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Chat => Tech Chat => Topic started by: burakkucat on June 10, 2015, 04:54:32 PM

Title: A Wandel & Goltermann Selective Level Measuring Set No 36A
Post by: burakkucat on June 10, 2015, 04:54:32 PM

A recent addition to the grotto is a Wandel & Goltermann LMS No 36A, built to a Post Office Telecommunications specification.

When built it was designed to be powered by two PP9 type batteries or by a POTel / BT Power Unit No 91A. Not having two PP9 batteries nor a PU No 91A to paw, a quick search produced an ITT MQ1B Professional Stabilised PSU whose output could be precisely set to 18V.

After performing the calibration process, as detailed in the extensive product manual, it was decided that the Oscar (http://forum.kitz.co.uk/index.php/topic,13306.0.html)'s output would be examined . . . as it was the subject of previous measurement attempts, when I was guided by the advice of 4candles. The result? It appeared that the Oscar, when set to send 0 dBm into 600 Ohms, was producing -0.5 dBm at a frequency of 1.15 kHz. ( :hmm:  Hmm . . . Perhaps I should repeat the measurement with the LMS No 36A bandwidth set to 24 Hz rather, than the 1 kHz which was previously used.)

[somewhat off topic]
There are a pair of Wandel & Goltermann "bricks", power supplies and manuals, all housed in an "Antler" case, up for auction at a certain on-line site --

http://www.ebay.co.uk/itm/161723353908

Currently there are no bids and b*cat will not be bidding for them!
[/somewhat off topic]

Title: Re: A Wandel & Goltermann Selective Level Measuring Set No 36A
Post by: burakkucat on June 11, 2015, 04:52:02 PM

Just occasionally a kitteh will get the urge to scratch an itch. My itch has now had a good scratching.  ;)

After setting up the LMS No 36A, the MQ1B PSU and the Oscar a sweep was made from 300Hz upwards, with the LMS' bandwidth set to 1kHz. The approximate frequency of the maximum power being sent by the Oscar was noted and the LMS' bandwidth was then reset to 24Hz. Using the slow motion control to adjust the frequency being measured, a precise value of the maximum power being sent and the precise frequency of that power maximum was noted.

I am calling it a power level of -0.2dBm (into 600 Ohms) at a frequency of 1.18kHz.

[Edited to correct the unit of power to be dBm not dBw. Oops!  :-[  ]

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