RE: [amsat-bb] Flexible Coax

["Edward R. Cole" <al7eb@xxxxxxxxxxxxx>]

At 08:07 AM 10/19/2002 -0400, Kenneth M. Brockel wrote:
>Just a thought, Has anybody ever tried the coax from the Wireman called
>"CQ Flexi 4XL"? It is there product number #102 and I have used it for
>several now and it works great. I have never had any problems with water
>ingression or other related problems. I use this product all over my
>shack for my VHF,UHF & HF installations. If interested, check out: 
>
>http://www.thewireman.com
>
>73, de Ken, N2SMT

I took a look at Wiremans site...listed many types of coax but I did not
find any specs for loss?
Belden and Times Microwave both publish complete specs for their cable so
you can make an informed decision.  CQ coax line might be good, just don't
have any experience with it or any numbers to compare with (i.e. "low-loss"
is kind of up to interpretation).

CoaxSeal is good in place of the Scotch-30 that I referred to, but a bit
more messy/sticky to remove.  I know some hams place a layer of
"electrical" Scotch-88 over the connector before a layer of coax seal so
that it can be removed easily, if needed.  Scotch-30 molds/fuses with
itself in the same manner but is a gray tape and peals off by simply
slicing it with a knife (but the cost is ouch!).  It must be protected with
a layer of electrical tape from mechanical wear and UV.

Not familiar with Bishops Tape.  Might be good.  Note everyone that gave
suggestions, used multi-layers (the secret to sealing).

At a conference this winter I was shown a cable product called Aircomm,
that uses an air-dielectric like 9913, but the polyethylene spacer is a
closed-cell plastic hexagonal shape that prevents migration of water or the
center conductor when bent tightly.  Quite flexible and comparable in loss
to LMR or Heliax cables of the same diameter.  They require special
connectors that Aircomm makes.  If on a ham budget it may be too much.

For my money LMR-400 works well in most applications up to 432 and for
short jumpers on 1296.  The closed-cell foam is impervious to moisture with
aluminum-foil shield bonded to the foam with a very dense copper braid
shield over it.

I agree for ground-burial to use a pvc conduit.  If you have rocky soil it
is mandatory.  If you ever need to remove it then you pull it out!  Hint
attach a cord to the last cable you pull in to serve as a pull-cord next
time you want to lay a new cable.

Testing your cables by cutting them off is one way, but you can just use a
power meter to measure the loss and SWR periodically.  Commercial folks
keep a cable log and make periodic measurements.  You can see from previous
measurements if there is trend toward deterioration.  Be suspicious if your
SWR starts climbing or fluctuates.  The commercial guys have access to
special test equipment like TDR's to test cables in-place.  A TDR will show
loss and impedance bumps and exactly where in the cable they exist.

Most hams can get away without much care with their cables (like on HF or
2m-FM), but if you are doing satellite or eme where every ounce of
performance counts, then it really pays off to use good products and good
construction.

Hope everyone on the list hasn't gotten bored with this topic...I'm done ;-)

Ed - AL7EB

----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org