I think it's going to be GREAT! And which end is down is perfectly
arbitrary if there's no circuit ground path to the "outside". And if it
were me I'd try it and if signal strength is poor then consider a
balun. I didn't spend much time with the datasheet but couldn't figure
out what the transmit level is. In the old days 50mW was absolutely
kosher with FCC but now it's all about field strengths but I'm
absolutely positive no agents will parachute down if you put 50mW into a
decent antenna. But my guestimate is a fraction of that will work very
well with anything vaguely approaching line of sight to cars not too far
away.
All the best,
Pete
On 9/29/20 1:33 PM, Brian via TriEmbed wrote:
<snip>
Hi responders!
Thanks a lot for your input! I knew I could count on the community's
expertise. Here's some more detail and why I don't want to go with
anything but a vertical dipole (I forgot to mention it was a vertical
dipole).
Space is at a great premium, and ease of setup/teardown is critical.
I don't have room for an antenna with a 0.75-meter-radius circular
footprint (e.g. a 1/4-wave monopole with 45-degree reflector elements).
Range is almost not an issue. The idea is to transmit from a literal
signpost to a car parked at most 20 feet away.
None of the audio is live; it's all prerecorded and simply triggered
by an actor in the scene in order to synchronize with the arrival of a
car.
With five scenes, we can have a five-car pipeline; that is, five
guests each at a different point in the program. The point of
switching among frequencies is to have a single guest not have to
re-tune at each scene; rather the transmit frequency "follows the car"
so to speak. This is also to reduce interference between scenes.
My design intent is to have the feedline as short as possible (on the
order of centimeters) so as not to have to worry about transmission
line effects. The radio circuit will be mounted to the side of the
signpost at the dipole feed point.
So the dipole will be oriented vertically, with the "ground" side
down, and positioned without any elevation. I've dropped a couple
very crude drawings here:
Bird's eye view of the layout:
https://imgur.com/wcjO41M
And a plan & elevation view of a signpost:
https://imgur.com/a/ZXTW5eF
I guess at this point what I'm really wanting to hear is mainly
"that'll NEVER work!!" or "yeah, that oughta work ok". XD
Cheers,
-B
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