[time-nuts] EIP545A 18GHz counter query

[David C. Partridge]

Hmmm you run the risk of deafening the counter with 5Vpp (2.5V into 50R). 

Dave
-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of Chris Wilson
Sent: 29 November 2012 15:57
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] EIP545A 18GHz counter query




> 29/11/2012 09:30

> The replacement for the missing U6 chip arrived this morning and it 
> now completes the 200 MHz self test It will read up to the limit of my 
> frequency generator on Band 3 which is only 1040 MHz, but looks 
> promising.

> Band 2 also works, but seemingly has an anomaly. I cannot get Band 2 
> to read below 185.000 MHz. If I input 184.900 it won't read it and 
> displays zeros. 185 and up is OK... Weird. It should read from 10 MHz 
> up to 1 GHz. It'll go to 1 GHz plus AOK.

> Band 1 appears to work fine.

> These tests are with both my GPS referenced external standard and the 
> internal reference used.

> So Band 2 appears to have a further issue. Will refer to the manual 
> and see if I can fathom it out. Any ideas as to why Band 2 will only 
> read from 185 MHz upwards please? Thanks.




29/11/2012 15:53

OK, I may be doing something foolish.

David Partridge was able to supply one of his last remaining frequency dividers to me, for use with my TB GPS standard. It works perfectly and is now in a nice enclosure feeding a small array of BNC sockets on my shack wall. I take the 10 MHz output of the Thunderbolt into David's frequency divider:

http://www.perdrix.co.uk/FrequencyDivider/index.html

I have the 10MHz output from David's divider feeding the counter. When fed from this the Band 2 seems unreliable starting at 10MHz. If I feed it 10Mhz at 50mV from my sig gen it starts reliably. Is it a mismatch from the divider, or has it perhaps not got enough drive level?

-- 
       Best Regards,
                   Chris Wilson.


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