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.

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3 Responses to Portable FM radios

  1. The Annoying Roach says:

    This enthusiast uses a Tecsun PL-390 (aka “Dabblers Dream” by some). It performs beautifully in areas remote from powerful transmitters, such as the Snowy Mountains. Jet scatter- courtesy of Sydney/Melbourne flights- brings up the Radio National outlet from Coonabarabran at 500 km.

    At home, 25 km from the Sydney sticks, the DD can hear scattery signals from Orange, Cootamundra, Coonabarabran and Batemans Bay (200-350 km), with noted splatter on some frequencies. It doesn’t perform so well in the inner suburbs of Sydney, with significant overload/image problems present at Marsfield, about 8 km from the Sydney sticks.

  2. Cheers for the free plug.It has so far yielded no hits,but I appreciate the effort. ;p

    This post is of course f-a-r too technical for me,so I’m unable to pass comment on the content therein.

    What’s a 5-gang radio,anyway?

    • fmdxing says:

      Tuners with an electronic equivalent of five gangs have better immunity from strong local signals entering the antenna.

      …A 3-gang tuner has only two tuned circuits to select the desired station and reject the rest. A 5-gang tuner has four tuned circuits to select only the desired station’s signal and this leads to better attenuation of the undesired signals, i.e., better image rejection and better overload protection from other stations removed from the desired station…

      The number of gangs used commercially in quality tuners has ranged from a low of 3 to a high of 9. Each tuning element inserts loss that must be compensated for by RF amplification or the gain of the antenna. Some tuners have different operating modes or bypasses that reconfigure or bypass gangs. We have found that tuners need a minimum of 5 gangs to perform optimally over a wide variety of reception conditions, but some 4-gang tuners will provide excellent performance in most situations. Even some 3-gang tuners are quite sensitive, but may have problems with strong signals showing up in many places across the dial due to front-end overload.

      http://www.fmtunerinfo.com/

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