Jan 212012

I’m very happy to report that thanks to a NOS pair of Eimac 4-125A modulator tubes from Antique Electronic Supply, my T-368C is back on the air for the first time since I got it! I’ll still have plenty of tinkering to enjoy on it, and plenty of work integrating it into a full system with my R-390A receiver. I’m also happy that my antenna BALUN didn’t burst into flame upon encountering the hefty output of this small monster of a transmitter.

I plan to experiment with outboard audio processing to see if I can improve the unit’s classic military audio sound, which is intelligible but not very clean-sounding. I am interested in experimenting with that stuff, but I would prefer to avoid modifying the transmitter’s innards as some other T-368 fans have done. So, my goal will be to see how much I can improve the stock audio using only outboard equipment. I’ll post any favorable results.

  6 Responses to “T-368C On the Air!”

  1. Avatar

    I would like to know how this outboard audio is working for you and if you don’t mind sharing it with me … I have several ideas of what I might want to try myself but I’m no tech and about afraid to blow something out of the water so to speak if I do something wrong .. I watch the internet for any thing that I can try myself without dragging my buddies into it . I have an ART 13 that I made part of the power supply and my buddy finished the rest it got a little hairy for me so I give it to him to finish .. but I’ve not put it on the air yet either .. dang .. I have 4 SP-600’s that 3 of them need to be recapped and I did one myself and painted the face and relettered it by myself and it looks awesome but I’m in no hurry to do any of the other 3 I have .. LOL .. more work then it looks like.. so lets here some updates ..

    73 Don WC4D

    • It’s working pretty well, and I get better signal reports using it than when I use a Motorola TMN6054A mic plugged in to the front panel.

      My outboard audio hardware is a Symetrix 528E Voice Processor, connected to the 600 ohm input on the back of the radio through a 1:1 audio transformer. I have the transformer located right next to the rear panel connector on the radio, and I run balanced audio through an XLR cable form the Symetrix to the transformer. I’ve been using a Heil headset with a dynamic boom mic.

      This combination doesn’t deliver “broadcast quality” audio, because the unmodified T-368C has a sharp audio filter intended for communications service. But it does give me a nice, clear signal. I think it helps wring out the best that my unmodified T-368C can deliver. I use the de-ess circuit, the compressor and the noise gate, and I give it a bit of midrange boost with the parametric EQ.

  2. Avatar

    easy mod is to remove the speech amp, find the filters and take thewire on the input of the filter and solder it to the filter output terminal, increases audio bandwidth and is reversable. to do this also unground said filters, remove the clipper tube and jumper a wire in the socket betwen 1 and 5 and put the shield back on sans tube. now you are ready.

  3. Hi i have a t368f and the swr unit when I load the tx i can get 400what’s but I notice that when I speak it goes down in power out i thought it should peak up in stead of going down any ideas? John

  4. To me it sounds like your loading it to much and you need to cut back on how much your trying to get out of the radio. I load mine up to about 350 to 375 watts and when I load it up to much I get so swing or backward swing which neither is good .. I’m sure there are lots more guys who can help you more then me .. but this is what I do any way .. 73

    Don WC4D

    • Hi Don tnx for your reply I have looked further at the modulator and have found that the speech amp has been got at I’ve looked up the internet to see if I could find the mods but don’t see any that looks like the mods done to mine.the only good thing is it’s tubes and tx,s are all still present so will try to ‘re build it .maybe there’s a spair sitting out there .I see that the clipper pot has been disc but is still present I’ll remove the amp and get a couple of photos to see if any one knows the mods i have guess they is a imbalance that’s why my mod is downward thanks john

Leave a Reply to Mark J. Blair, NF6X Cancel reply

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>