Re: [time-nuts] GPS Antenna Feed Line Decision

[Bob kb8tq]

Hi

> On Sep 5, 2017, at 5:19 PM, Charles Steinmetz  wrote:
> 
> Mike wrote:
> 
>> I tried to see if there was any difference in the signal quality reported by 
>> Motorola UT+ and U-Blox Neo 6M (not timing grade but has a good 1PPS) over 
>> 30m of 2 different cable types.
>> I only had RG58(75 Ohm) and RG174(50 Ohm).
> 
> RG58 is 50 ohm.  RG59 is the "equivalent" 75-ohm cable.
> 
> Also, there has been some discussion of internal reflections with mixed 
> source/cable/load impedances.  Yeah, there is some, BUT:  The reflections are 
> generated at the *interfaces* between impedances, not down the length of any 
> one cable.  "F" connectors are 75 ohms, so if any part of the system uses 
> them, they will generate approximately the same reflections at the interfaces 
> to 50 ohm components (cable impedance and impedance of source and/or load) as 
> would using 75 ohm cable.
> 
> To eliminate reflections "entirely" (in reality, "mostly"), you need to use 
> 50 ohm [or 75, or other] components exclusively (source and load Z, all 
> connectors, and cable).
> 
> Yeah, I could pull my Tbolts apart and replace the F connectors with SMA, 
> BNC, TNC, N, UF, whatever.  But any degradation caused by using 75 ohm cable 
> and connectors is completely swamped by other errors in the system.  One of 
> my Tbolts runs with about 30 feet of RG6 quad, the other with about 150 feet 
> of the same, and all timing and positional solutions are indistinguishable 
> from a test mule I cobbled together that used only an adapter (about an inch 
> and a half long) between the antenna and the Tbolt.  In that case, the 
> "cable" delay was so low that any reflections were time-displaced from the 
> direct signal by such a small amount that it was meaningless for all 
> practical purposes.

The next “bump” is the input impedance of the receiver. If you dig into it, 
receivers front ends rarely have 
good return loss numbers. There are a number of reasons for this. One is that a 
“mismatched” front end is
usually a lower noise solution.  If the front end is 103 -123J ohms, 75 ohm vs 
50 ohm cable is not the big 
issue. To a lesser extent, the same thing may apply to the antenna preamp 
output ….

Bob


> 
> Best regards,
> 
> Charles
> 
> 
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Re: [time-nuts] GPS Antenna Feed Line Decision

[Charles Steinmetz]

Mike wrote:


I tried to see if there was any difference in the signal quality reported by 
Motorola UT+ and U-Blox Neo 6M (not timing grade but has a good 1PPS) over 30m 
of 2 different cable types.
I only had RG58(75 Ohm) and RG174(50 Ohm).


RG58 is 50 ohm.  RG59 is the "equivalent" 75-ohm cable.

Also, there has been some discussion of internal reflections with mixed 
source/cable/load impedances.  Yeah, there is some, BUT:  The 
reflections are generated at the *interfaces* between impedances, not 
down the length of any one cable.  "F" connectors are 75 ohms, so if any 
part of the system uses them, they will generate approximately the same 
reflections at the interfaces to 50 ohm components (cable impedance and 
impedance of source and/or load) as would using 75 ohm cable.


To eliminate reflections "entirely" (in reality, "mostly"), you need to 
use 50 ohm [or 75, or other] components exclusively (source and load Z, 
all connectors, and cable).


Yeah, I could pull my Tbolts apart and replace the F connectors with 
SMA, BNC, TNC, N, UF, whatever.  But any degradation caused by using 75 
ohm cable and connectors is completely swamped by other errors in the 
system.  One of my Tbolts runs with about 30 feet of RG6 quad, the other 
with about 150 feet of the same, and all timing and positional solutions 
are indistinguishable from a test mule I cobbled together that used only 
an adapter (about an inch and a half long) between the antenna and the 
Tbolt.  In that case, the "cable" delay was so low that any reflections 
were time-displaced from the direct signal by such a small amount that 
it was meaningless for all practical purposes.


Best regards,

Charles


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Re: [time-nuts] GPS Antenna Feed Line Decision

[Mike Cook]

> Le 5 sept. 2017 à 16:17, Bob kb8tq  a écrit :
> 
> Hi
> 
> 
> 
>> On Sep 5, 2017, at 6:06 AM, Hal Murray  wrote:
>> 
>> 
>> Clay Autery  said:
>>> I will use something better than RG-59 or RG-6 (even if it is only "better"
>>> in my opinion).
>> 
>> Crazy thought department.  Can you also run a parallel run of RG-6 and run 
>> some tests to see if you can measure the difference?
> 
> There is pretty much no experiment you could run that would show a difference 
> between the two. With a normal GPS, the “front end” of the radio is in the 
> antenna. The
> filtering and RF amplification there determine a lot of things. The cable is 
> just a 
> chunk of wire in the middle of the system. 

Agreed.
I tried to see if there was any difference in the signal quality reported by 
Motorola UT+ and U-Blox Neo 6M (not timing grade but has a good 1PPS) over 30m 
of 2 different cable types.
I only had RG58(75 Ohm) and RG174(50 Ohm) . I used the signal quality graphics 
of the respective manufacturers utilities winoncore12 and u-center. There was 
very little visible difference in the levels and reported resolved positions 
were as in the same ball park ( I never get exact replication after surveys ). 
Neither was there any significant difference in the 1PPS signal. I only have a 
2 channel scope so had to measure each seperateley against a standard (PRS10). 
The receivers 1PPS quantization swamps the difference in the cable delay (which 
I was able to differentiate when measured separately). 
It make sense as the GPS signals are very weak and the receivers are good at 
getting data out, so just throwing in a bit of extra attenuation and noise 
doesn’t phase them at all. 

I was thinking of doing a test with just a twisted pair…. 


> 
> Bob
> 
> 
>> 
>> 
>> -- 
>> These are my opinions.  I hate spam.
>> 
>> 
>> 
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have not got it. »
George Bernard Shaw

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Re: [time-nuts] GPS Antenna Feed Line Decision

[Bob kb8tq]

Hi



> On Sep 5, 2017, at 6:06 AM, Hal Murray  wrote:
> 
> 
> Clay Autery  said:
>> I will use something better than RG-59 or RG-6 (even if it is only "better"
>> in my opinion).
> 
> Crazy thought department.  Can you also run a parallel run of RG-6 and run 
> some tests to see if you can measure the difference?

There is pretty much no experiment you could run that would show a difference 
between the two. With a normal GPS, the “front end” of the radio is in the 
antenna. The
filtering and RF amplification there determine a lot of things. The cable is 
just a 
chunk of wire in the middle of the system. 

Bob


> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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Re: [time-nuts] GPS Antenna Feed Line Decision

[Hal Murray]

Clay Autery  said:
> I will use something better than RG-59 or RG-6 (even if it is only "better"
> in my opinion).

Crazy thought department.  Can you also run a parallel run of RG-6 and run 
some tests to see if you can measure the difference?


-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] GPS Antenna Feed Line Decision

[Wes]

I'm dating myself again but when I was employed at Hughes Aircraft we had an HP 
salesman dedicated to servicing just us.  So most everything came direct from 
them or Wiltron.  I liked traveling to HP events with him.  Hughes had a miserly 
expense reporting process.  His was, "I count the money in my wallet before I 
leave.  I count it again when I get back.  The difference is my expense."


Wes

.  On 9/4/2017 2:26 PM, Bob kb8tq wrote:

Hi

A lot depends on just which outfit you buy your attenuators from. There
certainly *are* outfits out there that supply you just over 20 db RL when
the spec is 20. They also don’t charge very much for their attenuators ….

Bob



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Re: [time-nuts] GPS Antenna Feed Line Decision

[Bob kb8tq]

Hi

A lot depends on just which outfit you buy your attenuators from. There 
certainly *are* outfits out there that supply you just over 20 db RL when
the spec is 20. They also don’t charge very much for their attenuators ….

Bob

> On Sep 4, 2017, at 4:53 PM, jimlux  wrote:
> 
> On 9/4/17 1:18 PM, Wes wrote:
>> 
>> 
>> If these are COTS attenuators, their own return loss is unlikely to be
>> 40 dB.  In fact grabbing an old HP catalog off my bookshelf (I'm dating
>> myself) I see a typical type N attenuator specified as 1.2 VSWR (~21 dB
>> RL).  I went on a quick "shopping" trip looking for an L-band, type N
>> bias tee.  I'll spare you the links, but typically they are also rated
>> at 1.2 VSWR.
>> 
> 
> Be careful, that's the "catalog spec" which means "what we can inexpensively 
> measure"..
> 
> It's like SMA connectors, which are specified at 1.05:1 or 1.1:1 and <0.3dB 
> loss.
> https://www.amphenolrf.com/connectors/sma.html
> 
> 
> In reality, they are a LOT better, it's just that measuring that in a 
> production environment is tough.
> I'd not want to set up a manufacturing test set that measured loss with an 
> uncertainty of 0.01 dB.
> 
> I'll point folks to:
> Jesch's paper in 1976
> 
> http://ieeexplore.ieee.org/document/6312234/
> 
> 
> 
> and then Maury
> https://www.maurymw.com/pdf/datasheets/5A-021.pdf
> 
> Someone at Maury did a paper which I can't find right now where they measured 
> a bunch of SMA connectors over hundreds if not thousands of mate/demate 
> cycles.
> 
> 
> RF cafe has a nice summary
> http://www.rfcafe.com/references/articles/Joe-Cahak/rf-connectors-cables-joe-cahak-6-2014.htm
> 
> 
> 
> 
> 
> 
>> Perhaps NIST, with an unlimited supply of tax money, splurged and
>> manufactured bias tees with >40 dB RL.  Maybe they did the same with the
>> attenuators.  We'll never know because they didn't provide an equipment
>> list or a measurement procedure.  They said nothing about the cable
>> either, other than they started with RG-58 and replaced it with "better"
>> cable.
> 
> But you could probably send an email to the author and ask.  NIST, like JPL, 
> is one of those places where people work forever.  Tom Otoshi, who wrote a 
> report on N connectors in 1963 cited by Maury, above, still works at JPL (I 
> think.. I confess I haven't seen him recently, he might have retired, but he 
> was certainly around in the last 10 years), and given the span of years, that 
> N connector work was probably when he was a just out of school engineer.
> 
> 
> 
> 
> 
> 
> 
>> 
>> A few words about cable, since that is what this discussion is all
>> about.  Cable, regardless of type and manufacturer, has its own RL, also
>> known in that business as Structural Return Loss (SRL) See:
>> https://www.belden.com/docs/upload/hdcarltp.pdf and
>> http://www.keysight.com/upload/cmc_upload/All/E206COMPTEST_METHOD.pdf.
>> 
>> At least the authors admit, "Thus far we have seen little difference in
>> the data."
>> 
>> Wes
>> 
>> 
>> On 9/3/2017 3:02 PM, Bill Byrom wrote:
>>> For precision timing measurements, I would think that there would be
>>> concern about the double reflections of a badly mismatched low loss
>>> transmission line (such as using 75 ohm line in a 50 ohm environment).
>>> The re-reflected signal will act similar to  multipath (as a delayed
>>> aggressor) on all satellite signals equally. The impedance mismatch
>>> delayed reflection aggressor could aggravate timing errors due to
>>> changes in temperature or stress in the cable. Whether this is important
>>> for you depends on how time-nutty you want to get.
>>> 
>>> See these papers:
>>> 
>>> Effects of Antenna Cables on GPS Timing Receivers:
>>> http://tf.boulder.nist.gov/general/pdf/1384.pdf
>>> 
>>> Absolute Calibration of a Geodetic Time Transfer System:
>>> http://xenon.colorado.edu/paperIrevise2.pdf
>>> --
>>> Bill Byrom N5BB
>>> 
>> 
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Re: [time-nuts] GPS Antenna Feed Line Decision

