Topband: 12V through coax

Grant Saviers grants2 at
Sun Dec 8 11:55:52 EST 2019

For my relay reversible DHDL's used on 160 & 80m, I'm using 0.1uf 500v 
DC blocking capacitors, particularly the Kemet X7R MLCC SMD ones. 
digikey 399-6747-1-nd  There are enough parts for reversibility that I 
designed a small PCB with ExpressPCB so SMD parts made sense.

The RFC inductor choice depends on the current draw, for my design, all 
in was 92ma so a ferrite core design with a saturation current (10% 
reduction in L) of 120ma was ok at 450uH and an SRF of 4.5MHz.  From 
Wurth, SMD again. digikey 732-10766-1-ND

Automotive grade thick film 1/2 and 1w SMD resistors have very high 
surge ratings so are what I used for terminators.  If you have some old 
A-B carbon ones in your stash, they are a good choice.

These parts worked well at H40TT on two DHDLs and we had some T-storms 
nearby without damage.

Grant KZ1W

On 12/7/2019 20:59, tony.kaz--- via Topband wrote:
> I am making up new boxes for my Pennants. I will be switching directions
> with a relay in the box besides the terminating resistor and the choke.
> My question is what are the correct values of the components for feeding the
> 12V? I will be  using this only on 160 and 80M.
> For the coupling cap between the rig and antenna I have seen values from
> .01-.1uf. For the choke I have seen values from 100 uhy - 4.7 mh. On the 12V
> feed side I have seen values from .01 - .1 ufd.
> Is there a rule of thumb for the range of correct values for 80 and 160M?
> Thanks
> N2TK, Tony
> _________________
> Searchable Archives: - Topband Reflector

More information about the Topband mailing list