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Message |
    
Sandbagger106
Intermediate Member
Username: Sandbagger106
Post Number: 102
Registered: 11-2002
| | Posted on Saturday, April 21, 2007 - 10:36 am: | 
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Greetings, I picked up an amplifier at a swap meet, made by Triad, model #LA-101A. It says it is operates on 3 to 30 MHz. I would like to use it on 7 MHz if it works out. It uses a pair of TRW PT-9784 transistors, it is a solid state amp of course. I can't find any info on it and I have zero knowledge of amps, I've never used one, but I have a QRP rig that I would like to pair it with. I did not pay much for it, but it powers up and has AM and SSB modes as well as a pre amp. Any info is appreciated from any one who knows of this amp and if it is suitable for HF use or not. cheers sb106 |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2502
Registered: 9-2004
| | Posted on Sunday, April 22, 2007 - 2:31 am: |
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those are motorola transistors and are good ones.
they are rated at 75 watts PEP each at 28mhz.
at 7mhz, your output may be a bit different.
you should have no problem using it on 7mhz, and you should give it about 10-15 watts PEP input.
you could probably still drive it with 5 or less if thats what your QRP rig puts out.
you should be good to go.
matt
anyone wanting a "clean signal", just look to the left and build one of these!!!
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2600
Advanced Member
Username: 2600
Post Number: 589
Registered: 7-2002
| | Posted on Sunday, April 22, 2007 - 3:59 am: |
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That's a really old specimen, there. Pretty sure you'll need a (custom) 7 MHz low-pass filter for that use, but if nobody on 20, 15 or 10 meters complains, maybe not.
Those transistors have very high power gain, and will overdrive at about 12 to 14 Watts PEP from the radio. Don't remember if it has a "High/Low" switch to raise the drive power it will tolerate.
Don't think it included fixed bias for SSB use. Sure, it has a delay capacitor for the keying relay and a switch marked "SSB" connected to the capacitor. But if it has no fixed bias, it will sound terrible on SSB, and put out a rich soup of harmonic frequencies.
Thirty years ago, there were a lot of AM-only amplifiers sold that had a switch marked "SSB" on the front.
73 |
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