[jimlux]

On 9/4/17 1:18 PM, Wes wrote:



If these are COTS attenuators, their own return loss is unlikely to be
40 dB.  In fact grabbing an old HP catalog off my bookshelf (I'm dating
myself) I see a typical type N attenuator specified as 1.2 VSWR (~21 dB
RL).  I went on a quick "shopping" trip looking for an L-band, type N
bias tee.  I'll spare you the links, but typically they are also rated
at 1.2 VSWR.



Be careful, that's the "catalog spec" which means "what we can 
inexpensively measure"..


It's like SMA connectors, which are specified at 1.05:1 or 1.1:1 and 
<0.3dB loss.

https://www.amphenolrf.com/connectors/sma.html


In reality, they are a LOT better, it's just that measuring that in a 
production environment is tough.
I'd not want to set up a manufacturing test set that measured loss with 
an uncertainty of 0.01 dB.


I'll point folks to:
Jesch's paper in 1976

http://ieeexplore.ieee.org/document/6312234/



and then Maury
https://www.maurymw.com/pdf/datasheets/5A-021.pdf

Someone at Maury did a paper which I can't find right now where they 
measured a bunch of SMA connectors over hundreds if not thousands of 
mate/demate cycles.



RF cafe has a nice summary
http://www.rfcafe.com/references/articles/Joe-Cahak/rf-connectors-cables-joe-cahak-6-2014.htm







Perhaps NIST, with an unlimited supply of tax money, splurged and
manufactured bias tees with >40 dB RL.  Maybe they did the same with the
attenuators.  We'll never know because they didn't provide an equipment
list or a measurement procedure.  They said nothing about the cable
either, other than they started with RG-58 and replaced it with "better"
cable.


But you could probably send an email to the author and ask.  NIST, like 
JPL, is one of those places where people work forever.  Tom Otoshi, who 
wrote a report on N connectors in 1963 cited by Maury, above, still 
works at JPL (I think.. I confess I haven't seen him recently, he might 
have retired, but he was certainly around in the last 10 years), and 
given the span of years, that N connector work was probably when he was 
a just out of school engineer.










A few words about cable, since that is what this discussion is all
about.  Cable, regardless of type and manufacturer, has its own RL, also
known in that business as Structural Return Loss (SRL) See:
https://www.belden.com/docs/upload/hdcarltp.pdf and
http://www.keysight.com/upload/cmc_upload/All/E206COMPTEST_METHOD.pdf.

At least the authors admit, "Thus far we have seen little difference in
the data."

Wes


On 9/3/2017 3:02 PM, Bill Byrom wrote:

For precision timing measurements, I would think that there would be
concern about the double reflections of a badly mismatched low loss
transmission line (such as using 75 ohm line in a 50 ohm environment).
The re-reflected signal will act similar to  multipath (as a delayed
aggressor) on all satellite signals equally. The impedance mismatch
delayed reflection aggressor could aggravate timing errors due to
changes in temperature or stress in the cable. Whether this is important
for you depends on how time-nutty you want to get.

See these papers:

Effects of Antenna Cables on GPS Timing Receivers:
http://tf.boulder.nist.gov/general/pdf/1384.pdf

Absolute Calibration of a Geodetic Time Transfer System:
http://xenon.colorado.edu/paperIrevise2.pdf
--
Bill Byrom N5BB



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Re: [time-nuts] GPS Antenna Feed Line Decision

[Wes]

Not being as nutty as many on this list I only skimmed the papers you provided.  
Interesting and I will stand corrected regarding the use of 75 ohm cable in 50 
ohm systems in critical situations.  In situations like my own, I'm not going to 
fuss about it.


I realize this is NIST, the 1384 paper was probably peer-reviewed, and I 
shouldn't question, nevertheless fools rush in.


In the block diagram of Figure 3 and the accompanying text, is described 
installing attenuators to increase return loss (RL) to what is claimed to be 40 
dB.  Forty dB RL is in the realm of precision calibration standards. 
(https://www.maurymw.com/Precision/Precision_Fixed_Terminations.php) and it's 
not trivial to measure on a single device.  Here we have a cascaded of two 
attenuators, two bias tees and a length of cable.


If these are COTS attenuators, their own return loss is unlikely to be 40 dB.  
In fact grabbing an old HP catalog off my bookshelf (I'm dating myself) I see a 
typical type N attenuator specified as 1.2 VSWR (~21 dB RL).  I went on a quick 
"shopping" trip looking for an L-band, type N bias tee.  I'll spare you the 
links, but typically they are also rated at 1.2 VSWR.


Perhaps NIST, with an unlimited supply of tax money, splurged and manufactured 
bias tees with >40 dB RL.  Maybe they did the same with the attenuators.  We'll 
never know because they didn't provide an equipment list or a measurement 
procedure.  They said nothing about the cable either, other than they started 
with RG-58 and replaced it with "better" cable.


A few words about cable, since that is what this discussion is all about.  
Cable, regardless of type and manufacturer, has its own RL, also known in that 
business as Structural Return Loss (SRL) See: 
https://www.belden.com/docs/upload/hdcarltp.pdf and 
http://www.keysight.com/upload/cmc_upload/All/E206COMPTEST_METHOD.pdf.


At least the authors admit, "Thus far we have seen little difference in the 
data."

Wes


On 9/3/2017 3:02 PM, Bill Byrom wrote:

For precision timing measurements, I would think that there would be
concern about the double reflections of a badly mismatched low loss
transmission line (such as using 75 ohm line in a 50 ohm environment).
The re-reflected signal will act similar to  multipath (as a delayed
aggressor) on all satellite signals equally. The impedance mismatch
delayed reflection aggressor could aggravate timing errors due to
changes in temperature or stress in the cable. Whether this is important
for you depends on how time-nutty you want to get.

See these papers:

Effects of Antenna Cables on GPS Timing Receivers:
http://tf.boulder.nist.gov/general/pdf/1384.pdf

Absolute Calibration of a Geodetic Time Transfer System:
http://xenon.colorado.edu/paperIrevise2.pdf
--
Bill Byrom N5BB



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Re: [time-nuts] GPS Antenna Feed Line Decision

[Mark Spencer]

Although not time nuts related I believe this document speaks to some of the 
practical issues...

http://www.slac.stanford.edu/cgi-wrap/getdoc/slac-pub-6297.pdf



Mark Spencer


m...@alignedsolutions.com

> On Sep 3, 2017, at 4:56 PM, Mark Sims  wrote:
> 
> Real time nuts run phase stable cable (some well over $50 / foot) in climate 
> controlled ducts... which is all for nought unless you also climate control 
> the antenna.Which is all standard practice for precision geodesy.  Try to 
> keep it all with a milli-Kelvin or two.  Oh, and don't forget about Lord 
> Kelvin's sinister  step-sisters, humidity and pressure.  We won't get into 
> all his second-order cousins.
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Re: [time-nuts] GPS Antenna Feed Line Decision

[Bob kb8tq]

Hi

If you are running into a TBolt, it’s got an F connector and 75 ohm cable
spec’d already …. The 50 ohm / 75 ohm thing didn’t seem to bother 
Trimble. They certainly looked at it before going that way ….

Bob

> On Sep 4, 2017, at 12:31 AM, Ian Stirling  wrote:
> 
> On 09/02/2017 02:57 PM, Clay Autery wrote:
>> Having decision-making problems for the materials for my GPS main
>> feedline.  Going to use a TM LMR stock, just can't decide how big to go
>> with it...
> 
>  I have a modest 26dB antenna on a six feet pole of plastic piping, the 
> piping is
> strapped to my deck post. The antenna is probably ten feet high added to my 
> deck.
> I use a 40' RG6 that my Comcast chap overestimated, and he said, "Just use it 
> as you need."
> I measured the theoretical 1.4 SWR with as pretty much dead on. So long as my 
> GPS boxes
> agree with consumer time, as measured by the cheap "atomic" clocks from super 
> cheap vendors,
> I am happy with the set up. I have no need of phase and jitter, so long as 
> they average out.
> 
>  I just had to buy some "F" connectors and use adapters to convert to the GPS 
> 50 ohm inputs.
> Works like a charm. And good enough for me.
> 
> Best wishes,
> Ian, G4ICV, AB2GR
> --
> 
> 
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Re: [time-nuts] GPS Antenna Feed Line Decision

[Ian Stirling]

On 09/02/2017 02:57 PM, Clay Autery wrote:
> Having decision-making problems for the materials for my GPS main
> feedline.  Going to use a TM LMR stock, just can't decide how big to go
> with it...

