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Author Topic: Linear Amp for Just Below 40m  (Read 443 times)

Offline 0xAether

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Linear Amp for Just Below 40m
« on: November 03, 2018, 1717 UTC »
I've been searching around for a while and haven't been able to turn anything usable up. Hopefully someone here will know.

I'm looking for a linear amp that can is capable of accepting a AM or USB/LSB signal that's just below the 40 meter amateur band.

Does anyone know of one that capable of doing that? I'm not opposed to buying one that isn't capable of that if I had a reliable method of modifying it to be able to do that.

Any idea or advice would be greatly appreciated!

Offline moof

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Re: Linear Amp for Just Below 40m
« Reply #1 on: November 03, 2018, 1751 UTC »
12v like old school cb linear or a plug in the wall kind most likely with tubes or quite expensive?

Offline ThaDood

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Re: Linear Amp for Just Below 40m
« Reply #2 on: November 03, 2018, 1942 UTC »
You can check out the reviews of various RF amps here,   https://www.eham.net/reviews/products/10    I wouldn't go solid state, if you intend to use it where I suspect you might, since most solid state amps are still not forgiving. Tube based amps are, not only more forgiving with long key-ups, but are easier to tune down to where you want to. Just don't over drive one and watch those high voltages.
From DC to light, I take a huge spectrum bite!

Offline 0xAether

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Re: Linear Amp for Just Below 40m
« Reply #3 on: November 03, 2018, 2044 UTC »
12v like old school cb linear or a plug in the wall kind most likely with tubes or quite expensive?
My vision of it would be the plug in the wall type, either 120 volts or 220 volts (120 is preferred because I wouldn't have to go through the bother of installing a new receptacle)

You can check out the reviews of various RF amps here,   https://www.eham.net/reviews/products/10    I wouldn't go solid state, if you intend to use it where I suspect you might, since most solid state amps are still not forgiving. Tube based amps are, not only more forgiving with long key-ups, but are easier to tune down to where you want to. Just don't over drive one and watch those high voltages.
Thanks! I'll give those a look. Do you have a good resource on the theory on how to modify a tube linear amp? I don't mind about having to figure things out, I don't need to be spoon fed!

Offline radiogaga

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Re: Linear Amp for Just Below 40m
« Reply #4 on: November 03, 2018, 2242 UTC »
How much output are you looking for and what amount of drive power do you have?
Most ham amps are only rated for intermittent use at full output.
A tube amp will easily tune just above or below the ham bands without modification, further away a tap on a coil will need to be moved.

Offline 0xAether

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Re: Linear Amp for Just Below 40m
« Reply #5 on: November 03, 2018, 2346 UTC »
How much output are you looking for and what amount of drive power do you have?
Most ham amps are only rated for intermittent use at full output.
A tube amp will easily tune just above or below the ham bands without modification, further away a tap on a coil will need to be moved.
Depending on the situation of course, but I don't see a need for anything more than 500 watts. As for drive power, I can output anything between 1 and 100 watts.

Would it be safe to be say that most tube amps capable of 40 meter amateur use be able to accept a signal at say (for the sake of argument) 6925-6950 kHz without modification?
« Last Edit: November 03, 2018, 2357 UTC by 0xAether »

Offline radiogaga

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Re: Linear Amp for Just Below 40m
« Reply #6 on: November 04, 2018, 0058 UTC »
If I was to suggest one amp that fits your parameters it would be a used Drake L4B, it has a continuous duty rating, easily sourced tubes (2x3-500) and no mods needed for those freqs. mentioned.

Offline 0xAether

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Re: Linear Amp for Just Below 40m
« Reply #7 on: November 04, 2018, 0240 UTC »
If I was to suggest one amp that fits your parameters it would be a used Drake L4B, it has a continuous duty rating, easily sourced tubes (2x3-500) and no mods needed for those freqs. mentioned.
Perfect! Thanks for your help, I appreciate it!

Offline Stretchyman

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Re: Linear Amp for Just Below 40m
« Reply #8 on: November 04, 2018, 1849 UTC »
Oh Dear, still thinking toobs are where it's at?

BLF188XR has been around for a while now but yet no one has even mentioned it?

I've no idea why folk would use a tube amp anyway, nostalgia?

Even the 188 is a tad 'old hat' with more powerful devices running at 60V around now, however the 188 built up on a Cu spreader is available on eBay, just add LPF and drive with 3W.

Why use anything else?

Str.
« Last Edit: November 04, 2018, 1856 UTC by Stretchyman »
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