[time-nuts] GPS Antenna Feed Line Decision

[Mike Cook]

> Le 5 sept. 2017 à 16:17, Bob kb8tq <kb8tq at n1k.org> a écrit :
> 
> Hi
> 
> 
> 
>> On Sep 5, 2017, at 6:06 AM, Hal Murray <hmurray at megapathdsl.net> wrote:
>> 
>> 
>> Clay Autery <cautery at montac.com> 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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