[Repeater-Builder] Coax shielding
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 Thank You, Ian Wells, Kerinvale Comaudio, 3A Murchison Street,Biloela.4715 Ph 0749922449 or 0409159932 or 0749922574 www.kerinvalecomaudio.com.au
Re: [Repeater-Builder] Coax shielding
At UHF, possibly, at VHF unlikely... you did not specify :-) How close are the frequencies??? Lots of details left out for us to help. If the freq's are within a few hundred kiloherts at vhf, antenna separation is probably the issue... More details please?? Doug KD8B 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 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
RE: [Repeater-Builder] Coax shielding
I think the coax causing issues is a reasonable assumption… and probably the easiest thing to try. Good luck. 73, Mike WM4B _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of kerincom Sent: Sunday, June 27, 2010 10:51 AM To: mail=repeater-buil...@yahoogroups.com Subject: [Repeater-Builder] Coax shielding 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 Thank You, Ian Wells, Kerinvale Comaudio, 3A Murchison Street,Biloela.4715 Ph 0749922449 or 0409159932 or 0749922574 www.kerinvalecomaud http://www.kerinvalecomaudio.com.au io.com.au
Re: [Repeater-Builder] Coax shielding
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 Thank You, Ian Wells, Kerinvale Comaudio, 3A Murchison Street,Biloela.4715 Ph 0749922449 or 0409159932 or 0749922574 www.kerinvalecomaudio.com.au ---Original Message--- From: Doug Bade Date: 6/28/2010 12:59:24 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Coax shielding At UHF, possibly, at VHF unlikely... you did not specify :-) How close are the frequencies??? Lots of details left out for us to help. If the freq's are within a few hundred kiloherts at vhf, antenna separation is probably the issue... More details please?? Doug KD8B 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 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
RE: [Repeater-Builder] Coax shielding
Ian, RG-213 coax can definitely contribute to desense, as can cheap connectors and adapters. I suggest making up new jumpers using double-shielded coax such as RG-400 or RG-214, and fit these jumpers with high-quality, crimp-on connectors of the correct type on each end so that no adapters or barrels are needed. Don't use LMR400 or similar foil-and-braid cable, as that will add entirely new problems to the mix. If changing the jumpers still leaves some desense, then try increasing the spacing between the link and main antennas- lowering the link antenna should be the first step. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of kerincom Sent: Sunday, June 27, 2010 7:51 AM To: mail=repeater-buil...@yahoogroups.com Subject: [Repeater-Builder] Coax shielding 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 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
RE: [Repeater-Builder] Coax shielding
Jumpers between the TX ,rx and diplexer are rg223u .I thought of using rg223u for the link radio to its antenna because it is only aprox 2-3meters long but I felt I should try lmr400 because of the 100% shielding and the link radio is just a standard radio that works in either rx or TX mode and not in duplex mode Thank You, Ian Wells, Kerinvale Comaudio, 3A Murchison Street,Biloela.4715 Ph 0749922449 or 0409159932 or 0749922574 www.kerinvalecomaudio.com.au ---Original Message--- From: Eric Lemmon Date: 6/28/2010 1:24:37 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Coax shielding Ian, RG-213 coax can definitely contribute to desense, as can cheap connectors and adapters. I suggest making up new jumpers using double-shielded coax such as RG-400 or RG-214, and fit these jumpers with high-quality, crimp-on connectors of the correct type on each end so that no adapters or barrels are needed. Don't use LMR400 or similar foil-and-braid cable, as that will add entirely new problems to the mix. If changing the jumpers still leaves some desense, then try increasing the spacing between the link and main antennas- lowering the link antenna should be the first step. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups com] On Behalf Of kerincom Sent: Sunday, June 27, 2010 7:51 AM To: mail=repeater-buil...@yahoogroups.com Subject: [Repeater-Builder] Coax shielding 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 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
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
Re: [Repeater-Builder] Coax shielding
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 ---Original Message--- From: Doug Bade Date: 6/28/2010 1:44:27 AM To: 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
Re: [Repeater-Builder] Coax shielding
That's what I thought as I am currently using a 6ld450s notch diplexer and should change it to a band pass/band reject diplexer .I tried a experiment on site where I added 1 cavity inline with the receiver 478.675 and it seemed to improve the problem .so that was going to be the next step but I thought I might see what the thoughts were on the coax leaking Thank You, Ian Wells, Kerinvale Comaudio, 3A Murchison Street,Biloela.4715 Ph 0749922449 or 0409159932 or 0749922574 www.kerinvalecomaudio.com.au ---Original Message--- From: Doug Bade Date: 6/28/2010 1:44:27 AM To: 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
