VHF and UHF antenna polarization and on air testing
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- Опубликовано: 8 сен 2024
- Here is a video part 2 of the Cushcraft 13b2 VHF yagi, explaining and demonstrating the differences in vertical and horizontal polarization of VHF/UHF antennas, and the effects of the way you mount the antenna on the mast or tower.
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Good stuff mate you have helped me out as a Newham a hell of a lot .
Nice to see a video on an old problem we solved many years ago. On EME many of us run X-Pol or dual polarized antennas to combat "Faraday". We have always used fiberglass vertical mounts to eliminate this problem. Fiberglass sections with 1/8 to 1/4 inch wall thicknesses can be bought on line from a number of places.We always also run our feedline off the back of the antennas down to a power divider supported by another fiberglass mount. I'm a 20 year SSB/CW op on 144 thur 2304 and have worked many vertical stations during openings. Yes they are down several db as compared to those running H-Pol antennas. The Sat packages offered by M2 come with a fiberglass cross member to eliminate vertical issues and pattern/SWR problems also.
JD Dupuy can you share the web site link, where you can buy the fiberglass vertical mount?
Thank you and to your fine lady for the demo. I just asked Dave KE0OG about this. On one of his last videos he put up a Yagi to work with his DMR. He his now able to hit a repeater that is 80 miles away from his home in Montrose, Co.He had to use a boom to get some distance from his mast. This video is a good complement to that one.
Thank you again.
73
KE0OAP
You nailed it!! Did the same experiment with a 430 antenna back in the 80's. I tried to convinced the local radio club about metal mast going thru a vertical beam and the coax feed path. But to no avail. Even cushcraft photo ads of their verticals with a metal mast going thru the antenna didnt help the issue. What I noticed was the excessive side-lobes with the metal mast. This was cured by a fiberglass mast from KLM. Then I joined AMSAT and one of their newsletters discussed the metal mast and coax feed along the beam support issue. Thanks again for posting this! 73, Dave WA9IVB
Your thinking is perfect. Your solution with a fiberglass mast is ideal and minimising how long (distance wise) the coax exists in the antenna aperture is correct too. Effectively, that means routing the coax at 90 degrees away from the plane of the elements. Note that running the coax along the boom is not an issue in itself, as long as it runs on the side opposite where the elements are mounted and as you demonstrated, leaves the boom at 90 degrees to the plane of the elements and not parallel to the elements which is all too easy to do with a vertically polarised beam. This is why many hams choose "L" shaped masts for vertical yagis. Coax routing is straightforward then.
So glad I watched this. I’ve been considering a Yagi down here in Broward. 73 KN4VVD.
Remember in rotating your yagi from vertical to horizontal you will need to re-tune your trans-match (Gama match) in most cases. Great vids Eric
My Kind of Radio!! I had two of those..... miss the days of "Rat Shack" as lots of ham's called it!!
Sorry, didn't realize this was pt 2. Great video
I have the cushcraft 10 element. Have it at a 45 degree . Works good ssb and fm. I am sending am also using a wooden dowel I put inside a piece of conduit. Swr across the entire band is 1.2.1 or less.
Eric,
That looks like a T2X Tailtwister rotor. It has 6 bolts on the bell. The T2X is the only Hy-Gain rotor using 6 bolts, all the others use 4 bolts. Great info in the video. 73 WB3BJU
I got the smaller one the 10 element. I bought a wooden dowel cut it to about 4 feet. Then put it in PVC pipe and sealed the ends. No swr problems at all.
Great video
Interesting and informative. Thanks
If you don't spin it 360 you could do what I did 50 years ago, build a small wooden hinged mount with a cord hanging down, simply changing it when needed. I worked the world qrp 4 watts using a 3 element beam and it was on the business channels back then 27, 235 and 27,245 am, now channels 24 and 25 cb! Usually oil companies working all over the world.
Good information. I’m having the same issue with my 220 yagi, I can’t get it to tune below 1:7:1 I’ll have to try the fiberglass pipe trick.
Thank you for your time, VIDEO seeing is believing, 73...!
Outstanding video many thanks.
Great video Eric. I'll be putting up an A270-10S with an A224WB in a week or 2. Verticals just arent doing it for me. I live in a valley in a lake.. NEARfest is 2 weeks away and I am going to get some fiber glass mast so I can mount that dual bander in the center. End mounts scare me.
Fun demo, thanks!
