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Old 16-Aug-2013, 8:07 PM   #55
tripelo
Senior Member
 
Join Date: Jan 2010
Location: Dallas, TX
Posts: 127
Quote:
Originally Posted by Pete Higgins View Post
...The RCA draws <80 ma and my 3 PCT MA2-M’s were drawing almost ten times as much...
Yes, the drop amplifiers use more current. The regulators are more conservatively designed. And, all things being equal (which they seldom are), high dynamic range amplifiers consume more power.

Quote:
My Winegard AP-2870 overloaded ...expecting the RCA might overload on the tower as well. No such luck. ... no signs of overload
That is a bit puzzling. The Winegard preamplifiers that I have scrutinized are, in principle, not much different than the RCA design appears to be. Both use BJT, bipolar junction transistors. Might expect a few dB difference in overload characteristics but not many dB.

Quote:
Subjectively, I think the RCA is outperforming the PCT drop amps. ... I would sure like to know where the 1 dB compression point is reached with this design.
It appears to be similar to the original CM-7778, and by extension it would be similar to the CM-7777. Both CM's are about as good as one could expect for single-ended BJT designs. But, neither would be considered outstanding in terms of high dynamic range.

Quote:
...I calibrated my NTE/ECG U-106 ... I’m not impressed with the accuracy of these 3-wire rotors. My 40-50 year old 5-wire rotors always point where they say they are pointing.
Yes. The more mass the three wire rotors have to rotate, the more frequently they become uncalibrated. As you know, the principle involves two synchronous motors (one in the control and one on the mast) that rotate at about the same speed, no feedback loop for correction. Problem is that the mast motor runs slower.

Quote:
Do you think that ~1.5 wavelengths of spatial diversity is mitigating your frequency selective fading? It would certainly help explain improvements in excess of simple combining gain.
That is good thinking.

The antenna spacing of 1.5 wavelengths is sufficient to provide a signal path that is at least partially independent (not completely correlated with the other antenna). Independent, or at least partially independent paths are necessary for diversity gain.

It seems, with this configuration, there are some difficulties with realizing true space diversity, because of the method of combining the two antennas.

Maybe more thoughts on this later.

Last edited by tripelo; 16-Aug-2013 at 8:19 PM. Reason: clarify
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