[TowerTalk] 12V through coax to switch antennas remotely

N2TK, Tony tony.kaz at verizon.net
Tue Apr 3 11:15:59 EDT 2018


Tnx for the feedback and guidance.

N2TK, Tony


From: Don Havlicek [mailto:n8de at thepoint.net] 
Sent: Tuesday, April 03, 2018 11:08 AM
To: N2TK, Tony <tony.kaz at verizon.net>
Cc: towertalk at contesting.com
Subject: Re: [TowerTalk] 12V through coax to switch antennas remotely


Being the original "inventor" of this circuitry, I can attest to using 2.5 mh chokes for low bands.

For multi band use, I suggest TWO stages at each end, with two chokes, one 2.5 and one 100, as you noted.

Bypass caps of .001 seem adequate in all positions.

The coupling/isolating caps of .05 work well at both ends.

If building your own, remember to place electrolytic caps and reverse diodes across each relay.  

With good design before you begin, you will have little trouble getting things to work as it should.

Remember, there are FOUR states:

No voltage

Poitive voltage

Negative voltage

AC voltage (closes both relays)

Good luck!





Sent from my Verizon Wireless 4G LTE DROID

"N2TK, Tony" <tony.kaz at verizon.net <mailto:tony.kaz at verizon.net> > wrote:

Have a question about the values of the choke to keep RF from the relay and
the caps for coupling of the signal. In different products I see quite a bit
of different values of both components.

For the coupling caps I see values from .01-.2uf. It would seem increasing
the value of the cap reduces the Xc. And for the choke I see values of
100uh-2.5mh. And it seems increasing the value of the choke also increases

My application is for 160M and 80M only with receive antennas.

My question - does it really make a difference over the values listed above?
Do all the values offer enough Xc or Xl to not cause any problems?  Is there
really a recommended "good" value for the caps and coils? Even 100uh offers
1K ohms at 1.8MHZ and .1uf is .8 ohms.

Still learning.


N2TK, Tony


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