Repurpose power amplifier out of trunk mount radio.
I have a couple of GE Delta 110w trunk mount radios that are in working condition. I was wondering how hard it would be to extract the PA board from the radio and use it as an FM amplifier. Although I am unable to find any hard information on the exciter drive current, I am guessing that it is somewhere between 25 and 350ma And there is a separate keying voltage that is applied to turn the transmitter. It is somewhere in the range of 8 or 10 volts but I don't remember which.
I can get it wired up to try, but I don't have anything with a low enough output to drive it. Is there any way that I could attenuate the input drive enough to be able to drive this from an HT or a 10w mobile radio without an attenuator inline? Or a decent schematic for a fixed attenuator to tie onto the input would be good also.
The manuals are likely available here: http://www.repeater-builder.com/ge/lbi-master-list.html
I know that this can be done with a Mastr2 radio fairly easily, but I've not had much experience with tearing into the Delta radios.
What all is involved on the Mastr2 amps? I am sure that the process is quite similiar.
Not a whole lot. the M2 series radios where fairly modular, so it was a matter of just chopping off the receiver, exciter, and control boards off of them. This left you with three boards, the driver, the PA, and the T/R switching board. In the case of a repeater setup you don't need to switch the relay, so there's no PTT signal even needed. You could just power the amplifier with continuous +13.8V and feed it RF drive as needed.
I believe the drive was around 250mw, it's been years since I've worked on one of these. I believe the driver boosted it to around 25W, so you could bypass that and feed RF right into the final PA board if your drive was 10-20W.