  I have a modest 26dB antenna on a six feet pole of plastic piping, the piping 
is
strapped to my deck post. The antenna is probably ten feet high added to my 
deck.
I use a 40' RG6 that my Comcast chap overestimated, and he said, "Just use it 
as you need."
I measured the theoretical 1.4 SWR with as pretty much dead on. So long as my 
GPS boxes
agree with consumer time, as measured by the cheap "atomic" clocks from super 
cheap vendors,
I am happy with the set up. I have no need of phase and jitter, so long as they 
average out.

  I just had to buy some "F" connectors and use adapters to convert to the GPS 
50 ohm inputs.
Works like a charm. And good enough for me.

Best wishes,
Ian, G4ICV, AB2GR
--


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Re: [time-nuts] GPS Antenna Feed Line Decision

[jimlux]

On 9/3/17 3:41 PM, Charles Steinmetz wrote:

Attila wrote:


The supplies for LNAs are usually quite benign given two constraints:
   *   *   *
1) Low frequency (0Hz to bandwidth of signal) noise is low
   *   *   *
But 1) is a bit harder as it also includes 1/f noise, temperature,
(upstream) supply and load effects.


The LT3042 is better in this regard than anything short of a heroic
effort with discrete components, IF you use a larger-than-normal bypass
capacitor on the SET pin.  With Cset = 22uF, the noise density is
<20nV/sqrtHz down to 10Hz.  220uF is somewhat better, but not by a whole
decade because of the 1/f noise of the error/output amplifier.

The down side of a large Cset is that the power supply takes longer to
reach its final voltage.  A 5v supply reaches 90% voltage in about 25
seconds, and 99% in about 40 seconds.  A 10v supply takes twice as long,
and a 15v supply, three times.  The LT3042 does have a "fast start"
mode, which can reduce these times considerably (to ~0.5sec, ~1sec, and
~1.5sec, respectively) -- but still longer than usual for a regulated
supply.  For applications like continuously-on LNA power, there should
be no problem with any of these times.

The LT3042 is a bit of a pain to use, with its buried ground/heatsink
tab, but it is very good, and is the lowest noise fully integrated
regulator available, AFAIK.


I love that part - the PSRR is awesome up to MHz.  So many of those 
linear regulators are great at kHz, but not so hot up higher.

You want quiet, the 3042 is your friend.

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Re: [time-nuts] GPS Antenna Feed Line Decision

[Glenn Little WB4UIV]

I work with a broadcast station.
We just had a HD FM radio transmitter upgrade done.
In the upgrade package from GatesAir was a GPS antenna with a F fitting.
The provided feedline was RG-223 with a TNC on one end and a SMA on the 
other.

Also provided was a TNC to F adapter.
The new exciter has a GPS receiver installed to provide 1 PPS to the 
exciter.
There was also another piece of equipment that required 1 PPS and they 
provided an antenna and no feedline with that one.

Either piece would output 1 PPS, so the second antenna was not needed.

So you wonder what the "professionals" had in mind with the adapters.
Low bidder for the antenna??

73
Glenn
WB4UIV

On 9/3/2017 10:09 AM, Wes wrote:

On 9/2/2017 4:48 PM, Clay Autery wrote:

Thanks for the response...

Not sure why you and the other guy both recommended RG-6 75-Ohm cable
and F-connectors, when the nominal impedance of literally everything
else in the system is 50 Ohm, including the antenna and the HP GPS
Distribution Amp  And then adding N to F adapters?
As "the other guy" (I think) let me say that the impedance mismatch is 
immaterial and in my case I have one GPSDO with an SMA connector and 
another with a BNC and an antenna with an SMA.  So I "adapt" no matter 
what I do.  Because I understand the cascaded noise figure equations, 
I know that I don't need an active distribution amplifier to feed just 
these two devices, so a $5.00 "F" connector splitter is adequate. 
(https://www.markertek.com/product/201-232/2-way-2-4ghz-90db-satellite-splitter-dc-power-passing-to-one-port)

Doesn't make any sense unless one has $$ as a top priority, already has
a spool of RG-6 quad shield, etc...  but I specifically stated that $$
is not a top priority  Not really even in the top 5 or 10...

Then by all means you should use L-band waveguide. :-)

Wes

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--
---
Glenn LittleARRL Technical Specialist   QCWA  LM 28417
Amateur Callsign:  WB4UIVwb4...@arrl.netAMSAT LM 2178
QTH:  Goose Creek, SC USA (EM92xx)  USSVI LM   NRA LM   SBE ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"
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Re: [time-nuts] GPS Antenna Feed Line Decision

[Richard Solomon]

One of my "Hockey Puck" antennas has about 50' of RG-174 on it and I have

seen no problems locking up.


73, Dick, W1KSZ


Sent from Outlook<http://aka.ms/weboutlook>

From: time-nuts <time-nuts-boun...@febo.com> on behalf of William H. Fite 
<omni...@gmail.com>
Sent: Saturday, September 2, 2017 9:33:09 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] GPS Antenna Feed Line Decision

True, though a friend of mine used LMR-400.


On Saturday, September 2, 2017, Mark Sims <hol...@hotmail.com> wrote:

> Cheap RG-59 cable coax is more than sufficient for 50 .. 150+ feet (unless
> you are doing geodetic level GPS work).  It is recommended by several GPSDO
> makers.  The 50/75 ohm mismatch is not an issue.  No need to waste money on
> fancy pants artisanal luxury coax.
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Re: [time-nuts] GPS Antenna Feed Line Decision

[Charles Steinmetz]

Attila wrote:


The supplies for LNAs are usually quite benign given two constraints:
   *   *   *
1) Low frequency (0Hz to bandwidth of signal) noise is low
   *   *   *
But 1) is a bit harder as it also includes 1/f noise, temperature,
(upstream) supply and load effects.


The LT3042 is better in this regard than anything short of a heroic 
effort with discrete components, IF you use a larger-than-normal bypass 
capacitor on the SET pin.  With Cset = 22uF, the noise density is 
<20nV/sqrtHz down to 10Hz.  220uF is somewhat better, but not by a whole 
decade because of the 1/f noise of the error/output amplifier.


The down side of a large Cset is that the power supply takes longer to 
reach its final voltage.  A 5v supply reaches 90% voltage in about 25 
seconds, and 99% in about 40 seconds.  A 10v supply takes twice as long, 
and a 15v supply, three times.  The LT3042 does have a "fast start" 
mode, which can reduce these times considerably (to ~0.5sec, ~1sec, and 
~1.5sec, respectively) -- but still longer than usual for a regulated 
supply.  For applications like continuously-on LNA power, there should 
be no problem with any of these times.


The LT3042 is a bit of a pain to use, with its buried ground/heatsink 
tab, but it is very good, and is the lowest noise fully integrated 
regulator available, AFAIK.


Best regards,

Charles


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Re: [time-nuts] GPS Antenna Feed Line Decision

[Mike Naruta AA8K]

On 09/03/2017 06:02 PM, Bill Byrom wrote:

For precision timing measurements, I would think that there would be
concern about the double reflections of a badly mismatched low loss
transmission line (such as using 75 ohm line in a 50 ohm environment).
The re-reflected signal will act similar to  multipath (as a delayed
aggressor) on all satellite signals equally. The impedance mismatch
delayed reflection aggressor could aggravate timing errors due to
changes in temperature or stress in the cable. Whether this is important
for you depends on how time-nutty you want to get.

See these papers:

Effects of Antenna Cables on GPS Timing Receivers:
http://tf.boulder.nist.gov/general/pdf/1384.pdf

Absolute Calibration of a Geodetic Time Transfer System:
http://xenon.colorado.edu/paperIrevise2.pdf
--
Bill Byrom N5BB




Thank you Bill, very interesting.


Wes, that waveguide is looking better all the time.

It will be difficult to control the temperature of it though.


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Re: [time-nuts] GPS Antenna Feed Line Decision

[Bill Byrom]

For precision timing measurements, I would think that there would be
concern about the double reflections of a badly mismatched low loss
transmission line (such as using 75 ohm line in a 50 ohm environment).
The re-reflected signal will act similar to  multipath (as a delayed
aggressor) on all satellite signals equally. The impedance mismatch
delayed reflection aggressor could aggravate timing errors due to
changes in temperature or stress in the cable. Whether this is important
for you depends on how time-nutty you want to get.

See these papers:

Effects of Antenna Cables on GPS Timing Receivers:
http://tf.boulder.nist.gov/general/pdf/1384.pdf

Absolute Calibration of a Geodetic Time Transfer System:
http://xenon.colorado.edu/paperIrevise2.pdf
--
Bill Byrom N5BB


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Re: [time-nuts] GPS Antenna Feed Line Decision

[Attila Kinali]

On Sun, 3 Sep 2017 12:32:31 -0500
Clay Autery  wrote:

> - I saw in some aviation references where pilots claimed that they
> achieved "better performance" by running their antennas at higher
> voltages.  (Overclocking the antenna amp?  Who knows.)  But it piqued my
> interest, especially since the PCTEL antenna I have will "run" from
> below 5VDC through 12 VDC and has an even higher survival voltage.

There are a couple of LNA chips around that work at 3.3V and 5V.
Usually they exhibit better performance (higher amplification and
less degradation with frequency) with higher voltage. You should
not run those chips at higher voltage then spec'ed, though.

An antenna with a 5V-12V rating has most likely a local LDO, thus
it will not benefit from higher voltage, beside having more heat
generated localy, which might or might not stabilize temperature.

> Bottom Line: I'll read/research/design and build until I come up with a
> supply that meets my needs.  Just off the top of my head, a linear
> supply that charges a battery or batteries that provide the top voltage
> or voltages in multiple ranges which are then regulated/filtered to
> provide dead flat DC at the desired levels.
> I am not an engineer or an expert of any kind.  I'll have to go learn
> all this.  

The supplies for LNAs are usually quite benign given two constraints:
1) Low frequency (0Hz to bandwidth of signal) noise is low
2) High frequency noise within the signal range is low.

