[time-nuts] Substitute GPS in a Z3801A

Robert Benward rbenward at verizon.net
Thu Jun 24 11:24:48 EDT 2010


So there is no point in substituting another GPS RX?   What is the sawtooth 
compensation is see mentioned? What about the antenna cable length 
compensation?  How much does that affect the AVAR?

Bob


----- Original Message ----- 
From: "Steve Rooke" <sar10538 at gmail.com>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Sent: Thursday, June 24, 2010 11:11 AM
Subject: Re: [time-nuts] Substitute GPS in a Z3801A


Sorry to butt in on this thread but, although you need a number of
birds to get an accurate position,  you really only need one to get
timing. If you have a six sat tracking receiver there should be enough
to give accurate time. You can always set the elevation to limit what
sats you can see so to screen out multipath reflections and it can
still track six birds. OK, my Z3805A is currently tracking 9 birds but
3 of those are quite low horizon, although I really don't have
anything to cause multipath from where I'm situated. The minimum
number of sats I track is 4 and the max is 12 on a day, night cycle
and the average is about 6.

Steve

On 25 June 2010 02:01, Robert Benward <rbenward at verizon.net> wrote:
> Mike,
> Thanks for the info!. Does anyone know for sure if the timimg improves
> with more satellites tracked? I don't know how they derive the 1PPS, is it
> a blend or one satellite at a time? Maybe I will leave well enough alone.
>
> Bob
>
>
>
> ----- Original Message ----- From: "Mike S" <mikes at flatsurface.com>
> To: "Discussion of precise time and frequency measurement"
> <time-nuts at febo.com>
> Sent: Thursday, June 24, 2010 9:01 AM
> Subject: Re: [time-nuts] Substitute GPS in a Z3801A
>
>
>> At 10:48 PM 6/23/2010, Robert Benward wrote...
>>>
>>> Has anyone ever put another GPS in a Z3801A? Will the software
>>> accommodate
>>> another GPS that tracks say, 12 channels?
>>
>> Possibly 8 channels. You must use a Motorola Oncore VP. A 6 channel one
>> was what HP used. There are mixed reports on using an 8 channel VP -
>> some say it works fine, others say you must configure it in 6 channel
>> mode (but you do pick up improved reception). Whether the different
>> reports are due to changes in configuration or firmware of the z3801a,
>> the Oncore, or both - I have no idea.
>>
>> The commands/responses used by the z3801a prevent it from working
>> directly with newer GPS modules, like the GTs, UTs or M12s (even if you
>> adapted them physically).
>>
>> If you want to try and get better performance with a newer GPS
>> receiver, you should be able to leave the existing board in place, and
>> bypass the 1PPS input with the signal from the newer receiver. You'd
>> only get in trouble in exceptional conditions (new receiver loses sync,
>> but existing one is reporting good satellite lock, etc.). Of course,
>> the z3801a satellite reporting wouldn't be worth much.
>>
>>
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-- 
Steve Rooke - ZL3TUV & G8KVD
The only reason for time is so that everything doesn't happen at once.
- Einstein

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