Re: [Repeater-Builder] Coax shielding
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
Re: [Repeater-Builder] Coax shielding
Ok thanks .I will upgrade the diplexer and see how that goes I might have to change all my repeaters the same . Thank You, Ian Wells, Kerinvale Comaudio, 3A Murchison Street,Biloela.4715 Ph 0749922449 or 0409159932 or 0749922574 www.kerinvalecomaudio.com.au ---Original Message--- From: Doug Bade Date: 6/28/2010 2:08:45 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Coax shielding 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
Re: [Repeater-Builder] Coax shielding
While your logic is good on this, a Pass/Reject would help THAT transmitter be more friendly to other receivers... and protect from raw RF overload from other near-but-not-on-frequency transmitters... but the noise geration issue ( part 2 of my general site comments) needs to be plugged up on the tx that is causing itso filters need to be on the link TX itself... especially if you want to keep the link frequency agile.. the proposed notch filters would allow the link to be moved if you needed, as long as you stay at least 1 mhz away from the notched 478 frequency... Now.. if there are ever more receivers on site, those cases will need to be addressed with better filtering or antenna spacing :-) Doug kerincom wrote: That's what I thought as I am currently using a 6ld450s notch diplexer and should change it to a band pass/band reject diplexer .I tried a experiment on site where I added 1 cavity inline with the receiver 478.675 and it seemed to improve the problem .so that was going to be the next step but I thought I might see what the thoughts were on the coax leaking 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
RE: [Repeater-Builder] Coax shielding
Ian, Since RG-223 is double-shielded cable and is similar in construction to RG-400, it will be fine- provided you are using the connectors specifically made for RG-223 which has a larger OD than RG-400. Please don't even think about using LMR-400, 9913F, or any foil/braid cable because of their tendency to generate noise. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of kerincom Sent: Sunday, June 27, 2010 8:28 AM To: mail=repeater-buil...@yahoogroups.com Subject: RE: [Repeater-Builder] Coax shielding Jumpers between the TX ,rx and diplexer are rg223u .I thought of using rg223u for the link radio to its antenna because it is only aprox 2-3meters long but I felt I should try lmr400 because of the 100% shielding and the link radio is just a standard radio that works in either rx or TX mode and not in duplex mode 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: Eric Lemmon mailto:wb6...@verizon.net Date: 6/28/2010 1:24:37 AM To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Coax shielding Ian, RG-213 coax can definitely contribute to desense, as can cheap connectors and adapters. I suggest making up new jumpers using double-shielded coax such as RG-400 or RG-214, and fit these jumpers with high-quality, crimp-on connectors of the correct type on each end so that no adapters or barrels are needed. Don't use LMR400 or similar foil-and-braid cable, as that will add entirely new problems to the mix. If changing the jumpers still leaves some desense, then try increasing the spacing between the link and main antennas- lowering the link antenna should be the first step. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com [mailto:Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com ] On Behalf Of kerincom Sent: Sunday, June 27, 2010 7:51 AM To: mail=repeater-buil...@yahoogroups.com mailto:mail%3DRepeater-Builder%40yahoogroups.com Subject: [Repeater-Builder] Coax shielding 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 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 http://www.kerinvalecomaudio.com.au
[Repeater-Builder] Re: Coax shielding
kerincom kerin...@... wrote: Hi guys .I am just wanted to confirm a question on coax shielding . Simple answer... It's there and never seems to behave exactly how you would expect it to. With 2-10 watts transmitting through rg213u could RF be escaping that could cause desensitization to other radios. RF can escape through some types of hard line (believe it or not). There always will be local area RF around, just a question of how much is coming through/from the coax braid and what if any grief it may be causing. If you're working at the 2 to 10 watt (what many of us assume is a fairly low) power level and you've got desense gremlins, smart money says you probably (also) have other or additional issues to deal with. 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. Nothing wrong with RG-213u especially when compared to other possible choices like someone using RG-58au. Just a question of loss per length and your preference with the end result values when you use/install it. 