[time-nuts] RG6 or LMR400 for GPS Antenna (Symmetricom 58532A and T-bolt)

Mon Apr 25 00:21:14 UTC 2016

All,

So, went digging into my crawlspace just now, and found my RG6 that I thought was Belden. It’s actually Coleman 92003, which isn’t quad shield, but has a spec sheet that actually shows attenuation at 1500Mhz!

https://www.platt.com/CutSheets/Coleman%20Cable/92003.pdf

Interesting that there seems to be a “hump” between 1200 and 1500Mhz, as the attenuation jumps quite a bit, whereas it’s relatively flat between 700 and 1200Mhz. Then another bump above 2200Mhz, which is what this cable is rated to.

It’s sun resistant, which is good.

Anyone see any reason to not use this, and instead use some generic Quad Shield? It is gas injected, which supposedly improves it’s susceptibility to crushing, or other deformation of the insulator… but I can’t say I’ve seen this actually shown anywhere (I guess because it’s HDPE rather than LDPE insulator).

Thanks again everyone for all the input! It’s been pretty great to read this thread… even if it’s a bit “academic”. =P

-Ryan Stasel

On Apr 23, 2016, at 7:26 AM, billriches <bill.riches at verizon.net<mailto:bill.riches at verizon.net>> wrote:

RG6 for CCTV has copper shield and solid conductor.
RG6 for CATV has aluminum shield and solid conductor.
73,

Bill, WA2DVU
Cape May

-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Ryan Stasel
Sent: Friday, April 22, 2016 5:09 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] RG6 or LMR400 for GPS Antenna (Symmetricom 58532A and T-bolt)

Paul,

LOL! So, along those lines… one other question, since I can’t find my belden, I’ll be buying some coax. Anyone have any opinions about RG6 for CCTV vs CATV? My understanding is the CCTV version always has a solid copper center conductor (which in my mind would mean less voltage loss for the DC power going to the antenna), or I’m still overthinking it and should just go with standard RG6?

Thanks!

-Ryan Stasel

On Apr 21, 2016, at 13:04 , paul swed <paulswedb at gmail.com<mailto:paulswedb at gmail.com>> wrote:

Ryan a slight heads up.
Time Nuts is not about time accuracy as many people assume.
Its actually about the time we all waste looking for what we know we have.
We just measure that time accurately.
I do not use anti seize. Nothing against it just one more glob of
stuff to deal with.
If you use the heat shrink and it seals your done for my 2 cents.
Paul
WB8TSL

On Thu, Apr 21, 2016 at 1:07 PM, Ryan Stasel <rstasel at uoregon.edu<mailto:rstasel at uoregon.edu>> wrote:

All,

Really awesome answers, thanks!

For the sealing question, it was more of a “should I bother with
something like anti-seize” or the like on the actual thread-thread N
interface. The actual connector crimp, was planning on just using a
couple layers of the heat-shrink with adhesive. That is all going to
be internal to the mast anyway, so direct weather contact should be
minimal. It’s also on the side of my chimney, that gets very little
to no direct sun, so UV exposure should be minimal. But good note on that regard.

Pete, thank you very much for the info wrt the antenna and amp, and
also the fact the Trimble starter kit came with RG6. I’m going to see
what my seller wants for LMR400, but otherwise, I’ll just use RG6.
It’s certainly easier to handle. I did find some datasheets on the
stuff that Home despot (har har) sells (Southwire (
http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheetOEM80)).
I swear I have a box of Belden somewhere, but I can’t seem to find it.

Thanks again!

-Ryan Stasel

On Apr 21, 2016, at 06:02 , paul swed <paulswedb at gmail.com<mailto:paulswedb at gmail.com>> wrote:

With respect to sealing. Everyone has a method.
I use what I learned in the Navy. I could see how well the
connections
held
up in the worst conditions sun cold heat wet humidity...
Layer of rubber tape
scotch kote
Layer of plastic tape
scotch kote
If done well the connector releases just fine even after 5 or more
years. I
want to say 10. But then woodpeckers have a way of shortening the
life of connectors and coax.
The approach is really layers and the top to deteriorate over time...
But as I say everyone has their own approach.
Regards
Paul
WB8TSL

On Wed, Apr 20, 2016 at 9:03 PM, Ryan Stasel <rstasel at uoregon.edu<mailto:rstasel at uoregon.edu>>
wrote:

Bob/Paul,

Thanks. And there's the rub... Who knows what the specs are on "generic"
RG6 QS. I'll see what my seller wants for their LMR400, but
otherwise
yeah,
RG6 is just easier. I have both compression and crimp connectors
for it, including some RG6 N-connectors (yeah, they're probably for
LMR300, but they work).

Other question: any tips for the exterior N connection? I can
"weatherproof" the actual cable-connector crimp, but I'm curious if
anyone
bothers to "lube" the N connector to keep moisture from otherwise
seizing
it up.

Thanks!

Ryan Stasel
IT Operations Manager, SOJC
University of Oregon

Sent from my iPhone

On Apr 20, 2016, at 17:00, Bob Camp <kb8tq at n1k.org<mailto:kb8tq at n1k.org>> wrote:

Hi

RG-6 Quad Shield should be fine as long as it’s meeting the
published
specs. The advantage of LRM-400 is that you likely *know* where it
came from and what the specs are.

If you decide to split the antenna between GPSDO’s, a powered
splitter
is a really good idea. Each time you split another 2 ways, you
loose 3
db.
Get at least a 4 way splitter ….

Bob

On Apr 20, 2016, at 4:41 PM, Ryan Stasel <rstasel at uoregon.edu<mailto:rstasel at uoregon.edu>> wrote:

All,

I’m going to be installing a “permanent” antenna at home, and
will
need
a run of about 100ft to get from my workstation, to the mast I’ll
be mounting the antenna on (Symmetricom 58532A). I’ve seen some
indication that both the antenna and the Trimble Thunderbolt won’t
have any issues with running over 75ohm cable, but thought I’d ask
the “experts” whether I’d be better off with some RG6 Quad-shield,
or LMR400 (I’ve got a local source that doesn’t know what LMR400 is, or what it’s worth)?

Obviously I’d prefer to run and crimp RG6, but if I’d be better
off
with LMR400, I’d rather run that now than go back into the
crawlspace again. =)

Also, if it helps, I’ll probably have a Symmetricom/HP 58516A
at/near
the T-bolt so I can experiment with other GPS(DO)s as well
(especially
one
of the JRMiller boards I bought and built (but never finished) ages
ago).
Which brings the question, will the T-bolt provide the oomph needed
to power that splitter and the antenna over that length of cable?

Thanks!

-Ryan Stasel

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