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One of my close friends acquired this amplifier recently, and does not run a mobile station. I have given it a complete bench test. It runs balanced and has an original set of Toshiba 2SC2879 transistors. Not red dots or cheap Chinese counterfeits. Because it is very clean and the cost of...

Amplifiers with over current protection or sensitive FET transistors, may not like a stock D201. You know, the engineers left the DC shunt choke, out of the PA design for the final tube??? Every time you key, the DC blocking cap charges to almost 400 VDC, through a path that includes whatever is...

If you followed the thread on the new VDMOS amplifiers, I'll make this short. The entire project is available for any reasonable offer. Just send a message if you're interested.

I've been working on a homebrew remote control car for my friends grandson and have run into a unique problem. It's a 52 volt ,13 cell battery, powering a 750 watt brushless motor. The issue relates to the RC throttle control that currently operates a servo to turn the hall effect throttle...

Got some Cetron 572B's for my old Yaesu FL-2100 only to find the fans inside the amp are due for replacement. One runs at half speed no matter what I do and it's not mechanically bound up but runs hot. It was also under the tube that went flat in the last pair. So, I figured I'd just replace...

Since restoring my old hand wired D201, I've been using it on SSB for the first time since channel 16 was the place for SSB. As soon as you have to get off the crystal synthesizer board for a frequency above 23, the drift is bad enough to be an inconvenience. It takes like a half hour for the...

Contrary to popular belief, when Mitsubishi discontinued common radio RF output transistors like the 2SC2166, 2SC1969 and 2SC2312, they did not leave any void in the replacement market. Radio manufacturers were in no way limited to the inferior power supply switching transistors they all use...

After dealing with everything from the "waterproof" muffled TX audio, to the "square wave" PL encoder that no receiver can filter out, my VX-7R revealed yet another Yaesu factory design flaw, relating to the misuse of ceramic filters in their IF stages. It went deaf on all bands until you bypass...

Let face it, the selection of quality amplified microphones has become somewhat limited over the years. Many sound like junk and when you find one that doesn't, the switch fails and becomes "scratchy" in no time. Wouldn't it be nice to take a decent stock mic with an electret condenser type...

While the simple protection circuit described here will not prevent transistor failure in all cases, for AM use with carrier, it will save you 99% of the time. Ready? Install one 20 amp fast acting fuse inline feeding the DC into the center tap of each output transformer. With an 8 transistor...

Now that I've purchased all the ones I could find under $10.00, I'll share a little known 12 pin sweep tube substitute with the forum, after some info. The tube I'll mention is best suited for amps that run under 800 volts on the plate. Many with a high low switch are using a lower plate voltage...

When the original source for the Toshiba 2SC2879 dried up, I noticed several of the newest HF mobile rigs started using the Mitsubishi 2SC3240. Just today I looked up the datasheet for this part and it was very impressive! I was hoping it would be close to the 2SC2879 and had no idea it could be...

Anyone notice today's export radios with FM are more susceptible to adjacent channel interference on AM than an older radio like a Cobra 148GTL? If you don't care about FM or wire in some sort of switching, there is a way to improve that. Most radios with FM, only have one 455Khz. ceramic filter...

Can anyone provide some information on the U1 diodes used across the gates of many newer MOSFET amplifiers? I was told they are a pair of back to back diodes to protect the gate. I would think they would need to be zener diodes due to the voltages present on the gate. Any info would be appreciated.

If you live within a mile or so of any train tracks and you haven't noticed the band filling up with carriers, it's only because Positive Train Control has not be installed in your area yet. The device in question transmits a 27 MHz. signal from an antenna under every train. This signal is only...

If you own an early non "D" version of this radio and tried to use it on 6 meters, you may have found it to be useless there. These things oscillate so badly in this band they can form a full power carrier in the SSB mode! For years people have been chasing this problem around thinking it was...

Has anyone else noticed that that NB switch on this radio acts exactly like an Automatic Noise Limiter? As soon as you turn it on, it changes the sound of everything in the receiver. You hear a drop in high frequency response and a slight bit of distortion associated with the clipping action of...

It would appear that some Kenwood TS-940S radios transmit spurs at 910 KHz. above and below the fundamental frequency. If anyone has a 940 and another HF receiver, I'd like you to run a quick test. Transmit an AM carrier on any HF band and check the second receiver for a spur at +/- 910 KHz...

Yesterday I was called by a tech at one of the local marinas about a troubling new problem. All of the new boats are being equipped with the latest high efficiency LED lighting. Everything from overhead lighting to under the water line lighting is using them. Turn any of them on and all VHF...

Many of us have noticed the attractive price on the surplus Russian radar tubes and have wondered about using them as linear amps. The cost per watt of dissipation makes this attractive but you should remember you are getting what you paid for. They have been sitting on the shelf for decades and...