Microphone ground
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Does the Elecraft require a microphone ground as well as the usual
ground for its microphone connector? If so, should it go to to pin 7 or 8 on the Elecraft mike connector? If not, are both ground connections necessary to be made to pins 7 & 8 in the connector? Thanks, Lew W7EW #1560/1561 _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Good question .. others will answer it but I just had to comment thus...
I have had serious rf pickup problems with all of my radios and several different kinds of microphones. The root problem is that I have ladderline coming right into the shack but I can't change that. Microphone cable shields ought to protect the front end of the audio chain in the radio but very often the microphone cable shield is *not* directly grounded to the chassis of the radio. There is a suggestion on the Heil website that one can often solve rf pickup problems in the microphone by making sure that the microphone cable shield is *directly* connected to the metal microphone connector. Heil makes the point that often the mic manufacturer connects the cable shield to one of the pins on the mic connector but leaves it to the radio manufacturer to connect that pin to the chassis of the radio. The radio manufacturer designer does connect this pin to the chassis but that involves an extra inch or two (or more) of wire in the ground circuit and, especially at higher frequencies, that can be enough to allow rf on the outside of the mic cable shield to couple to the wiring inside the shield. I had that problem in spades on 10M and 6M with my K3. I fixed it by connecting the mic shield within the mic connector directly to the metal connector shell which, of course, screws onto the mic connector on the radio which is bonded to the chassis. This improvement was suggested by Heil on their website. What kind of mic am I using? An Elecraft MH2 .. which, I think, is made by Heil. Go figure. I'll bet I am not the only one with rf-in-the-mic-circuit problems. So, I thought I should pass along my experience. Don K7FJ > Does the Elecraft require a microphone ground as well as the usual ground > for its microphone connector? If so, should it go to to pin 7 or 8 on the > Elecraft mike connector? If not, are both ground connections necessary to > be made to pins 7 & 8 in the connector? > Thanks, > Lew W7EW > #1560/1561 > _______________________________________________ _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Lew-2
Lew,
The mic cable shield should be connected to the shield of the mic plug, and in turn the mic jack shell should be connected directly to the enclosure by a very short path. Unfortunately, that does not happen in most ham gear constructed on PC Boards - it is easy to connect the shell to the board ground, but that is the wrong place, it really should connect directly to the metal enclosure for best RF prevention. See Jim Brown's (K9YC) frequent posts referencing 'the pin 1 problem'. The shield should not be used for any of the signal returns. Normally the PTT return connects to pin 7 and the AF return connects to pin 8. lew wrote: > Does the Elecraft require a microphone ground as well as the usual > ground for its microphone connector? If so, should it go to to pin 7 > or 8 on the Elecraft mike connector? If not, are both ground > connections necessary to be made to pins 7 & 8 in the connector? > Thanks, > Lew W7EW > #1560/1561 > _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Lew-2
Lew, The Elecraft documentation shows the mic ground connected to pin 7, the PTT ground connected to pin 8 and both pins connected to chassis ground through a common RF choke. In some stations, the common RF choke results in common mode RF (also known as a "Pin 1 problem") feedback. The proper connection would be: mic return to pin 7, PTT ground (chassis) to the SHELL of the Foster plug and the SHIELD of the mic cable to the SHELL of the Foster plug. The mic cable SHIELD should NOT be connected to the MIC element (it should connect to the CASE or float). 73, ... Joe, W4TV > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]] On Behalf Of lew > Sent: Monday, October 13, 2008 12:34 PM > To: [hidden email] > Subject: [Elecraft] Microphone ground > > > Does the Elecraft require a microphone ground as well as the usual > ground for its microphone connector? If so, should it go to > to pin 7 or > 8 on the Elecraft mike connector? If not, are both ground > connections > necessary to be made to pins 7 & 8 in the connector? > Thanks, > Lew W7EW > #1560/1561 > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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