these terrain characteristics also pose a significant obstruction for long distance FM reception towards the south at Rainbow Beach.

Leisha track entrance to beach © 2014 FM DXing

Leisha track entrance to beach © 2014 FM DXing

Conversely, it is highly likely that this is also the reason for the FM reception deficiencies at Noosa towards the north, discussed in previous posts. Tewantin – Noosa is located near the southern boundary of the park. One afternoon, when checking briefly on the 4WD on the beach near the Freshwater camping & day use area (below) a haul of southern stations were found. These included the Gold Coast and were easily detected in flat conditions. Freshwater’s facility is NE of Teewah Beach, accessible by 4WD.

Freshwater track entrance to beach © 2014 FM DXing

Freshwater track entrance to beach © 2014 FM DXing

Much like Noosa, reception to the north west is obstructed by mountains. Fishing, surfing, swimming, walking, backyard cricket or drinking is probably a more fulfilling way for prospective campers to pass the time in this part of the park (below) than playing with a portable FM receiver!

Driving north towards Rainbow Beach © 2014 FM DXing

Driving north towards Rainbow Beach © 2014 FM DXing

Located NE of Freshwater camping & day use area is Double Island Point Conservation Park. Atop a cliff is the popular lighthouse attraction, accessible via walking track (below). The Double Island Point lighthouse has operated since 1884. The ‘light’ which guards passing ships from the rocky headland is supplied via solar electric panels. The lighthouse is an official weather station, often featured on television.

Lighthouse cliff track, Double Island Pt © 2014 FM DXing

Lighthouse cliff track, Double Island Pt © 2014 FM DXing

Rainbow Beach accommodation (sans 4WD)

Rainbow Beach (below) has a ‘party-like’ tourist atmosphere. To this writer, this felt reminiscent of Airlie Beach, the gateway to the Whitsunday Islands without the oppressive tropical summers. Granted, there is not the variety of restaurants & nightlife the Airlie Beach destination offers. Both destinations share the same sub-tropical climatic classification.

Rainbow Beach © 2014 FM DXing

Rainbow Beach © 2014 FM DXing

Rainbow Beach seems particularly popular with Dutch, German, Polish & Swedish twenty-something tourists. During the week, the location (cue The Specials’ classic, please deejay) almost resembles a ‘Ghost Town’!

It’s probably unsurprising as there is barely one school and no major supermarkets in the locality, with the overwhelming emphasis on tourism. Nearby Tin Can Bay seems to be the business, residential & recreational fishing and hub of the region.

Rainbow Beach to the south east, including Double Island Pt © 2014 FM DXing

Rainbow Beach to the south east, including Double Island Pt © 2014 FM DXing

Rainbow Beach’s weekday ‘slumber’ (above) is perhaps ideal for exploiting Rainbow Beach’s wonderful potential for FM reception. It is remote! How remote? The only local broadcast is a one watt Christian FM narrowcaster; on MW it is Classic Hits 4GY. The region only requires 75 watt digital television translators.

Tropospheric Ducting: Pack a yagi or get high!

Even during instances of ‘fair’ tropospheric ducting in mid-March (Autumn), distant reception is awesome. These were indicated by a light blue colour on the Hepburn tropo forecasts, easily viewed via even the most rudimentary cellular phone. (Conditions were confirmed after the vacation ended using the Marine Tracking peaks on the graphs at Gladstone).

Long distance FM reception from the north west as far as Mackay (687 km / 427 mi) is possible at Rainbow Beach. Just as rewarding is hearing the numerous low-powered mine relays from the same azimuth, rebroadcasting commercial stations Zinc (aka 4CC), Sea FM, Rebel & Breeze.

In total, 92 FM stations were logged at Rainbow Beach over three evenings. These included two re-broadcasts of cable television sporting channels, typically servicing large caravan parks.

As mentioned above, the obstructive nature of the Great Sandy NP at Rainbow Beach enable FM broadcasts from Gladstone (292 km / 181 mi) to obliterate those on the Sunshine Coast (100 km / 62 mi). This is a very pleasing terrain side effect, since the Gladstone broadcasts emanate from a low-elevation site with a tenth of the power of the coast stations!

