FM USB Tuner Shootout: PC Ear vs Instant Radio (ADS Tech RDX-155)

Welcome to another radio shootout, Boxing Kangaroo edition! These shootouts feature ‘dirt cheap’ radios and are intended to appeal to a variety of different potential audiences, including terrestrial FM radio listeners and hobbyists interested in elementary electronics or FM reception capabilities.

Boxing Kangaroos in the zoo © 2011 Scott Calleja

Digital Signal Processing on the cheap?

At the time of writing, the cheapest Chinese portable FM radio currently available incorporating Silicon Labs’ (Silabs) Digital Signal Processing (DSP) costs about $49 including delivery. This model is the Tecsun PL-606. For those with a laptop and access to a directional antenna, USB computer devices with the SI4700/01 integrated circuit (IC) are considerably more inexpensive, representing a cheap entry to Silabs DSP.

 Tecsun CR-1100 © 2013 James Case

 Tecsun PR-380 © 2013 James Case

The contenders: Two popular Silabs USB FM tuner

Instant FM Radio (Instant Radio) costs about $17 including delivery.

USB FM Radio Player © 2005 Silicon Laboratories ADS Tech RDX-155 Instant Radio under Windows 7, Canberra Australia ADS Tech RDX-155 Instant Radio marketing photographs

PC Ear FM Radio Player © 2014 FM DXing

PC Ear costs about $17 wholesale but is no longer readily available new.

PC Ear unboxed © 2014 FM DXing

Gunning for the best: PC Ear versus Instant Radio

A rudimentary inspection of the datasheets suggest the FM sensitivity measurements are equivalent for the Silabs ICs inside PC Ear and Instant Radio. To test this, a modest directional antenna was connected to the devices. Both devices were housed in a metal enclosure with two suppression chokes and operated with a Radio Frequency (RF) quiet laptop running from battery power.

Reception conditions were well below average with heavy, unrelenting rain. 15 stations were chosen for the test. Of these, 13 stations were detected with the minimum signal strength of 0, where signals are just audible above the noise floor. Because of the heavy rain, two of the usual weak signals were not audible during the test and accordingly, do not appear in the performance table.


PC Ear does NOT support firmware upgrades using the Windows-based Silabs configuration software utility. Firmware updates to PC Ear can be done under Ubuntu/Linux, but the process may be complicated. The Silabs Radio DLL software appears to function, but audio issues were evident when tested briefly with PC Ear. According to the developers, it is supported.

The upgraded firmware was used with Instant Radio. The upgrade was performed per the ADS Configuration user guide instructions for Silabs Radio DLL, developed by Beezer, Guino and Pete.

Characteristic PC EAR  INSTANT RADIO
Tunable frequency range 76 – 90 MHz, 87.5 – 108 MHz 76 – 90 MHz, 87.5 – 108 MHz
Circuit board approximate size 1.3 x 0.6 inches 2.4 x 1.1 inches
Tuning steps 50 kHz 50 kHz
Radio Data System support No Yes
Software support USB Radio 2.0-3.0 (supplied), FM Signal Strength Analyzer, Silabs Radio DLL, Silabs configuration software utility. Instant Radio (supplied), Silabs Radio DLL, FM Signal Strength Analyzer, Silabs configuration software utility.
Hardware version PC Ear 1.77 Silabs 1.7.15
Firmware upgradable No, Please refer to body of article Yes, ADS NoiseMod Primary.dec

The software support listed in the characteristics table (above) is NOT exhaustive. Please understand that the priority was to test reception performance.

Any frequency (or broadcast) can be easily recorded for hours ‘on schedule’ using third party Windows audio recording schedule software such as Fox Magic Audio Recorder (free) and High Criteria Total Recorder Professional ($36). The software supplied with the devices also offers recording ‘on demand’. ADS Tech Instant Radio software is especially recommended for this purpose, since it offers high resolution 96 kHz uncompressed recording capabilities.

Closeup of ADS Tech Instant FM Music PCB © 2014 FM DXing

Comparative performance

PC Ear is constructed on a double sided printed circuit board, whilst the Instant Radio device uses a much larger single sided board (above). Unsurprisingly, both designs feature surface mount components.

