Imax 2000 and SWR Issues

[Grogan]

My Friend just put up a tower aprox 50 Ft. with an Imax-2000 on top. The coax is new 9913 the radio is low power Am 11 meters or a mobil cb,power-supply power mic no amp as of now. In tuneing he had swr problems that could not be adjusted at the antenna. with several attemps at the antenna..Had a local teck come over with antenna analizer and Swr equipment and the end result was to add ( and dont quote me I forget how long) but like 80 ft of coax. everywhere I read you can not change your Swr by the legnth of coax. I read to add a balun of 6 to 8 turns and about 8 ft total at the antenna base. Was asking what is the best thing to do seems like a lot of coax 185 total legnth and he wants it in one full legnth from meter to antenna. I also think his highest swr is 1.5 to 1 on 40 chanels he is also thinking of buying an export that is why he thinks his match is an issue.

 

[wavrider]

Imax 2000 has good VSWR on 10/11/12/15 meters.

Adding coax is not the solution.

Either it is bad connections on the end of the coax or bad coax or a faulty Imax 2000.

Out of the box with no tuning it should be great VSWR on 11 meters.

 

[RatsoW8]

Imax 2000 has good VSWR on 10/11/12/15 meters.

Adding coax is not the solution.

Either it is bad connections on the end of the coax or bad coax or a faulty Imax 2000.

Out of the box with no tuning it should be great VSWR on 11 meters.

What is the SWR reading on the antenna that's so bad? Anything under 2:1 is fine for hf. And that's also good for a cheaply made antenna like the I-Max 2K (which I own and am using) If the antenna is working correctly he should have no problem getting an acceptable match. Something is wrong with the antenna or connectors ar maybe even a bad piece of coax.

Any "tech" that says to add coax to tune an antenna is not much of a tech to begin with, even if he owns an antenna analyzer.

 

[W5LZ]

The Imaxx has a set of tuning rings on it. Use them to get a reasonable SWR on 11 meters, that's what they are there for. Don't count on that SWR staying good if that antenna is used on other bands, or just 'out of band' on 11 meters.
If changing the length of the feed line changes the SWR, then the antenna isn't tuned correctly. It's as simple as that. Finding the reason for that sort of SWR change isn't all that simple. If changing those tuning rings can't correct things, then there's got to be some reason for it. The trick is to find that reason, not hide it with the feed line length.
- 'Doc

 

[Grogan]

As in the first he did adjust at the antenna or tuneing rings.

 

[W5LZ]

Then there are two possibilities. That adjusting was done incorrectly, or, there's something wrong with the antenna or how it's mounted. Or a third possibility, the '9913 is bad for some reason.
- 'Doc

 

[Grogan]

I will have to ask him about where the coax came from, but I think it was tested by the antenna analizer. I think I need to ask him more questions,I am told all conections and conectors are good. I am also wondering about wraping a balun. I read 8' and at 6 to 8 turns. To stop any Rf from comeing back down the coax that may be the cause of High Swr. now He is reading (I don't know where from 18 turns? ) ??? I have herd of bad Imax out of the box new.

 

[wavrider]

SWR readings using an MFJ-269 Analyzer and 55 feet of LMR-400.
20M .....10.0:1---NOT USEABLE.
17M .....2.7:1.....75 OHMS
15M .....1.9:1.....40 OHMS
12M .....1.4:1.....47 OHMS
11-10M - 26.0 to 29.7MHz... 1.1 to 1.4...50 OHMS

Copy and paste from another site.

When I used my analyzer the vswr's were pretty close to this.

As previously posted anything 2:1 is usable on HF frequencies.

Hope you get it figured out.

 

[psycho]

I-Max 2000s mattch in wel. Most poeple who use thme are satassfried.
You ether half a bad antenner or the coax/connectos are frapped. Maybee even a bad swr meter is giving funky reedings.
Gud luk!

 

[Grogan]

Over the weekend He droped the tower down and wraped a balun close to the antenna on a short piece of I think 5" pvc pipe and secured it. After standing the tower back op the swr came back as 1.2 on CB chanel 1 and 1.4 on chanel 40 he is now happy with the results. My guess is RF on the feedline was the swr problem. He still needs time to test to see if he still gets out good but for all the local talking he is doing fine.

 

[Robb]

The Imax has got to be the easiest antenna ever to install. Also true for the Antron A99. Just take it out of the box and assemble it. One, two, three sections screwed together - that's it. Couldn't take longer than two minutes if you take your time. Absolutely does NOT need to be adjusted. Just take it out of the box and assemble. They come from the factory pre-adjusted.

Neat. Easy. Cheap. Clean. Done.

Bad coax or connectors would be my guess if there is any problem at all.

You shouldn't have needed to adjust the rings.
That tells me what I needed to know . . .

 

[W5LZ]

"Absolutely does NOT need to be adjusted."
Don't bet too much on that, it's certainly not guarantied. You are expected to check the antenna to see if it does need adjustments. And if so, you are provided with a means of making that matching adjustment. Those rings are there for a purpose...
- 'Doc

 

[Robb]

"Absolutely does NOT need to be adjusted."
Don't bet too much on that, it's certainly not guarantied. You are expected to check the antenna to see if it does need adjustments. And if so, you are provided with a means of making that matching adjustment. Those rings are there for a purpose...
- 'Doc

Well, yes and no.
They are advertised by the factory as being pre-adjusted. Mine was. Several others in my area that had bought them found they were already adjusted too. This evidence may be anecdotal; but consistent.

But yes; better to check first.

 

[wavrider]

"Absolutely does NOT need to be adjusted."
Don't bet too much on that, it's certainly not guarantied. You are expected to check the antenna to see if it does need adjustments. And if so, you are provided with a means of making that matching adjustment. Those rings are there for a purpose...
- 'Doc

Doc that fishing pole is such a low Q with the matching network that it works 10/11/12/and 15 meters with no tuner.

Those adjustment rings will allow the op to "fine" tune the impedance where his favorite portion of the band is at.

If indeed the problem is as described it is either bad coax, bad connectors or bad VSWR meter/bridge.

Do not have to tune that antenna, unless of course there are metal structures nearby that may influence input impedance. It is a pretty decent dummy load without having to play with those rings. But that dummy load radiates pretty good

 

[copclyde]

Doc that fishing pole is such a low Q with the matching network that it works 10/11/12/and 15 meters with no tuner.

Those adjustment rings will allow the op to "fine" tune the impedance where his favorite portion of the band is at.

If indeed the problem is as described it is either bad coax, bad connectors or bad VSWR meter/bridge.

Do not have to tune that antenna, unless of course there are metal structures nearby that may influence input impedance. It is a pretty decent dummy load without having to play with those rings. But that dummy load radiates pretty good

I'm having the same problem. I have a large tower, guyed below the top section. 7/8 heliax, small jumper to antenna. Added 50 ft to get a lower swr.Never had to do that before. Had the same set up on same tower, only difference is I added a longer mast and a ground plane kit. Radio hears ok, but recently I had to replace my amp in the rear of my 2995 and now the finals are shot inside the radio. I could use some advice too. Maybe ground plane kit is reflecting RF off the tower ?