I was at a local hamfest looking for a cheap radio to sit on the workbench to work a few of the local repeaters - especially the ones where you want a little more power than a 5 watt handheld. Locating an Icom 3200A, I purchased it. 25 watts on 2 and 70, and as many as 8 memory channels!
Yes it’s a little on the “vintage” side but not much has exactly changed about FM Phone in 30 years…
The other end of the input power lead was missing, so I swapped the molex connector out for Anderson PowerPole connectors, like everything should be fitted with.
Not having a more suitable antenna handy, I built a lead up to bypass the duplexer in the Arrow satellite antenna (the duplexer’s only rated for 5W), pointed it in the rough direction of VK3REC, and keyed up. Signal reports said I sounded good, but there was a persistent buzzing in the background.
I later traced the buzzing to RF being conducted back into the radio… I thought I’d eliminate power supply issues by test running it from batteries but it seems this caused other problems through a lack of proper grounding. Ferrite beads on the power lead, coax and microphone lead greatly reduced but not elimintated the issue. I’ll have to try running it with the radio properly grounded…
I then decided to test another repeater which required a CTCSS tone for activation.
Consulting the service manual to see what the circuitry differences exactly are reveals this:
And checking the radio reveals that this is indeed not the US model.
All of these components except the S7116A Tone Generator IC are readily available - I could certainly retrofit the functionality by soldering the parts in. Searching eBay reveals a few suppliers who think they can get the tone generator chip… best case, it’s NOS but it could be a chip pull, dead or even a re-mark, and I’m not entirely willing to pay upwards of $15 to find out.
However, all we really need to do here is generate a tone - and 99% of the time, that tone is 91.5Hz, as noted here. I’m seriously considering stuffing an Arduino Nano in there - and I could even hook it up to the data lines to allow the CTCSS tone to be set from the front panel…