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Author Topic: I need a schematic for a Vocom UVC100-25 amp  (Read 2301 times)
K3CLT
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Posts: 58




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« on: June 23, 2015, 08:19:32 PM »

Have the amp and it is set to 461.00 . I need to schematic or manual to adjust it down to 449.525. Any Help?
Reply here or to cltoby600@yahoo.com
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AD4U
Member

Posts: 2541




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« Reply #1 on: June 24, 2015, 02:20:38 PM »

You won't find a schematic and VOCOM won't help.

I have a VOCOM 10 watts in -100 watts out UHF amp and looked for years for a schematic. There were several resistors burned beyond recognition in the amp, hence the need for a diagram. My guess is the resistors burned due to too high drive. FINALLY I saw a similar VOCOM amp at a hamfest and the seller let me look inside. I replaced the burned resistors in my amp with the same value resistors in the hamfest amp and it started working and worked for over 12 years until I sold it.

If your amp is working and all you want to do is retune the amp, my suggestion is to apply 10 watts drive at 461 MHz which is the design frequency. Note the power OUTPUT into a dummy load. Then apply 10 watts at 449 MHz and compare OUTPUT to what it was at 461.. If the output is the same or nearly so, I would use the amp without any retuning.

If your VOCOM is like mine there are no variable caps. Everything is fixed value which can be a pain to change out and get "right".

As I understand things these amps are fairly broad banded and the one you have just may work OK at 449.

One last suggestion. If you have a spectrum analyzer you may want to make sure the output is "clean" at 449.

Dick AD4U
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