[Elecraft] [K3] - Odd SWR readings ANT1 v ANT2

[The Smiths]

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: gw0etf at btinternet.com
> To: elecraft at mailman.qth.net
> 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:Elecraft at mailman.qth.net
> 
> 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