Salvage for salvation: budget FM radios in a post apocalyptic world

Historical records suggest that this electronics shoot out was conducted during a chilly, overcast winter morning. It was as bleak and lifeless as a post nuclear apocalyptic scene akin to the Terminator. It was speculated that a small gang of elitists running the incumbent government had somehow vaporized the masses of decent folk with their relentless, soul-destroying dogma and double talk.

Apocalypse  © 2008 Michael Lehenbauer

Apocalypse © 2008 Michael Lehenbauer

All was not lost. The ‘suits’ had left some populist toys to play with. The few broken souls that remained in the city post apocalypse grabbed their toy radios. These were amongst their only remaining electronic devices. Could these rescue them from sheer desperation?

Graffiti: Greed is deadly © 2007 Bart Everson

Graffiti: Greed is deadly © 2007 Bart Everson

It was rumoured that the internet – the old world hub of information transfer had been sold by the self-interested elite to the highest bidder. Restricted to the highest echelons, few mortals possessed the social connections to enable access to the electronic network that once had the capacity to empower the disenfranchised and wealthy alike. Now, social mobility was virtually impossible.

No weather indicators to were available. Accordingly, tropospheric enhancement to FM signals could be tracked on-line. Synoptic charts were not available. The FM band that did exist was as boring as hell, filled only with those routine permanent FM signals. DX enthusiasts (those that monitored distant radio signals) were a forgotten breed. In this new world order, survival was the only concern. Hobbies became solely the domain of the wealthy.

Wise words, In Greed We Trust © 2014 Ed Suominen

Wise words, In Greed We Trust © 2014 Ed Suominen

But the nightmare was only beginning. It is clear that the poor mortals (those determined few that were left) struggled on with their souls intact. As pointless as it seemed to be in that environment, their capacity to test and experiment would endure.

It is now known that amongst the ruins of their old municipalities they conducted many seemingly fruitless tests. What follows is one such test; a shoot-out. Where possible, the original source material is quoted from…

Populist’s dream radio shoot out

The simpletons focused on two cheap ‘bastards’ with a ‘fearsome’ reputation to uphold. When the economy still functioned, these radios were purchased at retailers like Junk World. It was said that the two machines the simpletons had chosen empowered them, coupled with their tenacity to ‘fight it out until the death’!

Junkworld © 2010 Danny Choo

Junkworld © 2010 Danny Choo

A populist’s dream, the contenders consisted of the ADS Tech RDX-155 Instant Radio USB device versus discounter Aldi’s entry level Bauhn ADS-215 dual band portable radio…

Bauhn Digital Receiver Geeks.com ADS Tech RDX-155 Instant Radio marketing photographs

Testers’ performance data

Table 1: Sensitivity equivalence illustrating selected moderate-weak stations

FREQUENCY  DISTANCE  POWER INSTANT RADIO BAUHN
88.5 53mi 26 kW YES YES
89.3 48mi 25 kW YES YES
90.5 43mi 200 watts YES YES
91.1 35mi 10 kW YES, RDS YES,  RDS
91.7 53mi 26 kW YES YES
92.1 43mi 5 kW YES YES
92.5 48mi 25 kW YES YES
94.1 48mi 25 kW YES YES
94.5 88mi 100 kW YES YES
94.9 26mi 50 kW YES YES
95.3 88mi 100 kW YES YES
95.7 53mi 26 kW YES YES
96.9 88mi 100 kW YES YES
97.7 53mi 26 kW YES YES
98.5 88mi 100 kW YES YES
102.9 25mi 48 kW YES YES
104.1 65mi 1 kW YES YES
105.7 48mi 10 kW YES YES
107.3 48mi 10 kW YES YES

 

Table 2: Marginal signals illustrating reception differences between the two budget receivers

FREQUENCY DISTANCE POWER INSTANT RADIO BAUHN
90.9 25 mi 48 kW 2 / 2 0 / 2 – ACI
95.9 40 mi 1.6 kW 0 / 2 – RFI 2 / 2
96.1 88 mi 100 kW 0 / 2 – RFI 1 / 2
99.4 48 mi 2 kW 2 / 2 1 / 2
100.6 48 mi 2 kW 2 / 2 1 / 2

Salvaging suitable antenna connections

The Bauhn ADS-215 radio was also connected to the rooftop antenna via a 1 m / 3.28 ft high grade RG59 cable. To connect the antenna internally would void the warranty. Moreover, it is difficult to achieve this as the plastic case must be plied open, since there are no screws!

