[PARC] Using open line to feed antennas

[Rick P]

Here is some info on using open line to feed an antenna that was 
mentioned on the Sunday evening net.
with links to youtube videos .

Rick
ve3iqz


*****************************************.
.
.Good morning Ron,1:30 AM.
open wire line at 50 minutes



---------- Forwarded message ---------
From: *Donald Hellen* <donhellen at roadrunner.com>
Date: Sat, Jan 15, 2022 at 7:19 PM
Subject: [Ham-Antennas] What you need to know about transmission lines
To: <main at ham-antennas.groups.io>


I could swear I posted about this video before but I don't see the post. 
I could
have deleted it instead of sending it.

This fellow has a degree in physics and does a great job of explaining
transmission lines, characteristic impedance, SWR, real vs indicated 
SWR, line
losses in real life, and more.

*If you have little time, start at the 50 minute mark and you'll learn 
about why**
**reflected power is not lost (in a lossless wire), that it eventually 
gets**
**delivered to the load (after Ohmic losses), and why using open wire 
line can be**
**used with high SWRs with negligible losses. *

I'm only an engineer who does CAD modeling work for a large semi truck
manufacturer, but he didn't talk over my head and made it fairly easy to
understand.

https://www.youtube.com/watch?v=uR8Rz0GrPVI

Donald KX8K


.


    [Ham-Antennas] Loop antennas and NanoVNA

Inbox
Dennis, your 4-inch spaced open wire is pretty high impedance.  Is that 
really what you wanted?  For example, assuming you used AWG #14 wire for 
the parallel conductor transmission line, that calculates to Zo = 580 ohms.
https://hamwaves.com/zc.circular/en/ <https://hamwaves.com/zc.circular/en/>

Further, two types of transmission lines will yield different results 
regarding the low SWR frequencies.  I'm not surprised the low SWR 
frequencies were different for the coax and the open wire feeders.  This 
is expected.  I'd recommend using SimSmith to take out the effect of the 
transmission lines.  Knowing the measured impedance (complex) at the end 
of a particular transmission line, you can put that in and add that 
length of line to observe what each line does no the Smith Chart 
(resulting impedance at the antenna).
http://www.ae6ty.com/smith_charts.html 
<http://www.ae6ty.com/smith_charts.html>

I'd leave the 4:1 out of the measurement picture.  Connect the 
transmission line directly to the S11 port of the NANO. Operate the NANO 
on battery and connected to NOTHING, not even your holding the NANO.  Be 
sure it is sitting on a non-conductor and well removed from close-by 
conductors. At HF frequencies, the measurement will be quite accurate 
and will not includ the 4:1 which may not be required in practice.

Dave - WØLEV


      W0LEV davearea51a at gmail.com via
      <https://support.google.com/mail/answer/1311182?hl=en> groups.io
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