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Imax2000 swr
- Thread starter Last man standing
- Start date
Assuming (dangerous to do) that the antenna is new and the coax isn't; then I will suspect the coax might have a problem. Used coax can (not saying that it is) deviate from its center. That can affect SWR.
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I don't think I can make a 4" coil out of this coax should I splice in some small stuff ?
Also I hooked up a Wilson 5000 mag mount at the end of the coax,and stuck it to deck table
Swr was the same as without the 86 ft of cable,I think the cable is good .
Also I hooked up a Wilson 5000 mag mount at the end of the coax,and stuck it to deck table
Swr was the same as without the 86 ft of cable,I think the cable is good .
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OK!!!!
Lets get back to the subject.
I would suggest taking the choke out, trying a different piece of coax, even a short jumper just for test purposes to see how the VSWR curve looks with a DIFFERENT transmission line.
If the antenna checks good and the VSWR is different with a short jumper then it may be the coax.
IF it is the same then it is the antenna.
I would do all of this AFTER the VSWR meter has been verified good.
Lets get back to the subject.
I would suggest taking the choke out, trying a different piece of coax, even a short jumper just for test purposes to see how the VSWR curve looks with a DIFFERENT transmission line.
If the antenna checks good and the VSWR is different with a short jumper then it may be the coax.
IF it is the same then it is the antenna.
I would do all of this AFTER the VSWR meter has been verified good.
I'm not sure, but I may be repeating information that some other member has already posted.
It is my opinion that the Imax is a CB antenna. As it is advertised to come pre-tuned to the middle of CB (@27.205)...it is intended to primarily work in this band. If your antenna came to you new, with the rings set from the factory near the middle of the adjustable range without any readjustment, then right off the bat I would expect one to see a much better SWR than the 1.8...you indicated above. If the I2 came to you second hand, then all bets are off...regarding the match.
For me the Imax is built as plug and play, and it was designed that way. If it doesn't work with a lower SWR than you report right off the bat, even at 8' feet, then I would try mounting the antenna somewhere else...before I even considered to move the rings.
This is to say nothing about cutting the tip down which could be a mistake if you really want to center it at 27.85 mhz.
Regardless of weather the higher SWR makes a difference or not in performance or safety as someone noted above...the I2 should show a much better match that 1.8 anywhere in the CB range. My Imax shows 1.13-1.15 SWR from a little below channel 1 to 27.555. This is almost a flat line curve across more that the CB range.
If your antenna already showed you a super low SWR at 28.3 - 28.5, and you wanted the best SWR down near 27.385, can you tell us why you decided to cut the antenna?
Robb, just for clarification on the 2" cut that was made. My Solarcon frequency chart for the I2K shows the following cutting schedule:
2" is not even close unless something else is going on with this man's antenna. I'm not convinced with the results reported in this case. The Imax should be much better than reported and that has to happen before even considering a cut in length.
My experience with old coax, under specific consideration of the line performance, is that as the coax get older the SWR will look better and better as a result of added line loss...until the line shows a short. I've never seen a short that I felt was due to age, but I think that probably happens rarely in real life.
The radio I had on hand was 40 channel cb,hooked it to antenna ,showed about 2.1 swr,I checked it at 1 and 40, 40 was better,I can't move further away ,cliff
10 foot behind my deck,so I thought let's try adjusting the rings,so I hooked up radio with a 3 ft jumper to antenna , as I moved the rings up swr dropped to about 1.7 to 1 yah , so I thought make antenna shorter,so I cut off 2" no change......later new 2970 showed up so I test higher 28,300 is good.
I am working on a tech license
There isn't much traffic in that band ?
10 foot behind my deck,so I thought let's try adjusting the rings,so I hooked up radio with a 3 ft jumper to antenna , as I moved the rings up swr dropped to about 1.7 to 1 yah , so I thought make antenna shorter,so I cut off 2" no change......later new 2970 showed up so I test higher 28,300 is good.
I am working on a tech license
There isn't much traffic in that band ?
If it is the urethane center insulation type and was used in a hot climate and/or had water intrusion, it is possible for the center to deviate. Deviation would probably more noticeable on VHF/UHF; but if poor enough condition it can affect HF too. Belden 9913 had that problem a few years back. Cheaper grades of coax makes it a real possibility.
Local op had a problem on 2m/VHF with his coax recently, in a mobile install after he wound a choke on it. Had a poor SWR no matter how he tuned the antenna. The center had deviated, and it was new, quality stuff. Don't know why he felt he needed to put a choke for a mobile install; but that is what he did.
EDIT:
Suppose one way to test the that coax is to terminate one end with a 50 ohm dummy load and test it with an antenna analyzer.
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Robb, I misunderstood your idea when you described a coax that was not new. I took you to mean old coax so I focused on my exerience with old coax:
Sorry!
I look to have missed your point about deviation of the center conductor. Thanks for helping me understand.
Sorry!
The center of CB is 27.185 (ch19).
I have nothing more to add, carry on
359, thanks for the info, but here is a link to my reference for the center frequency that Solarcon published describing their I2K in the manual. I thought I should be loyal to the source I used. Read the part that is a Note:
View attachment Imax Manual.pdf
My main point was that the I2K is a CB antenna.
On your point, I don't object to either view here. I'm not convinced, but I have heard your point argued, and I think the issue is mute.
Thanks,
"moot point (plural moot points)
An issue that is subject to, or open for discussion or debate, to which no satisfactory answer is found; originally, one to be definitively determined by an assembly of the people."
The difference between 26.965 and 27.405 is 27.185.
It's just a pet peeve that I like to highlight from time to time. I don't think it's moot, but not hugely important either.
I apologize for the disruption .....
359, I don't consider your position on this issue as a disruption.
You voiced your thoughts on the issue, and I did the same. Maybe some other's will form some opinions on the subject...as a result of our comments.
Maybe I should have referred to this as a "mute difference" rather than a "mute point," and then we could leave it to the people if they care.
You voiced your thoughts on the issue, and I did the same. Maybe some other's will form some opinions on the subject...as a result of our comments.
Maybe I should have referred to this as a "mute difference" rather than a "mute point," and then we could leave it to the people if they care.
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