External antenna connection on Bauhn ADS-215 © 2014 FM DXing

External antenna connection on Bauhn ADS-215 © 2014 FM DXing

On the unit, cable was connected to the DC adapter ground [not pictured] and the collapsed telescopic antenna. The radio was powered using the supplied 5 volt DC adapter.

Optionally, if cutting coaxial cables is unpleasant, connection can be easily made via a 30 cm / 1 ft twin-lead wire then a 4:1 matching transformer. To be perfectly honest, transformers do pose some insertion loss as part of any antenna system. Surprisingly, no difference in signal strength of weak stations was detected between connection methods.

RDX-155 Instant Radio was connected to the rooftop antenna via a 1 m / 3.28 ft high grade RG59 cable. This cable also may cause some loss of signal and be susceptible to interference from the USB device. Sure, RG6 quad shield cable is better, but in practice the centre conductor is too thick to reliably connect to a pint- sized USB PCB. The laptop was powered using a battery.

It is speculated that access to laptop computers was not a trivial matter. Computers were  rare and prized possessions in post apocalyptic life. Because access to the internet was predominantly impossible, these computers were useful for processing needs only and recording data.

Fortunately, Instant Radio posed few Central Processing Unit (CPU) demands and looks to have functioned remarkably well on these old machines. How the simpletons ever charged that battery without a reliable mains power grid (they could not afford the onerous electricity bills) remains a mystery…

Post apocalyptic broadcasting

Records show that only an FM test was possible. But it was noted (amongst the word processing files found) that with the Bauhn dual band radio, full strength DAB+ reception (174 – 240 MHz) was available with the rooftop antenna. Photos were found of the graphical bars of the signal meter. Its Gyro Signal 1128 chip permitted satisfactory dual band reception at this time. (We don’t know the manufacturer’s objective sensitivity measurements for this module, but an Adobe Reader document with the FM performance of their 2005 module can be found via the end links). Retailing at $30, the Bauhn ADS-215 radio was likely to be an affordable choice for those with limited fiscal capabilities.

No contemporary music was being released or recorded. The broadcasts on the DAB+ multiplexes in these times included songs performed by old school cover bands such as Il Divo & Celtic Thunder. Music that was deemed to be fodder for the oppressed was reportedly banned for broadcast. For example, ‘aggressive’ releases by Neil Young, Metallica, the Dixie Chicks & John Butler Trio were illegal to broadcast, even if the recordings had been retained by some members of the elite. It has been suggested that the themes in these artists’ works may have been incompatible with the extremist ideology of the ruling elite…

Bauhn ADS-215 post Apocalypse © 2014 FM DXing

Bauhn ADS-215 post Apocalypse © 2014 FM DXing

Luxurious RDS performance suggested

Seven signals in the [above] table are known to provide digital Radio Data System (RDS) data. Six of these signals were too weak to decode. Only one quieting-level signal was included in the test, a broadcast on 91.1 MHz. On this channel, RDS data decoded easily on both units. RDX-155 Instant Radio offers faster decoding than the Bauhn ADS-215 radio. The Programme Type data (alone) decoded reasonably quickly on the Bauhn radio, but Instant Radio has a clear edge.

PI code mode on Bauhn ADS-215 © 2014 FM DXing

PI code mode on Bauhn ADS-215 © 2014 FM DXing

Close up, PI code mode on Bauhn ADS-215 © 2014 FM DXing

Close up, PI code mode on Bauhn ADS-215 © 2014 FM DXing

The Bauhn ADS-215 radio will display unique station identification codes called PI codes as part of the RDS digital data. This feature may offer potential value for DXing.