I would like to see a video on the Cushcraft 2M Hi-Lo Cross Yagi that has Vertical and horizontal elements on the same mast (circular polarization) with the possibility of two different feed lines (one for the vertical elements and one for the Horizontal elements).
Thanks!
Make an L-shape in mounting the antenna so it will not align in the mast that is bothering the efficiency of the antenna. I experimented in the B7 series and it's efficient to make long-distance call, the disadvantage you cannot here station in the side or back of the orientation of the antenna.
Regards from Malawi , 73 from 7Q7CT
How long have you had your HTX-212?
Excellent test.
I have a diamond x50a, would I still be able to use ssb even though it’s vertical?
I would love to see a part 3 using sideband if you catch the band while its open.
It's coming on June 10th VHF contest day
awesome video! thanks
The penalty of having cross polarization between two antennas, can result in as much as 20 db path loss, between the 2 stations! For those wishing to use a none conductive mast, above the rotator, with a vertically polarized yagi, schedule 40 or 80 PVC pipe can work fine, if fiberglass isn't available.
Great video! Thank you for the tests! 73! KD2JPV
Would have like to see a test with the metal mast mounted flush with the yagi as in the case with the fiber glass. But, very interesting test as it relates to horizontal and vertical polarization on VHF. J88AZ
Axis I did have a test the first test was using the metal mast up in the yagi parallel to the elements
Sorry, I didn't see part 1 of the video, but what I meant, is the first part of this video test, the metal mast almost form part of the antenna vertically. But, when you tested the fiberglass mast, I noticed that the top of the mast was flush with the boom of the antenna. Just wondering the SWR results if the metal mast was likewise flush with the antenna boom. J88AZ
Great video nevertheless! 73 -J88AZ
Good demo - one thing that concerns me - did you see your impedence and difference between the metal and fiberglass mast? Be careful of that, too - mismatched impedence can cause heating issues among other things. Especially at the VHF range.
Eric, did you cut your coax to a resonant length? I’ve read that cutting coax to multiples of half wave plus a quarter helps with getting a good match. To be fair, the swr you are getting, would result in minimal losses anyway, but every little helps as they say!
Nice video does it affect receiving also?
So what will cover more ground? Horizontal or vertical if everyone picked one polarization.
If you made an L angel near the top of your main mast and goes out horizontal with X distance, then mount your Yagi in a vertical configuration for avoid the effect of the vertical main mast. How long distance out for not getting any influence?
Very informative, really enjoy your videos. Just got my ticket KN4CWT
Is it Better to run the coax strait down and away from the antenna ???? I’m using a cushcraft 148 10 S
Thanks...
Great stuff! de WB5PUN 😎
I run dual polarized antennas on 2/432 EME to combat Faraday. I hate been locked out and have to wait for conditions to change. I had a nice 250 mile QSO on 1296 years ago with a guy who could rotate his antenna from Vertical to horizontal. He had a local 1296 repeater that he used the antenna vertically polarized. Here's the neat video of that QSO ruclips.net/video/Wp6nrQZo_oY/видео.html
with that power line open like that, are you getting and interference?
Don't live there anymore
make a vedio on LUITON LT-25W HT radio
Flip it horizontal tell your friends to get on SSB!
I wonder what your actual SWR differences are at the antenna mast??? I'm betting the metal mast SWR is much worse than the numbers in your shack...
Great video, informative. 73 W9ACC
i use lmr400 minimum for everything. UHF gets hardline
This is a good example of someone rotating their antenna from H-Pol to V-Pol. Larry had a local repeater that he would work on 1296 but wanted to be able to rotate it to horizontal. Watch the difference in signal strength at 285 miles. ruclips.net/video/Wp6nrQZo_oY/видео.htmlm11s
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Too bad on the FM SWR 144 to 146 2.2 to 2.6 I tried a lot to no avail with the horizontal position👎🏼👎🏼👎🏼👎🏼👎🏼
That mast pole isn't hurting you as badly as the way you have the coax hanging down and TOUCHING your elements!
You need to run and dress that coax straight down the TOP of that boom to the mast and then 90 degree that coax down the mast and you'll fix your problems.
And that 45 degree idea is foolish! You are wasting the potential of that antenna. And anyone who tells you differently should NOT be listened to, probably about anything.
The accepted standard is that FM is vertically and SSB/CW Is horizontally polarized. There's no magic fix! Every degree you move that antenna off the the same polarity of your intended station you are working you are just losing db's, period!
Pick one and put up a separate antenna for the other.