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Slight hum (possible RF?) on the bnc connector

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Slight hum (possible RF?) on the bnc connector
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Regular poster
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Joined: 19 Aug 2004
Posts: 22
Location: Empire State,N.Y.

Post Slight hum (possible RF?) on the bnc connector Reply with quote
I've received Cyber MAX FM about a month ago and have been very pleased with it. The level of support I've received (due to my lack of understanding of some things) has been outstanding. Kudos to Marko and his crew for engineering a great product.

After a few minor items I got ironed out, there is one remaining thing I still seem to be experiencing.. a slight hum when the cybermax is on, and I don't believe it to be due to the power supply (a Pyramid PS-12 KX)
nor the audio line feeding the unit.

What I've experienced is a hum which I've managed to make go away by slightly jiggeling the antenna connecting to the back of the unit. My antenna is at least about 50-feet away from the unit, and on another side of my studio (which is actually located underground) and the Belden 9913 cable I'm using, I've tested for any shorts, that doesn't seem to be an issue.

I believe that because of the fact the hum will go away if Imanipulate the antenna cable, some RF feedback may be bleeding through (or back) to the unit somehow, but here is the weird thing; If I connect my SWR meter in line and run a cable out from the back of the cybermax first to the SWR and then connect the antenna to the output of the SWR, the hum is non-existant!

What I'm guessing is somehow by connecting the SWR meter, the power is being reduced somewhat, and not as much hot RF is coming right back out of the unit, and thus not causing a problem. Not being an engineer/techie type person, this is only conjecture on my part, but perhaps some of you who have used this device before or have a wider range of knowledge can impart some wisdom or insight on me?

Thanks in advance for any advice or thoughts.


Art is a lie that tells the truth." -- Pablo Picasso
> "Whatever Picasso said." --Radioboy
Mon Sep 13, 2004 2:48 am View user's profile Send private message Visit poster's website AIM Address Yahoo Messenger MSN Messenger ICQ Number
Site master
Site master

Joined: 18 Jan 2002
Posts: 3089
Location: Radio Land

Post Reply with quote
Putting SWR meter inline affects the SWR, that's probably it.
If nothing else, it adds to the total length of the cable.

Can you try to use that short piece of cable you use for SWR
and replace SWR with a double-sided connector/joint? Sometimes
cutting (extending) cable for a given length helps.

If your cable is flexible, you could try to spool it making it higher
inductance for any RF current coming back on the surface of the
cable. Some people even use ferrit cores to increase inductivity.

On a side note, leaving SWR inline won't cause any noticeable/
measurable effect on your range so if you don't need it elsewhere,
leave it in. Its a good feedback for you to be sure everyhing works,
too. Its best to have illuminated type since it looks cool in the dark.

Best regards,
Marko - PCS Electronics
Turn your PC into a FM radio station!
fax +386 4 2316 128
Mon Sep 13, 2004 9:28 am View user's profile Send private message Visit poster's website
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