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[aprssig] FRS radios and PTT

Bob Bruninga bruninga at usna.edu
Mon Mar 14 15:53:41 UTC 2011


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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