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. So do some testing... put a termination (dummy load) on the end of the feed-line (regardless of the type you're using) at the Link-Yagi end. See if the problem goes away when you've got the Link Radio (transmitter) working at full power into the test termination (load). 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. The proper type and placement of cavities will help, but you should first consider the Link Tx Termination Test I mention above. You don't yet know where the problem really originates from and you don't mention what type of repeater receiver you're using. Should we assume it's something of decent quality and that you have it properly protected. And what's the repeater transmitter doing when the link is active? Do you make the classic mistake of tie-wrapping the feed lines into one big bunch? 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. Please... If you feel you must change the feed line, don't use any LMR type of coaxial line or you'll be wasting your and our time with additional problems. LMR-400 is not good coax to use in and around duplex (repeater) radio or any high adjacent RF environments. 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 You're not yet sure that's the problem and I'll bet the coax shielding value is not the large problem contribution you think it is. We'd need to know more about the radios, antennas, power levels, receiver and transmitter filtering (what we call Duplexer) or pre-selectors and notch cavities you might have around. Even though you're running RG-213u, it's not the best but when applied in modest length runs it's not the train wreck you might think it is. And you're on the bottom side of the earth in Auzzie Land so we have to flip the computer screen upside down to read your posts, but that's relatively easy. :-) Thank You, Ian Wells, your turn, s.
[Repeater-Builder] Piston Trimmer Voltage Rating
Hi folks, Am just finishing up the 6 meter heliax duplexer project, and am getting some pretty good numbers. (3 'cans' on each side, 90dB notch about 1.2dB 'pass' attenuation).. Anyhow, I used some Johanson piston trimmers that I had, but evidently they are a bit shy on the working voltage rating, as the one closest to the transmitter (80 w, @53.15) didn't quite cut the mustard! A nice arc hole in the piston. Anyhow, was wondering what the working voltage is for these guys. Guess I need to look around for some substitutes. Thanks, Tim W5FN Utopia, TX
[Repeater-Builder] Battery Revert help for MSF 5000 Diode question
Hello Group, I need some help i am working on a MSF 5000 it has a TPN 1186b power supply i need to have a battery back up what i want to do is get a 10 amp automatic battery charger to keep the battery charged my question is what size of diode and how many? would i need to go from the battery to the repeater? to keep the power supply from charging the battery? Any idea Thanks Mike Henry
Re: [Repeater-Builder] Piston Trimmer Voltage Rating
Instead of piston trimmers you might want to try ARCO padders (postage stamp size that can tolerate higher levels of rf current) or small air variable capacitors. I have found both at reasonable prices at this site: http://www.danssmallpartsandkits.net/ 73 and aloha, Eric KH6CQ --- On Sun, 6/27/10, Tim tahr...@swtexas.net wrote: From: Tim tahr...@swtexas.net Subject: [Repeater-Builder] Piston Trimmer Voltage Rating To: Repeater-Builder@yahoogroups.com Date: Sunday, June 27, 2010, 11:18 AM Hi folks, Am just finishing up the 6 meter heliax duplexer project, and am getting some pretty good numbers. (3 'cans' on each side, 90dB notch about 1.2dB 'pass' attenuation).. Anyhow, I used some Johanson piston trimmers that I had, but evidently they are a bit shy on the working voltage rating, as the one closest to the transmitter (80 w, @53.15) didn't quite cut the mustard! A nice arc hole in the piston. Anyhow, was wondering what the working voltage is for these guys. Guess I need to look around for some substitutes. Thanks, Tim W5FN Utopia, TX
Re: [Repeater-Builder] Re: Coax shielding
Hi skip .The repeater radios are maxon sm4450sc and the link is a tait t2010 The test I have tried in the past have been definitely point to the link being the problem as when we turn the link off the repeater works to its full range but with it on we get desence. We used to have the link closer to the repeaters aprox 487mhz but we shifted it to 517mhz to fix desense and we find we are still having problems.I think the white noise could be the issue but I tried a notch on the link cable tuned to the repeaters receive and that seem to cause more interference and weaken the links Transmit range.I wondered about putting a BP cavity filter inline with the link but since our link frequencies are 5.2mhz apart I feel you can only tuned the filter for either TX or rx frequencies and not both Unless maybe you can install two in pararell ,one tuned to TX and the other rx . Thank You, Ian Wells, Kerinvale Comaudio, 3A Murchison Street,Biloela.4715 Ph 0749922449 or 0409159932 or 0749922574 www.kerinvalecomaudio.com.au ---Original Message--- From: skipp025 Date: 6/28/2010 2:50:00 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Coax shielding kerincom kerin...@... wrote: Hi guys .I am just wanted to confirm a question on coax shielding .
