RF problem
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Posted Thursday, October 25, 2012 11:03 AM
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Last Login: Thursday, October 25, 2012 2:04 PM
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Hi All,
I have a problem with RFI in my SDR-5000. When you connect a microphone Heil Yaesu MH31 or Heil HC6 and 8-pin socket in the bands 15-10m is the effect of RFI and machine gun during transmission. Does anyone have an undesirable phenomenon and knows how to remove it? The lower band is not present.
Slawomir SP6DLO


Slawomir SP6DLO
Post #6115
Posted Monday, January 7, 2013 8:11 PM
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Hi OM !

I had the problem of RFI feedback with ANY microphone pluged into the front panel 6 pin socket. No cure worked : ferrite beads, shielding and all kind of decoupling and conterpoise...

The only solution wich worked was to utilise the back panel balanced input on the Flex 5K. I utilise a Heil HM 5 mike : I rewired the cartridge symetrically with a 2 conductor + shield microphone cord.
The miracle was immediate ! even when running a kW.
No more RFI or RF into the audio wich produced that terrible echo due to processing time in the Flex. This balanced input has no preamp but pushing the mike gain up to 40 does it well. May be with some other microphone you'll need some preamplification...

Since I've completed this mod I get excellent audio report on all bands !

73', Phil.
Post #6270
Posted Wednesday, January 16, 2013 10:20 AM
Supreme Being

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RFI can come from various sources, common mode RFI , where RF actually is on the the shield of the coax and is being radiated into the shack. Various cures for a particular frequency, general cure is a common mode choke on the feed line BEFORE it gets to the shack.

http://kc.flexradio.com/KnowledgebaseArticle50471.aspx

Another way to get RF in the shack is near by antenna. Depending on the output power, a near by antenna , less than 30 feet for example will cause RFI in computers and everything else. Lost of chokes will help, but harder to cure.. To help find the source or just determine if there is an RFI problem, i use a simple field strength meter, which sets on top of my amp, should the little meter comes off the "0" peg, I have an issue.

Hope this little insight helps,


73,

Dudley

FlexRadio Systems Support
512-535-4713, Option 2
http://helpdesk.flexradio.com
Post #6298
Posted Friday, October 4, 2013 10:53 PM
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I was looking for something else and found this chain.

The reason for the RF is the mic input is balanced. If you have the shield on one input your are putting an antenna on one side of audio processor path. I fixed my problem, well sort of, by disconnecting the shield from the pin on the connector and hooking that pin back to chassis ground.

Not really the elegant solution but one that worked for me. I've read about the use of isolation transformers but have yet to try it.

Steve KC4SW


Steve Hanselman

Post #6875
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