Post war, it is known that the elite took control of electronics and computing power. Whilst the elite played real life games on the stock market, the mortals continued their desperate simple tests. Trivial? Indeed. But it is all they had. They continue…

Riding out the Apocalypse © 2011 David Blackwell

Riding out the Apocalypse © 2011 David Blackwell

Differences testers observed

Where differences were noted between receivers on any particular frequency, the test was conducted twice. Between 95.9 – 96.1 MHz, no signal was heard due to heavy interference obstructing potential reception on RDX-155 Instant Radio. The interference was caused by a spurious signal.

This annoying side effect is a widely reported issue with the device that cannot be readily remedied by ferrite suppression chokes. It will be offset by a masthead amplifier, of course. Conversely, no spurious signals were observed on the Bauhn ADS-215.

Bauhn ADS-215 post Apocalypse © 2014 FM DXing

Bauhn ADS-215 post Apocalypse © 2014 FM DXing

On 99.4 MHz & 100.6 MHz, only weak signals were detected. Nonetheless,  RDX-155 Instant Radio appeared to outperform its rival in terms of sensitivity. On 90.9 MHz, no signal was detectable due to adjacent channel interference obstructing potential reception of the broadcast on the Bauhn radio. Again, this suggests selectivity out-performance by the Silicon Laboratories’ (Silabs) integrated circuit inside in the Instant Radio.

It is thought that back in the ‘olden days’, Silabs produced radio electronics that every man, woman or android could afford. Although Silabs mainly produced chips for portable standalone radios at this time, the RDX-155 Instant Radio represented somewhat of an oddity; a discontinued $17 computer-based tuner in a tiny USB enclosure.

Intermodulation dynamic range was tested on empty or very weak channels. Strong signal immunity is extremely important for FM reception applications and arguably a more important characteristic for any FM tuner than any simplistic sensitivity measurement or test. It is pleasing to report that no ‘ghost signals’ were detected on either receiver, despite the congested band. Accordingly, a high quality signal amplifier (ideally a masthead amplifier, positioned at the antenna) may increase sensitivity without compromising performance.

Instant FM Radio post Apocalypse © 2011 Synx 508

Instant FM Radio post Apocalypse © 2011 Synx 508

Simpletons’ summarized observations

The test (as collated in the table) suggests that potential differences in sensitivity, (if any exist) are likely to be negligible between ADS Technologies’ RDX-155 Instant Radio & Aldi’s Bauhn ADS-215. Weaker signals, such as the 90.5 MHz translator are not readily detected in flat winter conditions. The performance of Instant Radio was superior on three stations (probably due to better sensitivity and selectivity) but internally generated interference tended to offset any gains.

These findings suggest that the simpletons were confident both units would provide satisfactory FM reception for the modest outlay they originally paid at retailers like Junk World.

The broken souls understood a masthead amplifier could be used with these inexpensive receivers to improve performance when coupled with an external antenna.

Junk electronics © 2007 Marco Bernardini

Junk electronics © 2007 Marco Bernardini

It was beyond the means of most, but they found some antenna pre-amplifiers on the streets; regrettably their beloved streets had become so littered with redundant electronics their suburbs resembled a rubbish dump. These cheap radios gave the broken souls hope for the future. Finally their story of hope can now be shared for the benefit of future generations.

Society’s future is unwritten. Government policy or individual action that promotes greed, entrenches class divisions & exacerbates poverty is the real ‘junk’ of the world!

Non-fiction reference material!

Extensive test of Instant Radio RDX-155

Boxing kangaroo test of Bauhn ADS-215

Gyrosignal 1122 FM/DAB receiver module specifications

Masthead amplifiers potentially benefit weak FM signals

Role of RDS data in long distance FM reception

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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?

