Topband: Ground loop isolator that passes DC

Frank Krozel kg9hfrank at gmail.com
Fri Dec 3 19:00:13 EST 2021


Are you thinking of a Bias-T?
MFJ sells them with some of their tuners.
-73-  Frank    KG9H
kg9hfrank at gmail.com




> On Dec 3, 2021, at 5:53 PM, Andrew Ikin <andrew.ikin at btconnect.com> wrote:
> 
> Chuck Hutton,
> 
> Wrote on Dec. 3.
> 
> <Many years ago I saw some ground loop isolators that pass DC.
> That is exactly what I need so that power can be sent over coax feeds to
> preamp at the antenna.
> I cant find anything on eBay that mentions passing DC in an isolator. None
> of the isolators I have will pass DC.
> Does anyone know an isolator that passes DC? I would like to avoid building
> one.>
> 
> I guess what Chuck means, is a Ground loop due to the antenna end of the coax. screen being connected to Earth thus causing the feeder shield to become a loop antenna with the ground RF return path to Rx. Hence, resulting in excess noise pick-up.
> Normally common mode choke will be of benefit. But I would guess that Chuck has already tried this.
> 
> One option could be fit a 1:1 isolation transformer at the Rx input or into the Bias T. Then use a floating power supply to the drive antenna pre-amp.. A bias T that already has a common mode choke on the DC input would help too.
> The Antenna Interfaces manufactures by Wellbrook have this choke feature.
> 
> 73
> 
> Andrew  Ikin  G8LUG
> 
> _________________
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