It is usually quite easy to achieve 2) by using some L-C filter.
But 1) is a bit harder as it also includes 1/f noise, temperature,
(upstream) supply and load effects. 


Attila Kinali

-- 
You know, the very powerful and the very stupid have one thing in common.
They don't alters their views to fit the facts, they alter the facts to
fit the views, which can be uncomfortable if you happen to be one of the
facts that needs altering.  -- The Doctor
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Re: [time-nuts] GPS Antenna Feed Line Decision

[Mark Spencer]

Hi.

The last time I looked at upgrading my GPS antenna feed line (I'm currently 
using RG58 style cable) I spent some time looking at the temperature vs 
propagation delay characteristics of various cables.

I also picked up a spool of cloned "LMR400 style" cable but ended up using that 
for my amateur radio hobby.  If I was going to throw more money at my Time Nuts 
GPS feed line I'd probably look for a "hard line" style cable with a favourable 
temperature vs propagation delay characteristic.   For a basic installation I 
expect I would just use RG6 style cable.

Good luck.

Mark S

m...@alignedsolutions.com
604 762 4099

> On Sep 3, 2017, at 9:57 AM, Clay Autery  wrote:
> 
> Thank you for your response.  Again, money is not the issue or
> priority.  Knowing that I am getting the best signal within reason (my
> reason   )
> Tangentially, you have provided me with the information I require.  As I
> do not know what I will hang off the end of that antenna in the future
> and I am in fact going to be doing some measurement/experimentation, I
> will use something better than RG-59 or RG-6 (even if it is only
> "better" in my opinion).
> 
> I am an incurable over-engineer... and this IS "Time NUTS" after all. 
> 
> 
> Thank to you AND to ALL who have made recommendations thusfar
> especially the ones with whom I disagree.  Those are the recommendations
> that keep me from completely abandoning rational decision-making.   grin>
> 
> 73,
> 
> __
> Clay Autery, KY5G
> MONTAC Enterprises
> (318) 518-1389
> 
>> On 9/2/2017 3:27 PM, Mark Sims wrote:
>> Cheap RG-59 cable coax is more than sufficient for 50 .. 150+ feet (unless 
>> you are doing geodetic level GPS work).  It is recommended by several GPSDO 
>> makers.  The 50/75 ohm mismatch is not an issue.  No need to waste money on 
>> fancy pants artisanal luxury coax.
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Re: [time-nuts] GPS Antenna Feed Line Decision

[Clay Autery]

Thank you for your response.  Again, money is not the issue or
priority.  Knowing that I am getting the best signal within reason (my
reason   )
Tangentially, you have provided me with the information I require.  As I
do not know what I will hang off the end of that antenna in the future
and I am in fact going to be doing some measurement/experimentation, I
will use something better than RG-59 or RG-6 (even if it is only
"better" in my opinion).

I am an incurable over-engineer... and this IS "Time NUTS" after all. 


Thank to you AND to ALL who have made recommendations thusfar
especially the ones with whom I disagree.  Those are the recommendations
that keep me from completely abandoning rational decision-making.  

73,

__
Clay Autery, KY5G
MONTAC Enterprises
(318) 518-1389

On 9/2/2017 3:27 PM, Mark Sims wrote:
> Cheap RG-59 cable coax is more than sufficient for 50 .. 150+ feet (unless 
> you are doing geodetic level GPS work).  It is recommended by several GPSDO 
> makers.  The 50/75 ohm mismatch is not an issue.  No need to waste money on 
> fancy pants artisanal luxury coax.
>
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Re: [time-nuts] GPS Antenna Feed Line Decision

[Clay Autery]

Actually haven't settled on an exact solution yet, Gilles.  The power
supply will likely become part of the observations/experiment that
prompted me to use the external supply in the first place.

- All of the devices WANT to supply the antenna.  2 are nominal 5VDC, 1
supplies nominal 3.3VDC...  so I was going to have to use DC blocking
anyway.  The HP amp provides a load resistor (to fool the devices
hopefully) and DC blocking on all ports.  Thus, I get to choose how I
provide the DC power to the PCTEL antenna.

- I saw in some aviation references where pilots claimed that they
achieved "better performance" by running their antennas at higher
voltages.  (Overclocking the antenna amp?  Who knows.)  But it piqued my
interest, especially since the PCTEL antenna I have will "run" from
below 5VDC through 12 VDC and has an even higher survival voltage.

Thus was born the secondary goal of finding out if there is anything to
these reports.  IF I can control the voltage supplied on a (preferably
constant) variable basis to the antenna, I can construct an experiment
to evaluate IF there are performance increase/degradation and in what
ways  over a wide range of voltages.  IF it pans out on MY antenna,
I will likely have to expand it to additional antennas.

BUT, in answer to your direct question:  Right now I do not know.  I do
know a FEW things.

1) It certainly will not be a switching PS.
2) While I would love to use a super-expensive "lab-grade" supply, I
would actually like to engineer a solution that I can integrate into the
shack/lab on a permanent basis for use in normal ops and future projects.
3) I'm leaning in the same direction that I am for powering everything
in my house that actually wants DC current  some combination of
linear power supplies and batteries.
4) A lot of this is simply an excuse to engage in an academic exercise
in order to learn/play.  

Bottom Line: I'll read/research/design and build until I come up with a
supply that meets my needs.  Just off the top of my head, a linear
supply that charges a battery or batteries that provide the top voltage
or voltages in multiple ranges which are then regulated/filtered to
provide dead flat DC at the desired levels.
I am not an engineer or an expert of any kind.  I'll have to go learn
all this.  

73,

__
Clay Autery, KY5G

On 9/3/2017 1:55 AM, Clemgill wrote:
> Hi Clay,
> Intersting subject.
> What design for ultra stable/clean power supply are you using please ?
> Thx,
> Gilles.
>
>> On Sep 2, 2017, at 22:47, Clay Autery  wrote:
>>
>> PCTEL GPS-TMG-HR-26NCM Antenna. 
>> http://www.neobits.com/pctel_maxrad_gps_tmg_hr_26ncm_high_rejection_gps_p2769137.htm
>>
>> Can't say what the gain tolerances are, but it appears to be a pretty
>> decent quality part.
>>
>> The distribution amp is an HP 58516A GPS L1 Distribution Amp with the
>> external power supply tap which will be fed with an ultras stable/clean
>> adjustable linear power supply.  As I understand it, this is a unity
>> gain amp, so there should be little to no insertion loss or distro losses.
>>
>> The distribution amp will be mounted near the devices such that amp to
>> device jumpers will all be < 1 meter/3.28 feet.  Likely a lot less.  ALL
>> Times N-connectors until reaching a connector TM doesn't make.
>>
>> __
>> Clay Autery, KY5G
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Re: [time-nuts] GPS Antenna Feed Line Decision

[Bob kb8tq]

Hi

The bigger issue with unsuspended cables is wind and weather. It’s not just a 
static weight issue.
When the wind blows the cable jerks around. You very much want to tie it off 
against the mast. You
also want a strain relief loop at the antenna. 

Bob


> On Sep 3, 2017, at 10:44 AM, Artek Manuals  wrote:
> 
> Clay
> LMR-400 is probably the best compromise , I doubt you will see any useful 
> improvement in system performance as a result of the improved 1.5db loss 
> characteristics of the larger cables. Losses due to atmospherics, 
> ionospherics and multi-path will be an orders of magnitude  higher than the 
> additional 1.5 db of signal improvement with the larger cables. We are not 
> talking comms with some guy in a space suit on Mars here :-)
> 
> AS for walking the mast  up I have done a number of installations of this 
> sort and the use of a block and tackle at the eve point is not difficult, and 
> will be appreciated more and more the older you get .  Mechanical 
> multiplicative advantages are easy to implement. Don't use block & tackles 
> which can pivot since depending on the weave/braid of the rope they will 
> twist around and bind.
> 
> Dave
> manu...@artekmanuals.com
> 
> On 9/2/2017 7:48 PM, Clay Autery wrote:
>> Thanks for the response...
>> 
>> Not sure why you and the other guy both recommended RG-6 75-Ohm cable
>> and F-connectors, when the nominal impedance of literally everything
>> else in the system is 50 Ohm, including the antenna and the HP GPS
>> Distribution Amp  And then adding N to F adapters?
>> 
>> Doesn't make any sense unless one has $$ as a top priority, already has
>> a spool of RG-6 quad shield, etc...  but I specifically stated that $$
>> is not a top priority  Not really even in the top 5 or 10...
>> 
>> The whole point of this exercise is to put up a semi-permanent SINGLE
>> antenna/feed-line install that will supply all 4 ports of the HP amp
>> with the least compromised signal within reason 4 now, and 8
>> whenever I can find the HP 8-way distro amp with external power input.
>> 
>> Strain relief solution:  Really depends upon which cable stock I end up
>> using  Obviously, the larger the cable, the more weight will be
>> suspended under the antenna (approx. 38 feet, depending on where I pull
>> the cable out of the mast at the bottom.  (The mast is on a tilt-base of
>> my own construction  which brings up a valid consideration.  it is
>> already a chore to walk the mast up manually.  The more weight added at
>> the top and inside the mast, the more difficult a manual walk-up will
>> be.  I'd prefer to keep this a manual tilt for now...  at least until I
>> add the tri-band vertical dipole)
>> 
>> LMR-400 would be less than 4 lbs total weight...  I'd likely suspend the
>> cable by the connector alone. (although, it wouldn't be JUST the
>> crimp...  The connector would have at a minimum, 1 layer of
>> adhesive-lined shrink tube... probably 2, with the second, overlapping.
>> Then a nice wrap of self-fusing tape and then electrical tape over that.
>> Even LMR-600 could be suspended by the connector alone, at 5 lbs max in
>> the 38 foot max vertical section.
>> I do have several methods of secondary suspension within the top (and/or
>> second) mast section though if I decide I need it.
>> 
>> Also prefer to keep all the connectors N-type as much as possible since
>> that is the station standard.
>> 
>> 73,
>> 
>> __
>> Clay Autery, KY5G
>> 
>> On 9/2/2017 6:07 PM, Mike Naruta AA8K wrote:
>>> Clay, you may wish to consider using a quality RG-6 with F
>>> connectors.  Grounding blocks are readily available for the base of
>>> your mast and the entrance to your house.  Also, off-the-shelf
>>> over-voltage protectors (Zap-Tech) are available. I even found an
>>> F-to-N adapter for the antenna on Amazon.  Watch out for the ones with
>>> metric N threads though.
>>> 
>>> For my 25 meter run I was going to use an existing one inch Heliax,
>>> but pulled a run of Belden RG-6 instead after learning that Trimble
>>> used RG-6.
>>> 
>>> It worked well directly connected to a Trimble Thunderbolt; now it is
>>> connected to a Symmetricon 58535A GPS L1 distribution amplifier.
>>> 
>>> 
>>> My Blitzortung System Red station has been running fine in my attic
>>> (Michigan) on a Motorola 97 Oncore patch antenna fastened against the
>>> roof underside.  It is looking through wood, shingles, and nails (and
>>> a tree and antennas and utility lines).
>>> 
>>> 
>>> How are you planning to do strain-relief on the vertical run of coax
>>> inside of your mast?
>>> 
>>> 
>>> Mike - AA8K
>>> 
>>> ___
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>> To 

