[K3] - Odd SWR readings ANT1 v ANT2
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No doubt the recent Es propagation has brought the following behaviour to my attention...it's only evident on 10m for some reason:-
Screw in a PL259 type dummy load into ANT1 (KAT3) and deselect ATU. Press TUNE (10w) and the indicated swr on the K3 is 1.7 to 1.8. Change dummy load to ANT2 and select and the indicated swr is now 1.0...! I've swapped the antenna leads on the KAT3 board to determine it's something to do with circuitry around the antenna relay and not PL259 sockets/interconnecting leads but according to the schematics each path is equivalent. Furthermore an external swr meter placed between dummy load and K3 indicates 1:1 on *both* ANT 1 and 2 so it seems to be something to do with the way the radio is sensing the swr between the two antenna sockets. I'm not at all hung up on swr but why the difference between the 2 antenna inputs - strays in the relay or surge arrestors? It also looks like the radio is 'thinking' about the power output when the swr indicates 1:1.8 and above and may cause power variations....? Thoughts?? 73, Stewart Rolfe, GW0ETF (K3 #145) ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: [K3] - Odd SWR readings ANT1 v ANT2
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I've found that some times the back panels on the K3's have not been masked off with tape properly when they were powder coated. Therefore what happens is, the SO239 connector on the back panel is not making a good ground connection, or ANY ground connection to the chassis of the K3. Take a VOM meter and check the resistance from the Shell (ground) of the rear Antenna connectors, both to each other, and to a Ground Screw on the K3. Make sure they all read 0 ohms. If not, this could be the source of your problem. You may need to take the back panel off and scrape away the powder coating and get a good ground connection. I've seen it so bad that there was a 10:1 SWR when you have a dummy load attached to the back of the ANT 1 jack and a 1.8 SWR on the ANT 2 jack. Keeping in mind that the Antenna 2 jack has the little Star washer that connects the antenna tuner wire to it. > Date: Fri, 11 Jun 2010 18:14:58 +0000 > From: [hidden email] > To: [hidden email] > Subject: [Elecraft] [K3] - Odd SWR readings ANT1 v ANT2 > > No doubt the recent Es propagation has brought the following behaviour to my attention...it's only evident on 10m for some reason:- > Screw in a PL259 type dummy load into ANT1 (KAT3) and deselect ATU. Press TUNE (10w) and the indicated swr on the K3 is 1.7 to 1.8. Change dummy load to ANT2 and select and the indicated swr is now 1.0...! > I've swapped the antenna leads on the KAT3 board to determine it's something to do with circuitry around the antenna relay and not PL259 sockets/interconnecting leads but according to the schematics each path is equivalent. Furthermore an external swr meter placed between dummy load and K3 indicates 1:1 on *both* ANT 1 and 2 so it seems to be something to do with the way the radio is sensing the swr between the two antenna > sockets. > I'm not at all hung up on swr but why the difference between the 2 antenna inputs - strays in the relay or surge arrestors? It also looks like the radio is 'thinking' about the power output when the swr indicates 1:1.8 and above and may cause power variations....? > Thoughts?? > 73, > Stewart Rolfe, GW0ETF (K3 #145) > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html _________________________________________________________________ The New Busy is not the old busy. Search, chat and e-mail from your inbox. http://www.windowslive.com/campaign/thenewbusy?ocid=PID28326::T:WLMTAGL:ON:WL:en-US:WM_HMP:042010_3 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: [K3] - Odd SWR readings ANT1 v ANT2
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In reply to this post by GW0ETF
