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?

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!