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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment. |
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16th Jan 2009, 5:07 pm | #1 |
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Microwave Modules RF Power Amplifier problem.
Hello i have just been given an old microwave modules 144/100 amp, (144 MHz) The problem is that it has a high input swr,the transistor in this is a sd1477, Could it be that it has been over driven and the matching input has been damaged?
Also the output is down to 40 watts! Thanks Garry |
16th Jan 2009, 7:34 pm | #2 |
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Re: Microwave Modules RF Power Amplifier problem.
Erm, 144 Mhz is a VHF frequency, not microwave...
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Al |
16th Jan 2009, 7:40 pm | #3 |
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Re: Microwave Modules RF Power Amplifier problem.
"Microwave Modules" is the name of a UK company who made two metre and 70 centimetre convertors and other stuff for use at VHF and UHF. It may be a misnomer, but that's what the company was called.
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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
16th Jan 2009, 7:45 pm | #4 |
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Re: Microwave Modules RF Power Amplifier problem.
Thanks Graham, how interesting. It wasn't clear from the OP that this was the name of a company (at least, it wasn't clear to me. )
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Al |
16th Jan 2009, 8:16 pm | #5 |
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Re: Microwave Modules RF Power Amplifier problem.
Hi Garry,
I have one of these or very similar, somewhere I have the circuit that came with it when new. If It's of any help, and I can find it, I'd be more than happy to send you a copy. Cheers
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Chris C G8TJR |
17th Jan 2009, 12:08 pm | #6 |
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Re: Microwave Modules RF Power Amplifier problem.
Thanks chris for your help, i was able to find a copy on the net. After donig so tests on it i have found that the main rf transistor is damaged! Thats a shame, must of been over driven.... or some one has turned up the bias to much.
Thanks again Garry |
17th Jan 2009, 3:03 pm | #7 |
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Re: Microwave Modules RF Power Amplifier problem.
I seem to remember that RF power transistors can have several junctions in parallel. Presumably they do not always fail simultaneously. We're more used to semiconductors either working or not aren't we.
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22nd Jan 2009, 2:47 am | #8 |
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Re: Microwave Modules RF Power Amplifier problem.
I remember the original Microwave Modules gear well, and very good they were too! Got many of us G8's up onto 70 and 23, and the ATV module has surely stood the test of time!
I too would guess that it's been badly overdriven. The original was intended for a max of 1 watt of input. I.E. 500mW in equals 50 Watt max out. I seem to remember later versions (but not under the original MM company) that were intended for the popular 2M transceivers of the 1980's. Certainly there was one version for the FT290 which took 2 Watts in for 80 out - and I dread to think what would happen if you drove this model with the 25W TX's also available at that time! Maybe worth checking exactly what it's specs really are, and then decide whether it's worth spending the money on it to revive it and integrate it into your system. |