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I had several further thoughts to add to yesterday's note but ran out

of time - so , as I was saying......



To John Cooper re: the noise filter inductor for the MT prop control

unit. Caution is advised if, as you surmised, the box does have a

switching converter power supply of some sort. Certain types of con-

verter topographies will come unhinged with just a little too much

inductance in series with the power input. Remember, the guy that

designed this thing was figuring that the input (power) was going to

be connected directly to the battery fed (low impedance) bus. I've

made a living in the past designing these kind of circuits and all I

can say is: Be careful. If a problem should develop, that large

electrolytic capacitor you tried by itself would probably help as

long as it is placed on the LOAD side of the choke. Also, by the way,

the ferrite is probably the best choice over the tape core as the DC

in the windings (depending on the no. of ampere-turns) would likely

saturate the core and render the whole thing to little more than an

air core inductor. The ferrite has an inherent air gap so it won't

saturate.



John, you mention the leakage of radio frequency (RF) energy from the

coax cables and I got the impression that it was somehow being related

to the quality of the bulk cable. This may be where the RF is leaking

into the other circuits but it's highly unlikely that the cable is the

root cause. If the cable and connectors are all fairly good, i.e., not

kinked, squashed or broken, etc., and the antenna is reasonably well

designed, not much RF will get away. However, the biggest culprit in

this area is almost always the antenna. If your antenna is sorta

typical, it won't match the cable characteristics perfectly, which

will result in a percentage of the energy your transmitter squirts at

it when you hit the "Transmit" button reflecting right back up cable.

(If interested, check out the definition and meaning of VSWR). This

causes the largest part of the RF "leaks" off the cable. Use antennas

with measured VSWR of 2:1 or better (a good avionics shop should be

able to do the measurement) and gauges shouldn't hear a thing.



To Scott Dahlgren. The next time I take this mini-bladder flying, I'm

going to try your grape juice idea. Be nice if it works. I go trout

fishing every year in eastern Idaho from here in SoCal and I can tell

you that there's not many places to land for a pee break over central

Nevada. Even with carefully limiting my coffee intake in the morning

to one cup (safety dictates at least one), after a little over three

hours in the saddle, I NEED to stop! And I can tell you, the owner of

the FBO up there at Elko doesn't appreciate Lancairs taxiing to the

building where the lavatories are at 100 MPH! Hope the grape juice is

the answer. And, oh yes - I do have a fishing pole (fly rod) carrying

tube built into the tail cone of N235SP.



Dan Schaefer









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