Access to a collapsible three or five element FM yagi (from $45) is recommended for receiving pleasant ‘quieting’ signals from the north west (such as Mackay) in Rainbow Beach. Not all accommodation may be ideally suited for the placement of a ‘stealth antenna’. Huh? Essentially, a stealth antenna in this context refers to the erection of a tripod-mounted small yagi on the balcony during darkness between 7 pm – midnight. A folded dipole resting on a balcony’s glass or wooden table may suffice. (The dipole is easily detached from a surplus five or eight element FM yagi).

Carlo Sandblow to the south, including Double Island Pt © 2014 FM DXing

Carlo Sandblow to the south, including Double Island Pt © 2014 FM DXing

Rainbow Beach’s elevated region is characterized by a gradual rise from beach level (i.e. the Pacific Ocean) to 87 m (285 ft) near the Cooloola Drive reservoirs. These water towers adjoin the extremely popular Carlo Sand Blow lookout (108 m / 354 ft ASL), so these are easy to spot! The Sand Blow is pictured above & below.

Unless one is lucky enough to secure scarce accommodation located around here (the author did not), experimentation with a portable receiver’s telescoping monopole antenna is virtually guaranteed to be frustrating as the effects of a federal budget! Unlike many holiday locations, at Rainbow Beach there are simply no towering high rise apartments on offer. Typically towers partially offset the performance of a ‘lossy’ telescoping antenna.

Carlo Sandblow to the south, including Double Island Pt © 2014 FM DXing

Carlo Sandblow to the south, including Double Island Pt © 2014 FM DXing

Provided one pays attention to the hilltops and gets mobile, there are still plenty of other alternative methods to ‘get in on the action’. In fact, one evening the Mackay stations were even audible via tropo in the car, albeit only on the western crests of Rainbow Beach Road. Reception from this north western azimuth seems optimal when this road transitions into Tin Can Bay Road, approaching Wolvi near Gympie. Signals from Mackay were typically heard just above the noise floor.

Distance calculations computed using FM Scan, with base (apartment) reception undertaken with a Yamaha TX-930 component tuner.

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Coolum’s hidden gem: Low’s Lookout

Low’s Lookout is a lookout and picnic shelter at the end of Grandview Drive at Coolum on Australia’s Sunshine Coast. Via road, the lookout is a one hour and 24 minute drive north of Brisbane’s Central Business District. Low’s Lookout is a 26 minute drive south of Noosa’s Hastings Street.

Coolum’s residential population was 7,175 in 2006, according to Queensland Places. The lookout is situated on the Point Arkwright (southern) side of Coolum. The name originates from Maroochy Shire chairman Edward (Ted) Low.

Grandview Drive leading to Low's Lookout © 2013 FM DXing at WordPress

History plaque at Low's Lookout © 2013 FM DXing at WordPress

The elevation is 73 metres above sea level (240 feet) but to the immediate south and south west there are blockages (NOT pictured) by Eurungunder hill, the Lutheran Youth camp at Luther Heights and surrounding ranges. Mount Coolum is only three kilometres (two miles) south and although it is only 207 m (679 ft) high, it is an exceedingly wide and prominent mountain.

The most obvious hill is pictured in the foreground of the photos. This is Emu Mountain (aka Mount Peregian) which is an easy half hour climb. Despite the modest 71 m (233 ft) elevation, a climb of Peregian provides spectacular views of the region.

Low's Lookout vista: Northerly aspect, including Emu Mtn © 2013 FM DXing at WordPress

The nearest mountains of merit include Mount Cooroy, Bottle & Glass and Eerwah (near old friend Point Glorious) which range in height from 388-409 m (1,273-1,342 ft). Whilst NOT apparent in the photos, these can be found about 18 km (11 mi) away in the quadrant from the west to northwest.

Picnic table at Low's Lookout, Northerly aspect © 2013 FM DXing at WordPress

Picnic table at Low's Lookout, Northerly aspect © 2013 FM DXing at WordPress

Early photographs of the lookout show how development has profoundly changed Coolum’s landscape in the last 50 years. In the 1980s and 1990s, Coolum was reportedly an exceptional location for MW (AM) reception. (The reason this blogger knows this is that after publication, a reader kindly shared his experiences at Coolum with beverage antennas. Thanks James!)

