One minor point. If your feed point impeadance is really 300 ohms (folded dipole) then you should be using a 6:1 balun.
73, Fred, AE6QL -----Original Message----- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Ray Spreadbury Sent: Tuesday, May 03, 2011 10:26 AM To: elecraft@mailman.qth.net Subject: [Elecraft] FW: K2 Frequency Shift On 80 Metres -----Original Message----- From: Ray Spreadbury [mailto:ray...@btinternet.com] Sent: 03 May 2011 10:25 To: 'd...@w3fpr.com' Cc: 'ho13d...@gmail.com' Subject: RE: [Elecraft] K2 Frequency Shift On 80 Metres Hi Don & Dave Thanks for the advice re RF in the shack. I tried it with a dummy load on 80 metres & the problem disappeared (!!!!), so good call both of you -I wasn't looking forward to trying to find a problem in the rig & ordering replacement parts from Elecraft in USA! The antenna is currently fed with RG213 cable and there is a 4:1 balun at the feed point so as the impedance at the dipole is supposed to be about 300 ohms I thought it would be a reasonable match for the 50ohms cable? Anyway the antenna was OK until yesterday, when I raised it a bit, but obviously changed something to now cause the rf in the shack. I might put up a balanced feeder to the OCFD or have a dedicated 80 metre dipole instead, what do you think or do you have other suggestions ? 73 & many thanks Ray, G3XLG -----Original Message----- From: Don Wilhelm [mailto:w3...@embarqmail.com] Sent: 02 May 2011 23:08 To: Ray Spreadbury Cc: elecraft@mailman.qth.net Subject: Re: [Elecraft] K2 Frequency Shift On 80 Metres Ray, Before you do anything desperate, try the same thing into a dummy load. If it does not happen with the dummy load, you can conclude that it is RF getting into the K2 somehow. Off-center fed antennas are notorious for creating RF in the shack unless you take drastic steps to suppress it. The proper place to do that is within the antenna system - maybe adding a balun at a point outside the house where the feedline changes from balanced to unbalanced. 73, Don W3FPR On 5/2/2011 5:21 PM, Ray Spreadbury wrote: > Hi Elecrafters > > I have recently bought a second-hand K2 with the KSB2 SSB module, the KPA100 > 100 watt amplifier& the KAT100-1 antenna tuner. Everything appears > fine running either QRP or 90+ watts on all bands except 80 metres. I > am using an > off centre fed dipole (133') and the KAT100-1 antenna tuner to match. > > Running in excess of 10 watts or so on 80 metres however when I switch > the microphone, the tuning apparently shifts to another frequency on the band. > The shift may be a few Hz or even a few 100Hz. The receiver is then on that > new frequency. Reducing power back to a QRP level, the transmitter& > receiver behave normally. > > I guess there's something wrong with the 80 metre sections of the > KPA100 and/or the KAT100-1. > > Any clues of what I should check please? > > 73 > > Ray, G3XLG > > > > ______________________________________________________________ > 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 > ______________________________________________________________ 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 ______________________________________________________________ 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