[Repeater-Builder] GR1225 VHF
Hello all. I have a very good working GR1225 VHF repeater that I can't really use. I would like to see if anyone would be interested in trading this vhf radio for a good working uhf radio?. I just don't need the vhf anymore and have my pair ready to go for UHF. Thanks and let me know.
RE: [Repeater-Builder] Piston Trimmer Voltage Rating
Hi Eric, I've been on Dan's site he has some good stuff. I had the piston trimmers 'in-stock', so that's what I used. (as did the original design) Was curious About the WV of them. Thanks, Tim -Original Message- From: Eric Grabowski ejgrabow...@yahoo.com Sent: Sunday, June 27, 2010 5:02 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Piston Trimmer Voltage Rating Instead of piston trimmers you might want to try ARCO padders (postage stamp size that can tolerate higher levels of rf current) or small air variable capacitors. I have found both at reasonable prices at this site: http://www.danssmallpartsandkits.net/ 73 and aloha, Eric KH6CQ --- On Sun, 6/27/10, Tim tahr...@swtexas.net wrote: From: Tim tahr...@swtexas.net Subject: [Repeater-Builder] Piston Trimmer Voltage Rating To: Repeater-Builder@yahoogroups.com Date: Sunday, June 27, 2010, 11:18 AM Hi folks, Am just finishing up the 6 meter heliax duplexer project, and am getting some pretty good numbers. (3 'cans' on each side, 90dB notch about 1.2dB 'pass' attenuation).. Anyhow, I used some Johanson piston trimmers that I had, but evidently they are a bit shy on the working voltage rating, as the one closest to the transmitter (80 w, @53.15) didn't quite cut the mustard! A nice arc hole in the piston. Anyhow, was wondering what the working voltage is for these guys. Guess I need to look around for some substitutes. Thanks, Tim W5FN Utopia, TX [The entire original message is not included]
RE: [Repeater-Builder] Re: Coax shielding
Hi Ian, I think I'd be taking a close look at both transmitters with a spectrum analyser and seeing if they are both suitable for repeater work. I'm not familiar with either radio, but usually radios designed for duplex work go to a lot more trouble with internal shielding than your average mobile set. The other issue to consider is the impedance matching between all the components in the system. If the SWR is bad somewhere then there will be RF voltage on the outside of the coax linking mis-matched devices, regardless of how good the coax is. For instance if the link transmitter is seeing a high SWR into it's bandpass cavity then the jumper cable could be radiating unfiltered noise straight into the repeater receiver cable. It could also be that putting the bandpass filter in line has upset the SWR seen by the Link Tx and now radiates MORE noise in the shack. I've also seen some cavities make PA stages become unstable, creating very broad band noise, requiring both the cavities and PA to be retuned to solve the problem. 73,Mark VK3BYY From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of kerincom Sent: Monday, 28 June 2010 08:19 AM To: mail=repeater-buil...@yahoogroups.com Subject: Re: [Repeater-Builder] Re: Coax shielding Hi skip .The repeater radios are maxon sm4450sc and the link is a tait t2010.The test I have tried in the past have been definitely point to the link being the problem as when we turn the link off the repeater works to its full range but with it on we get desence. We used to have the link closer to the repeaters aprox 487mhz but we shifted it to 517mhz to fix desense and we find we are still having problems.I think the white noise could be the issue but I tried a notch on the link cable tuned to the repeaters receive and that seem to cause more interference and weaken the links Transmit range.I wondered about putting a BP cavity filter inline with the link but since our link frequencies are 5.2mhz apart I feel you can only tuned the filter for either TX or rx frequencies and not both Unless maybe you can install two in pararell ,one tuned to TX and the other rx . Thank You, Ian Wells, Kerinvale Comaudio, 3A Murchison Street,Biloela.4715 Ph 0749922449 or 0409159932 or 0749922574 www.kerinvalecomaudio.com.auhttp://www.kerinvalecomaudio.com.au/
