[time-nuts] 10 MHz phase comparison using Bruel & Kjaer type 2971 phase meter

paul swed paulswedb at gmail.com
Sat Jan 30 18:27:07 EST 2016


Luca,
I am using a HP3575a phase and gain meter good to 1Hz-13 MHz but easily
goes to 15 MHz. It delivers a dc voltage that feeds a DATAQ 4 cnl USB A/D
coverter and chart program $25.
Its been working very well for comparing references long term.
Just suggesting the 3575 as a possible alternative.
Good luck
Regards
Paul
WB8TSL


On Sat, Jan 30, 2016 at 5:52 PM, Alex Pummer <alex at pcscons.com> wrote:

> Hi Luca,
> look here:  http://www.clmt.de/service-manuals/
> 73
> KJ6UHN
> Alex
>
> On 1/30/2016 12:49 PM, Luca Dal Passo wrote:
>
>> Hi All,
>>      while i was looking for an hp k34-59991A phase comparator on ebay in
>> order to make some long term measurements of frequency drift of a dut
>> against a reference (by logging the analog output of the meter) i found
>> and
>> bought a Bruel & Kjaer type 2971 phase meter instead of the hp.
>> It is a very nice unit, with digital and analog readout, high resolution
>> and high precision.
>> The drawback is that it is a very low frequency device, specified for the
>> range 2Hz to 200 kHz.
>> So, to compare two 5 or 10 MHz signals i'm thinking to use two simple
>> double balanced mixer, some low pass filtering on the IF outs of the
>> mixers, and a common local oscillator of about 5,1 MHz or 10,1 MHz to
>> convert signals into the range of the instrument.
>> The actual frequency of the local oscillator does not metter, because it
>> is
>> the same for the two input signal, and theoretically i could use even a
>> simple free oscillator, provided only the frequency falls in the correct
>> region regardless of phase noise and stability because their effects are
>> subtracted cancelling themselves. Anyway i think to use a simple ambient
>> temperature xtal oscillator for that.
>> What are your opinions? What i'm forghetting to consider? What kind of
>> drawback i have to expect?
>> The other question is about the availability of user/service manual (or at
>> least schematics) of the  Bruel & Kjaer 2971: i'm not able to find
>> anything
>> on the net.
>> Many thanks!
>> Luca
>> IW2LJE
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