Re: [time-nuts] GPS Antenna Feed Line Decision

[Artek Manuals]

Clay
LMR-400 is probably the best compromise , I doubt you will see any 
useful improvement in system performance as a result of the improved 
1.5db loss characteristics of the larger cables. Losses due to 
atmospherics, ionospherics and multi-path will be an orders of 
magnitude  higher than the additional 1.5 db of signal improvement with 
the larger cables. We are not talking comms with some guy in a space 
suit on Mars here :-)


AS for walking the mast  up I have done a number of installations of 
this sort and the use of a block and tackle at the eve point is not 
difficult, and will be appreciated more and more the older you get .  
Mechanical multiplicative advantages are easy to implement. Don't use 
block & tackles which can pivot since depending on the weave/braid of 
the rope they will twist around and bind.


Dave
manu...@artekmanuals.com

On 9/2/2017 7:48 PM, Clay Autery wrote:

Thanks for the response...

Not sure why you and the other guy both recommended RG-6 75-Ohm cable
and F-connectors, when the nominal impedance of literally everything
else in the system is 50 Ohm, including the antenna and the HP GPS
Distribution Amp  And then adding N to F adapters?

Doesn't make any sense unless one has $$ as a top priority, already has
a spool of RG-6 quad shield, etc...  but I specifically stated that $$
is not a top priority  Not really even in the top 5 or 10...

The whole point of this exercise is to put up a semi-permanent SINGLE
antenna/feed-line install that will supply all 4 ports of the HP amp
with the least compromised signal within reason 4 now, and 8
whenever I can find the HP 8-way distro amp with external power input.

Strain relief solution:  Really depends upon which cable stock I end up
using  Obviously, the larger the cable, the more weight will be
suspended under the antenna (approx. 38 feet, depending on where I pull
the cable out of the mast at the bottom.  (The mast is on a tilt-base of
my own construction  which brings up a valid consideration.  it is
already a chore to walk the mast up manually.  The more weight added at
the top and inside the mast, the more difficult a manual walk-up will
be.  I'd prefer to keep this a manual tilt for now...  at least until I
add the tri-band vertical dipole)

LMR-400 would be less than 4 lbs total weight...  I'd likely suspend the
cable by the connector alone. (although, it wouldn't be JUST the
crimp...  The connector would have at a minimum, 1 layer of
adhesive-lined shrink tube... probably 2, with the second, overlapping.
Then a nice wrap of self-fusing tape and then electrical tape over that.
Even LMR-600 could be suspended by the connector alone, at 5 lbs max in
the 38 foot max vertical section.
I do have several methods of secondary suspension within the top (and/or
second) mast section though if I decide I need it.

Also prefer to keep all the connectors N-type as much as possible since
that is the station standard.

73,

__
Clay Autery, KY5G

On 9/2/2017 6:07 PM, Mike Naruta AA8K wrote:

Clay, you may wish to consider using a quality RG-6 with F
connectors.  Grounding blocks are readily available for the base of
your mast and the entrance to your house.  Also, off-the-shelf
over-voltage protectors (Zap-Tech) are available. I even found an
F-to-N adapter for the antenna on Amazon.  Watch out for the ones with
metric N threads though.

For my 25 meter run I was going to use an existing one inch Heliax,
but pulled a run of Belden RG-6 instead after learning that Trimble
used RG-6.

It worked well directly connected to a Trimble Thunderbolt; now it is
connected to a Symmetricon 58535A GPS L1 distribution amplifier.


My Blitzortung System Red station has been running fine in my attic
(Michigan) on a Motorola 97 Oncore patch antenna fastened against the
roof underside.  It is looking through wood, shingles, and nails (and
a tree and antennas and utility lines).


How are you planning to do strain-relief on the vertical run of coax
inside of your mast?


Mike - AA8K

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--
Dave
manu...@artekmanuals.com
www.ArtekManuals.com


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Re: [time-nuts] GPS Antenna Feed Line Decision

[Bob kb8tq]

Hi

There is no need to feed the 58516 or the antenna with any sort of super power 
supply.
It’s just a simple RF amplifier in there. It’s designed to be feed off of the 
bias supply coming out of a GPS module. If a module has a dedicated
78L05 style regulator on it, it’s one of the better ones ….

Bob

> On Sep 3, 2017, at 2:55 AM, Clemgill  wrote:
> 
> Hi Clay,
> Intersting subject.
> What design for ultra stable/clean power supply are you using please ?
> Thx,
> Gilles.
> 
>> On Sep 2, 2017, at 22:47, Clay Autery  wrote:
>> 
>> PCTEL GPS-TMG-HR-26NCM Antenna. 
>> http://www.neobits.com/pctel_maxrad_gps_tmg_hr_26ncm_high_rejection_gps_p2769137.htm
>> 
>> Can't say what the gain tolerances are, but it appears to be a pretty
>> decent quality part.
>> 
>> The distribution amp is an HP 58516A GPS L1 Distribution Amp with the
>> external power supply tap which will be fed with an ultras stable/clean
>> adjustable linear power supply.  As I understand it, this is a unity
>> gain amp, so there should be little to no insertion loss or distro losses.
>> 
>> The distribution amp will be mounted near the devices such that amp to
>> device jumpers will all be < 1 meter/3.28 feet.  Likely a lot less.  ALL
>> Times N-connectors until reaching a connector TM doesn't make.
>> 
>> __
>> Clay Autery, KY5G
>> 
>>> On 9/2/2017 3:26 PM, Bob kb8tq wrote:
>>> Hi
>>> 
>>> A lot depends on what comes after the feed cable. The “disto amp” will 
>>> determine 
>>> a lot. You likely need 10 db of net gain in front of it to keep things 
>>> running ok. For an
>>> antenna that is *really* 26 db (as opposed to 26 db +/- 6 db), that would 
>>> come out to
>>> 16 db of feed line loss. This isn’t a terribly surprising outcome. The 
>>> antennas are designed
>>> for installations that run 150’ or more of coax ….
>>> 
>>> Bob
>>> 
 On Sep 2, 2017, at 2:57 PM, Clay Autery  wrote:
 
 Having decision-making problems for the materials for my GPS main
 feedline.  Going to use a TM LMR stock, just can't decide how big to go
 with it...
 
 26 dB 5vdc antenna on top of a 38 foot mast.  Feed will come down the
 inside/center of mast and exit near the bottom, thence routed through a
 window and to the GPS distro amp. Antenna will feed GPSDO, NTP Server,
 Blitzortung System Blue station, and one other device TBD.
 
 Just cannot decide how big to go with the antenna to distro amp feed... 
 Assuming 50 feet total (38' mast + 12 feet to amp in shack) @ 1800 MHz
 (closest to 1725 MHz), here are the losses from just this piece
 (ignoring the amp to device jumpers):
 
 -240 = 5.45 dB XXX - too much loss?
 -400 = 2.85 dB
 -500 = 2.30 dB  XXX - too hard to find
 -600 = 1.85 dB
 -900 = 1.25 dB
 
 Money not necessarily a consideration as this is a short run for a
 permanent installation.  Don't anticipate ever moving the GPS antenna to
 the tower.
 For 900 and likely 600, likely would not be able to do it in one piece
 as routing it out of the mast and into the shack would get complicated. 
 Would likely bring it out of the mast at the bottom with a right angle
 connector, and then use a smaller diameter jumper for the last 12 feet.
 500 is pretty uncommon stock wise and it and connectors are harder to find.
 
 I already have the tooling for both 240 and 400... but I definitely
 don't want to challenge ANY of the devices for signal gain.
 
 So it mostly boils down to easy vs. more effort ($$ aside)  Is it
 worth the additional trouble to move from -400 to -600 or -900?  To NOT
 lose the 1-1.6 dB additional?
 
 I'd appreciate your recommendation and reasoning. Thanks in advance!
 
 73,
 
 -- 
 __
 Clay Autery, KY5G
 MONTAC Enterprises
 (318) 518-1389
>> 
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Re: [time-nuts] GPS Antenna Feed Line Decision

[Wes]

On 9/2/2017 4:48 PM, Clay Autery wrote:

Thanks for the response...

Not sure why you and the other guy both recommended RG-6 75-Ohm cable
and F-connectors, when the nominal impedance of literally everything
else in the system is 50 Ohm, including the antenna and the HP GPS
Distribution Amp  And then adding N to F adapters?
As "the other guy" (I think) let me say that the impedance mismatch is 
immaterial and in my case I have one GPSDO with an SMA connector and another 
with a BNC and an antenna with an SMA.  So I "adapt" no matter what I do.  
Because I understand the cascaded noise figure equations, I know that I don't 
need an active distribution amplifier to feed just these two devices, so a $5.00 
"F" connector splitter is adequate. 
(https://www.markertek.com/product/201-232/2-way-2-4ghz-90db-satellite-splitter-dc-power-passing-to-one-port)

Doesn't make any sense unless one has $$ as a top priority, already has
a spool of RG-6 quad shield, etc...  but I specifically stated that $$
is not a top priority  Not really even in the top 5 or 10...

