High SWRs with Dipole

[codeman]

I recently bought a dipole antenna from Ebay. It is very well made and I hooked it up last night and the skip came rolling in. But my problem is that I have high SWRs. I have it hanging horizontally from two trees only about 7 feet high.

I know it gets out locally for about 4 -5 miles. But no luck on DX. This antenna is already tuned for 11 meters, so why would I have high SWRs?

I have seen videos and heard people mounting them in rafters, apartment walls and such. So I know that the height I have it at should be ok as far as SWRs go. Right??

Would I use the same type coax as I do in my truck?

 

[Marconi]

I recently bought a dipole antenna from Ebay. It is very well made and I hooked it up last night and the skip came rolling in. But my problem is that I have high SWRs. I have it hanging horizontally from two trees only about 7 feet high.

I know it gets out locally for about 4 -5 miles. But no luck on DX. This antenna is already tuned for 11 meters, so why would I have high SWRs?

I have seen videos and heard people mounting them in rafters, apartment walls and such. So I know that the height I have it at should be ok as far as SWRs go. Right??

Would I use the same type coax as I do in my truck?

NOPE, you're wrong regarding you're being OK. The statements you give us suggest you are not OK.

The images below indicates why your antenna shows a high SWR.

It likely does not have a high SWR...if installed correctly.

This also helps explain why you might not be getting out too far and unable to contact what you might hear from DX. Most of your signal is going straight up being that low to the ground. This antenna was probably tuned to be installed at least 20' high. Also, the antenna being horizontal will reduce your local contacts some if they are mobile or vertical base antenna signals. This is due to the polarity differences.

View attachment Codeman's dipole.pdf

 

[W5LZ]

The assumption that get's everybody is that 'pre-tuned' thingy. It can certainly be pre-tuned to be 'close' to right, but there's no way that can account for all the variables with any installation. Probably the biggest 'catch' to that pre-tuned thingy is height above ground and what's around the antenna that will affect it's impedance matching (SWR). Any antenna has to be tuned for where it is placed. That adjustment may not be large by any means, but it still has to be done.
So how far 'off' is your antenna, and is it too long or too short? If the SWR is lower at the high end of the band it's too short. If it's lower at the bottom end of the band then it's too long. There are two (quick'n'dirty) ways of lowering SWR. One is by 'drooping' the legs a little bit, the other is by changing the length of the antenna. With a dipole, that means equal amounts added/removed from both 'sides'. (And before you do any 'removing', try to get the thing higher above ground to start with!) Which of the two methods would be easiest for you?
there's going to be some differences in how you mount the thing, horizontally/vertically. That's a polarization thingy. Mixing polarizations (H/V) means you are not going to hear things very well before the signal 'skips', local stuff will be weaker than further stuff. That's normal, nothing wrong with the antenna, just the polarization.
- 'Doc

 

[Beetle]

You use the term "high SWRs" [sic], but you don't quantify it. What, exactly, is the SWR on Channel 1, Channel 20, and Channel 40?

Seven feet off the ground? Get it up about 20 more feet and then try it. A dipole isn't going to be a great DX magnet even if installed at 50 feet. Seven feet, however, is a joke.

 

[codeman]

Beetle, I would love to have the antenna at 20 feet or better, but I am renting this place so 7-8 feet is about as good as it will get.

Like I said in my original post, people are using these dipole antennas hanging in garages, apartments and the such. So I know it is possible to make some DX contacts with them. Sure, it is not the optimal setup. But, I want to give it a shot.

If you will read the article below, you will see he only had his mounted about 7 feet off the ground and was making dx contacts


CBRadioMagazine.com - Radiowavz Bazooka Antenna Review



My main concern is to not damage my radio with high SWRs. My meter is showing over 3 across the band. I'll try to shorten the antenna and see what happens.

Marconi, is there any way of telling if the readings from my meter are accurate?

 

[Robb]

Codeman:

Just because you read that someone made some impressive contacts with the dipole set up low to the ground doesn't mean that it is correct - or even consistent. The physics of dipoles requires a higher clearance from the ground for best performance - as has already been explained. If you live in a location that won't permit you to put it up any higher; then I suggest that you turn it vertically for better performance and consistency.

