Thanks Skipp. We had just gotten the duplexer back from tx/rx so I am going to assume it is not a problem with the cans. Especially since it was doing the exact same thing before they went through them.
The owner just ordered a new synth receiver from Hamtronics so we will soon see if it was an issue with the receiver. Thanks for your time and help. -----Original Message----- From: "skipp025" <[EMAIL PROTECTED]> Date: Tue, 22 Mar 2005 18:29:43 To:[email protected] Subject: [Repeater-Builder] Re: Better RX with feedline partailly disconnected? Hello back, A lot of things could be playing into this but I do feel you need to add the helical front end to the early Hamtronics Receiver to make it play properly in repeater service. Especially with power levels in excess of 5 watts. Onward... I've had problems with pitted cavity tune plungers causing generated noise into receivers. You can sometimes adjust the plunger while experiencing the problem to see it (noise or undesired signals) drop in and out of generation. This problem can occur with energy as low as the leakage from the oscillator chain back through the receiver front end. Bargain Cavities are sometimes not, when the plunger body is pitted near the desired frequency of operation you have big problems which require physical repair or plunger body burnishing. I now run all cavity plungers through 80% plus of their range with a motor jig I have here to allow the fingerstock to clean and scrap (where possbile) any oxide or pitting build up. ...all this done before any alignment/tune-up. You really should add the helical front end to that early Hamtronics receiver if you want it to work for your application. Your post reads like you're fighting two problems, but you're only currently aware of one issue. But you should also check the duplexer for problems, which read like the pitting issue I mention above. I suspect adjusting a cavity under modest amounts of power will cause the pitting and resulting problems when the fingerstock doesn't make good contact with the plunger body for reasons of oxide, dirt (dis-metal) or some other alien residue - oxide build-up. In my opinion, adjustment of an aged cavity (before "range/plunger cleaning" under nominal rf power is not great practice. ... especially when "the fix" is so easy to do. Another easy and quick test might be to see how the duplexer preforms with another plain jane 220 receiver. There might be some type of L-C pole interaction between the receiver front end and the duplexer cavities. It would be the second such case reported back to me this year. The fix for the earlier case was to change the presented reactance of the duplexer probes. So you probably have two dragons to slay. Pick your lance or sword and a direction to charge..! cheers, skipp skipp025 at yahoo.com www.radiowrench.com/sonic > "Michael Singewald" <[EMAIL PROTECTED]> wrote: > I am running the service monitor into the duplexer, not an antenna. I don't see how desense could be the problem with the tx off and a service monitor for a source. > > I am using the monitor for a source and going thru the duplexer and testing, then bypassing the duplexer. Through the duplexer I have this problem, not direct. > -----Original Message----- > From: "skipp025" <[EMAIL PROTECTED]> > Date: Tue, 22 Mar 2005 17:14:08 > To:[email protected] > Subject: [Repeater-Builder] Re: Better RX with feedline partailly disconnected? > > > > > "Michael Singewald N1PLH" <[EMAIL PROTECTED]> wrote: > > 220 Hamtronics receiver (very old, no labeling on > > the board). > > The early receivers don't have a very selective or > dynamic rf front end. Blocking and desense is a > common problem with the early type less protected > receiver front end circuits in repeater service. > > A good fix would be to install the Hamtronics > HRG-450 Helical Resonator Amplifier in front of the > receiver. > > You can pick the Helical unit with or without a preamp. > I bought and used the preamp included HRG-450 Helical > on the same exact receiver and it worked very well. > > Adding a Helical Front end pre-selector makes a lot > of early receivers semi usable. They are a welcome > addition to converted Midland 13-509 and Clegg to > repeater radios. > > cheers, > skipp > > > > > > > > > Yahoo! Groups Links Yahoo! Groups Links Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
