Building a Portable 20m Vertical Moxon Antenna by K5ACL

Greetings hams!

Back at it with another HF antenna - the experimenting never stops

This time we're constructing a Portable Vertical Moxon Antenna for 20 Meters using simple hardware and some telescopic poles.

You can find the associated write up here: https://www.k5acl.net/a-vertical-moxon-antenna-for-20-meters/

This is my first Moxon attempted, I think the results are pretty decent & I can't wait to try it over salt water!

Thanks for watching,

73
K5ACL

 

intresting

 

That's very cool.

 

Did you check you the VDA design. It should be pretty close in performance and only require one pole (and a smaller cross member) which should make it easier to turn.

 

Very interesting. I have been using a Moxon for 15M for long time and it is a vertical configuration like yours but with only one fishing pole. I had excellent results allover the world operating from a local park battery operated.



Thank you and 73 de W6LDM

 

Nice antenna project, and excellent video as always.

Best 73,

 

The conundrum of center fed vertical dipoles is one that few want to discuss. The fact is the coax is in the near field and (by definition) near the current max. That means, at the very least, it will distort the power pattern, and more likely radiate itself--unless it is at a right angle to vertical, and thus horizontal.

Your one choke won't stop this.

45 degrees for the coax orientation is a good rule of thumb, but 90 degrees, at least 1/2 wave away in extent, is better assurance that the power pattern won't distort from the presence of the coax.

I suspect some of your 'unexpected' results come from the power pattern distortion.

Vertical Moxons are very popular in Japan, BTW.

 

In addition to a really good balun at the feedpoint:
About a dozen #31 mix ferrite beads along the coaxial cable in the near field can help a lot with that problem.
Using a half-wavelength section of RG-174 makes it lighter weight; the ferrites can be smaller diameter and lighter.

 

Interesting! Thanks for this explanation - that would explain a bit. I'll have to figure out a way to get the coax perpendicular - which would be easy for Field day, just support the coax in a nearby tree, but might be a bit harder at other locations!

73

 

RG174 would probably work great! Great idea - I use the same on my SOTABeams link dipole with great success, would definitely alleviate a lot of the weight on the driven element pole! Thx!

73

 

That's the first I've heard of 'VDA' - i'll check'em out, was trying to figure out a way to do a 2 element beam with just two poles - this looks interesting thx!

 

Probably that effort is not really worth pursuing, as it takes up too much real estate. Best advise is make sure the bottom of the antenna (horizontal section) is as high above ground as possible. On 20m, at least 4 or 5 feet

 

I think the worries about pattern are there, but overstated. For portable ops, just put it up and work some stations! You can always move it around armstrong style, too.

Heck, I have this huge flat roof at 5 stories high, which allows me space to try out all kinds of antennas at 50 to 70 feet up. There's all sorts of crap up here... air conditioners, a high TV antenna, other antennas... just get something resonant up, do your best to mitigate issues, and start working DX!



More pics if you search me at HL1ZIX. And a moxon video is on the way from me, also... love them!

 

Incidentally, I'm having troubles finding the post someone made in the news recently about making an X between the four points of a horizontal wire beam, and feeding the coax down from that X support. I want to highlight that in a video, soon. Anyone know what thread that was?

Thanks!

 

You do a very good job with your video production. I have ADD and most ham videos lose me in less than a minute.