[TowerTalk] RF Inquiry HI-Q Filter CF5KV

[Jim Lux]

----- Original Message -----
From: "Rob Atkinson, K5UJ" <k5uj at hotmail.com>
To: <towertalk at contesting.com>
Sent: Monday, February 21, 2005 7:35 AM
Subject: [TowerTalk] RF Inquiry HI-Q Filter CF5KV


> I think these are typically a PVC pipe with uhf females on the ends,
between
> them around 10 or 12 inches of small 50 ohm coax with teflon dielectric
and
> beads strung on it.  they are aka 1:1 ununs, common mode filters, and line
> isolators.  they stuff foam into the pipe so the beads don't clack
together
> and break.  that unfortunately also holds in heat.   so you can make one
> without too much trouble and i would leave off the foam and pvc, but it
> might wind up costing more to make it than to buy it (well, not the RF
> Inquiry ones).
> The chief advantage to making one is you get to design it to do well, what
> you want it to do.
> My experience with the mfrd. ones for example is their attenuation begins
to
> rapidly fall off below 7 mhz.  they do not do all that well on 75 m. and
are
> transparent at 160.  if you want one to work on 3.5 and 1.8 mhz you could
> make one with mix 77 beads but it might be cheaper to wind 20-30 turns of
> coax on a paint bucket or garbage can.


Which brings up the interesting point... Is there a manufacturer of these
sorts of things that tells you what the innards are?  Or that will build to
order (at a low cost..)?  Then you get the advantage of making your own
evaluation of expected performance, but also the quantity purchase of
components and assembly by someone who does a lot of it.  I'd much rather
have connectors installed by someone who does it 200 times a day than
someone (like me) who does it every few months.  It IS a craft or art, and
regular daily practice helps a lot.

Is this a market niche that is not being addressed?

Jim, W6RMK
>