90.5 0 3 No 43mi (200 W)
91.1 2 – Quieting Mono 19 – Quieting Mono Instant 35mi
92.1 0 6 N/A 43mi
93.7 0 0 N/A 62mi
94.9 0 6 No 27mi
95.3 1 6 N/A 88mi
98.5 1 – Quieting Mono 9 – Quieting Mono N/A 88mi
99.4 0 0 No 48mi (2 kW)
99.5 No signal, Slight high adjacent channel interference (99.7) 0 N/A 208mi
102.9 0 6 N/A 48mi
104.5 4 – Quieting Stereo 50 – Quieting Stereo Instant 11mi
105.7 0 5 No 48mi
107.7 5 – Quieting Stereo 57 – Quieting Stereo N/A 11mi

Instant Radio consistently offered a slight edge with superior adjacent channel suppression on one station and the advantage of RDS. PC Ear did ‘stutter’ occasionally on one RDS-enabled station. A change to the device settings (below) and immediately unplugging the device solved the problem. This trivial audio issue could not be replicated again after 15 minutes of listening to the station, nor the next day.

PC Ear FM Radio Player custom settings © 2014 FM DXing

There were no consistently observable differences in sensitivity, audio quality or immunity to internally-generated spurious noise (interference) between the devices. This result was somewhat unexpected because PC Ear is rumoured to be an earlier Silabs USB tuner prototype with its share of critics on the world wide web. Perhaps the critics use the supplied wire antenna (in both devices, 29 inches long) and therein lies the problem? But the test suggests PC Ear performs just as well as Instant Radio with a directional antenna. If anything, the test was biased against PC Ear because of expectations the device was of poor design quality relative to its sister models.

Performance improvements

It should be stressed that Instant Radio and other Silabs devices require antenna modifications (below) for connection to a directional antenna such as a rooftop television antenna. Soldering skills are recommended for permanence. The use of other alternatives to ‘mate’ the device with an external antenna, such as passive induction as used in some mobile broadband device antennas might also be feasible, but discussion is beyond the scope of this shootout.

With the additional expense of a metal enclosure, shielded five metre USB cable, pre amplifier and several ferrite suppressors, the total cost equates to approximately $135. Many readers may already own much of this equipment, but it does represent a potential outlay. In this blogger’s opinion it is only worth pursuing such a project for the sheer fun of experimentation!

Instant Radio customization © 2014 FM DXing

Notwithstanding the extra Do It Yourself (DIY) effort and cost required to extract the device’s DX potential, Silabs tuners feature satisfactory signal separation and strong signal handling. With the above modifications, Instant Radio is sensitive enough for daily signals from in excess of 265 miles. Momentary meteor pings from distant FM stations are possible to receive. Although untested at the time of writing, it is anticipated that modifications to PC Ear would accomplish the same. The bottom line is that these Silabs devices were designed for learning projects. It is NOT suggested to ‘throw good money after bad’.

Comparative performance with expensive stand alone tuners

As one should realistically expect because of the tiny footprint and price, the devices are outclassed by stand alone tuners with a proper shielded tuner module. Even with a preamplifier used in-line to desperately boost sensitivity, this is apparent. Head-to-head, the following tuners or SDRs (tested without preamplifiers, using the same antenna) all noticeably outperform Instant Radio (FM usable sensitivity* is listed in brackets):

  • Blaupunkt Casablanca CD51 (1.68 microvolts),
  • Elad FDM-S2,
  • Sherwood TX-5090 RDS (1.58 microvolts),
  • Yamaha TX-950 (0.8 microvolts).

For example, in a ‘dead-of-winter’ test, the Blaupunkt automotive receiver consistently achieved better performance than Instant Radio. Improved RDS sensitivity meant that the car radio decoded digital RDS data from two extra stations. Like all models in the Sharx range, the car radio more readily discriminated stations spaced 100 kHz apart.

Instant Radio was capable of receiving 2/3 of the 15 weak signals chosen for the test, whilst the car radio nabbed 93% of weak signals! The Silabs devices enable reception of the same stations from in excess of 265 miles as standalone tuners. However, this reception will obviously be more transient and weaker signals are unlikely to be audible. From a DX enthusiast’s perspective, that may be a frustrating prospect.

The number of RDS decodes achieved with Instant Radio was equivalent to the Bauhn ADS-215 dual band portable radio connected to a carefully aligned rabbit ears antenna mounted near a window. Invariably, Instant Radio outperformed the Bauhn portable radio using its inbuilt telescopic antenna. PC Ear marketing photographs


The device incorporating the Silicon Labs’ SI4701 IC (marketed as ‘Instant Radio’, above) is one breed of flash-drive sized computer tuner that offers modest potential for weak FM signals. It suits receiving locations with a congested FM band. Its full RDS capabilities can be exploited in locations where broadcasters support the system. PC Ear also offers similar performance, without RDS decoding.