Then by all means you should use L-band waveguide. :-)

Wes

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Re: [time-nuts] GPS Antenna Feed Line Decision

[Attila Kinali]

On Sat, 2 Sep 2017 18:48:52 -0500
Clay Autery  wrote:


> Not sure why you and the other guy both recommended RG-6 75-Ohm cable
> and F-connectors, when the nominal impedance of literally everything
> else in the system is 50 Ohm, including the antenna and the HP GPS
> Distribution Amp  And then adding N to F adapters?

Because it doesn't matter in a receive only application.
The transmission coefficient for a 75R<->50R step is 0.8, or -1.9dB.
In return, you can get a much better cable for half the price with
less damping. Not to talk about all the other bits and pieces that
are readily available for 75R F connectors. Like lightning arrestors
and grounding blocks. And please, include at least a lightning arrestor
at the point where the cable enters the building!


> Doesn't make any sense unless one has $$ as a top priority, already has
> a spool of RG-6 quad shield, etc...  but I specifically stated that $$
> is not a top priority  Not really even in the top 5 or 10...


If you have more than enough money, then by all means go for the 50R
solution :-)
 
> Strain relief solution:  Really depends upon which cable stock I end up
> using  Obviously, the larger the cable, the more weight will be
> suspended under the antenna (approx. 38 feet, depending on where I pull
> the cable out of the mast at the bottom.  (The mast is on a tilt-base of
> my own construction  which brings up a valid consideration.  it is
> already a chore to walk the mast up manually.  The more weight added at
> the top and inside the mast, the more difficult a manual walk-up will
> be.  I'd prefer to keep this a manual tilt for now...  at least until I
> add the tri-band vertical dipole)
> 
> LMR-400 would be less than 4 lbs total weight...  I'd likely suspend the
> cable by the connector alone. (although, it wouldn't be JUST the
> crimp...  The connector would have at a minimum, 1 layer of
> adhesive-lined shrink tube... probably 2, with the second, overlapping. 
> Then a nice wrap of self-fusing tape and then electrical tape over that.
> Even LMR-600 could be suspended by the connector alone, at 5 lbs max in
> the 38 foot max vertical section.
> I do have several methods of secondary suspension within the top (and/or
> second) mast section though if I decide I need it.

You do not want to have 2kg of weight on a RF connector.
Even if it will hold now, over time material creep will lead to
intermediate faults. Better use a dedicated strain relieve. This
can be something as simple as a wire wound around the cable that
holds the weight.

 
Attila Kinali

-- 
You know, the very powerful and the very stupid have one thing in common.
They don't alters their views to fit the facts, they alter the facts to
fit the views, which can be uncomfortable if you happen to be one of the
facts that needs altering.  -- The Doctor
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Re: [time-nuts] GPS Antenna Feed Line Decision

[Clemgill]

Hi Clay,
Intersting subject.
What design for ultra stable/clean power supply are you using please ?
Thx,
Gilles.

> On Sep 2, 2017, at 22:47, Clay Autery  wrote:
> 
> PCTEL GPS-TMG-HR-26NCM Antenna. 
> http://www.neobits.com/pctel_maxrad_gps_tmg_hr_26ncm_high_rejection_gps_p2769137.htm
> 
> Can't say what the gain tolerances are, but it appears to be a pretty
> decent quality part.
> 
> The distribution amp is an HP 58516A GPS L1 Distribution Amp with the
> external power supply tap which will be fed with an ultras stable/clean
> adjustable linear power supply.  As I understand it, this is a unity
> gain amp, so there should be little to no insertion loss or distro losses.
> 
> The distribution amp will be mounted near the devices such that amp to
> device jumpers will all be < 1 meter/3.28 feet.  Likely a lot less.  ALL
> Times N-connectors until reaching a connector TM doesn't make.
> 
> __
> Clay Autery, KY5G
> 
>> On 9/2/2017 3:26 PM, Bob kb8tq wrote:
>> Hi
>> 
>> A lot depends on what comes after the feed cable. The “disto amp” will 
>> determine 
>> a lot. You likely need 10 db of net gain in front of it to keep things 
>> running ok. For an
>> antenna that is *really* 26 db (as opposed to 26 db +/- 6 db), that would 
>> come out to
>> 16 db of feed line loss. This isn’t a terribly surprising outcome. The 
>> antennas are designed
>> for installations that run 150’ or more of coax ….
>> 
>> Bob
>> 
>>> On Sep 2, 2017, at 2:57 PM, Clay Autery  wrote:
>>> 
>>> Having decision-making problems for the materials for my GPS main
>>> feedline.  Going to use a TM LMR stock, just can't decide how big to go
>>> with it...
>>> 
>>> 26 dB 5vdc antenna on top of a 38 foot mast.  Feed will come down the
>>> inside/center of mast and exit near the bottom, thence routed through a
>>> window and to the GPS distro amp. Antenna will feed GPSDO, NTP Server,
>>> Blitzortung System Blue station, and one other device TBD.
>>> 
>>> Just cannot decide how big to go with the antenna to distro amp feed... 
>>> Assuming 50 feet total (38' mast + 12 feet to amp in shack) @ 1800 MHz
>>> (closest to 1725 MHz), here are the losses from just this piece
>>> (ignoring the amp to device jumpers):
>>> 
>>> -240 = 5.45 dB XXX - too much loss?
>>> -400 = 2.85 dB
>>> -500 = 2.30 dB  XXX - too hard to find
>>> -600 = 1.85 dB
>>> -900 = 1.25 dB
>>> 
>>> Money not necessarily a consideration as this is a short run for a
>>> permanent installation.  Don't anticipate ever moving the GPS antenna to
>>> the tower.
>>> For 900 and likely 600, likely would not be able to do it in one piece
>>> as routing it out of the mast and into the shack would get complicated. 
>>> Would likely bring it out of the mast at the bottom with a right angle
>>> connector, and then use a smaller diameter jumper for the last 12 feet.
>>> 500 is pretty uncommon stock wise and it and connectors are harder to find.
>>> 
>>> I already have the tooling for both 240 and 400... but I definitely
>>> don't want to challenge ANY of the devices for signal gain.
>>> 
>>> So it mostly boils down to easy vs. more effort ($$ aside)  Is it
>>> worth the additional trouble to move from -400 to -600 or -900?  To NOT
>>> lose the 1-1.6 dB additional?
>>> 
>>> I'd appreciate your recommendation and reasoning. Thanks in advance!
>>> 
>>> 73,
>>> 
>>> -- 
>>> __
>>> Clay Autery, KY5G
>>> MONTAC Enterprises
>>> (318) 518-1389
> 
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Re: [time-nuts] GPS Antenna Feed Line Decision

[Clay Autery]

Thanks for the response...

Not sure why you and the other guy both recommended RG-6 75-Ohm cable
and F-connectors, when the nominal impedance of literally everything
else in the system is 50 Ohm, including the antenna and the HP GPS
Distribution Amp  And then adding N to F adapters?

Doesn't make any sense unless one has $$ as a top priority, already has
a spool of RG-6 quad shield, etc...  but I specifically stated that $$
is not a top priority  Not really even in the top 5 or 10...

The whole point of this exercise is to put up a semi-permanent SINGLE
antenna/feed-line install that will supply all 4 ports of the HP amp
with the least compromised signal within reason 4 now, and 8
whenever I can find the HP 8-way distro amp with external power input.

Strain relief solution:  Really depends upon which cable stock I end up
using  Obviously, the larger the cable, the more weight will be
suspended under the antenna (approx. 38 feet, depending on where I pull
the cable out of the mast at the bottom.  (The mast is on a tilt-base of
my own construction  which brings up a valid consideration.  it is
already a chore to walk the mast up manually.  The more weight added at
the top and inside the mast, the more difficult a manual walk-up will
be.  I'd prefer to keep this a manual tilt for now...  at least until I
add the tri-band vertical dipole)

LMR-400 would be less than 4 lbs total weight...  I'd likely suspend the
cable by the connector alone. (although, it wouldn't be JUST the
crimp...  The connector would have at a minimum, 1 layer of
adhesive-lined shrink tube... probably 2, with the second, overlapping. 
Then a nice wrap of self-fusing tape and then electrical tape over that.
Even LMR-600 could be suspended by the connector alone, at 5 lbs max in
the 38 foot max vertical section.
I do have several methods of secondary suspension within the top (and/or
second) mast section though if I decide I need it.

Also prefer to keep all the connectors N-type as much as possible since
that is the station standard.

73,

__
Clay Autery, KY5G

On 9/2/2017 6:07 PM, Mike Naruta AA8K wrote:
>
> Clay, you may wish to consider using a quality RG-6 with F
> connectors.  Grounding blocks are readily available for the base of
> your mast and the entrance to your house.  Also, off-the-shelf
> over-voltage protectors (Zap-Tech) are available. I even found an
> F-to-N adapter for the antenna on Amazon.  Watch out for the ones with
> metric N threads though.
>
> For my 25 meter run I was going to use an existing one inch Heliax,
> but pulled a run of Belden RG-6 instead after learning that Trimble
> used RG-6.
>
> It worked well directly connected to a Trimble Thunderbolt; now it is
> connected to a Symmetricon 58535A GPS L1 distribution amplifier.
>
>
> My Blitzortung System Red station has been running fine in my attic
> (Michigan) on a Motorola 97 Oncore patch antenna fastened against the
> roof underside.  It is looking through wood, shingles, and nails (and
> a tree and antennas and utility lines).
>
>
> How are you planning to do strain-relief on the vertical run of coax
> inside of your mast?
>
>
> Mike - AA8K
>
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Re: [time-nuts] GPS Antenna Feed Line Decision

[Clay Autery]

HP 58516A GPS L1 Disribution Amplifier ( 4-way with external power
supply input)

