<<<Which brings up the interesting point... Is there a manufacturer of these
sorts of things that tells you what the innards are?>>>
as far as i know, the pvc pipe guys don't say what's inside. i have not cut
one open to find out, however i have read about them getting fried and the
owner finding remnants of charred foam.
the coax with beads on it guess seems to have a reasonable likelyhood of
being correct to me.
There is one mfr that sells them as coax with uhf males, beads strung on the
coax and covered with shrink wrap. I like that assembly method better.
The coax I have seen used (in balanced tuners) is the teflon stuff (i think
it is RG303) which is about the same diam. as 58 and I bet that is what is
used in these pvc pipe isolators. Why not use 213 you may ask. Good
question and in fact when i make one that's what i use.
I suspect 303 is used because it can handle ham limit power but is small
enough to take small (cheaper) beads. the resulting product is smaller,
weighs less and is cheaper to ship.
But 213 handles much more voltage and is therefore more robust. I find it
is also easier to solder pl259s on it. But it needs bigger heavier beads
and the choke is going to wind up being larger and heavier. If you make it
for yourself this doesn't matter because you aren't shipping it to anyone
for profit.
So you can still make your own bead balun or unun and you have a choice of
coax and beads so you can make the mother of all isolators if you want to
and use a mix that focuses on a range of frequencies or even have 43 and 77
if you want to cover MW and SW as they aren't really hard to make. why
doesn't a business make them to order for hams? the market. custom
isolators would not sell to cheap hams. A kit maybe but not assembled.
Custom work for hams is normally limited to things that are difficult to
homebrew, are very expensive and the ham market for them is very very small.
Things that require expensive shop tools and parts that can't be purchased
in small quantities for example.
rob/k5uj
BTW if you have trouble soldering connectors you can buy a made up jumper of
a foot or more and clip split beads on it and still have your choice of
length, coax, connectors and bead mix.
You can get a connector on one end and have the other end open for a 1:1
balun.
<<<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>>>
_________________________________________________________________
Express yourself instantly with MSN Messenger! Download today - it's FREE!
http://messenger.msn.click-url.com/go/onm00200471ave/direct/01/
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|