6 meter question

[n9ysq]

I am wanting to assemble a repeater for a single frequency on 6 meter AM. AM equipment is what I have and want to use. Is this feasible? I know nothing of repeater systems. What will I need in addition to the following: I have 2 radios, antennas, mast, rg8 coax, power supply. Is there much more? I know I need a basic controller, are there some homebrew ones? As you may have guessed I've never built one before. I don't know what I am doing and will have help later on. My help has never built one either but knows electronics in general. But not related so much to Ham equipment.  Ideas? 

[K5WLF]

http://www.arrowantennas.com/main/uconrtoller.html has a microcontroller that might do the job for you. It's not the most feature-loaded, but it works. If you want a more capable controller, try the CAT controllers at http://www.catauto.com/. We're using the CAT controllers on our K5IIY repeater here in Stephenville TX and having great results.

[WB6NVH]

What kind of radios?  What do you mean by "single frequency?"

AM is somewhat difficult to reliably operate a carrier operated relay from, among other things, but it is possible.

On FM, I have found that split sites are really the only practical way to go unless I wanted to spend the price of a good late model used car on a duplexer for 50 MHz.  Sites linked by UHF 420 MHz.

There were some AM repeaters back in the 1960's but they faded into history because FM was vastly superior for that application.  The U.K. never seems to have gotten that message as many of their police systems were AM until quite recently when the national change to UHF TETRA was made.

I think your main problem is going to be that ham grade AM gear is too junky and cheaply designed to ever make it as a repeater.  The Motorola and GE stuff from FM service in the same era was orders of magnitude more stable, selective and reliable than ham gear and usually continuous duty.  

It's technically possible to take some low band Motorola or GE strips and make them AM, which might be the best way to go.  But be prepared for a lot of hassle getting it to run right.

[kb3ouk]

if you seperate the dc input to the finals from everything else, you might be able to modulate the power to the PA to make AM.

[Opcom]

This is/was used by the military. What is the R/T separation on 6M?

I used them with a 2-tranceiver system while in the Texas Guard. Never 'tested' the 2MHz minimum separation spec, as I operated two half duplex circuits about 4-7MHz apart using the diplexer as a means to share an antenna.

CU-2194/URC, VHF Diplexer
"This is a Diplexer, passive two-port notch filter and combiner network which allows simultaneous use of two transmitters, receivers, or transceiver on a common antenna provided that operating frequencies are slightly offset. Usable over range of 30-76 MHz FM and intended for use with PRC-25-77 and VRC-12 transceivers. NSN 5895-01-025-9507, has NULL METER and separate TUNE controls and Fine-Coarse-Monitor MODE SWITCH, and RT1-RT2 BNC connections. Unit may also be used as man-portable relay terminal. Maximum RF power capability to each channel: 65 watts continous. Operational isolation: 45 DB min @ 2 MHz separation. Insertion loss: 2 DB max; VSWR 2.0:1 max."

They sell for about $20-50 online depending on condition. The full manual is somewhere around here, a nice design with some protection built in.

[n9ysq]

I am now having more trouble in having to use what I have on hand.  It w?ill be a struggle as is to pull this off. I am needing to find out what some unmarked crystals I have are made for. But I don't have a frequency counter. I will have to find some one local who does. The radios seem to have a fixed 455khz offset. The reciever is crystal controlled. Since they are mixed I can change offsets by switching out crystals. I may only end up with 5 frequencies to choose from.

[W2PFY]

When I was in the army stationed at Ft Ord, CA there was a AM repeater located  Salinas on Two meters. I worked for a long time grinding a crystal for the input. It operated AM and worked great. It worked on a separate input & output just like today's FM repeaters. There was also a system that recorded your transmission and played it back on the same frequency. That must have been really slow?  Anyhow, my point is, don't give up. Nice to see something retro going on. I hope you can find others to be on there with you. And finally, wish you were doing it around here