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On Aug 12, 2020, at 17:05, David Eckhardt <davearea51a@...> wrote:

?You are most concerned with the impedance the end of the coax presents to
your matching network/radio. Therefore, you should measure at the shack
end of the coax. Calibrate the VNA as a stand-alone instrument. Once
calibrated, connect it to the shack end of the coax and make your
measurements.

Remember, the native VNA without using Saver supported on a PC has only 101
points. Measuring from 2 to 30 MHz is not appropriate as it will yield a
measurement poist every 0.3 MHz, not good for looking for narrow
resonances. So, either make the measurements in small increments across
the HF bands or use NANOVNA Saver supported on a PC or laptop which offers
up to 1024 measurement points (and cal points).

Dave - W?LEV

Dave - W?LEV

On Wed, Aug 12, 2020 at 9:57 PM Darrell Carothers <rescuemedic1@...>
wrote:

It is my understanding that this Matchbox is a 9:1. The system gets good
reviews on 80-10m. So if I am using this system, would I need to calibrate
the NanoVNA using the coax, then get my measurements from the antenna or
calibrate the NanoVNA as normal and get measurements from the entire
system? I appreciate your detailed explanation.

Darrell

Sent from my over-rated IPhone 7 Plus. Any Mis-spellings or grammar
errors are due to my IPhone auto correct feature.

On Aug 12, 2020, at 16:37, David Eckhardt <davearea51a@...> wrote:

?Not quite correct! Ladder line is a transmission line just like coaxial
line. However, they perform their function differently.

1) The center fed dipole is a balanced source/load - differential
source/load.

2) Ladder line is a balanced transmission line - differential
transmission line. It is the correct transmission line to connect

directly

to a balanced/differential source/load (dipole). It does NOT participate
in radiation. As a transmission line, fields close onto themselves
(between the two parallel conductors) and do not open onto free space, so
no radiation occurs.

3) Coax is an unbalanced transmission line - common mode transmission
line. Fields are intended to close between the inner conductor and the
inside of the outer shield/braid. It is NOT the correct transmission

line

to connect directly to a balanced/differential source/load (dipole).

4) If coaxial cable it is connected directly to a dipole, the outer
portion of the shield/braid WILL participate in radiation and gather

noise

on receive that will couple into the antenna and receiver.

5) The correct manner in which to connect a coaxial transmission line
(unbalanced transmission line) to a dipole (balanced source/load) is
through a 1:1 current balun or common mode choke. This will prevent the
outer layer of the coaxial braid from participating in radiation and
coupling local noise into the antenna/receiver.

6) 4:1, 2:1, 9:1,.......are NOT appropriate for the purpose stated in
(5). These are TRANSFORMERS and NOT BALUNS.

7) If you MUST use a transformer for impedance transformation, follow it
with a 1:1 current balun or common mode choke.

Dave - W?LEV

On Wed, Aug 12, 2020 at 9:20 PM Darrell Carothers <

rescuemedic1@...>

wrote:

I am slowly getting parts in to try my end fed long wire antenna.

Correct

me if I am wrong. With a center fed dipole, the 300 or 450 ohm ladder

line

feeding it is part of the antenna. I would think I would use my NanoVNA

at

the end of the feed to check where it would be resonant and for SWR. If

so,

would the coax feeding the end fed long wire antenna also be considered
part of the antenna and use the NanoVNA to measure accordingly? I am

told

this doesn’t need a counterpoise.

Am I correct or am I missing something?

Thanks
Darrell
N5FTW



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*Dave - W?LEV*
*Just Let Darwin Work*

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*Dave - W?LEV*
*Just Let Darwin Work*