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Author Topic: 40 meter rfi using mzr700 sony mini-disc recorder  (Read 1921 times)
KA7GKN
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Posts: 147




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« on: March 25, 2003, 10:42:12 PM »

I'll keep this brief. I have Behringer audio stuff. I use a sony MZR700 mini-disc unit to record and playback audio bites. All is wonderful except when I go to 40 meters. I record ok but yuk! rfi in the transmit audio!!!!
I use a sommer 10-40 meter multiband log beam at 70 feet, an Icom IC-775dsp an ACOM 2000A ...So, all high end gear and again, no problems no hum, no buzz, no rfi except on 40 with recording playbacks.

I also experienced the same 40 meter rfi using a panasonic rrqr80 digital recorder. I suspect the mini-disc and digital recorders have clocks around 7mhz and when transmit they go nuts!

of course I have double shielded cable and ferrite beeds

any thoughts?Huh?

thanks marty ka7gkn
ka7gkn@arrl.net
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N9FXW
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Posts: 1


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« Reply #1 on: May 04, 2003, 08:14:55 AM »

Hi Marty,

I have had the same problem you just pointed out here. The cure for me was a Audio Transformer I bought from a Local Grocery Store! Yes, I found a real nice ground loop isolator at a grocery store..it is a model-ES-034 made by SCOSCHE..It was made for use in an automobile stereo unit, real nice unit too, it has two transformers inclosed in a nice plastic case and rca connectors, female and male on both transformers for a stereo. So it works wonderful on a sound card, or a mini disk player. ( you can isolate both in and out)
Now I know your going to say that a ground loop is not the problem, that the 7mhz rf is getting directly into the mini disk, I thought the same thing....but after I tried this little $13.00 dollar unit, I was supprized that all my 40 meter rfi was gone in both my mini-disk, and my sound card.

Not sure if this helps at all, but thought it was worth sending...

73 my friend

Bill Hummer
N9FXW@arrl.et

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N4EKZ
Member

Posts: 15




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« Reply #2 on: May 10, 2003, 03:42:03 PM »

I recently cured a 40 meter tvi problem by making a 8-10 turn coil in the coaxial feedline... diameter app. 10". It worked when a combination of a lowpass filter on the rig and highpass filter on the TV did not.

Good luck. Oh, and if you do try it, would you let me know if it was successful for you or not. I'm just curious.

Thanks!

James (n4ekz@earthlink.net)
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