[aprssig] FRS radios and PTT

Wes Johnston, AI4PX wes at ai4px.com
Mon Mar 14 14:10:14 EDT 2011

I really liked using RINO radios for tracking (and slurping up the positions
of local RINOs via one "dummy" unit in the commo trailer), but alas the
radios have too many buttons that are too easy to hit and knock off
frequency.  We ended up buying 40 icom fg-21 radios for use by nonlicensed
people at events.  We call them PHD radios (push here dummy).

This trick of sending the 4.5khz signal which is out of the audio pass band
of the radio sounds like a blue box trick from the 60's!! ha!  old school
rides again!
The world needs more geniuses with humility because there are so few of us

On Mon, Mar 14, 2011 at 11:53, Bob Bruninga <bruninga at usna.edu> wrote:

> Just did a circuit to be able to key a VOX radio either with audio or
> keyline without having DC connectivity.  Just a single transistor twin-T
> oscillator set to 4.5 KHz.  Either VOICE can key the radio, or I can
> manually key it over a long wire without having to turn the VOX on/and/off
> (from front panel buttons).
> The 4.5 KHz cannot be heard, yet it keys the radio and can be mixed with
> any
> other audio as needed.
> Idea is an FRS STOCK radio 200' away on top of my building with a 3
> conductor audio line plugged into the external speaker/audio jack.  Radio
> is
> inside a short PVC pipe for the weather, but now I can key it from
> downstairs..  Where I can monitor the local student activity with a speaker
> (and Mic audio source).
> I just bought 10 packs (20 radios with chargers) for $299 including free
> shipping.  Think about it.  That is the cost of 1 ham radio HT, yet now I
> can supply 20 radio club students with radios and not all of them even need
> a ham license to contribute. It's a small price to pay to get 20 people on
> the air.
> [No, APRS is not legal on them, nor is connecting two of them back-to-back
> to make a repeater...]
> These FRS radios have 22 UHF channels, have VOX and have all 38 PL/CTCSS
> and
> also all 83 DCS codes too.  Plus NiCd batteries and chargers for only $15
> per radio.  Oh, they not only scan the channels but also have TONE and DCS
> scan!  They operate at 1 watt on most channels (.5W on the 7 FRS only
> channels).  Each ham radio response organization should consider investing
> in dozens of these radios to have on hand for ANY local event. It
> multiplies
> our capabilities by letting more bodies participate.
> I have tested them compared to my Kenwood TH-D7 and they have the SAME
> excellent sensitivity on the FRS/GMRS frequencies as the D7 has on the ham
> bands.
> Bob, Wb4APR
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