In contemporary times, Low’s Lookout is useful for FM radio reception to the north, although parking spaces are extremely limited. During an instance of coastal tropospheric ducting, the Mackay FM broadcasts were receivable from roughly the NNW (azimuth: 325°) at Low’s Lookout. This was heard at 8:30 pm on the evening of Monday, December 16 in the car:

Although the broadcast site is a distance of 743 km (462 mi) away, the Mackay 100 kilowatt broadcasts have been observed regularly at the Sunshine Coast by this blogger during December. The signals usually last for at least two hours and occasionally persist until dawn.

Perhaps on Queensland’s Sunshine Coast these conditions are a fortnightly (or weekly) occurrence during December, providing rooftop FM directional antennas can be used? Even quality, Australian-made fibreglass AM/FM monopoles (e.g. GME, Mobile One or ZCG Scalar) may suffice on the rooftop, providing a signal preamplifier is used.

The 50 watt public broadcasts from Miriam Vale (distance: 288 km/179 mi, azimuth: 329°) were also audible at Low’s Lookout. Miriam Vale is situated between Gladstone & Bundaberg. Although these distant tropospheric signals were NOT audible at beaches (that is, sea level), around sunset the reception of transient jet reflected signals can be readily exploited with virtually any contemporary automotive receiver. Opportunities abound!

Coolum Beach including Emu Mtn © 2013 FM DXing at WordPress

It must be emphasized that NOT all of the Sunshine Coast is ideally suited to tropo from the north; such generalizations are completely misleading! Mooloolaba and the northern regions up to Peregian Beach are preferable. Based on limited past experience, Caloundra & Bribie Island for example, seem to be located too far south on the coast; also the nearby Blackall Ranges (including Flaxton, Mapleton, Montville & Maleny) may block signals from the SW to the NNW. Multiple mountain ranges from Landsborough through to Eumundi (Point Glorious) are potential impediments. Reception in Noosa suffers from problematic terrain obstructions; it seems to be the most challenging region for FM/UHF reception from the north on the entire coast by a significant margin. There is good reason for all those translators!

Data was sourced from FM Scan, Google Maps, Hey What’s That & Where Is? The recording was undertaken with an Olin OVR-101 stereo voice recorder at 128 kbps MP3 resolution. An amplified, vertical, dual diversity automotive FM antenna system was used in this instance.

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Returning to the scene of the Glorious crime!

Welcome to 2014 dear readers!

Back in December (sadly, yes it is January already) there was a return visit to Point Glorious undertaken for a hike on the dry dirt roads that were generously littered with horse excrement. This tower was spotted by a companion at the deserted lookout, whose eyesight is evidently better than this humble blogger.

Black Mtn broadcast site servicing Gympie, Cooroy © 2014 FM DXing at WordPress

The towers are situated nine kilometres (5.5 mi) away in a straight line, or 26 kilometres (16 mi) via the shortest vehicular route. This broadcast centre is sited off Eungella Drive at Black Mountain near Cooroy. Three 20 kilowatt FM public broadcasts originate from this site. In addition, five regional television affiliate stations are broadcasting on UHF from this site with power of five kilowatts. More photos, taken by photographer Tallowwood Place .net can be found on Panoramio.

Apart from precipitation that accompanies heavy-duty thunderstorms, rain has been rare in this region throughout December. Weather conditions have remained extremely dry (along with excruciating humidity) as is clearly evident in the photographs. Professionals expect this hot weather will continue: it may be South East Queensland’s hottest summer on record since 2008.

Vista from Point Glorious © 2014 FM DXing at WordPress

Yes, these are new photos. It is probable these are even duller than usual but it is New Year’s Day! Let’s not be too critical please! 🙂

Vista from Point Glorious © 2014 FM DXing at WordPress

On this occasion, a sedan was used on the sealed dirt road to access the lookout. This time, a German-engineered FM receiver was better suited for mountaintop reception but the fact that particular automobile was taken was more a matter of luck rather than any foresight!

Images from the four FM broadcast sites within 15 kilometres (9 mi) were not readily encountered. This includes the site pictured in the first photograph. Inter modulation and cross modulation was acutely obvious with the factory 2011 Nissan X-trail Four Wheel Drive radio used in 2012. On both occasions, a six-band shark fin antenna was used, as is typically supplied with modern vehicles with on board Global Positioning Service (GPS).

