Topband: 12V through coax
grants2 at pacbell.net
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.
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?
> N2TK, Tony
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