__
Clay Autery, KY5G

On 9/2/2017 3:38 PM, Pete Lancashire wrote:
> What are you using for a distribution amplifier ?
>
> On Sat, Sep 2, 2017 at 11:57 AM, Clay Autery  wrote:
>
>> Having decision-making problems for the materials for my GPS main
>> feedline.  Going to use a TM LMR stock, just can't decide how big to go
>> with it...
>>
>> 26 dB 5vdc antenna on top of a 38 foot mast.  Feed will come down the
>> inside/center of mast and exit near the bottom, thence routed through a
>> window and to the GPS distro amp. Antenna will feed GPSDO, NTP Server,
>> Blitzortung System Blue station, and one other device TBD.
>>
>> Just cannot decide how big to go with the antenna to distro amp feed...
>> Assuming 50 feet total (38' mast + 12 feet to amp in shack) @ 1800 MHz
>> (closest to 1725 MHz), here are the losses from just this piece
>> (ignoring the amp to device jumpers):
>>
>> -240 = 5.45 dB XXX - too much loss?
>> -400 = 2.85 dB
>> -500 = 2.30 dB  XXX - too hard to find
>> -600 = 1.85 dB
>> -900 = 1.25 dB
>>
>> Money not necessarily a consideration as this is a short run for a
>> permanent installation.  Don't anticipate ever moving the GPS antenna to
>> the tower.
>> For 900 and likely 600, likely would not be able to do it in one piece
>> as routing it out of the mast and into the shack would get complicated.
>> Would likely bring it out of the mast at the bottom with a right angle
>> connector, and then use a smaller diameter jumper for the last 12 feet.
>> 500 is pretty uncommon stock wise and it and connectors are harder to find.
>>
>> I already have the tooling for both 240 and 400... but I definitely
>> don't want to challenge ANY of the devices for signal gain.
>>
>> So it mostly boils down to easy vs. more effort ($$ aside)  Is it
>> worth the additional trouble to move from -400 to -600 or -900?  To NOT
>> lose the 1-1.6 dB additional?
>>
>> I'd appreciate your recommendation and reasoning. Thanks in advance!
>>
>> 73,
>>
>> --
>> __
>> Clay Autery, KY5G
>> MONTAC Enterprises
>> (318) 518-1389
>>
>> ___
>> time-nuts mailing list -- time-nuts@febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/
>> mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
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Re: [time-nuts] GPS Antenna Feed Line Decision

[Clay Autery]

PCTEL GPS-TMG-HR-26NCM Antenna. 
http://www.neobits.com/pctel_maxrad_gps_tmg_hr_26ncm_high_rejection_gps_p2769137.htm

Can't say what the gain tolerances are, but it appears to be a pretty
decent quality part.

The distribution amp is an HP 58516A GPS L1 Distribution Amp with the
external power supply tap which will be fed with an ultras stable/clean
adjustable linear power supply.  As I understand it, this is a unity
gain amp, so there should be little to no insertion loss or distro losses.

The distribution amp will be mounted near the devices such that amp to
device jumpers will all be < 1 meter/3.28 feet.  Likely a lot less.  ALL
Times N-connectors until reaching a connector TM doesn't make.

__
Clay Autery, KY5G

On 9/2/2017 3:26 PM, Bob kb8tq wrote:
> Hi
>
> A lot depends on what comes after the feed cable. The “disto amp” will 
> determine 
> a lot. You likely need 10 db of net gain in front of it to keep things 
> running ok. For an
> antenna that is *really* 26 db (as opposed to 26 db +/- 6 db), that would 
> come out to
> 16 db of feed line loss. This isn’t a terribly surprising outcome. The 
> antennas are designed
> for installations that run 150’ or more of coax ….
>
> Bob
>
>> On Sep 2, 2017, at 2:57 PM, Clay Autery  wrote:
>>
>> Having decision-making problems for the materials for my GPS main
>> feedline.  Going to use a TM LMR stock, just can't decide how big to go
>> with it...
>>
>> 26 dB 5vdc antenna on top of a 38 foot mast.  Feed will come down the
>> inside/center of mast and exit near the bottom, thence routed through a
>> window and to the GPS distro amp. Antenna will feed GPSDO, NTP Server,
>> Blitzortung System Blue station, and one other device TBD.
>>
>> Just cannot decide how big to go with the antenna to distro amp feed... 
>> Assuming 50 feet total (38' mast + 12 feet to amp in shack) @ 1800 MHz
>> (closest to 1725 MHz), here are the losses from just this piece
>> (ignoring the amp to device jumpers):
>>
>> -240 = 5.45 dB XXX - too much loss?
>> -400 = 2.85 dB
>> -500 = 2.30 dB  XXX - too hard to find
>> -600 = 1.85 dB
>> -900 = 1.25 dB
>>
>> Money not necessarily a consideration as this is a short run for a
>> permanent installation.  Don't anticipate ever moving the GPS antenna to
>> the tower.
>> For 900 and likely 600, likely would not be able to do it in one piece
>> as routing it out of the mast and into the shack would get complicated. 
>> Would likely bring it out of the mast at the bottom with a right angle
>> connector, and then use a smaller diameter jumper for the last 12 feet.
>> 500 is pretty uncommon stock wise and it and connectors are harder to find.
>>
>> I already have the tooling for both 240 and 400... but I definitely
>> don't want to challenge ANY of the devices for signal gain.
>>
>> So it mostly boils down to easy vs. more effort ($$ aside)  Is it
>> worth the additional trouble to move from -400 to -600 or -900?  To NOT
>> lose the 1-1.6 dB additional?
>>
>> I'd appreciate your recommendation and reasoning. Thanks in advance!
>>
>> 73,
>>
>> -- 
>> __
>> Clay Autery, KY5G
>> MONTAC Enterprises
>> (318) 518-1389

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Re: [time-nuts] GPS Antenna Feed Line Decision

[Bill Hawkins]

My HP conical antennas had N connectors, so I used 50 feet of RG-8.
Z3801 receivers never had a problem.

RG-8 is a sturdy cable, which may be the primary consideration for a 38
foot drop unsupported through the mast.

Don't have any comparison to lighter cable, though.

Bill Hawkins
 

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Clay
Autery
Sent: Saturday, September 02, 2017 1:57 PM
To: Time Nuts
Subject: [time-nuts] GPS Antenna Feed Line Decision

Having decision-making problems for the materials for my GPS main
feedline.  Going to use a TM LMR stock, just can't decide how big to go
with it...

26 dB 5vdc antenna on top of a 38 foot mast.  Feed will come down the
inside/center of mast and exit near the bottom, thence routed through a
window and to the GPS distro amp. Antenna will feed GPSDO, NTP Server,
Blitzortung System Blue station, and one other device TBD.

Just cannot decide how big to go with the antenna to distro amp feed...
Assuming 50 feet total (38' mast + 12 feet to amp in shack) @ 1800 MHz
(closest to 1725 MHz), here are the losses from just this piece
(ignoring the amp to device jumpers):

-240 = 5.45 dB XXX - too much loss?
-400 = 2.85 dB
-500 = 2.30 dB  XXX - too hard to find
-600 = 1.85 dB
-900 = 1.25 dB

Money not necessarily a consideration as this is a short run for a
permanent installation.  Don't anticipate ever moving the GPS antenna to
the tower.
For 900 and likely 600, likely would not be able to do it in one piece
as routing it out of the mast and into the shack would get complicated.
Would likely bring it out of the mast at the bottom with a right angle
connector, and then use a smaller diameter jumper for the last 12 feet.
500 is pretty uncommon stock wise and it and connectors are harder to
find.

I already have the tooling for both 240 and 400... but I definitely
don't want to challenge ANY of the devices for signal gain.

So it mostly boils down to easy vs. more effort ($$ aside)  Is it
worth the additional trouble to move from -400 to -600 or -900?  To NOT
lose the 1-1.6 dB additional?

I'd appreciate your recommendation and reasoning. Thanks in advance!

73,

--
__
Clay Autery, KY5G
MONTAC Enterprises
(318) 518-1389

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Re: [time-nuts] GPS Antenna Feed Line Decision

[William H. Fite]

True, though a friend of mine used LMR-400.


On Saturday, September 2, 2017, Mark Sims  wrote:

> Cheap RG-59 cable coax is more than sufficient for 50 .. 150+ feet (unless
> you are doing geodetic level GPS work).  It is recommended by several GPSDO
> makers.  The 50/75 ohm mismatch is not an issue.  No need to waste money on
> fancy pants artisanal luxury coax.
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-- 
I wanted to be a rocket scientist but my advisor said I'd be wasting my
talent.
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Re: [time-nuts] GPS Antenna Feed Line Decision

[Bob kb8tq]

Hi

Modern distribution amp chips are likely to be sub 2 db NF. Gain is generally 
just a bit more than
the loss through any post filtering and the passive power splitter after it. 

Bob

> On Sep 2, 2017, at 7:02 PM, Wes  wrote:
> 
> This is just a cascaded noise figure situation.
> 
> The first stage is the antenna (preamp) which has 26 dB gain (assumed) and an 
> unknown noise figure. Assume it's a dB or so. Let the second stage gain be a 
> negative value equal to the cable loss and the second stage noise figure be 
> equal to the cable loss in dB.  Assume a lousy 10 dB NF and 10 dB gain for 
> the distribution amp.
> 
> If the cable loss is 5 dB then the cascaded noise figure and gain are: 1.26 
> dB, 31 dB gain.
> 
> If the cable loss is 2 dB then the cascaded noise figure and gain are: 1.13 
> dB, 33 dB gain.
> 
> I would use RG-6.
> 
> See: https://www.pasternack.com/t-calculator-noise-figure.aspx
> 
> The secret here is the 26 dB gain.
> 
> 
> Wes  N7WS
> 
> On 9/2/2017 11:57 AM, Clay Autery wrote:
>> Having decision-making problems for the materials for my GPS main
>> feedline.  Going to use a TM LMR stock, just can't decide how big to go
>> with it...
>> 
>> 26 dB 5vdc antenna on top of a 38 foot mast.  Feed will come down the
>> inside/center of mast and exit near the bottom, thence routed through a
>> window and to the GPS distro amp. Antenna will feed GPSDO, NTP Server,
>> Blitzortung System Blue station, and one other device TBD.
>> 
>> Just cannot decide how big to go with the antenna to distro amp feed...
>> Assuming 50 feet total (38' mast + 12 feet to amp in shack) @ 1800 MHz
>> (closest to 1725 MHz), here are the losses from just this piece
>> (ignoring the amp to device jumpers):
>> 
>> -240 = 5.45 dB XXX - too much loss?
>> -400 = 2.85 dB
>> -500 = 2.30 dB  XXX - too hard to find
>> -600 = 1.85 dB
>> -900 = 1.25 dB
>> 
>> Money not necessarily a consideration as this is a short run for a
>> permanent installation.  Don't anticipate ever moving the GPS antenna to
>> the tower.
>> For 900 and likely 600, likely would not be able to do it in one piece
>> as routing it out of the mast and into the shack would get complicated.
>> Would likely bring it out of the mast at the bottom with a right angle
>> connector, and then use a smaller diameter jumper for the last 12 feet.
>> 500 is pretty uncommon stock wise and it and connectors are harder to find.
>> 
>> I already have the tooling for both 240 and 400... but I definitely
>> don't want to challenge ANY of the devices for signal gain.
>> 
>> So it mostly boils down to easy vs. more effort ($$ aside)  Is it
>> worth the additional trouble to move from -400 to -600 or -900?  To NOT
>> lose the 1-1.6 dB additional?
>> 
>> I'd appreciate your recommendation and reasoning. Thanks in advance!
>> 
>> 73,
>> 
> 
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Re: [time-nuts] GPS Antenna Feed Line Decision

