[amsat-bb] Exciting Coax

Tue Jan 23 22:52:28 UTC 2018

Checking the datasheets for 9913, 9913F7 and LMR-400DB shows no real
world difference at UHF. 2-3 dB (round number) at 500 MHz per 100'.
Most ops don't have the gear to measure that small a difference
reliably.

Personally would not use 9913 due to it's problems.

Never had a problem with F7. Used two 130' runs of LMR-400DB for 7
years in FL. Replaced the UHF run with LDF4-50A 3 years in. Difference
was remarkable. UHF and up for any significant length is worth the
time and effort to install hardline. Checked the VHF side on the
hardline, doing an A/B comparison. Could not tell the difference.

Next time I've got the sitemaster out, I'll try measuring the loss of
two different pieces of F7. One brand new, the other 20 years old,
exposed to the elements most of that time. Stay tuned.

Bottom line is that good coax with correctly installed connectors,
weatherproofed well will perform identically. Measuring the difference
would be very hard.

OTOH, while less quality connectors and coax may measure the same at
instillation, will degrade faster. (I.E. moving pieces like antenna
whips)

Hardline is cheep these days. New OEM connectors can be had very
reasonably and are almost idiot proof to install. (Older ones need
special tools!)

I hate doing things twice. These things tend to fail at the worst time.

Personal opinion: this is where pennies and sweat count.

Blah, blah, blah, blah.....

Norm n3ykf

On Tue, Jan 23, 2018 at 5:00 PM, Burns Fisher <burns at fisher.cc> wrote:
> You know how the phone company used to keep paper-insulate thousand (or
> whatever) conductor, lead sheath cables dry inside?  Dry nitrogen pumped in
> from the central office, and extra bottles soldered in when leaks were
> found :-)
>
> On Tue, Jan 23, 2018 at 4:35 PM, Bob- W7LRD <w7lrd at comcast.net> wrote:
>
>> Some years ago I had some 9913, well sealed (so I thought).  Gradually the
>> swr crept up.  Without a thought, it got trashed and was replaced with LMR
>> 400.  Yes the idea of syringing water out of 9913 can work, also a constant
>> blower blowing into the 9913 can work, we can also insert small sponges
>> into the 9913 and replace them when necessary, or we can have the 9913
>> running down hill the whole way so the water can drip out (makes for a wet
>> ham shack), or we can build a roof over the 9913 to keep it out of the
>> moisture.  I could go on and on and I am sure many of you have even  more
>> creative ideas!  Am I being facetious?  Of course I am!  Hams can be
>> "cheap" bunch but there is place where a few extra bucks is money well
>> spent.  Anything above 70cm I use LMR600.  Just having fun today!
>>
>> 73 Bob W7LRD
>>
>> > On January 23, 2018 at 1:03 PM Greg D wrote:
>> >
>> >
>> >     Yes, but wet 9913 has a loss of ?
>> >
>> >     While searching for some hardline to replace my 9913 run some years
>> ago,
>> >     I resorted to drilling a hole in the bottom end of the cable, and
>> >     sucking out the water periodically with a syringe. It was not an
>> >     insignificant amount, and made a huge difference. Eventually found
>> >     someone with some leftover LDF4-50A hardline, and made a swap with
>> him
>> >     for a UHF beam antenna I had extra. Best deal on the planet.
>> >
>> >     If you can truly keep your 9913 dry inside, by all means, go for it.
>> >     But how do you know it's still dry? To me, it's not worth the
>> trouble.
>> >     If you like that size cable, I'd go with LMR-400 instead of either
>> >     variety of 9913.
>> >
>> >     Greg KO6TH
>> >
>> >
>> >     Glenn Miller - AA5PK wrote:
>> >
>> >         > > 9913F7 has nearly 10 dB attenuation/100 feet at 400 MHz.
>> 9913 has
>> > >         about 2.6 dB.
>> > >
>> > >         https://edesk.belden.com/products/techdata/metric/pdf/
>> 9913F7.pdf
>> > >         https://catalog.belden.com/techdata/EN/9913_techdata.pdf
>> > >
>> > >         I know which I'd choose.
>> > >
>> > >         -----Original Message----- From: Norm n3ykf Sent: Tuesday,
>> January 23,
>> > >         2018 1:09 PM To: Greg D Cc: <, amsat-bb at amsat.org mailto:
>> amsat-bb at amsat.org >, ;
>> > >         anderson58625 Subject: Re: [amsat-bb] Exciting Coax
>> > >         9913 is not 9913F7
>> > >
>> > >         Google is your friend, or perhaps if one is lazy, not.
>> > >
>> > >         Norm n3ykf
>> > >
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