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eHam Forums => VHF / UHF => Topic started by: LB5KE on November 04, 2013, 04:50:24 PM



Title: So few UHF linear amplifiers.
Post by: LB5KE on November 04, 2013, 04:50:24 PM
I have a 857D with 20 watts and i have been looking for a good hi power PA. I Can't find any good ones at 70cm, only a few expensive at 100 watts max. On 2 meter however there are plenty, i am a bit tempted to go back and run 2m only.


Title: RE: So few UHF linear amplifiers.
Post by: W4KYR on November 04, 2013, 06:08:39 PM
I have seen some inexpensive Motorola N1275A amps on sale on E-Bay from time to time, I believe these put out 35 to 50 watts. I have seen these sell $50 +/-  .

Many years ago in one of the VHF Sweepstakes my ham radio club was using some surplus 220 and 440 mhz amps which I believe they bought from Fair Radio Sales. Unfortunately I can't remember the company name of the amp manufacturer...I want to say it wasn't a regular ham radio manufacturer but I think they put out well over 100 watts.


Title: RE: So few UHF linear amplifiers.
Post by: KA4POL on November 04, 2013, 09:48:27 PM
Is it just for fun or do you see a need for the higher power. Quite obviously there is no market so no PAs are being produced. Many repeaters are close by and the usual output is sufficient. This is a different story with SSB.


Title: RE: So few UHF linear amplifiers.
Post by: LB5KE on November 05, 2013, 12:10:23 AM
My main interest is ssb, i was also hoping to try EME with J65. What i am looking for is a decent amp on 200w or more.


Title: RE: So few UHF linear amplifiers.
Post by: K1CJS on November 05, 2013, 05:57:26 AM
The reason you don't see many is that the higher the frequency and the power output, the greater the danger is from RF energy exposure.  An 800 watt microwave oven will boil a cup of water in a minute, and even though the microwave energy that ovens use is a higher frequency than the 440 mhz band we use, there is still a very real danger of RF burns and tissue destruction with high power exposure that will take a long time to heal--if it heals at all.  


Title: RE: So few UHF linear amplifiers.
Post by: WB2WIK on November 05, 2013, 08:46:35 AM
Jim Klitzing W6PQL has components, kits and fully assembled 70cm solid state amplifiers up to 1 kW output power:

http://w6pql.com/parts_i_can_provide.htm

In terms of "cost per Watt," they're actually a very good deal.


Title: RE: So few UHF linear amplifiers.
Post by: KE6KA on November 06, 2013, 02:11:07 PM
SSB Engineering has several amplifiers available.

Tokyo Hy-Power has a 200 watt amplifier that will be coming out.


Title: RE: So few UHF linear amplifiers.
Post by: K4JJL on November 13, 2013, 07:45:28 AM
You can usually find one from an old GE Mastr II repeater.  Most are 100w (some are 40w).  It's pretty low input (1/2 watt), so you'll have to make an RF sampling setup with a dummy load to give you a -20db sample to run it.  You'll also need some sort of TR switching setup to bypass the amp during receive.

If you really want to get creative, you can do a splitter/combiner setup to give you 200w using 2 amps.


Title: RE: So few UHF linear amplifiers.
Post by: LB5KE on November 13, 2013, 10:27:20 AM
Actually i have just bought a RF Concepts RFC4-110. I Already have a 170W VHF amp from RF Concepts that has been excellent.The only disappointing thing is that the built in preamp has a noise figure between 2-3, but with a ft-857 or a Ts-811 it will help. At some point i might need to get a mast preamp. In the long run i might get another one to run 200w if it's safe for the amplifiers.

I am hoping that this amp a 19 element yagi an Jt-65 can give me a few contacts on EME.


Title: RE: So few UHF linear amplifiers.
Post by: N5XO on November 17, 2013, 06:52:06 AM
I have a 857D with 20 watts and i have been looking for a good hi power PA. I Can't find any good ones at 70cm, only a few expensive at 100 watts max. On 2 meter however there are plenty, i am a bit tempted to go back and run 2m only.

What do you consider Expensive?

I am a big fan of TE amps, they have performed flawlessly for me over the years, I use with 300+ watts on 2, 220 and 440.

Stay away from Mirage/MFJ for my personal history they are crap.