Sorry, the screwed up posting format ended up with me just sending this
to Don initially.
On 11/2/2010 6:18 PM, n8de@thepoint.net wrote:
> The '240' specifies the outer diameter of this 50-ohm coax .240 inches.
>
> http://awapps.commscope.com/catalog/andrew/product_details.aspx?id=1257
>
> The specifications say 1.5 db loss in 100 feet at 30mhz.
>
> Looks like it's better than most 50 ohm stuff being used by the average ham.
That would not be my take except for loss Vs size. I chose CNT-240 over
8X, but after using a 500 foot spool of CNT-240 I've changed my mind.
However it is good coax.
I have used a lot of CNT-240 and would not consider it for an
interconnect cable, or one that gets much movement/flexing.
CNT 240 is a semi rigid coax, or perhaps I should just call it a rather
stiff coax, the same size as RG-8X, but *NOWWEHERE* near as flexible.
Also the braid over foil shield is very fragile as far as the braid
goes. That makes installing connectors be they UHF, N, crimp, or clamp a
bit problematic. You do not cut the jacket off, you score it *lightly*
with a sharp knife or box cutter, then flex it slightly until the jacket
separates at the score mark, then pull the end piece off. It takes very
little to break the shield wires. IF you cut the jacket the braid wires
will just fall off. I have used CN240 as feed line from the remote
switch to the balun at the antenna and run the full legal limit on 40
with a low SWR. I did this for two reasons. One is the low cross
sectional area of the cable which is important in windy areas. The
other is the light weight and small size allow the end of the cable to
be incorporated into 5 or 6 turns on five, 2.4" cores for a relatively
light weight balun. However I found that the rigidity of the CNT-240
was just too much and it would end up breaking at either end at the
connector. I replaced it with RG-8X, LMR-400, and Davis BuryFlex (TM).
The 8X is flexible with a low enough cross sectional area that I've had
no breaks yet. Although not very flexible the LMR-400 is strong enough
I've had no problems with it either. Davis BuryFlex(TM) is both strong
and flexible although not as flexible as 8X. It's also very rugged, but
a bit heavier than the LMR-400. Due to the hostile environment I have
picked the Davis BuryFlex(TM) as the cable of choice. Although it also
makes a great interconnect cable, the 8X is just so much easier to work
with in tight places 8X with foil plus braid is my choice for the low
power interconnect coax. I do run Bury Flex from the amp to the patch
panel. From there to the tower and antennas it is mostly LMR-600 with
the exception of from the remote switches to sloping dipoles. I do use
the 600 all the way to the feed point on the 160 half sloper.
I've found the characteristics (rigidity, fragile center conductor and
shield) to make it unsuitable for most ham use ...at least for me.
Yes, 8X has a bit more loss, but 8X with shield plus braid is very
flexible, rugged, and easily handled. It's also much easier to install
connectors on 8X than CNT-240 and once installed they stand up better.
RG-8X makes a great interconnect cable with good shielding in an area
where loss is not usually considered very important. Loss is also
negligible on HF as long as the SWR is kept low. I'd not use it on 160
where the SWR rises quickly as you move from resonance. Nor would I use
8X on 75 unless operating with a very low SWR, or no more than a couple
hundred watts.
I've blown out N connectors on 75 including one double female due to low
impedance and high SWR at roughly 1200 PEP. The same conditions that
cause antenna tuners to be derated
But, but back to the original question. Yesm CNT-240 is good coax,
but... No, I don't think CNT-240 is a good coax to use for station
interconnect, BUT if I had a bunch of it I'd not hesitate to use
it...even as much as I've sworn at it because of that braid.
73
Roger (K8RI)
> 73
> Don
> N8DE
>
>
>
> Quoting Eugene Jensen<eugenejensen@nyc.rr.com>:
>
>> I have came by 2 spools of Andrew CNT-240-FR new cable and was thinking of
>> using for all my interconnect in my station and on to the outside box that
>> has all the runs of Hardline out to the tower. No run's would no longer than
>> 30 feet. Comments pro or con and anyone use thing this cable. Thanks Gene
>> K2QWD
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