[ARC5] Signal Generator Output Coupling

[Robert Eleazer]

"I think the output may be of the wave guide beyond cut-off type 
also used on some Hewlett-Packard VHF and microwave generators."

The SG-297 oscillator coupling resembles that of the HP-3200B that I recently repaired.  On the 3200B a probe goes into and out of the oscillator tank with the more withdrawn positions representing lower output.  However, on the 3200B with some frequencies putting the probe all the way in will result in lower or even NO output.  Also, the position of the probe affects the output frequency to a degree.  So for each frequency over the 10 MHZ - 500 MHZ range there will be a probe position that is best in terms of accuracy and output level.  It's a nice instrument but a bit tricky to use and a separate frequency counter is pretty much a must for accurate adjustment.

The SG-297 has a much more sophisticated design for the probe that goes into and out of the oscillator tank, with precision rack and pinion gearing as well as a fine adjustment that enables you to set it for calibrated output.  Nonetheless, adjustment of the output level does affect the frequency to a small degree.  By the way, the SG-297's oscillator tank has 0.5 inch thick Aluminum walls.

Thanks!

Wayne
WB5WSV



      

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