Radiotracking with commercial scanners

Hand held commercial scanners are very effective receivers for radiotelemetry due to competitive price, size, large memory, circular scanning and high level of general flexibility (all bands incl. Argos etc.). Their drawnback are: a bit lower sensitivity, less selectivity, low quality indicator and mostly do not have manual gain control. Since 1994 I use them in many projects. We can use only models with SSB (beat oscilator - single side band: LSB,USB, CW) like: Alinco (DJ-X10, DJ-X20, DJ-X2000, Yupiteru (MVT7100, MVT7200, MVT 7300), Aor (AR8000, AR8200), Icom (IC-R10, IC-R20) etc.

In order to find the best type and to solve the problem of accurate identification of tag frequency I tested available products (Stabo XR100= Yupiteru MVT7100, AR8000, AR8200, Yupiteru MVT7200, Yupiteru MVT 7300, Alinco DJ-X2000, IC-R10, IC-R20). All scanners are equipped with AGC except the IC-R10 and R20, which switchs on manual gain control for all SSB modes automatically. Due to a bit lower selectivity, the spacing of channels (tags) should be 16 kHz or more to avoid interference and miss tuning (opposite SB). The display indicator is scanning the signal level with a low frequency and thus only beeps 20ms and longer are correctly displayed. Low sensitivity (beginning of function) of this indicator can be easy improved using a preamplifier (MOSFET, GaAs, etc., this is main effect rather than better input sensitivity). The German company GFT offered reconstruction of Stabo XR100 for better indicator function (delayed in maximum) and manual gain control. Similar reconstruction is probably available for AR 8000. Mode CW ("telegraphy") is seemingly "sharper", but in fact it has the same filters and due to added tuning shift it is the worst solution. Aor and Icom models have the best sensitivity.

The comparison of tuning and construction parameters of different scanners:

I compared the output acoustic frequencies (y, kHz) and displayed frequency figures (x) of different scanners for a test tag 172.152 MHz (continuous ton) in room and outside temperatures. Tag beeps of about 3 kHz (2.5-4 kHz) provide the best acoustic impression and good identification (not 800Hz as sometimes noticed). This makes in general large differences between declared/transmitted and tuned (displayed) frequency. In additon, the difference between USB and LSB must be 6 kHz or more for same signal. In the following graphs you can see that there is NO stable position (SB "mirror" side) of USB, LSB, CW (!) and also a shift of CW in different products is different, but particular models are more or less consistent in technical parameters. Thus, for precise identification of tag frequency you need to know not only displayed values but also the type of receiver, mode used and in some cases even consider outside temperature! In opposite, for correct tuning of a new tag the displayed frequency must be shifted according to mode used and type of scanner. This shift can be calculated from following graphs.


Technical details about available scanners can be found e.g. here: http://www.cbradio.cz/scanner/scan.php3 and manuals on web pages of producers.

Detailed graphs for all commercial scanners

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