On 9/22/19 2:24 PM, Grant Saviers wrote:
The extra dielectric is going to increase the stray capacitance and the
PVC has loss. So expect a lower self resonant frequency and more loss.
I'm trying to make some high Q coils and conclude PVC pipe is a poor
form, even machined into a skeleton support. That's CW but I thought a
skeleton might be ok - NOT. I think grey PVC is grey in part to a clay
filler to make it UV resistant.
WHy not use some form of fiberglass tube? McMaster has it in all sizes
and shapes that would be suitable.
Yes, glass is somewhat lossy at microwave frequencies, but this is for a
HF antenna.
Or choose a traditional material like linen or paper phenolic.
Then a challenge is the grease should have very low moisture absorption
or the (I suspect) reason for it is negated or worse.
On my RG400/316/179 etc pigtail ends I apply a little red insulating
varnish which wicks into the braid amazingly far. The plan is to
prevent water from wicking. A downside of TFE coax is almost nothing
will stick to it. I also apply the varnish around all bulkhead
connector flanges and screws.
Grant KZ1W
On 9/22/2019 11:46 AM, Robert Harmon wrote:
I am making a current balun with a 2.4" OD Fair Rite core wound with
RG-400. PVC pipe is going thru the center and the RG-400
is routed thru the inside to SO-239's in PVC pipe caps on the ends.
I am planning on flooding the choke with dielectric grease
before completing the assembly and I'm trying to decide what
dielectric grease to use. What would you use ? Super Lube is supposed
to be a dielectric greae, would it be suitable ?
Bob
K6UJ
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