[amsat-bb] Re: CW from an FM HT

Patrick STODDARD (WD9EWK/VA7EWK) amsat-bb at wd9ewk.net
Sat Oct 28 08:14:35 PDT 2006

> > Key the PTT line of your UHF FM transmitter for a CW uplink. Turn the
> > mic gain  down or remove the mike all together.
> > It will chirp a bit, but it can be copied.
> If your HT does odd splits and has wide coverage, you might be able to reduce
> or eliminate this.  Generally, the VFO has to switch from receive to transmit
> by the amount of the IF.  That's probably where the chirp comes from.  I have
> not done this experiment with a service monitor to see exactly what happens,
> but you might try an odd split such that the RX frequency has been shifted by
> the IF frequency (you might have to try both +/- to see which works for your
> rig).  Then when you key the rig, the VFO doesn't have shift very far (if at
> all) and that might make the chirp go away. If you try the experiment, please
> let me know.

I was doing some testing here at home with this.  I used an IC-W32A and IC-T7H
with a straight key plugged into the mic jack on each radio.  Nothing fancy from
the key, just an adapter to fit the 3/32" (2.5mm) jack, and I could key the
transmitter.  When I did this, listening on another radio, I could
hear only the
carrier.  No audio was coming from the HTs' built-in mics.

I might try this on FO-29 this evening, and maybe VO-52.  One additional
drawback with an HT for a CW transmitter is the fact that most HTs
(including these two I tried this morning) have 5 kHz as the smallest tuning
step.  I also have an FT-817ND, but I only have one of those radios.
Otherwise, I would be trying all of this with a pair of FT-817s and making
some CW and SSB contacts.



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