 

[Beercanman]

When you go to tune your dipole keep in mind that you can fold the ends in about an inch at a time rather than cutting it. This way you can experiment more and not worry about going too short. Chances are though, being that low to the ground you are going to continue to see high reflect or swr.

Sent from your mom's mobile phone.

 

[stoneman]

I have a Workman dipole in the attic, works great..Swr's are 1,1. Also it came from Ebay as well..

 

[2RT307]

Beetle, I would love to have the antenna at 20 feet or better, but I am renting this place so 7-8 feet is about as good as it will get.

Like I said in my original post, people are using these dipole antennas hanging in garages, apartments and the such. So I know it is possible to make some DX contacts with them. Sure, it is not the optimal setup. But, I want to give it a shot.

If you will read the article below, you will see he only had his mounted about 7 feet off the ground and was making dx contacts


CBRadioMagazine.com - Radiowavz Bazooka Antenna Review



My main concern is to not damage my radio with high SWRs. My meter is showing over 3 across the band. I'll try to shorten the antenna and see what happens.

Marconi, is there any way of telling if the readings from my meter are accurate?

Codeman, watch the video at 1:44. You'll have to turn your head to watch it, sorry. No, a bazooka is not optimal at 7 feet off the ground. Fix your SWR's, and don't get discouraged.... if that's the only way you can run it, RUN IT!

73,
RT307

 

[Marconi]

Beetle, I would love to have the antenna at 20 feet or better, but I am renting this place so 7-8 feet is about as good as it will get.

Like I said in my original post, people are using these dipole antennas hanging in garages, apartments and the such. So I know it is possible to make some DX contacts with them. Sure, it is not the optimal setup. But, I want to give it a shot.

If you will read the article below, you will see he only had his mounted about 7 feet off the ground and was making dx contacts


CBRadioMagazine.com - Radiowavz Bazooka Antenna Review



My main concern is to not damage my radio with high SWRs. My meter is showing over 3 across the band. I'll try to shorten the antenna and see what happens.

Marconi, is there any way of telling if the readings from my meter are accurate?

Sorry, I know little about radios. I do hear claims that the meters in radios are not accurate.

 

[Marconi]

Codeman, watch the video at 1:44. You'll have to turn your head to watch it, sorry. No, a bazooka is not optimal at 7 feet off the ground. Fix your SWR's, and don't get discouraged.... if that's the only way you can run it, RUN IT!




73,
RT307

307, your video link did not work.

BTW, codeman you can adjust the antenna to get a better SWR to be safe for your radio. My model shows you can probably get a near perfect match at 7' feet, but it makes no difference to the performance according to this model. If possible, how about just raising the antenna up higher between the two trees and then you might not have to cut the wire? It probably is the height that is causing your wire to be out of resonance. That way you will gain, big time, on the performance you want.

What is the SWR reading you are seeing at 7' feet.

Good luck.

 

[Beetle]

If your meter is "showing over 3 across the band", something is wrong. You should see a curve, typically starting high at one end, getting less in the middle, and then high again at the other end. If you're reading exactly the same on each of the 40 channels, you essentially have a dummy load connected. You need to determine whether the antenna is too long, or too short, and the best legal thing for that is an antenna analyzer.

 

[HomerBB]

I know you said you could not get your dipole up higher. However, if you have something like a extendable painter pole you might try using it in the center of your dipole where the coax attaches and at least push the center up as many more feet as you can get away with. Another option might be to find a structure or tree and take one end of the dipole up as high a possible and let the other end travel diagonally toward the ground as a sloper. Another option is to have one half of the antenna straight down with the other half horizontal, etc.

I agree something is amiss when you have a 3+ SWR across the band. Beside the issue of length or height, be sure you've not got something in your feed line disconnected, or shorted across between the center coax connector and the braid.

 

[2RT307]

Sorry guys. I'll try again.

http://www.youtube.com/watch?v=PkJPbJVah2s

73,
RT307

 

[Brake Weight]

Vertical vs. Horizontal dipoles.