On 2/22/07, fxbuilder <[EMAIL PROTECTED]> wrote: > I didn't have a load on the 3rd port when I tuned it. I only have 1 > dummy load. I can add an antenna to the 3rd port though I know that > would less than ideal but better than nothing I suppose. I have found > some schematics for the pads and will be working on that this weekend. > On a side note anyone know what the sensitivity should be on my uhf > Mitrek when it is tuned correctly? A low level but noisy signal seems > to break squelch at .5mv (assuming I'm reading my old tube Navy > generator correctly) and full quiet seems to be around 5mv. Is this > close to what it should be? It just doesn't seem to have "great ears". > Could be the nearby hills are just heavily blocking the antenna. > Finding a good location that doesn't cost my first born is tough in > this area. > Craig
I'm not a "Motorola guy", so I have no idea what the factory spec of the Mitrek receiver sensitivity is... but... For repeater service using older radios, it's pretty common to need a pre-amp to get maximum receiver performance. But your original posts were that you were tuning a small flat-pack style duplexer for this project -- it may simply not have enough rejection. Are you doing the sensitivity tests with the transmitter on or off? You could be fighting good old fashioned desense. A couple of the articles here in the RB site might be useful: http://www.repeater-builder.com/antenna/deaf.html (The link to Remec/Wacom in that article goes to someone else now... since Wacom was acquired... and the link goes to a redirect that leads to a company in Lynchburg who does other types of filters, looks like...) http://www.repeater-builder.com/rbtip/preamps.html ( I disagree with a statement in this article... "If you have the ability you can probably construct a preamp that will more closely suit your needs than can be found commercially." -- Chip Angle at AngleLinear gets rave reviews from many repeater owner/operators, and a lot of us use Advanced Receiver Research's pre-amps without undue headaches... which are both commercial products. They both suit a lot of people's needs! GRIN... ) I'm also not quite sure about this statement talking about using the pre-amp after the duplexer and before the receiver... : "Again, since we are not making up for a great deal of loss, we do not need a great deal of gain. This example works great in UHF systems but likely shouldn't be tried on 2 meters." Off the top of my head, I can think of more than five VHF systems here locally that do this with fine results...? Different clubs, different techs. Some have bandpass filtering, some don't... Kevin might explain what he was thinking there...? But anyway... check for desense before anything ... if you have that going on, making the receiver hear better will only make it worse. (GRIN) Nate WY0X
