[time-nuts] New timing receivers?

Tom Van Baak tvb at LeapSecond.com
Sun Apr 27 23:32:46 EDT 2014


Jim,

Most (all?) timing receivers allow you to virtually shift the 1PPS forwards and backwards to compensate for antenna delay or other factors. But the physical 1PPS output will still have clock quantization and the only way to deal with this is external h/w or s/w sawtooth correction.

Imagine some GPS timing receiver with 50 MHz clock and 20 ns quantization. Each 1PPS is one of those 50 MHz clock edges. The sawtooth correction is some number between +/- 10 ns. If you were to add 1 ns to the antenna delay, the 1PPS output would still be one of those clock edges, but the sawtooth correction number would now be 1 ns less. So there is no electrical or mathematical advantage in doing this.

Speaking of which, has anyone watched what happens if you change the antenna delay by 2000, 200, 20, or 2 ns in a TBolt GPSDO?

/tvb

----- Original Message ----- 
From: "Jim Miller" <jim at jtmiller.com>
To: "time-nuts" <time-nuts at febo.com>
Sent: Sunday, April 27, 2014 8:05 PM
Subject: Re: [time-nuts] New timing receivers?


>I spent some time reading the uBlox-6 documentation. I found the TIM-TP ubx
> message and format. I see that there is also the ability to feed back to
> the uBlox-6 time shift info for the PPS in 1ns increments.
> 
> Does it make sense to feed the TIM-TP info back this way to provide
> correction?
> 
> Or is an external delay line or TIC plus software the only way?
> 
> Thanks
> 
> jim ab3cv
> 
> 
> On Sat, Apr 26, 2014 at 7:59 PM, Jim Miller <jim at jtmiller.com> wrote:
> 
>> I'm reading though the manual for my recently acquired M12+T which I'm
>> looking forward to using.
>>
>> I notice that the manual is dated 09FEB05.
>>
>> So the M12+T has been around for about a decade.
>>
>> Are there more recent timing receivers available now or has the ubiquity
>> of the consumer GPS market distracted all investment from timing receivers
>> except at the high end?
>>
>> Thanks
>>
>> Jim AB3CV





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