All software tested works successfully on both receivers without noticeable bugs. There is a range of tuning software to choose from. Both Silabs devices are suited to DIY modifications.  Users of Instant Radio benefit from access to the latest firmware.

Further reading

Gadget tunes in to FM via USB

Instant Radio for distant FM reception

Instant Radio satirical shootout

Instant Radio slideshow

Radio recording saved the radio star

Silabs Radio DLL

* Standard DIN sensitivity specifications, tested with THD 3% & S/N of 26 dB. Official data, sourced from manufacturers. Lower numbers (approaching zero) indicate the best FM sensitivity. The Elad FDM-S2 sensitivity is measured differently from conventional tuners. This SDR offers better than 2 microvolts using the 12dB SINAD measurement on the extended FM band.

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

Butchering the Winfast TV2000XP for FM DX

Please consider the risks involved with modifying a tuner before proceeding with any project. The author shall not be liable for any loss or damage whatsoever (including human or computer error, negligent or otherwise, or incidental or consequential loss or damage) arising out of, or in connection with any use or reliance on these instructions.

The Leadtek Winfast TV2000XP is a Peripheral Component Interconnect (PCI) card to receive FM and analogue television broadcasts. The card also provides analogue video capture functionality via an S-video input. At the heart of the card is the Philips FM1216 / PH hm tuner. The module may be used in a number of other manufacturers’ analogue TV and FM cards, including:

  • Hauppauge WinTV FM;
  • AverMedia AverTV Stereo Edition Desktop TV Personal Video Recorder &
  • Conexant Fusion 878A Easy TV.

The tuner includes the following Philips’ integrated circuits:

  • TDA5736;
  • TSA5523;
  • TDA9809 &
  • TDA7040.

Since analogue television is ‘done and dusted’ these cards (below) may be classified as redundant technology. Accordingly, most sell for less than 10 bucks on Ebay!

Card featuring Philips FM1216 tuner © 2007 Whazilla

The card may be used with Dscaler noise reduction software for weak signal detection, such as low VHF band Sporadic E in regions where analogue television is still operational. Because of the wide frequency coverage, Klaus Hirschelmann suggests the tuner offers potential to receive International Radio and Television Organisation (OIRT) broadcasts still on-air in Eastern Europe.

Live recording with TV2000XP

According to Philips:

The tuner [Automatic Gain Control] AGC for both TV and FM radio operation is generated with a novel AGC detector which measures the [Intermediate Frequency] IF signal level directly at the tuner IF output pins. As opposed to the conventional AGC detector, this new circuit allows a higher take-over level and offers superior immunity against tuner overload.

The tuner offers satisfactory strong signal immunity. Performance is markedly better than the E4000, R820T or FC0013 tuners used in a Realtek Software Defined Receiver (SDR) or a Silicon Laboratories’ Si4734 based portable receiver connected to the same rooftop antenna. Philips’ tuner typically features an Image Rejection of 65 decibels for the FM band. In terms of benchmarking, a Yamaha TX-930/950 component tuner features a more favourable 90 decibels. AM Suppression – the ability of the tuner to reject AM signals, is specified at 38 decibels.

Whilst the tuner features interference suppression, the separation of FM stations is not up to contemporary requirements. When Philips Components designed the tuner, Digital Signal Processing (DSP) was at its infancy. These days, DSP based tuners are perhaps taken for granted. Whilst away interstate recently, this blogger noticed that even a cheap TDK Ipod dock supplied in the apartment featured a DSP FM tuner!

Timer Radio Recording with TV2000XP

The scheduled timer recording functions for recording (above) on the TV2000XP is a boon. Therefore, it is a shame that the tuner is not suited to a congested FM dial. When it was used for television recording, the software accompanying this product worked flawlessly.

The tuner does not permit a listener to separate fringe stations 100 kHz apart, and to hear several stations without interference from strong local stations, it was necessary to off-tune 50 kHz to prevent audible interference. Fortunately, sensitivity seemed fine, for example daily reception (a 26 kW broadcast) out to 208 miles (335 km) was possible with a modest combination rooftop antenna without a preamplifier. Sensitivity for a weak signal with a 26 dB signal to noise ratio is 2.24 uV, compared to a Yamaha TX-930 with a more favourable 0.8 uV. Most tuner software (including Leadtek and Hauppauge) features a five segment signal strength meter.

