On 11/1/2010 23:36, KF4VTT wrote: > > Did this problem happen after you connected the amp? > > I ran into a similar problem. My external Ameritron T/R relay failed and > held the amp in transmit. The only way I realized that the amp was stuck in > transmit besides the diminished receive was the heat I noticed coming off > the amp. I could see the heat rising against the backdrop of the wall. :-) > Thank goodness I did not have drive going to the amp that amount of time. I > would be buying a brand new pair of 3-500's. I removed the external T/R > relay and started using the internal ability of the K3 to trigger the amp. > > Besides checking the ideas from the other guys, check your T/R circuitry for > your amp. > > 73, > Doug > KF4VTT > K3 #1289 > P3 #371
Any relay in the RF chain can exhibit signal drop out on RX but work fine on xmit. The problem is usually caused by corroded/burned contacts. Higher transmit voltage can punch through the corrosion while weaker signals cannot. This is especially true for relays which are outdoors. Relay replacement is the only real solution. Contact cleaner is iffy. Filing the contacts for some relays destroys the plated contact material and can result in even worse performance. Some designs use "double contacts" to almost eliminate the problem. Use paralleled contacts (dpdt relay) or find a relay with "bifurcated" contacts. These relays have a pole with a "tuning fork" type design. Each arm has a separate contact. If one contact doesn't work, maybe the other will. The same goes for corroded antenna connectors and connections to the antenna elements. The real work is in finding which of the above is the culprit. If one has a low voltage portable RF source, e.g. the XG1, and a buddy in the shack, one can connect it at various points of the system and find where the dropout occurs. 73 de Brian/K3KO ----- No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1153 / Virus Database: 424/3233 - Release Date: 11/02/10 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
