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.
73!
Patrick WD9EWK/VA7EWK http://www.wd9ewk.net/