[time-nuts] RG6 or LMR400 for GPS Antenna (Symmetricom 58532A and T-bolt)
Bob Stewart
bob at evoria.net
Fri Apr 22 20:45:56 EDT 2016
Hi Bob,
There's one thing I forgot to mention: the 5 yards of RG-174 that an active puck antenna usually has connected. That's probably a loss of more than 15DB right off the bat. But, if you're using a puck, you're probably using a short cable to your receiver, so you shouldn't cut the RG-174, otherwise you may overload the receiver's front-end.
Bob
--------------------------------------------
On Fri, 4/22/16, Bob Camp <kb8tq at n1k.org> wrote:
Subject: Re: [time-nuts] RG6 or LMR400 for GPS Antenna (Symmetricom 58532A and T-bolt)
To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
Date: Friday, April 22, 2016, 6:17 PM
Hi
Ok, well, let’s over think this a bit
more:
The antenna has 38 db
gain. It *might* have a noise figure of 0.7 db. A typical
modern GPS has < 2db noise figure. Anything over 6 db of
net
gain is “good enough”. On that
basis, a line loss of 32 db would be OK. Your 100 M of quad
shield at 21 db still gives you enough for three levels of
passive
splitter (8 outputs). Yes, it’s
not going to work with an old Oncore. It will work with the
new stuff at that level of splitting.
Bob
> On
Apr 22, 2016, at 6:45 PM, Ryan Stasel <rstasel at uoregon.edu>
wrote:
>
> Bob,
>
> Fair enough. I’ll
just stop worrying about it. =)
>
> I believe that number sounds like per 100
meter, not per 100 foot. Once I have the actual coax, as
someone suggested, I’ll just hook some ends up, and check
it. =)
>
> Sadly, I
don’t have an SA, so checking the attenuation might be
problematic. Though, could I not just use a function gen
(signal gen), and a scope? Trying to think… I don’t have
anything that’ll do 1.5Ghz though (or even close).
>
> Meh, overthinking…
what Paul said. =) I’m sure it’ll be fine. Will the
T-bolt actually complain about poor signal, or just not work
reliably? And lastly, I guess, there’s a setting on the
T-bolt to compensate for cable length. I assume that’s
compensation for antenna cable length? I know I can figure
that out with an SG and Scope, assuming the propagation
delay is what the spec sheet claims to be (most RG6 seems to
be right around 80%) (the home depot stuff seems to be
79%).
>
> -Ryan
Stasel
>
>> On Apr
22, 2016, at 14:38 , Bob Stewart <bob at evoria.net>
wrote:
>>
>> Hi
Ryan,
>>
>> For
the few years I've been on time-nuts, I understood the
consensus view to be to get a good quality RG-6QS satellite
cable. A few of the posts in this thread have made me
wonder if the consensus is changing, or if it's just too
much trouble to stand up to the crowd. I've got about
300 ft of CerroWire RG-6QS leftover from Home Depot in the
garage. I looked at the datasheet, and it's
confusing. For the attenuation at 1000MHz, they list
21.45DB per hundred with the superscript "1".
However there is nothing on the page noting whether that
"1" means per 100 feet or per 100 meters.
Looking at the competition it would appear that that's
per meter. Unfortunately, I don't have the right
connectors to hook it up to my SA to see. OTOH, 100 ft
runs from this spool don't show any noticeable (i.e.
problematic) attenuation of the signal. Maybe someone else
with a spool of RG-6 in the garage could give use some real
world attenuation figures at L1?
>>
>> But, rather than over-engineering
or over-angsting this issue, it's probably OK to just
pick one and use it. It's not likely to make any real
difference unless you have a run in the many hundreds of
feet.
>>
>> Bob
- AE6RV
>>
>>
--------------------------------------------
>> On Fri, 4/22/16, Ryan Stasel <rstasel at uoregon.edu>
wrote:
>>
>>
Subject: Re: [time-nuts] RG6 or LMR400 for GPS Antenna
(Symmetricom 58532A and T-bolt)
>> To: "Discussion of precise time
and frequency measurement" <time-nuts at febo.com>
>> Date: Friday, April 22, 2016, 4:09
PM
>>
>> 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>
>> 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>
>> 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>
>> 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>
>>>> 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>
>> 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>
>> 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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>>>>>>>
>>
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