John, The tee/sampler slug is simply a loosely coupled connection to the coax so one can insert say a generator signal into the coax without dumping the power of the transmitter back into the signal gen.
One way to build one is to take a coaxial T connector, remove the center pin of the vertical part (it often unscrews) of the T essentally making it a barral connector with the vertical part of the T open except for a few pf of capacitance between the center of the line and the vertical T output. One can then connect a signal gen to the vertical part of the T while it is in the regualar coax line with power from the tx on/keyed. To do a desense test insert the barral in the antenna line with sig gen connected to the vertical part of the T. First with TX UNKEYED cranks up the sig gen to get a low level say 12 db quieting with some noise at the receiver. This level will be much higher than if connected directly to the receiver. Then key the transmitter and see what happens to the receiver. It will probably show some desense, but very little in a good system. If a lot then crank up the sig gen to get the same rcvr quieting level as without the TX and this tells you how much desense you have. It is the same as having a weak DX station transmit to the repeater with the TX keyed and unkeyed. However, with the sig gen you can get more of an idea of any problem. Also this can be done with a dummy load in the event you suspect an antenna/feedline problem. Any repeater will not only have desense or noise from the tepater transmitter. It will have noise from outside sources so using this with the antenna connected can tell you the system noise. I did not invent it...it was around I am sure decades ago and there are professional built units on the market. A modified T connector is just an inexpensive way to get one. 73, ron, n9ee/r >From: John Transue <[EMAIL PROTECTED]> >Date: 2008/07/09 Wed AM 10:06:35 EDT >To: [email protected] >Subject: RE: [Repeater-Builder] Re: New Repeater Desense Problems > > >So,please, someone tell me, what is an iso tee/sampler slug? How is the >equipmenthooked up for the desense test? > >John > >-----Original Message----- >From:[email protected] [mailto:[EMAIL PROTECTED] On Behalf Of >de W5DK >Sent: Tuesday, July 08, 2008 11:47PM >To:[email protected] >Subject: RE: [Repeater-Builder]Re: New Repeater Desense Problems > >I think he was Laryn. I could see anargument that it may not have been aligned >and caused the situation. But,, > > In this case the matching circuitwas installed and set properly, also the >duplexers and all were perfect. Thesystem was stable for years then boom, >desense. > >All I was saying was that this stationworked Perfect into a dummy load (zero >desense and all to spec) but did notinto feedline(+15db) . So we cringed and >focused there. > >We were getting ready to replace theantenna at 580 ft and spend some money >after the dummy load test. Luckily theamp finished failing. What I relayed >locally after this experience was that acomplete system that works flawlessly >into a dummy load may not be flawless. > >I do think the majority of desense problemscan be diagnosed with a dummy load >and a sampler slug / iso tee. I just wantedto throw a recent experience / >monkey wrench into the thread hi. >73 >Don W5DK > > > > >m: [EMAIL PROTECTED]:[EMAIL PROTECTED] On Behalf Of Laryn Lohman >Sent: Tuesday, July 08, 2008 8:50PM >To: [email protected] >Subject: [Repeater-Builder] Re:New Repeater Desense Problems > >--- In [email protected],wd8chl <[EMAIL PROTECTED]> wrote: > >> It sounds to me like the PA wasn't aligned properly. Or the duplexer is >> not aligned properly. Most, but not all, MastrII PA's have an output >> filter section that is tricky to align correctly. > >Are you referring to the Z matching adjustments on continuous-duty amps? > >Laryn K8TVZ > >__________ NOD32 3192 (20080616) Information __________ > >This message was checked by NOD32 antivirus system. >http://www.eset.com > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
