Fellow builders, I searched the archives and came up with nothing -- if I missed it, please go easy on me. I've been using a Hamtronics T304 UHF exciter -- the synthesized one that has a "real" FM modulator, is supposed to be much better than the crystal controlled, etc. I have two complaints, one really annoying:
#1 to get enough CTCSS modulation to reliably work on all of the amateur receivers I've tried, I hear a very high pitched ring/noise in the audio. Most users don't even notice it, but it bugs the heck out of me. Dead silent with no CTCSS. I'm using a CTCSS encoder circuit of my own design based on the MXCOM/CML MX165C. The output of it is sent through a 2nd order lowpass filter.... the tone is REALLY clean (oh yeah, the onboard CTCSS encoder of an SCOM 7330 does it too). So, does anyone have experience with the same and ideas for a fix? I've seen Kevin Custer's mod for the crystal exciters, but this is not the same animal. #2 SLOOOOWWWW synthesizer lock-up time. I run the thing at my house, so leaving the synth run means it keeps the noise squelches open all the time. I tried letting the MCU and Synth chip stay up and powered and just un-power/power the transistor in the loop chain, but still, that synth takes forever to lock up. Soooo... Anyone smarter than me have any ideas on (non-relay) ways to break the coupling of the synth's weak signal through the rest of the amplifier chain and out the TX output? I say this because if I don't have anything connected to the TX port on my very well shielded enclosure, I cannot hear it, but just about anything connected to it (even a dummy load with RG400) causes me to have low level signal -- enough to break squelches within about 200 feet. 73 DE N0MJS
