Albert, I don't have the manual for that unit, but I can state with some confidence that you can terminate the output with a wattmeter and feed the input with one or two watts from a handheld at the desired frequency, and tune for maximum output. If the power output does not pass through a peak as you tune the capacitors, you may need to tweak some coils or add some capacitors to get the amp to work efficiently at 2m.
73, Eric Lemmon WB6FLY -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Albert Sent: Thursday, March 12, 2009 2:50 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Help with N1274A VHF amplifier please Thanks for the info Eric. I first learned of these amps from the Repeater-Builder genesis page. I am going to use it with my Genesis convertacom. I never knew they were used as far back as the MX300 and MT500 radios. That is interesting. Again, thanks for the info. I appreciate the model number of the manaul. Maybe I can find one of those. (you don't happen to have one do you???) Another gentleman has offered me a schematic, so I am at least heading in the right direction. You wouldn't happen to know the procedure for tuning the amp would you? I do have a watt/swr meter but nothing fancier than that. Albert --- In Repeater-Builder@yahoogroups.com <mailto:Repeater-Builder%40yahoogroups.com> , "Eric Lemmon" <wb6...@...> wrote: > > Albert, > > Yes, you must tune the amplifier for the narrow range of frequencies that > you will be using. The N1274A amplifier was used with MT500 and MX300 > Converta-Com Consoles to boost the output of the Handie-Talkie in mobile > service. The unit has a sensor to detect the transmit signal and switch the > amplifier into the circuit, The manual which covers this specific amplifier > is 6881020C90- which, unfortunately, is NLA from Motorola Parts. > > 73, Eric Lemmon WB6FLY > > > -----Original Message----- > From: Repeater-Builder@yahoogroups.com <mailto:Repeater-Builder%40yahoogroups.com> > [mailto:Repeater-Builder@yahoogroups.com <mailto:Repeater-Builder%40yahoogroups.com> ] On Behalf Of Albert > Sent: Tuesday, March 10, 2009 11:04 PM > To: Repeater-Builder@yahoogroups.com <mailto:Repeater-Builder%40yahoogroups.com> > Subject: [Repeater-Builder] Help with N1274A VHF amplifier please > > I have very cheaply acquired a Motorola N1274A amplifier and would like to > use it on 2 meters. > > My first question, is, since this amplifier was originally designed for > 150-174MHz do I need to do any retuning. I assume the answer would be yes. > On the board, on the far left and the far right I see two components that > appear to be tuning capacitors. They are marked Johanson 9612. (Looking them > up on the net confirmed they were tuning caps) Are these what I need to > adjust? If so, what is the procedure? Tune for max power? Min SWR? Any > assistance would be appreciated. Also, what tool is used for this? I kind of > looks like a tiny hex head, but I haven't looked at it under a magnifier > yet. > > Secondly, I was wondering if anyone has a schematic for the amplifier. I > looked on the net but turned up nothing. There is one component inside the > amplifier that appears what "used to be" a capacitor. It obviously suffered > a catastrophic failure and the magic smoke came out quite rapidly. It is > located on the board next to a large 1 ohm power resistor. I obviously need > to replace this component and could possibly need to replace others. Again, > any schematic or parts list info anyone could share with me would be greatly > appreciated. > > Thanks > Albert >