Sangean PR-D8 recorder on AM: Crude review

The Sangean PR-D8 is a two band portable radio for Medium Wave (MW) and FM. The radio is designed to easily record radio broadcasts, wherever one may roam. The test unit was purchased from Amazon dot com. Carriage took two weeks via USPS First Class International postage.

How does recording work?

Press the ‘Rec’ button for five seconds on the unit and the tuned station is recorded to an SD card. The end product is a relatively high resolution 192 kbps MP3 file that can be immediately shared via the internet. Modern computers typically furnish SD card readers as a standard feature. For older computers, USB ‘all-in-one’ card readers can be purchased (for next to nothing) to access the recordings encoded to the SD card.

Recording screen including dual VU meters - Sangean PR-D8

ADVANTAGES

Excellent recording fidelity at 192 kbps bitrate. Digital artifacts may be audible if the 128 kbps encoding quality is chosen.
Accurate recording level meter suits both radio and line-in recordings.
Fully customizable timer recording and alarm functions. May be used as an alarm clock.
Tuning stations is user-friendly. Easy to navigate, review and delete clips.
Well designed instruction manual which is readable & written with satisfactory grammar.
Excellent build quality. Strong likelihood of maintaining value in the secondary market.
Compatible with modern SD cards, including smaller breeds via an adapter. A 32 gigabyte HC Class 10 card was used in test.
Satisfactory sensitivity on MW. The 20 kW broadcast Premiere (1ère) 666 kHz Noumea is received with this radio on a daily basis at 920 miles. As is the 50 kW broadcast Radio New Zealand National 567 kHz Wellington, at a distance of 1,565 miles. Antenna is a 11.5 x 100 mm ferrite bar inside the unit.
Satisfactory sensitivity on FM. 4JJJ 99.3 MHz Biggenden was received on a daily basis at 143 miles. Antenna is a telescoping antenna, sited directly above the MP3 recorder.
Tuning increments can be selected to suit the listener’s region.
Includes quality AC power supply for indoor use. Satisfactory battery life whilst recording (up to 10 hours).
Full suite of features. Twin (stereo) microphones suit outdoor recordings. Line level audio output is provided in addition to the standard Headphone output.
Reasonable FM sensitivity when connected to an external antenna.

 

DISADVANTAGES

NOT recommended for portable FM recordings. Please refer to the detailed discussion in the body of the article.
Wide filters are NOT suitable for separating all FM stations 200 kHz apart. The FM selectivity may be improved by a simple ceramic filter mod. Such a project voids the warranty & requires a conventional front end design.
Expensive purchase price relative to offerings made by the group that produces the Degen/Tecsun portable radios.
No provision for external antenna, but this can be circumvented with minimal effort.
No signal meter although a stereo indicator is included.
The inclusion of the 64 kbps bitrate recording option seems superfluous. Those recordings exhibit significant compression artifacts, to the point of the clips NOT being usable.

Love AM? This may be the radio for you

The author of this review has a bias towards FM. With that disclosure out of the way, the most fundamental flaw of the design is not catering for FM recording enthusiasts. Why make the MW section virtually immune to interference when encoding recordings, whilst not doing the same for FM? It seems bizarre for Sangean to pursue such a strategy. Did (former) Prime Minister Kevin Rudd or Opposition Leader Tony Abbott (now Prime Minister) help design this ill conceived recording radio? And why can’t Turnbull (Communications Minister) can fix it?

MW enthusiasts vastly outnumber FM enthusiasts. Effectively FM listeners ‘lose out’ since the manufacturer seems to have designed a recording radio to satisfy the largest segment of consumers.

Recording mode & Backlight - Sangean PR-D8

According to C. Crane:

Traditionally AM radio is very difficult to record into MP3 format because of unwanted noise generated by the digital components inside the radio. The PR-D8 overcomes this problem by using good circuit craftsmanship techniques.

This radio does cause some interference when recording weak MW signals from an external tuner, even in ‘Recording Pause’ mode. This symptom seems to be easily solved by moving the component’s passive indoor MW loop well away from the recording radio, using a higher gain loop (especially an amplified variety) or an outdoor antenna.

