[TriEmbed] OT: RF questions

[Pete Soper]

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
>
> _______________________________________________
> Triangle, NC Embedded Computing mailing list
>
> To post message: TriEmbed at triembed.org
> List info: 
> http://mail.triembed.org/mailman/listinfo/triembed_triembed.org
> TriEmbed web site: http://TriEmbed.org
> To unsubscribe, click link and send a blank message: 
> mailto:unsubscribe-TriEmbed at bitser.net?subject=unsubscribe
>