[time-nuts] Z3805A/58503A time receiver : 2 questions

Volker Esper ailer2 at t-online.de
Sat Mar 2 10:04:10 EST 2013


Claude,

I see a jump even smaller than the first one and as I calculated before 
(in an answere to Said's mail) this latest jump is much less than the 
first one of 550 microHz. I agree with Said that this could be a crystal 
jump.

If you want to check the GPSDO's absolute frequency you'd need a second 
GPSDO... If you want to check it's stability - how do you know that it's 
the GPSDO that jumps? Ok, you see a synchonous jump on the EFC voltage, 
that's a good evidence.

If you want to compare the frequency of your 5334B (nice thing, by the 
way), the accuracy of your locked GPSDO should be sufficient - the 
uncertainty of your locked GPSDO might be in the range of several uHz...

Since GPSDOs make use of highly stable OCXOs to maintain short time 
stability (and improve side band noise) it depends on your oscillators, 
which one has better stability, the 5334B built-in osc, or the GPSDO 
osc. On the picture on ebay I recognize an HP type (most likely 10811) 
which is known for it's very good stability performance. I guess it's 
not easy to find an oscillator that can beat the 10811.

I use my GPSDOs as external references for my counters and all that 
stuff (amateur radio equipment, spectrum analyzer,...) and I'd recommend 
that.

 >...The receiver is a 6 channels and it outputs two 10 MHz and one PPS.

I think my statement about the osc frequency was a bit unclear. All the 
Z38xx have 10 MHz outputs (as far as I know). But the OCXOs inside the 
units are different - there are 10 MHz types (HP 10811) (like yours, as 
it seems) and 5 MHz types (Symmetricom), which have a doubler to achieve 
the 10 MHz.

To cut a long story short, I think, your GPSDO is working fine. With an 
antenna seeing some more of the hemisphere it would be working even 
better, I think... :-)

Volker


Am 02.03.2013 13:15, schrieb Claude Fender:
> Thanks you both for your answers.
>
> I had another jump (positive this time, 24h after the first one) and the efc curve came back to its previous state, see : http://uppix.net/f/4/d/c5a277798ca58bb04b41481ece6e7.png.
>
> The receiver is a 6 channels and it outputs two 10 MHz and one PPS.
> The antenna has noname and it is installed on a balcony, that's why it has a poor reception. Sure this is not perfect and I have to improve that.
> The log is running every 5 minutes and I didn't notice a holdover mode of the oscillator.
>
> (I've bought this GPSO to check the frequency of my 5334B for gates times of 60s and 100s. I know I can use the 10MHz of the GPSDO as Frequency Reference for the 5534B but I wanted to check its frequency first !)
>
>
> ________________________________
>   De : Volker Esper<ailer2 at t-online.de>
> À : time-nuts at febo.com
> Envoyé le : Jeudi 28 février 2013 2h12
> Objet : Re: [time-nuts] Z3805A/58503A time receiver : 2 questions
>
>
> If your unit is exactly like that on ebay 251226027893, it has a 10 MHz HP oscillator in a double oven, and it's absolutely sure that it's got a 6 channel receiver.
>
> I should have read before, sorry.
>
> I'm still not sure about your antenna, is it a Garmin? Well, it's most likely an active type, so what gain does it have? If you installed it on a roof top, it should see sufficient field strength.
> Then do that simple test: disconnect your antenna from the receiver unit and measure with a multimeter the voltage at the center pin of your N connecter antenna plug. It has to show 5 Volts, otherwise your antenna can't be working well.
>
> Volker
>
>
> Am 28.02.2013 01:26, schrieb Volker Esper:
>    
>> Hi Claude!
>>
>> Said says, you should see 6+ sats, I guess he means _at_least_ six. I'm almost sure, you've got a 6 channel receiver, so you naturally cant't get more than 6 sats at a time.
>>
>> There are some different models of the Z3805A out there, though they're all named the same. I've got two units, one with an 8 channel and one with a 16 channel receiver. My 8channel unit never receives more than 6 sats at a time, never. So I'm shure, it's a 6 channel type...
>>
>> Maybe I should improve my antenna. But the same antenna provides enough voltage to receive 12 to 14 sats at once with the 16 channel unit. On the other hand, my 6/8 channel gizmo very rarely shows less than 6 sats, so, like Said, I too think, that there is some space for improving your antenna. What antenna do you have?
>>
>> One day, while using the 16 channel unit, I experienced the same hops as you did. All time nuts told me that it had to be a crystal jump. I read about such phenomenons and all I found was, that the jump in my receiver was too big to fit to the idea of a crystal jump. Unfortunately my receiver gained fun in jumping. Now I'm absolutely not sure what it is. Maybe it's a faulty oscillator. Which one do you have built in? A 5 or a 10 MHz type? I've got a 10 MHz HP and a 5 MHz Symmetricom oscillator.
>>
>> Cheers
>>
>> Volker
>>
>>
>>
>> Am 28.02.2013 00:17, schrieb Claude Fender:
>>      
>>> Hello,
>>>
>>> This is my first message here although I read this list for a few weeks.
>>>
>>>     I bought a Z3805A/58503A frequency receiver  and I didn't notice on the pictures that the model number was not  written on the front panel. It's not important but is there a reason for that, if you know ?
>>> The item : http://cgi.ebay.fr/ws/eBayISAPI.dll?ViewItem&item=251226027893
>>>
>>>
>>> I log some parameters of the receiver and today I notice a "gap" in the frequency.
>>>
>>> Picture : http://uppix.net/e/2/4/cf39ac772e5a69fc616f5cf30f208.png
>>>
>>> I have a Rubidium and I measure it's frequency with a 5334B counter locked to the GPS, and I can see the "gap" too :
>>> http://uppix.net/f/b/a/d86c2737ad135264e4a2b78e503d5.png
>>> measurements are with Gate Time of 10s, 60s and 100s,
>>>
>>>
>>> Do you know why this happens and how to prevent this behaviour ?
>>>
>>> Thanks for yours advices
>>>
>>>
>>> Claude
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>>>
>>>        
>>
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>>      
>
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