Re: home-brew cantenna

[Bernard Cleyet <anngeorg@PACBELL.NET>]

I just realized anyone w/ a detector (diode or thermistor) probably
already has an adapter.  Bolt the transmitter wave guide to the detector
wave guide (after removing the horns), remove the detector and replace
with a stub (Cu wire sized to fit the sleeve the pin of the detector
fitted).  One may then either fit a 1/4 wave piece of wire in the BNC
socket of if it's an N solder the plug's center sleeve to the wire and
push it over the N socket pin.  If the detector wave guide is not
tunable (the blanked off end is fixed), first tune the oscillator for
max. output from the detector, then replace the detector w/ the stub and
tune the 1/4 ant.  (Start too long and cut the wire a few mm at a
time.)  One should tune the stub also similarly as done the ant.  The
wave guide is an incomplete gnd. plane.   Or connect a cable to a better
ant.

I note the cantenna is the same as Ramsey's transceiver antenna for
their speed RaDaR gun.

bc



John Denker wrote:

> Hi --
>
> Somebody mentioned in passing that it is possible "buy"
> coax-to-waveguide adaptors.  Well, I suppose they are
> buyable, but it's sometimes more fun to make them from
> scratch.
>
> In particular, here's a scenario that might provide a
> nice opportunity to teach about wave mechanics, including
> waveguides, antennas, polarization, and a bunch of other
> details ....  *AND* provide a memorable answer to the
> question of what physics is good for.
>
> Here's the motivational scenario:  Really and truly, on
cut