started building a 6m Moxon antenna... the best swr i can find is about 1.6 at abot 48mhz but there is at best about a 22 reactance... ideas?
-
You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
Moxon antenna high SWR and reactance
- Thread starter mr_fx
- Start date
More details please. Is it at operating height ? how is it made ? can you do a sweep and give us the R and X readings .Without more information my guess is you just need to shorten your driven element a little .
If you use the Mox-Gen free Moxon building software to make your antenna you should land very closely to your expected center frequency when done.
Using wire for the elements I used the center of the wire for the measurements. Using tubing I made sure I put the over all diameter of the tubing in the Mox-Gen calculator. When I built it I used the measurements to the outside of the tubing and came out very close, too.
1. Be sure the driven element is split in the middle like a dipole is usually done.
I used 1/2 inch between each side of the driven element.
2. The reflector is not split, but a single continuous element from one end to the other.
3. The distance between the ends of the two element as they point backward and forward toward each other is critical. Do not just "get it close".
As little as 15' above the earth I was able to obtain a good SWR match with either of my Moxons antennas. They are wide-banded, and forgiving, not requiring that you operate directly on your center frequency to perform well.
When constructed carefully with due attention to isolating the elements where they are mounted with non-conducting materials expect a very low SWR, a near, if not exact 50 Ohm impedance, and a resonant antenna.
This is an 11 meters Moxon with a hoped for center frequency at 27.385.
I agree with vkrules about the length of the driven element potentially being long. The Mox-Gen Calculator got me very close. Shortening the driven element slightly got me the reading you see above.
Before shortening it I was here:
Using wire for the elements I used the center of the wire for the measurements. Using tubing I made sure I put the over all diameter of the tubing in the Mox-Gen calculator. When I built it I used the measurements to the outside of the tubing and came out very close, too.
1. Be sure the driven element is split in the middle like a dipole is usually done.
I used 1/2 inch between each side of the driven element.
2. The reflector is not split, but a single continuous element from one end to the other.
3. The distance between the ends of the two element as they point backward and forward toward each other is critical. Do not just "get it close".
As little as 15' above the earth I was able to obtain a good SWR match with either of my Moxons antennas. They are wide-banded, and forgiving, not requiring that you operate directly on your center frequency to perform well.
When constructed carefully with due attention to isolating the elements where they are mounted with non-conducting materials expect a very low SWR, a near, if not exact 50 Ohm impedance, and a resonant antenna.
This is an 11 meters Moxon with a hoped for center frequency at 27.385.
I agree with vkrules about the length of the driven element potentially being long. The Mox-Gen Calculator got me very close. Shortening the driven element slightly got me the reading you see above.
Before shortening it I was here:
Last edited:
At the moment it the antenna is hanging in a tree.... i lowered the antenna to 4 or 5 feet and it was at 1.6 swr 15x.... @ 49.5mhz or so that was as good as it got... then the wind rotated the antenna and it dropped to 1.1:1 and 9x. I am thinking the antenna is reacting to the trees and/or the steel garage / being under a few dipoles
Simple to construct.
Cheap to build.
More gain than a halo.
So if an OP just wants to feel out 6 meters and see if they enjoy the magic band why not use a simple, inexpensive gain antenna to test the waters before jumping into a set of stacked 6 elements?
I agree with vkrules about the length of the driven element potentially being long. The Mox-Gen Calculator got me very close. Shortening the driven element slightly got me the reading you see above.
Before shortening it I was here:
do you recall the length of slightly??
moxgen gave you dimensions based on 27.385 which yielded meter reading of 26.949 = .525 low. inserting 27.910 in moxgen gives a difference of 2.94" in the A dimension.
When you shortened driven, did you widen the feed point and pull the ends closer
together leaving the reflector and driver ends matching?
It's been a day or two since then, but as I recall, I removed a 1/2" from the ends of the driven element (dimension B) where it is separated from the reflector leaving all other dimensions as they were. I may have done this more than once until I was satisfied.
I did not change the width of the antenna, nor the gap at the feed point.
I did not change the width of the antenna, nor the gap at the feed point.
Fellas, this antenna has been retuned and is working great, I have made several contacts, many of them well over 1000 miles, it has been up on the stack for a few months now and was on the test pole for a few months before that
- No one is chatting at the moment.