Re: [Repeater-Builder] Piston Trimmer Voltage Rating
Usually 250V. The more robust ones are rated for 500V, but generally as capacitance range goes up working voltage goes down. See if you can find some Russian surplus on ebay, those trimmers are built like a tank. On Sun, Jun 27, 2010 at 5:58 PM, Tim tahr...@swtexas.net wrote: Hi Eric, I've been on Dan's site he has some good stuff. I had the piston trimmers 'in-stock', so that's what I used. (as did the original design) Was curious About the WV of them. Thanks, Tim -- From: Eric Grabowski ejgrabow...@yahoo.com Sent: Sunday, June 27, 2010 5:02 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Piston Trimmer Voltage Rating Instead of piston trimmers you might want to try ARCO padders (postage stamp size that can tolerate higher levels of rf current) or small air variable capacitors. I have found both at reasonable prices at this site: http://www.danssmallpartsandkits.net/ 73 and aloha, Eric KH6CQ --- On *Sun, 6/27/10, Tim tahr...@swtexas.net* wrote: From: Tim tahr...@swtexas.net Subject: [Repeater-Builder] Piston Trimmer Voltage Rating To: Repeater-Builder@yahoogroups.com Date: Sunday, June 27, 2010, 11:18 AM Hi folks, Am just finishing up the 6 meter heliax duplexer project, and am getting some pretty good numbers. (3 'cans' on each side, 90dB notch about 1.2dB 'pass' attenuation).. Anyhow, I used some Johanson piston trimmers that I had, but evidently they are a bit shy on the working voltage rating, as the one closest to the transmitter (80 w, @53.15) didn't quite cut the mustard! A nice arc hole in the piston. Anyhow, was wondering what the working voltage is for these guys. Guess I need to look around for some substitutes. Thanks, Tim W5FN Utopia, TX [The entire original message is not included]
RE: [Repeater-Builder] Re: Coax shielding
Currently I have no filters between the link transmitter and its antenna. Thank You ,Ian Wells Kerinvale Comaudio, 3A Murchison Street, Biloela.4715 Ph 0749922449 Mb 0409159932 Hm 0749922574 Fx 0749922767 www.kerinvalecomaudio.com.au ---Original Message--- From: Mark HARRISON Date: 06/28/10 11:10:52 To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Re: Coax shielding Hi Ian, I think I'd be taking a close look at both transmitters with a spectrum analyser and seeing if they are both suitable for repeater work. I'm not familiar with either radio, but usually radios designed for duplex work go to a lot more trouble with internal shielding than your average mobile set. The other issue to consider is the impedance matching between all the components in the system. If the SWR is bad somewhere then there will be RF voltage on the outside of the coax linking mis-matched devices, regardless of how good the coax is. For instance if the link transmitter is seeing a high SWR into it's bandpass cavity then the jumper cable could be radiating unfiltered noise straight into the repeater receiver cable. It could also be that putting the bandpass filter in line has upset the SWR seen by the Link Tx and now radiates MORE noise in the shack. I've also seen some cavities make PA stages become unstable, creating very broad band noise, requiring both the cavities and PA to be retuned to solve the problem 73,Mark VK3BYY From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups com] On Behalf Of kerincom Sent: Monday, 28 June 2010 08:19 AM To: mail=repeater-buil...