[time-nuts] Thunderbolt not seeing satellites

Steve steve65 at suddenlink.net
Thu Jun 10 22:43:29 EDT 2010


Hi Bob,

I took a look at the 10MHz output. The unit had been unpowered on my 
bench for an hour or so. It took about 10 minutes to stabilize at 1.9Hz 
on the high side of 10MHz as measured on a GPS-referenced counter. 
Oscilloscope indicates a level of about +12dBm and a clean looking sine 
wave. So the OCXO would appear to be functional. Thanks for the suggestion.

Anyone know of a source for board layout/schematics/parts list? Might be 
interesting to look at, although it is likely beyond my skill set to 
effect a repair :-\

Steve

On 6/10/2010 9:59 PM, Bob Camp wrote:
> Hi
>
> I suspect that the unit puts out an ok 10 MHz signal. That would suggest that the +12 and likely the +5 supplies are ok. If the monitor software can talk to it, that's another indication that the +/-12 and +5 are fairly close to working.
>
> I think that a problem with the GPS front end / antenna connection is the most likely issue.
>
> Here's another one to consider though:
>
> How far off *is* the 10 MHz output? If the OCXO has gone way off frequency, the GPS may not be able to lock. It should be pretty simple to check with a counter and the second TBolt.
>
> Bob
>
>
> On Jun 10, 2010, at 8:22 PM, Didier Juges wrote:
>
>    
>> The TB has an error flag if there is no antenna connected (open) or if it is shorted. The tboltmon PC software reports these flags, and so does my GPSMon firmware in the fluke.l monitor.
>>
>> It is possible but unlikely that there would be something wrong with the bias circuit that would not be reported by the TB.
>>
>> Didier
>>
>>
>> ------------------------ Sent from my BlackBerry Wireless thingy while I do other things...
>>
>> -----Original Message-----
>> From: Arthur Dent<golgarfrincham at yahoo.com>
>> Date: Thu, 10 Jun 2010 15:49:00
>> To:<time-nuts at febo.com>
>> Subject: [time-nuts] Thunderbolt not seeing satellites
>>
>>
>> It may or may not tell you what's wrong but a quick check of the
>> Thunderbolt would be to put a tee in series with the antenna and
>> see if the unit is supplying +5 volts under load to the antenna.You
>> have verified that the antenna works with a second unit so you can
>> rule that out. Where you are getting some data from Lady Heather
>> showing it picks up at least 1 satellite I suspect the +5 Vdc power
>> supply that supplies the logic is functioning properly or you'd probably
>> see no data. The +12 Vdc mainly supplies the oscillator so if that's
>> working properly, the +12 is probably ok, It may well be a component
>> in the receiver section on the Thunderbolt board.
>>
>> The Thunderbolt receiver board I looked at had a Macom AM50002 amplifier
>> ( http://cs.utsource.net/goods_files/pdf/71/71500_MACOM_AM500002.pdf )
>> located on the top side of the board directly behind the antenna connector.
>> The bottom side of the board has D1, Q1, and R1 directly behind the 1PPS
>> connector and they apparently supply the +5 to power the antenna. Those
>> two areas would be likely suspects.
>>
>>
>>
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>
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