[TowerTalk] DC and UNUNs

[Dave_K9NX]

At 12:29 PM 2/24/99 +0000, Pete Smith wrote:
>
>The standard 50/75 ohm UNUN has a short between the center conductor and
>ground for DC and low frequency AC, rendering it unusable with "cableless"
>antenna switches and other devices that send various DC and AC voltages
>down the coax.  Does anyone know of a design that does not have this
handicap?
>

I had the situation at one time in the past. I used a couple of really
large caps (.1uf @5KV, about the size of hockey pucks) that I found at a
swapfest. I put everything in a plastic box, Caps on either side of the
UNUN along with a high current rf choke to act as a DC path around the
caps. Seemed to work fine. Thing to remember with this approach is that
more than the voltage the caps need to be handle 8 to 10 Amps of RF current.

Dave K9NX



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