[TriEmbed] OT: RF questions

[Brian]

Hi Folks,

I know there are several radio-smart people on this list, so I hope the 
rest will forgive the noise as I pose a couple questions here.

The questions first; I'll provide background afterward.

I have settled on a digital FM transmitter chip (Silicon Labs' SI4721), 
and a simple dipole antenna.  Two questions arise from this decision:

1. The transmitter has a single-ended RF output, but will be fully 
isolated from earth ground in operation (running on batteries or an 
isolated AC/DC supply).  A dipole is a balanced load, but since "ground" 
of the radio circuit is isolated, can I just treat it as "balanced" and 
connect the circuit ground to the other half of the dipole?  Or do I 
really need to use a balun for a proper balanced output?  Coverage area 
actually needs to be very small (< 100'), so I'm not majorly concerned 
with impedance mismatch losses, etc.

2.  I'll be using 1/2" copper pipe as the elements, held inside a larger 
PVC enclosure.  What's the best way to bond wires to the pipe?  Should I 
just solder them on?  Tap a hole and use a screw to clamp them?  Some 
kind of shark-bite approach?  Does it even matter at all?

Here's the background:

My church does a Christmas program called the Drive-Thru Christmas, 
which is made up of five live-actor scenes distributed around our 
parking lot.  Guests are typically given a narration on CD which they 
play inside their vehicles as they move from scene to scene.  In order 
to improve our social isolation this year, I'm doing some R&D on the 
"talking sign" idea, using five separate short-range FM transmitters to 
broadcast the scene's narration to the guest's FM radio in their car. 
Each transmitter would broadcast on a different frequency, and some 
system would step each transmitter through the list of frequencies in 
time with the car's movement through the scene, so we can maintain our 
5-car pipeline but not require the guest to re-tune their radios.  We 
tried using an internet streaming option last year (for folks with 
smartphones linked to their car stereos) but that, I hear, was an abject 
failure with many people unable to access the stream.

Well anyway, thanks in advance for any advice!

Cheers,
-Brian