[Mike Naruta AA8K]

On 09/02/2017 02:57 PM, Clay Autery wrote:

Having decision-making problems for the materials for my GPS main
feedline.  Going to use a TM LMR stock, just can't decide how big to go
with it...

26 dB 5vdc antenna on top of a 38 foot mast.  Feed will come down the
inside/center of mast and exit near the bottom, thence routed through a
window and to the GPS distro amp. Antenna will feed GPSDO, NTP Server,
Blitzortung System Blue station, and one other device TBD.


...


I'd appreciate your recommendation and reasoning. Thanks in advance!

73,



Clay, you may wish to consider using a quality RG-6 with F 
connectors.  Grounding blocks are readily available for the base 
of your mast and the entrance to your house.  Also, 
off-the-shelf over-voltage protectors (Zap-Tech) are available. 
I even found an F-to-N adapter for the antenna on Amazon.  Watch 
out for the ones with metric N threads though.


For my 25 meter run I was going to use an existing one inch 
Heliax, but pulled a run of Belden RG-6 instead after learning 
that Trimble used RG-6.


It worked well directly connected to a Trimble Thunderbolt; now 
it is connected to a Symmetricon 58535A GPS L1 distribution 
amplifier.



My Blitzortung System Red station has been running fine in my 
attic (Michigan) on a Motorola 97 Oncore patch antenna fastened 
against the roof underside.  It is looking through wood, 
shingles, and nails (and a tree and antennas and utility lines).



How are you planning to do strain-relief on the vertical run of 
coax inside of your mast?



Mike - AA8K

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Re: [time-nuts] GPS Antenna Feed Line Decision

[Wes]

This is just a cascaded noise figure situation.

The first stage is the antenna (preamp) which has 26 dB gain (assumed) and an 
unknown noise figure. Assume it's a dB or so. Let the second stage gain be a 
negative value equal to the cable loss and the second stage noise figure be 
equal to the cable loss in dB.  Assume a lousy 10 dB NF and 10 dB gain for the 
distribution amp.


If the cable loss is 5 dB then the cascaded noise figure and gain are: 1.26 dB, 
31 dB gain.


If the cable loss is 2 dB then the cascaded noise figure and gain are: 1.13 dB, 
33 dB gain.


I would use RG-6.

See: https://www.pasternack.com/t-calculator-noise-figure.aspx

The secret here is the 26 dB gain.


Wes  N7WS

On 9/2/2017 11:57 AM, Clay Autery wrote:

Having decision-making problems for the materials for my GPS main
feedline.  Going to use a TM LMR stock, just can't decide how big to go
with it...

26 dB 5vdc antenna on top of a 38 foot mast.  Feed will come down the
inside/center of mast and exit near the bottom, thence routed through a
window and to the GPS distro amp. Antenna will feed GPSDO, NTP Server,
Blitzortung System Blue station, and one other device TBD.

Just cannot decide how big to go with the antenna to distro amp feed...
Assuming 50 feet total (38' mast + 12 feet to amp in shack) @ 1800 MHz
(closest to 1725 MHz), here are the losses from just this piece
(ignoring the amp to device jumpers):

-240 = 5.45 dB XXX - too much loss?
-400 = 2.85 dB
-500 = 2.30 dB  XXX - too hard to find
-600 = 1.85 dB
-900 = 1.25 dB

Money not necessarily a consideration as this is a short run for a
permanent installation.  Don't anticipate ever moving the GPS antenna to
the tower.
For 900 and likely 600, likely would not be able to do it in one piece
as routing it out of the mast and into the shack would get complicated.
Would likely bring it out of the mast at the bottom with a right angle
connector, and then use a smaller diameter jumper for the last 12 feet.
500 is pretty uncommon stock wise and it and connectors are harder to find.

I already have the tooling for both 240 and 400... but I definitely
don't want to challenge ANY of the devices for signal gain.

So it mostly boils down to easy vs. more effort ($$ aside)  Is it
worth the additional trouble to move from -400 to -600 or -900?  To NOT
lose the 1-1.6 dB additional?

I'd appreciate your recommendation and reasoning. Thanks in advance!

73,



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Re: [time-nuts] GPS Antenna Feed Line Decision

[Pete Lancashire]

What are you using for a distribution amplifier ?

On Sat, Sep 2, 2017 at 11:57 AM, Clay Autery  wrote:

> Having decision-making problems for the materials for my GPS main
> feedline.  Going to use a TM LMR stock, just can't decide how big to go
> with it...
>
> 26 dB 5vdc antenna on top of a 38 foot mast.  Feed will come down the
> inside/center of mast and exit near the bottom, thence routed through a
> window and to the GPS distro amp. Antenna will feed GPSDO, NTP Server,
> Blitzortung System Blue station, and one other device TBD.
>
> Just cannot decide how big to go with the antenna to distro amp feed...
> Assuming 50 feet total (38' mast + 12 feet to amp in shack) @ 1800 MHz
> (closest to 1725 MHz), here are the losses from just this piece
> (ignoring the amp to device jumpers):
>
> -240 = 5.45 dB XXX - too much loss?
> -400 = 2.85 dB
> -500 = 2.30 dB  XXX - too hard to find
> -600 = 1.85 dB
> -900 = 1.25 dB
>
> Money not necessarily a consideration as this is a short run for a
> permanent installation.  Don't anticipate ever moving the GPS antenna to
> the tower.
> For 900 and likely 600, likely would not be able to do it in one piece
> as routing it out of the mast and into the shack would get complicated.
> Would likely bring it out of the mast at the bottom with a right angle
> connector, and then use a smaller diameter jumper for the last 12 feet.
> 500 is pretty uncommon stock wise and it and connectors are harder to find.
>
> I already have the tooling for both 240 and 400... but I definitely
> don't want to challenge ANY of the devices for signal gain.
>
> So it mostly boils down to easy vs. more effort ($$ aside)  Is it
> worth the additional trouble to move from -400 to -600 or -900?  To NOT
> lose the 1-1.6 dB additional?
>
> I'd appreciate your recommendation and reasoning. Thanks in advance!
>
> 73,
>
> --
> __
> Clay Autery, KY5G
> MONTAC Enterprises
> (318) 518-1389
>
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> mailman/listinfo/time-nuts
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>
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Re: [time-nuts] GPS Antenna Feed Line Decision

[Bob kb8tq]

Hi

A lot depends on what comes after the feed cable. The “disto amp” will 
determine 
a lot. You likely need 10 db of net gain in front of it to keep things running 
ok. For an
antenna that is *really* 26 db (as opposed to 26 db +/- 6 db), that would come 
out to
16 db of feed line loss. This isn’t a terribly surprising outcome. The antennas 
are designed
for installations that run 150’ or more of coax ….

Bob

> On Sep 2, 2017, at 2:57 PM, Clay Autery  wrote:
> 
> Having decision-making problems for the materials for my GPS main
> feedline.  Going to use a TM LMR stock, just can't decide how big to go
> with it...
> 
> 26 dB 5vdc antenna on top of a 38 foot mast.  Feed will come down the
> inside/center of mast and exit near the bottom, thence routed through a
> window and to the GPS distro amp. Antenna will feed GPSDO, NTP Server,
> Blitzortung System Blue station, and one other device TBD.
> 
> Just cannot decide how big to go with the antenna to distro amp feed... 
> Assuming 50 feet total (38' mast + 12 feet to amp in shack) @ 1800 MHz
> (closest to 1725 MHz), here are the losses from just this piece
> (ignoring the amp to device jumpers):
> 
> -240 = 5.45 dB XXX - too much loss?
> -400 = 2.85 dB
> -500 = 2.30 dB  XXX - too hard to find
> -600 = 1.85 dB
> -900 = 1.25 dB
> 
> Money not necessarily a consideration as this is a short run for a
> permanent installation.  Don't anticipate ever moving the GPS antenna to
> the tower.
> For 900 and likely 600, likely would not be able to do it in one piece
> as routing it out of the mast and into the shack would get complicated. 
> Would likely bring it out of the mast at the bottom with a right angle
> connector, and then use a smaller diameter jumper for the last 12 feet.
> 500 is pretty uncommon stock wise and it and connectors are harder to find.
> 
> I already have the tooling for both 240 and 400... but I definitely
> don't want to challenge ANY of the devices for signal gain.
> 
> So it mostly boils down to easy vs. more effort ($$ aside)  Is it
> worth the additional trouble to move from -400 to -600 or -900?  To NOT
> lose the 1-1.6 dB additional?
> 
> I'd appreciate your recommendation and reasoning. Thanks in advance!
> 
> 73,
> 
> -- 
> __
> Clay Autery, KY5G
> MONTAC Enterprises
> (318) 518-1389
> 
> ___
> time-nuts mailing list -- time-nuts@febo.com
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