@yahoogroups.com Subject: Re: [Repeater-Builder] Re: Coax shielding Hi skip .The repeater radios are maxon sm4450sc and the link is a tait t2010 The test I have tried in the past have been definitely point to the link being the problem as when we turn the link off the repeater works to its full range but with it on we get desence. We used to have the link closer to the repeaters aprox 487mhz but we shifted it to 517mhz to fix desense and we find we are still having problems.I think the white noise could be the issue but I tried a notch on the link cable tuned to the repeaters receive and that seem to cause more interference and weaken the links Transmit range.I wondered about putting a BP cavity filter inline with the link but since our link frequencies are 5.2mhz apart I feel you can only tuned the filter for either TX or rx frequencies and not both Unless maybe you can install two in pararell ,one tuned to TX and the other rx . Thank You, Ian Wells, Kerinvale Comaudio, 3A Murchison Street,Biloela.4715 Ph 0749922449 or 0409159932 or 0749922574 www.kerinvalecomaudio.com.au faint_grain.jpg
[Repeater-Builder] 1/2 or 7/8 coax needed
I am in need of 1/2 or 7/8 coax. I live in Olympia, WA and I am willing to pick up within 100 miles or pay shipping to Olympia, WA. I need 300 feet total or two pieces 150 feet. Thanks, Larry KC7CKO
[Repeater-Builder] Re: Piston Trimmer Voltage Rating
Instead of piston trimmers you might want to try ARCO padders (postage stamp size that can tolerate higher levels of rf current) or small air variable capacitors. I have nfound both at reasonable prices at this site: A generic statement that has merit in this subject Q is everything and the Q of an Arco cap (padder) is probably no where near as good as a decent piston cap. Ebay provides the occasional deal on nice piston caps. If you're not at a critical current location, the A49 piston caps in the following sale ad work for some applications. http://www.hamtronics.com/sale.htm s. http://www.danssmallpartsandkits.net/ 73 and aloha, Eric KH6CQ --- On Sun, 6/27/10, Tim tahr...@... wrote: From: Tim tahr...@... Subject: [Repeater-Builder] Piston Trimmer Voltage Rating To: Repeater-Builder@yahoogroups.com Date: Sunday, June 27, 2010, 11:18 AM Â Hi folks, Am just finishing up the 6 meter heliax duplexer project, and am getting some pretty good numbers. (3 'cans' on each side, 90dB notch about 1.2dB 'pass' attenuation).. Anyhow, I used some Johanson piston trimmers that I had, but evidently they are a bit shy on the working voltage rating, as the one closest to the transmitter (80 w, @53.15) didn't quite cut the mustard! A nice arc hole in the piston. Anyhow, was wondering what the working voltage is for these guys. Guess I need to look around for some substitutes. Thanks, Tim W5FN Utopia, TX
Re: [Repeater-Builder] Re: Piston Trimmer Voltage Rating
1/4 super flex makes a pretty decent gimmick capacitor. On Sun, Jun 27, 2010 at 10:16 PM, skipp025 skipp...@yahoo.com wrote: Instead of piston trimmers you might want to try ARCO padders (postage stamp size that can tolerate higher levels of rf current) or small air variable capacitors. I have nfound both at reasonable prices at this site: A generic statement that has merit in this subject Q is everything and the Q of an Arco cap (padder) is probably no where near as good as a decent piston cap. Ebay provides the occasional deal on nice piston caps. If you're not at a critical current location, the A49 piston caps in the following sale ad work for some applications. http://www.hamtronics.com/sale.htm s. http://www.danssmallpartsandkits.net/ 73 and aloha, Eric KH6CQ --- On Sun, 6/27/10, Tim tahr...@... wrote: From: Tim tahr...@... Subject: [Repeater-Builder] Piston Trimmer Voltage Rating To: Repeater-Builder@yahoogroups.com Date: Sunday, June 27, 2010, 11:18 AM Â Hi folks, Am just finishing up the 6 meter heliax duplexer project, and am getting some pretty good numbers. (3 'cans' on each side, 90dB notch about 1.2dB 'pass' attenuation).. Anyhow, I used some Johanson piston trimmers that I had, but evidently they are a bit shy on the working voltage rating, as the one closest to the transmitter (80 w, @53.15) didn't quite cut the mustard! A nice arc hole in the piston. Anyhow, was wondering what the working voltage is for these guys. Guess I need to look around for some substitutes. Thanks, Tim W5FN Utopia, TX Yahoo! Groups Links
