I don't pretend to hold a candle to the knowledge or expirence of the group- the light bulb over my head is illuminated with a half-dead AAA battery... I don't think the problem is desense in it's traditional form. I have done the desense tests and I have yet to realize any desense on the 50 watt radio even at full power output (If I remember correctly it was @ 57 watts out of the transmitter). Also- I had the duplexers on the bench about 2 months ago and peaked them up, all looked good on the spectrum analyzer. The output of the radio was clean as well. The noise is intermittant and to me sounds like intermod. Another observation: There was a little noise last night- and I noticed that VHF and UHF were sightly enhanced (Hearing some distant machines). There was no noise this morning and I noticed no enhancement, and tonight there was a touch as a few storms passed and there was enhancement again. Intermod mix enhanced/caused by the preamp? I am leaning towards the pad, or another cavity? I have a spare pass cavity (1504). I will try either bypassing the preamp first or a pad and see where I get. If that does not work I'm shutting it all down, selling it all and getting an I-Phone. ;) Tom W9SRV
skipp025 <[EMAIL PROTECTED]> wrote: Please light the "no free lunch" rule lamp for the duration. If it's a converted Mitrek Repeater...running the same in cabinet transmit and receive sections..? I would suspect more in cabinet desense than most other people. The preamp simply brings the beast out of hiding. If you can... crank down the pa to 10 watts output and see if the desense goes away. Also check the Motorola BpBr Duplexer notches with a real spectral display to be sure they are properly placed. I know a lot of you say in cabinet desense is not a problem in Converted Mitrek, Micor and MVP mobiles... but I once measure in-cab desense starting about 13 to 18 watts output depending on the PA model and radio model/type. High Power Mitrek Repeater Operation should be done from different radios... the tx radio having a well made blower (not a cheap fan) moving air over the heatsink. cheers, skipp > TGundo 2003 wrote: > Ok- > > I think I may be expierencing this. I have a converted mitrek repeater with a T-1504 duplexer and an ARR preamp inserted between the radio and the duplexer on the RX side. I have not noticed a loss in sensitivity- but every once in a while were getting a strange, nasty sounding signal coming thru on the unkeys and occasionally you hear it mix in on the weaker signals (BTW- this is a different problem thatn the Railroad interference we had before). It sounds like a strange mix of intermod. I was just wondering if the preamp is the suspect here. I may go bypass it for a few days and see if it goes away. > > I would assume some sort of pad would be in order if this is the case the preamp is the problem. Any recommendations of pads to use? before or after the preamp? > > Thanks!! > > Tom > W9SRV > > Ken Arck wrote: > At 10:05 AM 6/27/2007, you wrote: > > >What symptoms would one notice if a preamp is overloading the front end > >of a reciever? Noises, quirks, wierd phonenomia? > <---Overloading of a (pre)amplifier results in non-linear operation, > which typically manifests itself as susceptibility to intermod and > other interfering signals and perceived loss of sensitivity > > Ken > ------------------------------------------------------------------------------ > President and CTO - Arcom Communications > Makers of repeater controllers and accessories. > http://www.arcomcontrollers.com/ > Authorized Dealers for Kenwood and Telewave and > we offer complete repeater packages! > AH6LE/R - IRLP Node 3000 > http://www.irlp.net > "We don't just make 'em. We use 'em!" > > > > > > > Yahoo! Groups Links > > > > > > > --------------------------------- > Ready for the edge of your seat? Check out tonight's top picks on Yahoo! TV. > Yahoo! Groups Links --------------------------------- Get the free Yahoo! toolbar and rest assured with the added security of spyware protection.
