<div dir="ltr"> Brian,<div><br></div><div>Yea, at those power levels and balun is probably not needed. What happens without one is you get some radiation on the coax feeding the antenna. One simple way though to add a little bit of a choke balun is to create a couple a loop with a couple turns of the feed line right before the antenna.</div><div><br></div><div>As far as attaching to the antenna, soldering or using tap screws will work just fine. I've seen it done both ways.</div><div><br></div><div>Good luck on your project.</div><div><br></div><div>Dan W9EQ</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, Sep 28, 2020 at 12:36 PM Brian via TriEmbed <<a href="mailto:triembed@triembed.org">triembed@triembed.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hi Folks,<br>
<br>
I know there are several radio-smart people on this list, so I hope the <br>
rest will forgive the noise as I pose a couple questions here.<br>
<br>
The questions first; I'll provide background afterward.<br>
<br>
I have settled on a digital FM transmitter chip (Silicon Labs' SI4721), <br>
and a simple dipole antenna. Two questions arise from this decision:<br>
<br>
1. The transmitter has a single-ended RF output, but will be fully <br>
isolated from earth ground in operation (running on batteries or an <br>
isolated AC/DC supply). A dipole is a balanced load, but since "ground" <br>
of the radio circuit is isolated, can I just treat it as "balanced" and <br>
connect the circuit ground to the other half of the dipole? Or do I <br>
really need to use a balun for a proper balanced output? Coverage area <br>
actually needs to be very small (< 100'), so I'm not majorly concerned <br>
with impedance mismatch losses, etc.<br>
<br>
2. I'll be using 1/2" copper pipe as the elements, held inside a larger <br>
PVC enclosure. What's the best way to bond wires to the pipe? Should I <br>
just solder them on? Tap a hole and use a screw to clamp them? Some <br>
kind of shark-bite approach? Does it even matter at all?<br>
<br>
Here's the background:<br>
<br>
My church does a Christmas program called the Drive-Thru Christmas, <br>
which is made up of five live-actor scenes distributed around our <br>
parking lot. Guests are typically given a narration on CD which they <br>
play inside their vehicles as they move from scene to scene. In order <br>
to improve our social isolation this year, I'm doing some R&D on the <br>
"talking sign" idea, using five separate short-range FM transmitters to <br>
broadcast the scene's narration to the guest's FM radio in their car. <br>
Each transmitter would broadcast on a different frequency, and some <br>
system would step each transmitter through the list of frequencies in <br>
time with the car's movement through the scene, so we can maintain our <br>
5-car pipeline but not require the guest to re-tune their radios. We <br>
tried using an internet streaming option last year (for folks with <br>
smartphones linked to their car stereos) but that, I hear, was an abject <br>
failure with many people unable to access the stream.<br>
<br>
Well anyway, thanks in advance for any advice!<br>
<br>
Cheers,<br>
-Brian<br>
<br>
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