loaded antenna testing 101

[Thee Middleone]

I have a cushcraft MA5VA which I bought second hand.

I find that I can only get close to 1.5 SWR on the 12 meter section of this antenna. All other sections show >25 SWR on my 259C.


When testing, I will set the 259C for the desired band and then try to get a SWR reading close to 1:1 in that band. I will then sweep up the bands and try to get the same results in all other bands on this antenna. I was told to touch the end element of the band under test and see if it changes the results on the meter, and it will.

I am finding that when testing any of the other sections I can touch any element and it will affect any other section during testing, except for the 12 section of course.

Is there a step by step process that is spelled out somewhere that I can follow just to make sure I am doing this right? or does this sound like I have multiple coils that are damaged?

[Jeff Liebermann]

On Mon, 24 Jan 2022 07:13:23 -0800 (PST), Thee Middleone

Post by Thee Middleone
I have a cushcraft MA5VA which I bought second hand.
I find that I can only get close to 1.5 SWR on the 12 meter section of this antenna. All other sections show >25 SWR on my 259C.
When testing, I will set the 259C for the desired band and then try to get a SWR reading close to 1:1 in that band. I will then sweep up the bands and try to get the same results in all other bands on this antenna. I was told to touch the end element of the band under test and see if it changes the results on the meter, and it will.
I am finding that when testing any of the other sections I can touch any element and it will affect any other section during testing, except for the 12 section of course.
Is there a step by step process that is spelled out somewhere that I can follow just to make sure I am doing this right? or does this sound like I have multiple coils that are damaged?

Manual:
<http://manuals.repeater-builder.com/Cushcraft/MA-5VA/MA-5VA.pdf>

I found this comment in a review at:
<https://www.dxengineering.com/parts/csh-ma5va>
"Works well on all bands, requires careful tuning of the extendable
elements and the usable, low swr (1.2 -2.0) is narrow, about 100 khz."
I suggest you read the entire review as the owner also had a "won't
tune" problem.

Note that the extendable elements are part of the tuning.

Perhaps using a VNA will prove more accurate and allow you to see
narrow VSWR dips that are radically off frequency:
"How to use the NanoVNA to sweep / measure an antenna system's SWR and
optimize its tuning"

(6:06)

Also, testing a vertical antenna usually requires a counterpoise and
grounding system. Testing such an vertical, laying on the ground
isn't going to work. Try assembling and installing the vertical in
something close to the typical operating configuration.

Good luck.

[Thee Middleone]

Post by Jeff Liebermann
On Mon, 24 Jan 2022 07:13:23 -0800 (PST), Thee Middleone

Post by Thee Middleone
I have a cushcraft MA5VA which I bought second hand.
I find that I can only get close to 1.5 SWR on the 12 meter section of this antenna. All other sections show >25 SWR on my 259C.
When testing, I will set the 259C for the desired band and then try to get a SWR reading close to 1:1 in that band. I will then sweep up the bands and try to get the same results in all other bands on this antenna. I was told to touch the end element of the band under test and see if it changes the results on the meter, and it will.
I am finding that when testing any of the other sections I can touch any element and it will affect any other section during testing, except for the 12 section of course.
Is there a step by step process that is spelled out somewhere that I can follow just to make sure I am doing this right? or does this sound like I have multiple coils that are damaged?

<http://manuals.repeater-builder.com/Cushcraft/MA-5VA/MA-5VA.pdf>
<https://www.dxengineering.com/parts/csh-ma5va>
"Works well on all bands, requires careful tuning of the extendable
elements and the usable, low swr (1.2 -2.0) is narrow, about 100 khz."
I suggest you read the entire review as the owner also had a "won't
tune" problem.
Note that the extendable elements are part of the tuning.
Perhaps using a VNA will prove more accurate and allow you to see
"How to use the NanoVNA to sweep / measure an antenna system's SWR and
optimize its tuning"
http://youtu.be/xa6dqx9udcg (6:06)
Also, testing a vertical antenna usually requires a counterpoise and
grounding system. Testing such an vertical, laying on the ground
isn't going to work. Try assembling and installing the vertical in
something close to the typical operating configuration.
Good luck.
--
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff,

I appreciate the links and the advice.

I have already read through assembly manual and have reassembled this antenna after some steel wool and dab of Ideal NOALOX on each connection point.
all my measurements were spot on and I did the work with this laying on sawhorses.
MFJ said that I would not have an issue working on them in a horizontal position and they did not mention needing a ground plane, maybe as this model has 8 counterpoise?
I like the idea of trying again and but with it in its working position.
I also like your's and Jims suggestion on a graphing antenna analyzer.
And this time I will go as slow as possible to see if I passed over the very narrow

Going to check the nano link now.

Thanks to you both!

Rodney

[Jim Pennino]

Post by Thee Middleone
I have a cushcraft MA5VA which I bought second hand.
I find that I can only get close to 1.5 SWR on the 12 meter section of this antenna. All other sections show >25 SWR on my 259C.
When testing, I will set the 259C for the desired band and then try to get a SWR reading close to 1:1 in that band. I will then sweep up the bands and try to get the same results in all other bands on this antenna. I was told to touch the end element of the band under test and see if it changes the results on the meter, and it will.
I am finding that when testing any of the other sections I can touch any element and it will affect any other section during testing, except for the 12 section of course.
Is there a step by step process that is spelled out somewhere that I can follow just to make sure I am doing this right? or does this sound like I have multiple coils that are damaged?

I bought a new MA6VA once upon a time and a graphing antenna analyzer
showed no resonance for any trapped element band anywhere close to an
amateur band.

A complaint to Cushcraft resulted in a second set of elements that
worked perfectly upon installation.

As your antenna is used, first clean everything if you haven't already,
then carefully and slowly see if you can find a resonant frequency.

These antennas are narrow band it is easy to miss resonance with
something like a 259C.

If you can borrow a graphing antenna analyzer it will be much easier to
determine if the elements are in need of replacement or just badly
maladjusted.