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307 Amps?
- Thread starter 338_MtRushmore
- Start date
That is what Peakaboo built, a very nice regulated AB amplifier. I loved the one I had, should never have sold it.
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Didn't the SKYWAVE amps have that? Telstar DX350 amps? I think a guy in NM built them. They got real expensive I know that, and were amps only, no preamps built in.
Simple thermal tracking can be applied by mounting the clamping diode to the top of one of the RF output transistors.
It's so very easy to implement a simple unregulated thermal tracking bias I don't know why anyone would build without it.
Of course if you are biasing up around the .7 volt range on your transistors (which is necessary for clean operation on SSB, that .35 volt on the base just don't cut it) you can't run unregulated 20 volt supply's!! I suppose that B bias stuff is for the guys that run higher voltage supplies. Of course I don't think any regulated bias designs would be very happy being "volted" either.
I don't mind the unregulated bias as long as it has the simple diode heat tracking trick, and applies .7 volts to the base of the transistors. The biggest problem with it is supply voltage has to fall no less than about 12 volts and no more than about 15 and the clamping diode has to be picked carefully so it doesn't supply to much voltage to your RF transistor base and blow them up. It needs to maintain no less than about .6 volts at 12 volts supplied to amp and no more than about .8 volts with around 15 volts supplied to amp.
This also will increase the gain factor of the transistors so less drive is required for the amp.
By the way I'm speaking from a Toshiba 2879 point of view. Numbers will vary with different RF output devices.
Bias those amps!
Panic Attack got down!
I got a pic from the builder. I know the bias has a diode with 2 caps under those resistors someplace, but it's pretty hard to see in the pic.
Good, bad, or just another copy?
Good, bad, or just another copy?
With 100 in, it swings past the 1000 scale to 12 or 14 hundred? Just a guess obviously. It's an ameritron awm-35... the 1k watt version
So what would you realistically charge? No I'm not looking for a "I don't want to" price.
I just can't imagine it would take a skilled tech such as yourself more than 2 days to complete, would it?
Yes, don’t buy from him. He builds “great” boxes for his buddies and everyone else gets cheaply made ones. A buddy of mine is out over $2,000 because Jim put a cheaply made power supply in his box and it blew within using it a few times. He does this to have people keep going back to him to “fix” the issue. I highly do NOT recommend him. He builds cheap to keep you coming back for repairs.