For those seeking to purchase this radio for the sole intention of MW recording, this receiver performs admirably and would be recommended primarily for this purpose.

Samples of MW recordings

873 kHz talk: interstate fringe signal

1242 kHz music: fringe signal

1368 KHz music: interstate fringe signal

Recording mode & Backlight - Sangean PR-D8

 

Further reading

Enthusiast Review – Herculodge blog

Customer Reviews – Amazon & C.Crane

The author acknowledges the assistance of David in the composition of this review. Photos of the Sangean PR-D8 may be reused under a Creative Commons license. Simply link to this blog or attribute the blog in a photograph mouse hover or caption. Medium Wave distance calculations calculated using coordinates from Asia Waves.

Portable FM radios

European hard core FM enthusiasts tend to use the Grundig satellite 700, Eton E5 (Grundig G5), Degen 1103 (Kaito 1103), Grundig satellite 3400, Grundig satellite 500 & Sangean ATS-909.

These radios require a filter modification in order exceed the selectivity of modern radios with Digital Signal Processing (DSP). Usually replacing the last 150 kHz or 180 kHz filter in the Intermediate Frequency (IF) circuit for a 80 kHz variety does the trick. In unmodified form, the radios rarely provide equivalent selectivity of a DSP radio.

Sangean ATS-909 worldband receiver © 1996 Mysid

Sangean ATS-909 © 1996 Mysid

So why do European enthusiasts go to this trouble? Apart from the obvious fun of learning about the internal circuitry of the particular radio, in this blogger’s experience there are overwhelming advantages in ‘modding’:

  • better performance 200 kHz above local stations;
  • better separation of stations spaced at 100 kHz;
  • better sensitivity due to the narrower filters; &
  • ability to plug in an external antenna (without a plague of images) due to sophisticated attenuation switches.

DSP based radios such as the Tecsun PL606 probably still offer better immunity from strong signals, a key feature of the Silicon Laboratories’ (Silabs) tuner design. For example, at a high rise apartment tower within 20 kilometres (12 mi) of a major FM broadcast site, the Degen DE1121 will start to overload before the Tecsun PL300WT (Grundig G8) will. It is also hard to overlook a Silabs design for the convenience factor: it is a functional radio ‘out of the box’.

De1103 © 2007 Igor K ico.livejournal.com

De1103 © 2007 ico.livejournal.com

In the field

The chief problem with portable radios is that all receivers tend to overload near mountain tops. This can be immensely frustrating. What tends to happen is the listener is increasingly likely to inadvertently make mistakes. Whether it is mistaking images for legitimate stations or missing weak signals (because the weak stations are covered up by distorted images) the experience is often not rewarding!

For this reason, this blogger argues that a portable radio has a limited role to play for field trips. Their use is primarily suitable for inaccessible terrain or very remote areas perhaps 30 kilometres (19 mi) away from broadcast sites. Perhaps this suggestion is a controversial and extreme stance?  (It is important for every writer to remember that enthusiasts often hold strong views. Respect these differing opinions. Entering into robust on-line debates typically ends with instances of dysfunctional behaviour and worse case scenario, a loss of friendships).

Importantly, using a portable radio in a popular location makes it likely for others to think the listener is strange. As this difficult hobby is supposed to be about enjoyment and fun, no one needs to be ridiculed in public. The trick is to switch to a cricket or football broadcast – pretend that is the reason for lugging the radio. Of course, this writer does not need to pretend, although listening to cricket matches (hell, even briefly) can be tiresome when Australia exhibits poor form!

Nonetheless, it’s yet another reason to stick to the safety of a car receiver. Moreover, by using a car radio, a better antenna may be utilized (in many cars, a proper monopole). Car tuner performance makes listening far more comfortable, especially with regard to inter modulation distortion (IMD) – the unwanted mixing of two or more stations. Protection from adverse temperature extremes, in particular summer heat and thunderstorms cannot be lightly dismissed. For example, air conditioning is essential for comfortable mobile DX in cities and towns along eastern Australia.

