Topband: 12V through coax

tony.kaz at tony.kaz at
Sun Dec 8 15:40:28 EST 2019

Hi Grant.
Tnx for the info. Putting up a DHDL like at H40TT is on my list. I want to install another BOG first for a comparison to my 3-el W1FV and two dual feed Pennants. I miss my 625' beverage I had in Joisey. I don't have the room here.
N2tK, Tony 

-----Original Message-----
From: Grant Saviers <grants2 at> 
Sent: Sunday, December 8, 2019 11:56 AM
To: tony.kaz at; topband at
Subject: Re: Topband: 12V through coax

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
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