linear amp question

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kc5uta

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I want to try to build an amplifier. still not sure what band, but I am leaning to HF. But maybe also vhf. What I do have so far is a transformer I picked up at a hamfest. multiple voltages, secondary out 700volts +/- , with another at 130 v or so +/- and what is obviously a filament voltage at 6v +/- .The transformer itself is about 60lbs or so 110v primary. So far to test, I rigged up 10 100 watt bulbs in series to the high side, and it lit them quite nicely. The transformer didn't even warm up after 5 minutes. You could really feel the heat from the lights though! So my big question is........what tube would be "optimal" with 700volts or maybe with a doubler to 1400"ish" or maybe try a DC-DC boost instead? Finding a straight forward answer to what would be best is difficult at best. Thanks ....Dave
 

prcguy

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Unless you find and use an appropriate choke for the power supply you will end up with something in the mid 900 volt range after rectifying and filtering. You can Google transformer specs and find formulas for measuring the size of the transformer core and estimating a power rating, then you can shop for appropriate tubes.

Some large RF tubes use a lot of filament current and you need to know if the low voltage tap will handle that.
prcguy

I want to try to build an amplifier. still not sure what band, but I am leaning to HF. But maybe also vhf. What I do have so far is a transformer I picked up at a hamfest. multiple voltages, secondary out 700volts +/- , with another at 130 v or so +/- and what is obviously a filament voltage at 6v +/- .The transformer itself is about 60lbs or so 110v primary. So far to test, I rigged up 10 100 watt bulbs in series to the high side, and it lit them quite nicely. The transformer didn't even warm up after 5 minutes. You could really feel the heat from the lights though! So my big question is........what tube would be "optimal" with 700volts or maybe with a doubler to 1400"ish" or maybe try a DC-DC boost instead? Finding a straight forward answer to what would be best is difficult at best. Thanks ....Dave
 

N0IU

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Sep 26, 2009
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With all due respect, if it was me wanting to build an amplifier, I would look at various designs and pick out one that best suited my needs... and then would look for the parts to build it.

So where do you find the designs? Of course you can search the Internet, but the ARRL Handbook has several designs.

Yeah, I know they are expensive, but...

See if your local library has a copy. I just got a copy of the 2012 edition a couple of months ago FOR FREE because my library throws away the previous year's copy when they get the current one! No kidding!
 
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