After quite a few drinks one night the author decided that it would not hurt to rip the tuner module open and see what was inside! It was no risk, because a replacement card is dirt cheap. Worst case scenario, if secondhand supplies dissipate, one can simply solder in a new tuner module, pictured below.

FM1216 tuner module © 2013 Max's Depot

The fact the aluminium lid of the Philips FM1216 / PH hm tuner module could be easily plied open was a surprise. What was inside was even more interesting. Staring up at this ‘butcher’ were two 230 kHz Murata ceramic filters and one ceramic discriminator. The block diagram (below) shows the role of the two 10.7 MHz IF filters.

Block Diagram of FM1216 © 2013 Philips Components

To aid easy identification of components (in this case, the existing filters), it is recommended to refer to an online source such as Bruce Carter’s Ceramic Filter page.

Was this ‘elderly beast’ a candidate for a filter butchering? Hell yeah! Hence this article is basically another instalment of the ‘narrow filter modification’ project. It never gets old. 🙂

TV2000XP inside tuner module

Because the rear of the tuner module cannot be easily accessed, the existing wide filters are perhaps best removed from the enclosure… by force! Pliers were – again – used to ‘throttle and crumble’ the existing filters, easily identifiable by the Murata logo. The replacements are soldered in place of the old ones.

The tuner module features a large Printed Circuit Board (PCB) as illustrated on the left half of the photograph above. Even ‘old eyes’ are unlikely to encounter problems with such a simple project. This is a five minute project requiring little equipment, consisting of:

  • general purpose pliers;
  • a soldering iron;
  • solder;
  • desolder braid (optional);
  • philips head screwdriver (optional) &
  • replacement 10.7 MHz filters of one’s choice.

Mike Bugaj is another enthusiast who enjoys ‘butchering’ FM tuners as much as this blogger! He prefers to change one filter first and test performance before proceeding with replacing the other wider filters. This blogger takes the same approach. One of the two 230 kHz filters was removed and a 80 kHz filter soldered in its place. The butchering is not pretty (below), in fact it is possibly one of the ugliest mods ever performed… ‘but she works!’ Stations 100 kHz apart can now be heard, whilst the distortion levels of FM broadcasts remain satisfactory.

80 kHz filter replacement pictured lying flat, E10.7T - FM1216 module

Whilst not mandatory, a preamplifier improves sensitivity. As mentioned above, the module may not be up to component tuner standards for weak monophonic or quieting stereo signals.

Ferrite suppression chokes for RG6Q coaxial cable - TV2000XP card in far rear expansion slot

For the finishing touch, it is recommended to purchase a few ferrite suppression chokes to clip onto the coaxial cable (above) to minimize Electro Magnetic Interference (EMI) problems from a desktop PC. The blogger can recommend jteam Electronic Components. Their chokes (below) were posted quickly from Perth, Western Australia and were very inexpensive compared to retail supplies.

Ferrite suppression chokes for RG6Q coaxial cable

To minimize interference from the desktop PC, so as to maximize FM tuner sensitivity:

  • A CRT computer monitor should NOT be used;
  • Internet routers should be switched off;
  • Remove all unnecessary or unused leads connected to the desktop computer such as USB extension cables &
  • Use RG-6 Quad Shield Coaxial Cable for all connections from the tuner to the antenna wall plate.

A recommended source for replacement 110 kHz narrow ceramic filters is Greg Gortman of Lexington, Kentucky. International carriage is available from these sources. Prior to publication stocks were available.

Programme details in RDS Spy © 2013 Jan Kolar, Czech Republic

Klaus Hirschelmann notes that the tuner module features an Multiplex Output for RDS use. Whilst this blogger has not tried it yet (perhaps after the Ashes test cricket series) the Data and Clock signals (found on pins 13 & 14) can be fed via a shielded cable to the Line Level Input on a sound card. In theory, this should enable RDS decodes with RDS Spy software, illustrated above and below.

Sound card input in RDS Spy © 2013 Jan Kolar, Czech Republic

For those craving more experimentation, H. Chew suggests the Philips tuner can also be used as an SDR under a Linux operating system. Polish enthusiasts have even built the module into a ‘stand alone’ RDS component tuner!

Specifications quoted above may not necessarily be indicative of performance. There is nothing preventing manufacturers from using different test signals to make measurements in an effort to improve performance specifications for marketing purposes.

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

De1103 © 2007

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

De1121 guts © 2010

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

De1121 accessories © 2010

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.