In theory most xtal radios are quieter than synthesized ones, but a filter would seem to be the better thing to do as it really stops the problem...even a bandpass can or 2 on the link radio would be acceptable if a notch is not available.. I just offered a notch duplexer option as they can be bought sub 150.00 usd... and probably a lot less off ebay..
"I" would fix the noise potential rather than swap the tx for another model.. but I have different options available to me than maybe you do... If the site were at a "remote" location for me.. I try to make it bulletproof so I do not have to deal with it.. :-) Doug kerincom wrote: > > > Would it be better to change the link radio to crystal instead of > programmed .It is currently a tait t2010 > > > > > > Thank You, > Ian Wells, > Kerinvale Comaudio, > 3A Murchison Street,Biloela.4715 > Ph 0749922449 or 0409159932 or 0749922574 > www.kerinvalecomaudio.com.au <http://www.kerinvalecomaudio.com.au/> > > /-------Original Message-------/ > > /*From:*/ Doug Bade <mailto:k...@thebades.net> > /*Date:*/ 6/28/2010 1:44:27 AM > /*To:*/ Repeater-Builder@yahoogroups.com > <mailto:Repeater-Builder@yahoogroups.com> > /*Subject:*/ Re: [Repeater-Builder] Coax shielding > > > > Ian; > It would seem that at uhf ~30mhz away cable leakage in the shed > would seem to be less likely than antenna to antenna interference. In > general it is the white noise generated by a transmitter on other > frequencies that is most likely to cause desense to a co located rx. > > Assuming you have double shielded or better on the repeater, the leakage > in the shed from the single shielded link radio would not seem to > radiate enough to be an issue. If the radio side of the main duplexer is > also rg213, well that is another matter :-) > If you are using a notch only duplexer for the main duplexer, it would > not protect you from another transmitter besides it's own.. Typical > mobile type size duplexers at UHF are really only designed to protect > the rx from it's local tx, any other can slip right in.. > > I would try a notch filter ( or half a notch duplexer ) on the link tx > to suppress the station rx frequency from it's output.. that noise is > probably the culprit.. > > As said by others, good double shielded cables and /or 100 % corrugated > types are suggested in sites with multiple transmitters to deal with.. > but most on site desense I have dealt with from other transmitters comes > from one of 2 things.. raw power front end overload of the rx when the > antennas can see each other... or white noise generated on broad > frequencies from an unfiltered transmitter. I am suggesting a notch > cavity on the 517 transmitter output that notches 478.675 in this case.. > 3 slugs ( one side) on a mobile duplexer will suppress that noise ~65db, > and provide no significant insertion loss to the link tx..And double > shielded cables like RG142 for radio to filter connections is perfectly > adequate up to 520 mhz and beyond... with isolation to -120dbm at a > minimum.. > > Doug > KD8B > > kerincom wrote: > > > > > > Uhf the link is 517mhz and the repeater TX/rx pair is 473.475 and > > 478.675mhz on one repeater and it is in a weak area with the main > > site so it has to transmitt aprox 10 watts > > > > > > > > > > kerincom wrote: > > > > > > > > > Hi guys .I am just wanted to confirm a question on coax shielding . > > > With 2-10 watts transmitting through rg213u could rf be escaping that > > > could cause desensitization to other radios .The repeater I have > > > setup uses 9 meters of heliax from the main diplexer to ant and > > > rg213u from the link radio to its antenna . > > > I am finding I am getting problems with the link > > > transmission interfering with the repeater rx The link antenna is a > > > yagi 3 meters above the ground and the main repeater antenna is 6 > > > meters above it .I am currently trying band pass cavity on the > > > receiver rx or band pass/band reject diplexer with some success but I > > > am wondering if the rf escaping from the cable is causing problems > > > inside the repeater shed even at a low wattage .I am definitely > > > changing the rg213u to either rg223u or lmr400 as it is only on the > > > link radio and shouldn't have any effect on the repeater's operation > > > .Has anyone else had the same sort of problem where the rf energy > > > leaks out of the cable in the shed and causes problems to the repeater > > > and they had to upgrade the link cable to 100% coverage cable > > > > > > > > > > > > > > > > > >