 ‘100 years of Surf Lifesaving’ exhibition for Australia Day 2007, National Museum of Australia © 2009 Hil

These are a compromised design to preserve space but frequently provide satisfactory FM reception. It helps enormously if the shark fin antenna’s inbuilt preamplifier is built to the highest contemporary standards using GaAs pHEMT Monolithic Microwave Integrated Circuits (MMICs), for example.

Golfito, Puntarenas in Costa Rica © 2009 Christian Haugen

A curtailed five-minute FM band scan performed the early afternoon revealed few surprises. Only the 100 kW public broadcasts from 425km (264 mi) from the coastal south could be heard belting in. Last time, the 80 kW public broadcasts 389 km (242 mi) north-west were audible even from the edge of Lake Cooloolabin, with coastal tropospheric enhancement playing a starring role.

Data furnished from FM Scan, the ACMA Register of Radio Communications Licences & Google Maps.

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The three photographs of Point Glorious may be freely used for non-commercial activity provided attribution is given. Should readers choose to use those photos elsewhere, please link back to this page or attribute this blog as the copyright holder.

Related blog posts

Off road: Conondale National Park & Cooloolabin Dam

Mapleton National Park & Cooloolabin Dam

Point Glorious

FM Portable Shootout: Bauhn ADS215 versus Degen DE1121

The following post is a ‘quick and dirty’ portable receiver shootout between the Bauhn ADS215 and Degen DE1121.

The DE1121 was chosen as the contender as it is consistently the most sensitive radio this writer owns, offering outstanding performance on weak FM signals. Whether playing with FM signals on a mountain top, or in a beachside apartment or garage surrounded by steel & concrete… if a (more preferable) component tuner absolutely cannot be utilized, this portable radio shines the brightest.

Sensitivity data for the Bauhn ADS215 dual band receiver is NOT available, so a comparison test is one crude and fun way to gauge significant differences in receiver performance.

Biker Laurel in Gun Shootout © 2012 Edward Liu

Methodology

Since both radios offer FM reception, this band is to be the subject of the test. To avoid potential interference from the mains power supplies, battery power was used. The telescoping monopoles on both receivers were used. It is important to be fair and perform the test with considerable urgency. Transient propagation changes over time affect VHF/FM receiver testing. Anomalies such as jet reflected signal improvements may distort results.

Bauhn Digital Receiver

The Degen radio was tested first. The Bauhn radio was tested immediately after; perhaps five minutes had elapsed. Seven provincial FM signals were tested for 45 seconds each. The test was repeated the next day to ensure that potential propagation changes during the test had NOT affected the preliminary test.

Characteristic Bauhn ADS215 Degen DE1121
Price Sale $30 retail From $91 delivered
Availability Exclusively through ALDI stores Exclusively through online merchants
Tuner Gyro Signal 1128 (Taiwan) Toshiba TA7358AP (Japan)
FM Sensitivity N/A Better than 5 microvolts for a signal with 30 dB S/N at 98 MHz
IF and Selectivity Stock: Digital Processing of analogue IF Custom modified: 180 kHz + 56 kHz Murata filters
Origin China by Tempo Australia China by same parent as Tecsun
Coverage DAB: 174 – 240 MHz, FM: 87.5 – 108 MHz, Radio Data System, 50 kHz steps, RDS: PT, PS, RT & PI data Longwave:  50 kHz – 521 kHz, Medium wave: 522 – 1719 kHz, Shortwave: 1700 kHz – 30 MHz, FM: 70 – 108 MHz, 10 kHz steps
Telescopic Antenna 80 cm Stainless Steel 90 cm Stainless Steel
Batteries 4 x AA 3 x AA
DC Supply 5 volts, 600 mA 6 volts, 300 mA
Inputs Headphones Headphones, Auxiliary Audio, External FM Antenna
Speakers Single, 1 watt Single, 77 mm diameter

Comparisons with other DAB+ receivers

Surprisingly, the Bauhn receiver offers superior sensitivity on the FM band than the far more expensive Pure One Mini and Bush BR10DAB. The latter contains Frontier Silicon’s Venice 5.1 module, which was released in the third quarter of 2008. That module was also included in the Yamaha TSX-120 Ipod dock and many other receivers. At that time, Frontier Silicon manufactured 80% of the chipsets, modules & platforms for over 300 DAB receivers.

Commerce & economics graduates are taught that purchase price is a guide to what the market will bear, NOT necessarily quality. That is certainly applicable for this product!

