Topband: (no subject)

[Rick Karlquist]

Tom Rauch wrote:
>> Can anyone give me a recommendation for the value of a
>> choke to use to isolate DC on a coaxial feed line on 160?
> Watch out for water in the connections! If the connectors
> get wet inside they will make noise.


I used to use DC on the coax to control my beverages.
As Tom says, if you get any water in the connectors, or
in the coax because a critter chewed on it, the noise will
be S9+.  If you do not have DC on the coax, water incursion has
to be severe before it takes you off the air.  I eventually
decided to bite the bullet and put all my coax in "conduit"
(actually sprinkler pipe, Sch. 200).

You can get cat 5 cable cheap/free if you scrounge it or
buy it on sale (3 cents a foot).  I just pulled cat 5 through
the conduit with the coax and then had 8 conductors to put
DC on.  Use a pair for each relay, rather than having a common
return conductor.  The common return conductor has too much
trouble with DC drop.  It is also a bad idea to use the coax
shield as the return conductor.

BTW, if you insist on putting DC on the coax, I have found
that negative DC is less susceptible to water noise.

Rick N6RK