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Just put up I-Max 2000

Heavy Metal

Heavy Metal

Active Member
Aug 23, 2014
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just put my antenna up kinda weird swr but dunno.


2:1
24.425.00 to 28.950.00
just starts 1.5:1
26.340.00 to 28.120.00
Less that 1.6:1
25.025.00 to 28.585.00

Under 2:1
19.010.00 to 22.665.00
1.5:1 19.195.00 to 22.175.00
And Dead flat on
19.775.00 to 20.370.00


Are these readings common?
 

Short answer Yes. Long answer no it shouldn't Although it's close to a resonate 1/2 wave on 21 mhz the impedance and swr should be through the roof.I found when I fitted ground planes and a choke the swr at 21 went up and went down at 27 so it might be due to cmcs on the coax masking whats really going on.Anyway a lot of people report similar swr curves. Real handy if you are a ham operator
 
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vkrules said:
Short answer Yes. Long answer no it shouldn't Although it's close to a resonate 1/2 wave on 21 mhz the impedance and swr should be through the roof.I found when I fitted ground planes and a choke the swr at 21 went up and went down at 27 so it might be due to cmcs on the coax masking whats really going on.
Click to expand...


cmcs?

Explain?
 
If you take the antenna down...then put it on two wooden saw horses and check the match at the feed point or as close as you can get. Check your feed line for RF through put in watts also.
 
Have 97' RG8x

Is this bad or what it is dark so cannot do much at all? I appreciate any suggestions and explanations on dealing with it ect. Getting back into all this just curious and all on things and why they happen as well.

Thanks
 
What Marconi is saying is if you want to see just what the antenna SWR is doing without the coax effecting it, you should check it right where the coax attaches to the antenna, that is called the feed point.
The way to check the coax for RF through put is to measure the power ( in watts ) going into the coax then place the power meter on the other end of the coax and measure the power coming out of the coax.
You would do this if you want to see if there are substantial losses in the coax itself .
I would recommend that you do that test with a dummy load, not a antenna.
If the SWR is good across the cb band were you talking I would just run it for tonight, or even a few days and see how it is working for you.
Many hams use these antennas to work 10/11/12/15/17 meters because they will work there....most, often use some sort of a tuner, and I am sure the efficiency falls off the further you get away from 11 meters, but they do work.

73
Jeff
 
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LOL, I know, i talked to several guys on open coax laying on top of the house once just for grins.
For his use i think it will be fine.....someone once said that we are lucky that our antennas don't necessarily have to be perfect to work.

73
Jeff
 
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Heavy Metal said:
Have 97' RG8x

Is this bad or what it is dark so cannot do much at all? I appreciate any suggestions and explanations on dealing with it ect. Getting back into all this just curious and all on things and why they happen as well.

Thanks
Click to expand...

97' is ok if the feed line through put for your 100' foot line is close to 93% of input or better.

I always try and check my coax at the radio end of the feed line too, and see if adding a couple of extra feet makes a notable change in my SWR results too...if I ever get concerned. Then, if it does make a difference you can see the results on your inline meter. If this happens, then your problem may be as others have described here already...CMC. If such a condition is not bad however...it is not the end of the world.

Before I install an antenna high up, I try and always check the antenna match at the feed point when possible, else get as close as possible with a shorter run of coax. Even though you have to test close to the Earth in this case, that is better than no check at all. To be clear I'm not suggesting the match near the ground will be the same as it can be when raised up high.

HM, if you don't understand this, or how to check this...let me know.

AudioShockwav said:
LOL, I know, i talked to several guys on open coax laying on top of the house once just for grins.
For his use i think it will be fine.....someone once said that we are lucky that our antennas don't necessarily have to be perfect to work.

73
Jeff
Click to expand...

I agree Jeff, we all may have experienced similar events. I don't see anything in Heavy Metal's report above that indicates his situation might cause damage either. Maybe he is just putting too much importance on his SWR. We all have probably been down that road.

Jeff, if you check out my signature below, you will read that I make a similar claim as you note.

My old radio mentor use to make similar remarks to me all the time, and for me, I've never forgotten such implications in those important remarks.

You also gave HM a good description on how and what to check.

BTW Jeff, aside from a really bad physically damaged feed line...have you ever worked a feed line that had very high losses due to deterioration from "old" water in the feed line? You might be surprised at what you could notice with such a feed line.
 
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Ok what would cause rf to flow back down? When in put the connector on the one side of the coax I took the braided part and folded it over the jacket part should I have done that or not I have not yet soldered it on yet and it is a connector that has the down sizer in place for it since it is RG8x. Everything seems good just not dead 0 on cb bands but way below 1.5:1 wonder it top sections not bad or rings are slightly separated or need to take ground wire off base of attenna were you bold it onto the post?
 
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For a 5/8 wave NGP antenna less that 2:1 across that spectrum I'd call it good the difference between 2:1 and 1:1 is about 1 s unit. So long as the finals in the radio can handle a 2:1 load I'd leave it alone it would work just fine on my privileges.
 
Dipole said:
For a 5/8 wave NGP antenna less that 2:1 across that spectrum I'd call it good the difference between 2:1 and 1:1 is about 1 s unit. So long as the finals in the radio can handle a 2:1 load I'd leave it alone it would work just fine on my privileges.
Click to expand...

Just a note...

There is far less difference in going from 1:1 to 2:1 SWR than there is to make an s-unit worth of difference. To increase your signal by a calibrated 1 s-unit on the receiver's side it takes 400% more power to be transmitted, and to drop 1 calibrated s-unit on the receiver's side takes a 75% drop in power. the difference between 1:1 and 2:1 SWR, and this is making the common mistake of assuming all of the reflected power is lost, is 11%. This 11% figure is a worst case scenario, not a typical occurrence, and even if it would happen, it would take almost 7 times as much reflection to get that 1 s-unit difference.


The DB
 
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I don't know what the details are for Dipole's claim or DB's counter claim, but I believe DB is closer to correct.

I've operated CB antennas before with over 2.0:1 SWR and I could not tell one iota of difference in performance just using my radio, and I sure could not see 1 sunit of difference in receive signal for sure.
 

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