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Re: LF: Re: G7NKS multiple spots

To: [email protected]
Subject: Re: LF: Re: G7NKS multiple spots
From: John P-G <[email protected]>
Date: Wed, 16 Sep 2009 21:42:11 +0000
In-reply-to: <[email protected]>
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The classical method is to use audio isolation transformers between the rig audio in/out and the soundcard, and opto-isolators on the serial port line(s) used for the PTT switching (assuming you use serial port handshaking lines for this) so that there's no DC connection between radio "earth" and PC "earth".
I've got the audio transformers in my homemade interface, but no
opto-isolators - so there's still some connection between radio and PCs
(and I mean 3 radios and 2 PCs....) but still have no mains hum evident.
Perhaps I'm just lucky?
Ferrites are good to keep RF out of places it's not wanted, but not sure
what they'd do to keep 50Hz out.

James Cowburn wrote:
Ferrite, Ferrite and more Ferrite then!

Any suggestions as to where best to place clip on cores? Mains lead? Power lead from PSU (Icom PS55) to rig (IC735)?
All leads from ZLP interface to laptop? (Dell D610) (I currently have
ferrite clip ons on the microphone and speaker leads from ZLP to laptop)
Dell Laptop PSU?

All the above??

With best regards
Jim Dr. James Cowburn
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Graham
Sent: 16 September 2009 21:59
To: [email protected]
Subject: Re: LF: Re: G7NKS multiple spots


I think you find that is caused by 50 hz mains hum .... may be a hum loop in the audio system / pc-tx earthling , not likely to be psu problem as frequency is 50 (fund) and 150 ( 3 rd harm)
I had a similar problem with my  valve HF set , that was a slight  ripple on

the PA HT line caused by the 100% duty cycle of wspr, not part of the design criteria for ssb/cw , caused spots to appear +/- 100 Hz due to the full wave rectification in the psu
G .

From: "James Moritz" <[email protected]>
Sent: Wednesday, September 16, 2009 9:40 PM
To: <[email protected]>
Subject: LF: Re: G7NKS multiple spots

Dear Jim, LF Group,

Me too.  I am getting 3 traces (!) from Jim M (he is 9+10 and audible!)
a biggish one from Gus too
I am seeing low-level (about -25dB) sidebands on your signal at +/-50Hz and
+/-150Hz, which are giving rise to the extra spots.  I think something
similar is happening when you receive my signal. I am not getting similar
multiple spots from other nearby stations, nor am I seeing the same
sidebands on other strong signals, so I think they must originate in your
station somewhere - possibly audio being affected by mains noise, or some
sort of residual FM of an oscillator in your rig?

Cheers, Jim Moritz
73 de M0BMU

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