"Phil Allison" wrote in message
...

"john jardine"

http://www.tubedata.org/unknown_sylv..._sylvania.html


I read those patents at the bottom of the page and am still none the
wiser
about the detection method. The patents say phasing in/out reflections
from
the aircraft, modulate the oscillator anode current at an audio
frequency
and trigger the detonator. (ie a Doppler effect but not mentioned as
such).


** That the modulation frequency is stated to drop as the shell approaches
a
target is a dead give away for Doppler being involved. As a shell passes
nearby a target, the relative speed and hence Doppler frequency shift
drops
to near zero.


Would have thought current variations due to that cause would be
immeasurable.


** Then you did not do much thinking.

I spent ages. About a minute!.

1. The wavelength of the radiated energy ( circa 200MHz) is many times
smaller than the wingspan of a fighter or bomber aircraft.

Yes. I assumed an infinite metal sheet.

2. The proximity for detonating the shell with effect is roughly
comparable
with the wingspan of such aircraft.

I didn't know that. I was using something like one wavelength at 100MHz
but on reflection this is too close to be of practical use.

3. Egro - an ( all metal) aircraft will be a significant reflector of
such
radiated energy when it is within range of being damaged.

It appears from the circuit arrangement that RF modulation of less than 1%
at around 100Hz would be more than enough to cause detonation.

Yes. This is the key point I missed. Oscillator 'RF modulation' as the
working mode. The oscillator tuned circuit Q being altered at an audio
rate by variable aerial loading dependant on resonant frequency,
velocity and strength of reflection. A 3.7" AA shell seems about a 250Hz
shift, which fits nicely in the audio bandpass.


No mention in the patents though of any audio effects due to
the shell spinning at 300Hz,


** There is unlikely to be any - AA shells being nicely symmetrical.

Yes, indeed. Looking at the pics I see the full cone radiator element acting
with the symmetrical shell body. I'd read the drawing as an arrow head
shaped dipole.


...... Phil



It's interesting historical stuff this. I'll look for that "The Deadly Fuze"
book.




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