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Old 17th Apr 2023, 11:41 pm   #80
jamesinnewcastl
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Join Date: Jul 2009
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 722
Default Re: Standard Beam Approach - Rebuild update

Hi Richard

It's very difficult to know what the glide meter should be doing since the bulk of the documents I have relate to later versions where the glide wasn't used as a glide. It was still connected and was used later as a "come and go" indicator. So a descending field strength meaning that you were flying away and vice versa.

There are hints such as "with no signal the glide meter should read no higher than the lowest dot on the scale, if so replace the VR108". This would be true if not for the resistor I mentioned earlier that causes the meter to deflect the wrong way.

AP1186 for the version states that the glide path meter is an ordinary ammeter, it is operated by the DC space current of the detector valve, the current being directly proportional to the R/F input to the valve. Thus the glide meter is simply a field strength meter". I don't know what strength RF signal to apply for testing but the issues at the moment are the 'no signal' voltages.

Another operating hint is that "with the controller set to NORMAL the glide meter should not go off the top of the scale - .. suspect one of the VR106 valves.

The glide meter resistance is 250 ohms and with the 50 ohm shut (I used 47 ohms) it is about 39 ohms. I've made a small rig to measure the fsd characteristics of the meters and they give glide: 3.17mA fsd and Course: 1.28 mA fsd.

When in course the agc should keep the measured signal strength constant so I would imagine that the glide meter would rise as the signal strength were too weak to operate the agc, then stop at some point where the agc kicks in. Of course I would think that the overriding consideration would be not to burn the coil out under any conditions.

Cheers
James

Last edited by jamesinnewcastl; 17th Apr 2023 at 11:55 pm.
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