Notable features of the Bauhn receiver

 

Unlike the latter two receivers, internally generated spurious interference was absent on the FM band on the Bauhn DAB+ receiver. By accident, this tester discovered that the Bauhn ADS215 will in fact decode PI codes, making it advantageous for long distance FM (DX) enthusiasts as PI codes. DX enthusiasts use these unique station identification codes since this parcel of RDS data will decode most readily.

Accessing PI code data seems to be a hidden feature (aka Easter Egg) of the receiver. Certainly, there is no mention of such capability in the instruction booklet. To access the PI code mode, simply hold down the INFO button for about five seconds or longer. This is the radio’s software menu. Continue to press the INFO button until the current FM station’s PI code is displayed. Once PI code mode is activated, tuning in 50 kHz increments can be performed as per usual.

De1121 © 2013 FMdxing

Weak Signal in MHz Distance in Miles Bauhn ADS215 Degen DE1121
89.1  86  (15 kilowatt ERP) No signal Mono
91.5  88  (1 kilowatt ERP) No signal Negligible signal
92.5  45 Mono Stereo
96.1  85 Poor signal Stereo
100.9  143 Indoor interference Mono
102.9  45 Negligible signal Mono
107.3  90 Mono Quieting Stereo

Bauhn Digital Receiver

Sensitivity

The sensitivity results compiled in table two (above) suggests that unsurprisingly, a dedicated FM radio (as usual) will outperform a DAB+ radio. Similarly, high-end DAB+ component tuners do NOT take advantage of the compromised FM section of the DAB+ modules, but employ a dedicated FM tuner module for optimal reception.

Brief word on DAB+ 

This mode was NOT tested thoroughly on this occasion, since this receiving location suffers no coverage deficiency. However, the Bauhn ADS215 is an extremely capable performer on DAB+. These transmissions are the primary choice for digital radio broadcasts outside of the Americas, which uses IBOC (In Band On Channel).

Digital radio mode on Bauhn ADS-215 © 2014 FMdxing

Many forum correspondents report the Bauhn ADS215 to be the most sensitive DAB+ receiver they own.  British hi-fi manufacturer AudioLab uses the same DAB+ module as this radio in their high sonically rated 8200T component tuner, according to the service manual.

DAB+ versus FM

The penetration of DAB+ continues in Australia and is expected to reach 16 percent of households by June 2014, according to PwC estimates. With new spectrum allocated to DAB+ in regional areas (now that analogue high band VHF television has been switched off), the future of digital radio broadcasting offers great potential across the continent.

Anecdotal reports suggest DAB+ programming in this country may have improved. At the very least, the discussion of DAB+ station content seems to be flourishing like never before! Unfortunately, the use of low bitrates to broadcast specialist music stations may continue to be problematic for those listening on component tuners within hi-fi installations.

Degen De1121 interior © 2013 nice.kaze.com

Summary

The FM performance of DAB+ modules seems to be improving each year. The FM performance of a DAB+/FM combination radio might still NOT meet the onerous portable demands of long distance FM enthusiasts. Earlier articles listed below focus heavily on that very topic, and attempt to explain why some of these individuals may prefer custom modified portable FM radios such as the Degen DE1121.

The test results indicate that the Bauhn ADS215 is likely to provide satisfactory FM performance. Ideally this radio is suited to those listeners who suffer from patchy DAB+ reception, which means the fallback radio entertainment becomes analogue FM broadcasts.

Further reading

AudioLab Component tuner

AudioLab Component tuner Review – Adobe Reader document

Bauhn ADS215 discussion on Whirlpool forums

DAB chips to be in smartphones

DAB radio’s reception gaps proved to be a matter of life or death – Telegraph (UK)

Degen DE1121 detailed specifications – German export version

Degen DE1121 user reviews – Translated Russian

DE1121 Block Diagram – Adobe Reader document

GyroSignal Technology DAB+  tuner modules

Indicative sales prices for DAB+ radios

Kaito KA1121 detailed specifications – North American version

Toshiba TA7358AP FM front end – Adobe Reader document

Related blog articles 

Bauhn ADS215 satirical shootout

Inject your DAB+ portable radio with steriods

Portable FM radios favoured worldwide – Digital Signal Processing versus a Conventional IF section

Receiving Sporadic E reception with portable receivers

Survey of portable receivers used by European enthusiasts

What if analogue FM radio ended in the United States?