Open antenna connectors are like baby antennas. Terminate the antenna port in question before proceeding.
Jim ab3cv On Feb 10, 2016, at 7:25 PM, Don Wilhelm <w3...@embarqmail.com> wrote: Since the problem occurs without an antenna connected, it is a version of the "RF in the shack" problem, although the RF field is coming from the nearby FM station rather than the classic situation where the transmitted signal is the source of the RF. Jim makes some very good suggestions for 'taming' that problem. It would be very difficult to cure the K3 of the "pin 1" problems. For those who are not familiar with the "pin 1" problem, that is a situation where the shields of interconnecting cables are connected to the circuit boards rather than directly to the outside of the transceiver enclosure. That allows any pickup on attached cables to be imposed into the boards of the transceivers. In days of old when we mounted all connectors to the enclosure rather than to the circuit boards, the enclosure itself provided a shield for whatever trash was picked up by the external wiring - because those trash signals would flow on the 'outside' of the enclosure and not affect the circuits inside. With modern transceivers where cable jacks are connected to the ground plane of the circuit boards rather than to the enclosure, the external signals are coupled to the ground plane of the internal boards, and will couple the offending signals into the transceiver. In other words, "board ground plane" does not equal "ground" - variations in the ground plane reference will cause "funny happenings" within the interior circuits. In other words, the enclosure does not offer a sufficient shielding effect for the circuits inside the enclosure. The K3 is not alone in this problem, it is shared by any transceiver that does not ground the connectors directly to the enclosure. 73, Don W3FPR 73, Don W3FPR 73, Don W3FPR > On 2/10/2016 6:57 PM, Jim Brown wrote: > Yes, this hit me between the eyes as well. The K3 has Pin One Problems at > many (most?) connectors, so RF current flowing on shields of cables plugged > into those connectors will couple into the K3. I've been preaching to Wayne > about Pin One Problems since 2004, when we met in Dayton. > > If the problem is around 90 MHz, I'd use multiple one-turn and two turn > chokes with #43 material on every cable except the SO239 output, which IS > actually bonded to the chassis. Also choke the power cable. > > 73, Jim K9YC > >> On Wed,2/10/2016 2:53 PM, Fred Jensen wrote: >> I easily could have misread the original emailed problem, but he included >> the note that this RFI occurred with all antennas [and I guess other cables] >> disconnected which is very strange indeed. If that is so, then I doubt >> stubs/filters on the antenna circuits would cure the problem. > ______________________________________________________________ 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 Message delivered to j...@jtmiller.com ______________________________________________________________ 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 Message delivered to arch...@mail-archive.com
