[Lowfer] Need a VLF-LF Coax Choke

[C. Turner]

If you have one, a bunch of turns of coax on a core from a TV flyback 
transformer works:  It's easy to get 2-10mH that way and that's how I 
keep my shack and roof separate from each other.  When we've been 
junking CRT computer monitors, I've wielded the heat gun to free the 
core from the flyback transformer:  If they break, simply super-glue or 
epoxy them back together.  (If it's a close fit, there's negligible 
effect on the effective permeability.)

I used solid-core RG-58 and got a couple of mH while you could likely 
get well over 10mH with a reasonable number of turns of RG-174 - and 
that much inductance is useful down into ALPHA territory.  I wouldn't 
wind RG-6 on it or a toroid, however, as the center conductor can "cold 
flow" through the foam and short out.

As far using 50 ohms coax for the choke and RG-6 being 75, the mismatch 
and the loss of the RG-174 is irrelevant at LF - especially when using 
an active antenna.

Another place that I had to add a flyback core was on a USB cable that 
connected the SDR box to the computer:  Several millihenries on that 
kept the computer garbage out of the receiver, too.

Clint
KA7OEI



Bill & Becky wrote:
> Hi Group  I'm planning to buy a Clifton Labs Z1501d Combo Active antenna.  Does anyone have directions or info on making a coax choke.i.e
> materials, vendor's for a good LF Core??
>
> I need to make (2) on each end on the RG6 type coax.
>
> Thank you!
>
> Best DX
>
> Bill KB9IV