Galaxy 800 Base Amplifier

[digitalwacker73]

Hoping someone knows something about these amps. I recently picked one up, but can find no information beyond a schematic on cb tricks. Anyone know what the recommended input wattage is for this amp on both AM and SSB? Is it a high drive amp? Any information would be greatly appreciated!

 

[nomadradio]

This amplifier was built with several different tube types. They are not interchangeable between versions of the amplifier.

They would first buy a skid of the cheapest tube they could get in quantity. The amplifier's design would be modified to match that tube, and the whole production run would be built with that type tube.

The model number alone doesn't tell is whether it uses 20LF6, 8950, 8975 6p45c, or 6KD6 tubes.

But all of them share some common properties. This is a low-drive ONLY amplifier. The single-tube driver stage works a lot better with a small 40-channel type radio's power level. Most any 10-meter radio is likely to overdrive it.

The input of an amplifier should fool the radio into thinking that it's connected to an antenna with a low SWR. This is called "input impedance match". If the amplifier's input circuit is close to 50 ohms, the SWR the radio feeds into while the amplifier is keyed will be low.

And if you got one of these in which that design corner was cut too short, the radio could be keying into a 3-to-1 or 5-to-1 or higher SWR. Some radios don't tolerate that very well.

In short, it's a hot rod. Built to go fast, with no emphasis on safety. Only the parts that make a wattmeter go higher get included. Parts that would limit the damage when something goes wrong are all left out of it, pretty much.

73

 

[digitalwacker73]

This amplifier was built with several different tube types. They are not interchangeable between versions of the amplifier.

They would first buy a skid of the cheapest tube they could get in quantity. The amplifier's design would be modified to match that tube, and the whole production run would be built with that type tube.

The model number alone doesn't tell is whether it uses 20LF6, 8950, 8975 6p45c, or 6KD6 tubes.

But all of them share some common properties. This is a low-drive ONLY amplifier. The single-tube driver stage works a lot better with a small 40-channel type radio's power level. Most any 10-meter radio is likely to overdrive it.

The input of an amplifier should fool the radio into thinking that it's connected to an antenna with a low SWR. This is called "input impedance match". If the amplifier's input circuit is close to 50 ohms, the SWR the radio feeds into while the amplifier is keyed will be low.

And if you got one of these in which that design corner was cut too short, the radio could be keying into a 3-to-1 or 5-to-1 or higher SWR. Some radios don't tolerate that very well.

In short, it's a hot rod. Built to go fast, with no emphasis on safety. Only the parts that make a wattmeter go higher get included. Parts that would limit the damage when something goes wrong are all left out of it, pretty much.

73

This amplifier was built with several different tube types. They are not interchangeable between versions of the amplifier.

They would first buy a skid of the cheapest tube they could get in quantity. The amplifier's design would be modified to match that tube, and the whole production run would be built with that type tube.

The model number alone doesn't tell is whether it uses 20LF6, 8950, 8975 6p45c, or 6KD6 tubes.

But all of them share some common properties. This is a low-drive ONLY amplifier. The single-tube driver stage works a lot better with a small 40-channel type radio's power level. Most any 10-meter radio is likely to overdrive it.

The input of an amplifier should fool the radio into thinking that it's connected to an antenna with a low SWR. This is called "input impedance match". If the amplifier's input circuit is close to 50 ohms, the SWR the radio feeds into while the amplifier is keyed will be low.

And if you got one of these in which that design corner was cut too short, the radio could be keying into a 3-to-1 or 5-to-1 or higher SWR. Some radios don't tolerate that very well.

In short, it's a hot rod. Built to go fast, with no emphasis on safety. Only the parts that make a wattmeter go higher get included. Parts that would limit the damage when something goes wrong are all left out of it, pretty much.

73

Nomadradio, Thanks for responding. My amps tubes have been replaced with 5, 31js6 tubes at some point. Not sure if that's a good idea or not? I tested my amp using 5 watts on AM and I'm dead keying 110 watts on Low Power and swinging to 400 watts. High Power keys at 200 and is max at 400 watts on my Swan WM-2000A. SSB is puzzling, I'm actually maxing out around 375 regardless of low or high power. Thanks for mentioning the possible high SWR issue, It does seem to be a problem with my amp. Only other thing to mention is the preamp is not working. I didn't pay much, so not much to complain about. If anyone else has anything to share, I'm all ears?

73s