For everyday use in high rise dwellings, the weaknesses of portables become much less evident. In fact, packing a portable in the luggage is a simple way to turn a potentially boring trip into a DX opportunity.

De1121 © 2010 nice.kaze.com

De1121 guts © 2010 nice.kaze.com

Favourite FM portable

The beauty pictured above and below is the DE1121. Despite the relatively high purchase price, the modified Degen DE1121 is the blogger’s favourite! The designers did made some mistakes; flaws include a complicated user interface and relatively poor build quality. However, this modified radio provides superior FM performance compared to DSP-based competitors with both indoor and outdoor antennas.

Little wonder that Degen’s sister DE1103 remains so popular amongst European FM enthusiasts. Between 76-108 MHz, the DE1103 features better 12 dB SINAD sensitivity than the Sangean ATS-909, that is 0.5 versus 1.8 microvolts.

De1121 station labelling © 2013 FMdxing

De1121 station labelling © 2013 FMdxing

Features of the DE1121 include:

  • Station labelling (all stations can be labelled using a computer);
  • Three level signal attenuator;
  • External antenna input;
  • Full length telescopic FM antenna;
  • 128 kbps MP3 recording (with noticeable artifacts);
  • MP3 playback;
  • Direct frequency entry;
  • Audio Input from other portable radios (to permit recording);
  • High sensitivity tuner (virtually identical to the DE1103);
  • Full aluminium tuner shielding  &
  • SSB decoding up to 30 MHz.
De1121 © 2010 nice.kaze.com

De1121 accessories © 2010 nice.kaze.com

De1121 © 2013 FMdxing

De1121 © 2013 FMdxing

De1121 © 2013 FMdxing

De1121 backlit © 2013 FMdxing

Recommended reading

2012 comparison of portable shortwave FM receivers by Universal Radio (Archived PDF file)

DE1121 world band receiver review by Dave N9EWO

Is DXing a hobby only for the rich?

Mt Canobolas Sharx in-car band scan by Dr Nobody (No longer available)

Portable DSP pain at Point Glorious by FM DXing

European data is compiled from tropospheric loggings in 2012. Enthusiasts who provided loggings reside in Belgium, Finland, France, Germany, Holland, Italy & Poland. This article was updated in December 2013.

Inject your DAB+ portable with steriods

DAB+ Digital radio has been dogged with criticism since inception. Criticisms levelled by consumers and audiophiles included:

  • an excessively high initial purchase price for portable receivers (the average price was approximately $200);
  • poor or excessively restricted coverage areas;
  • deceptive or misleading advertising about CD audio quality by the digital broadcasting lobby group;
  • poor audio quality relative to FM broadcasts and digital music downloads (e.g. Bigpond Music, Apple Itunes) &
  • a restricted choice of radio programming offerings, including frequently repeated content.

Somewhat of a resurgence appears to be underway due to the affordability of receivers. USB computer receivers with the E4000 tuner (photographed below) can be purchased from $20. These plug into the external television antenna. Decoding of DVB-T (Terrestrial Digital Video Broadcasting) reception is included.

Portable receivers (photographed below) can be purchased from $40. These incorporate a telescoping monopole antenna for use in strong signal areas or elevated and unobstructed coastal regions.

Component receivers (photographed below) can be purchased from $70. These plug into the external television antenna. Recording facilities to a USB flash drive may be included.

Your humble servant blogger modified an inexpensive portable receiver Pure One Mini (priced from $70 or $50 for clearance stock) for use with the external FM antenna. This half an hour project only requires a short piece of shielded RG6 quad shielded coax and an F-type balun (total cost $5). The balun (AKA transformer) is photographed below. It’s a shocking photograph but that does at least prove that this blogger took it. The ubiquitous television coaxial cable probably doesn’t require a photograph!

