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I recently purchased a 4 channel crystal controlled RCA Mark VII tube base station. It has a 4 channel crystal controlled transmitter. The receiver can be tuned by either a 23ch VFO or four receive crystals. The radio has been recapped, works and sounds great, but the 4 channel limitation of...

Upon closer inspection, It turns out that the VFO works with the cobra 135 half way through the HF band, with output power decreasing from about three watts to zero from 27.305mhz on up. Looks like I'm going to have to align the cobra to be more broad banded, in order to operate correctly on...

I was able to get ahold of a Siltronix Model 90. It's hooked up now, the CB band works fine, but the HF band doesnt seem to work. Was it disabled somehow at the factory?

I've been working on restoring a Johnson Messenger 223 I purchased on ebay. The synthesizer board contains two diodes in the receiver section, d102 and d103, that are completely open. They're 1n881 diodes, an obsolete component that I cant find a modern equivalent for. I found a datasheet that...

Thanks so much for the Info! I really appreciate it! Would it be possible for you to take a look inside to see how the Crystal and switch was installed? I'd love to get this radio working on the upper 20! If not, than I've been keeping my eye on a few VFO's on ebay. Hopefully I win one.

How hard would it be to use an external VFO with the old cobra 135 or another 23 channel crystal synthesized CB?

I've got a mid 70's Cobra 135 base that I'd like to use for SSB Dx. It's a 23 channel radio, and has really good sounding audio and a great receiver section. I'd like to use it on sideband, but most LSB calling happens up on channel 38. This presents a bit of a problem on a 23 channel radio. I...

Well, I got the bias in line. I added a 7.2k resistor between the gate and a 12v source. The radio is now Dead keying at 10w and swinging to 35. I tried it out on a drive down to school yesterday and got a contact around 15 miles from me. Thanks for all the help. I just modded another, older 25...

Where would I find a good 12v source on the board to jump the 100k potentiometer to?

Everything is installed as it should be. I removed the final, R38, R40, C45, and the slug from L10. I installed the MOSFET, the 1230 companion part (polarity observed), and the 68pf cap across C42. Still, I'm only deadkeying about 1 watt and swinging to 3.5.

Sorry to keep bugging you guys, but I just checked the Bias voltage on the gate of the ERF2030, and I'm only getting about 1.3v at transmit. Is there a way to adjust the bias voltage so that it is closer to the recommended 2.7v?

I already adjusted the AM Power and Modulation pots. Four watts is the most I've been able to get out of this radio with the ERF2030 installed. Is there anything else I could be missing?

Hello Everyone! I just finished installing the ERF2030 MOSFET upgrade in a Cobra 25. It works, but the problem is, I'm only seeming to get a 1 watt dead key, and about 4 watts swing into a dummy load with the mic gain maxed. I followed the instructions on cbtricks.com to the letter. Shouldn't...