OT ... Coax DC Isolator

[John Saxon]

Many, many thanks for the fine comments and suggestions.  I am going with the MFJ-4712 which is the bias tee and the relay and switch...complete and ready-to-go.

Thanks again & 73,
John
K5ENQ
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[daleputnam]

With a pair of KAT100s and a pair of K2s, I need to send 12v up the openline feeder to control a latching relay at the top of the tower. The easiest way would be to run the dc on the feedline.and it would be even easier.. if the isolator would stop the dc from continuing on through the antenna.. that is also a dc short, inone of its configurations. I can insert the dc in the shack.. with a coax "T"... but there isn't a coax place at the top of the tower.Thoughts or ideas?

Have a great day,
 
 
--...   ...--
Dale - WC7S in Wy
 
 

> Date: Tue, 11 Feb 2014 15:53:05 -0800
> From: [hidden email]
> To: [hidden email]
> Subject: [Elecraft] OT ... Coax DC Isolator
>
> Many, many thanks for the fine comments and suggestions.  I am going with the MFJ-4712 which is the bias tee and the relay and switch...complete and ready-to-go.
>
> Thanks again & 73,
> John
> K5ENQ
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

     
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[Don Wilhelm-4]

Dale,

While you could put a bias Tee in each side of the balanced line to make
it work, you need to be aware of the impedance at the points in the
feedline where the DC is taken off.  The isolating inductance should
have 5 time (or greater) impedance at all frequencies of interest.

I assume you are running a multiband antenna, so it may be easier and
simpler just to 'bite the bullet' and run separate wire for the relay
control.

73,
Don W3FPR

On 2/11/2014 7:23 PM, Dale Putnam wrote:
> With a pair of KAT100s and a pair of K2s, I need to send 12v up the openline feeder to control a latching relay at the top of the tower. The easiest way would be to run the dc on the feedline.and it would be even easier.. if the isolator would stop the dc from continuing on through the antenna.. that is also a dc short, inone of its configurations. I can insert the dc in the shack.. with a coax "T"... but there isn't a coax place at the top of the tower.Thoughts or ideas?
>
>

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[Mike WA8BXN]

Hi Dale,

You can't inject DC into a coax feedline that carries RF with a simple T
coax connector.You have to use a bias T circuit as has been recently
discussed. It sounds like you have some coax from the rig to I assume a
balun of some sort that connects to you balanced line. You should be able to
adapt the bias T concepts to send DC thru the coax from the rig end to just
before the balun using a pair of bias Ts. Then use the bias T concept on the
other side of the balun to send DC through the balanced feedlilne to just
before the antenna, isolating the DC from the antenna and isolating the
relay from the RF.

73 - Mike WA8BXN

 

 

 

 

-------Original Message-------

 

From: Dale Putnam

Date: 2/11/2014 7:23:31 PM

To: [hidden email]

Subject: [Elecraft] Balanced feedline - DC Isolator

 

With a pair of KAT100s and a pair of K2s, I need to send 12v up the openline
feeder to control a latching relay at the top of the tower. The easiest way
would be to run the dc on the feedline.and it would be even easier.. if the
isolator would stop the dc from continuing on through the antenna.. that is
also a dc short, inone of its configurations. I can insert the dc in the
shack.. with a coax "T"... but there isn't a coax place at the top of the
tower.Thoughts or ideas?

 

Have a great day,

 

 

--... ...--

Dale - WC7S in Wy

 

 

 

 

> Date: Tue, 11 Feb 2014 15:53:05 -0800

> From: [hidden email]

> To: [hidden email]

> Subject: [Elecraft] OT ... Coax DC Isolator

>

> Many, many thanks for the fine comments and suggestions. I am going with
the MFJ-4712 which is the bias tee and the relay and switch...complete and
ready-to-go.

>

> Thanks again & 73,

> John

> K5ENQ
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[Dick Dickinson]

Are there possible precautions to take when running DC through a remote
antenna (coax) switch that may go to ground when the power is off?

 

 

Dick - KA5KKT

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