Stewart, The K3ANT does not do a "hard" bypass. Instead it sets the tuner to the memorized 50 Ohm : 50 Ohm position. Since the tuner memories are "by band" and "by antenna" - plug the dummy load into the ANT 1 position, enable the tuner and hit the "ATU Tune" button. That will "teach" the tuner the 50 Ohm setting for ANT 1 and you won't see the issue in the future. 73, ... Joe, W4TV On 6/11/2010 2:14 PM, Stewart Rolfe wrote: > No doubt the recent Es propagation has brought the following > behaviour to my attention...it's only evident on 10m for some > reason:- Screw in a PL259 type dummy load into ANT1 (KAT3) and > deselect ATU. Press TUNE (10w) and the indicated swr on the K3 is 1.7 > to 1.8. Change dummy load to ANT2 and select and the indicated swr is > now 1.0...! I've swapped the antenna leads on the KAT3 board to > determine it's something to do with circuitry around the antenna > relay and not PL259 sockets/interconnecting leads but according to > the schematics each path is equivalent. Furthermore an external swr > meter placed between dummy load and K3 indicates 1:1 on *both* ANT 1 > and 2 so it seems to be something to do with the way the radio is > sensing the swr between the two antenna sockets. I'm not at all hung > up on swr but why the difference between the 2 antenna inputs - > strays in the relay or surge arrestors? It also looks like the radio > is 'thinking' about the power output when the swr indicates 1:1.8 and > above and may cause power variations....? Thoughts?? 73, Stewart > Rolfe, GW0ETF (K3 #145) > ______________________________________________________________ > Elecraft mailing list Home: > http://mailman.qth.net/mailman/listinfo/elecraft Help: > http://mailman.qth.net/mmfaq.htm Post: > mailto:[hidden email] > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Thanks for the explanation Joe - that makes sense now and indeed after doing as you suggest all is 'normal'.
The "soft" bypass concept isn't what I'd call intuitive so my only suggestion would be an explanatory footnote to this effect in the manual, always assuming I haven't missed it.... Who says you can't teach an old dog new tricks? 73 and thanks, Stewart, GW0ETF (Original owner of K3 #145)
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No argument with what you are saying, Joe, just a curiosity...
>> The K3ANT does not do a "hard" bypass. Instead it sets the >> tuner to the memorized 50 Ohm : 50 Ohm position. >> >> Since the tuner memories are "by band" and "by antenna" - plug >> the dummy load into the ANT 1 position, enable the tuner and >> hit the "ATU Tune" button. That will "teach" the tuner the 50 >> Ohm setting for ANT 1 and you won't see the issue in the future. >> ... Joe, W4TV What do you do to tell the K3 that this is the dummy load 50 ohm to use for the bypass setting? Or does the K3 already know that. And if it does, how did it know that? 73, Guy. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: [K3] - Odd SWR readings ANT1 v ANT2
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Guy, I don't know how it works. All I know is that's the procedure that Elecraft have recommended to others for the same "problem" and it appears to work. 73, ... Joe, W4TV On 6/12/2010 10:41 AM, Guy Olinger K2AV wrote: > No argument with what you are saying, Joe, just a curiosity... > >>> The K3ANT does not do a "hard" bypass. Instead it sets the >>> tuner to the memorized 50 Ohm : 50 Ohm position. >>> >>> Since the tuner memories are "by band" and "by antenna" - plug >>> the dummy load into the ANT 1 position, enable the tuner and >>> hit the "ATU Tune" button. That will "teach" the tuner the 50 >>> Ohm setting for ANT 1 and you won't see the issue in the future. >>> ... Joe, W4TV > > What do you do to tell the K3 that this is the dummy load 50 ohm to > use for the bypass setting? Or does the K3 already know that. And if > it does, how did it know that? > > 73, Guy. > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Joe Subich, W4TV-4
Joe,
Just been playing with this some more and there does seem something odd about 28MHz. If I do as you instruct the swr does indeed now indicate 1:1 on bypass to a dummy load. However if I turn on the ATU and 'tune' it to match to an antenna and then go back and check bypass into the dummy load I get a high reading again. It's as if invoking the ATU to match the antenna is wiping the 50 ohm setting previously set up - all other bands seem fine. ANT1 and 2 behave the same...TUNE power by the way is 10 watts. Stewart, GW0ETF
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