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


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



---------- Forwarded message ---------
From: Donald Hellen <[email protected]>
Date: Sat, Jan 15, 2022 at 7:19 PM
Subject: [Ham-Antennas] What you need to know about transmission lines
To: <[email protected]>


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


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[Ham-Antennas] Loop antennas and NanoVNA

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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. 

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).

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 [email protected] via groups.io