For the purposes of testing ‘the mod’, an indoor 19 decibel preamplifier and rooftop five element FM antenna was connected to the sacrificial lamb, in the Pure One Mini (photographed below).

With ‘the mod’, it was easy to receive permanent FM signals up to 232km from the northwest, 174km from the southwest & 329km from the south.

Full DAB+ reception is also achieved. On FM, permanent RDS (Radio Data System) decodes are possible up to 71km. That figure should be considerably more distant but the prevalence of stations using RDS is low, and the occurrence is diminishing.

Due to the high quality tuner module, strong signal immunity comes close to a three or four gang component FM tuner. It is infinitely better than the Tecsun portable receivers. Nonetheless, the Tecsun radios offer better separation between FM stations (200 kHz adjacent channel selectivity). The purchase of an inline preamplifier or masthead distribution amplifier is mandatory to extract the best FM performance from the tuner module. Why? The tuner appears to have low 30 decibel quieting FM sensitivity relative to a high quality component tuner or car receiver.

By connecting the antenna lead (this wire runs to the telescopic rod) and power ground (-5V DC) to an F-type balun using shielded coax (chosen to minimize interference from the display and internal circuit board) it seems plausible that the project provided reception gains equivalent to the performance of a $70 component tuner.

Those entry-level DAB+ component tuners are likely to incorporate the same tuner module inside! Mauro Grassi says ‘This module is widely used in many, if not most, DAB+ radios’. Further, the discussion on Whirlpool and Mysnip provides additional support to this assertion.

When it works, DIY (Do It Yourself) can be awesome. Although not quite as easy as the television shows (The Block, Better Homes & Gardens et. al.) suggest! Rest assured, this project is so easy it does not even require a soldering iron. Many listeners and enthusiasts have implemented such a project with immensely rewarding results!

Just can’t get enough?

Just can’t accumulate enough Dabbler’s Dream™ portable receivers? Curious about the new model releases? Check out the blog from the Cosmos Monitor II. Until about a year ago, the Monitor was also blogging on WordPress.

Mark discusses the (one & only) Dabbler’s Dream™ in this blogger’s possession in this entry. Using this beast, troposcatter and tropospheric ducting is discussed in this entry. Sporadic E is discussed in this entry. The modified Degen De1121 exhibits better selectivity and sensitivity for everyday use. On the downside, that radio exhibits slightly inferior strong signal immunity, as the design is older, without the benefit of R&D associated with the Silicon Labs’ integrated circuit inside the Dabbler’s Dream™ & other ‘rebadged’ equivalent receivers.

Popular portable receivers

Let’s examine the portable receivers used by active European FM enthusiasts!

Where an enthusiast uses multiple portable receivers at any one location, all their chosen portable equipment is included. Due to their size or weight, some of these receivers may be less ‘portable’ than others. These portable receivers may be modified by enthusiasts to increase FM selectivity, that is, the separation between FM stations. For example, this blogger has replaced the second 180 kHz Asian-made filter in his Degen De1121 with a 56 kHz Murata filter, whilst leaving the first FM filter intact. Incidentally, the integrated circuits used in the FM section of the De1121 are virtually identical to the very popular De1103.

The radios pictured above & below are amongst the most popular portable receivers suitable for long distance FM reception.

These polls are merely intended to provide a superficial snapshot. The sample size (10) and the rules for inclusion (above) may skew results.

De Fine Print

Data is compiled from tropospheric & meteoric loggings submitted to Peter Schwarz for the April 2012 edition of German-language Reflexion magazine (edition number 243). Enthusiasts who provided loggings reside in Belgium, Finland, France, Germany, Holland, Italy & Poland. Four enthusiasts did not provide details of the equipment used with their loggings, thus restricting the sample size. A two-year subscription to the electronic version of Reflexion magazine costs approximately $38 when paid via foreign draft. Graph created by Online Chart Generator, one of 22 Useful Online Chart & Graph Generators.

The next polls to be included will cover the most popular external FM antennas & component FM tuners used in Europe.