Common mode choke question.

[mrweather]

If the antenna is properly installed (tight connections, good counterpoise) the coax length should be irrelevant.

A change in SWR with a change in coax length means it's acting as the counterpoise which is not what you want.

 

[Varmonter]

Well I took the run between the choke and antenna and the swr was 1.14 :1 I then tested from inside the truck to the antenna with the choke inline 1.14:1.
I also had placed a wattmeter/swr meter in line..and this is where the swr went to hell..I had an older coax jumper that I used to go from the radio to the meter.And am thinking this may be the suspect..as I've no
Pl259s left (more coming in the maiI)I can't confirm until I get a new jumper made..but the choke I made is fine..And has improved my receive..I don't need the meter in line but will attempt to leave it there as I like the visual confirmation of swr and power.
Coax length?? I've always been skeptical . I had 25ft between my radio and antenna. I cut that up to make the choke and I now have 11ft between the radio and antenna plus however many feet it took to wind the choke. So I have maybe 6feet left over. So 19feet and the swr didn't change..I did add more pl259s to the run and the so239s chassis mounts for the choke box..all places to fail(but they are all good and not contributing to my higher swr..Unfortunately I can't hook my vna to a so239 I need an adaptor..also on order..
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[slowmover]

I’ve not ever used SWR meter inline past testing and wouldn’t.

Ck SWR against meter on radio.
It’s usually close, sometimes exact.

I’ve got over 20k hours of rough ride mobile use just the past dozen years says it’s not worth it to have one in-line.

You do as you will, but if you’re wavering, then . . . .

Now, bad jumpers, that’s a whole other more likely problem. Good to strip shield and use it for case grounds.

Glad to hear the choke tuned things up.

Looking forward to your additions to this thread on that subject (images and such).

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[Varmonter]

Either you messed up on installing connectors or your antenna system is sensitive to coax length, both bad situations. I would take off the choke, measure SWR then temporarily replace the choke with an equal length of coax to see if the length is the problem. Then test the choke with an antenna analyzer with a good 50 ohm load on it to prove the connectors are happy.

So i hooked up the vna to the short lead I have between the choke and the antenna and got 1.14:1 then to the long coax from the radio to the antenna (thru the choke) and got 1.14:1 then I hooked it thru my pwr meter back to the radio and got 1.86:1. So im assuming it's in this loop where the issue is.
I have some more pl259s coming..but the radio is working direct to antenna (thru the choke) ..just not thru the pwr meter..
So right now I don't know if it's the power meter or the jumper..

 

[Varmonter]

If the antenna is properly installed (tight connections, good counterpoise) the coax length should be irrelevant.

A change in SWR with a change in coax length means it's acting as the counterpoise which is not what you want.

I agree and my vna seems to confirm this.
I still have great swr from the radio to the choke to the antenna..even though I removed several feet. Only when I loop it thru the meter does it go up ..I'm hoping it's the jumper and not the meter..

 

[Varmonter]

I’ve not ever used SWR meter inline past testing and wouldn’t.

Ck SWR against meter on radio.
It’s usually close, sometimes exact.

I’ve got over 20k hours of rough ride mobile use just the past dozen years says it’s not worth it to have one in-line.

You do as you will, but if you’re wavering, then . . . .

Now, bad jumpers, that’s a whole other more likely problem. Good to strip shield and use it for case grounds.

Glad to hear the choke tuned things up.

Looking forward to your additions to this thread on that subject (images and such).

.

Ugh I know I still have some lmr 400 I want to strip the shield out of..

I’ve not ever used SWR meter inline past testing and wouldn’t.

Ck SWR against meter on radio.
It’s usually close, sometimes exact.

I’ve got over 20k hours of rough ride mobile use just the past dozen years says it’s not worth it to have one in-line.

You do as you will, but if you’re wavering, then . . . .

Now, bad jumpers, that’s a whole other more likely problem. Good to strip shield and use it for case grounds.

Glad to hear the choke tuned things up.

Looking forward to your additions to this thread on that subject (images and such).

.

Thx I suppose I should have snapped some pics..but I'm planning on building another choke for the transceiver end..I don't like the one on the antenna end as it's a straight line..if I can find a box deep enough I will make one with 90⁰ so239d this will work better up top and the one I just made will go under the passenger seat in the ram 3500 close to the radio..
The swr meter on the radio is close. its just out of the way and small to read..but it can suffice ..

 

[Varmonter]

"You do as you will, but if you’re wavering, then . . . ."

Turns out it was that old jumper..
And is now working thru the meter
And 1.14 on 27.185..
I will heed your advice and not leave this inline as it is just going to be iffy rolling down our great highways and byways..But at least I know where the issue was..

 

[slowmover]

"You do as you will, but if you’re wavering, then . . . ."

Turns out it was that old jumper..
And is now working thru the meter
And 1.14 on 27.185..
I will heed your advice and not leave this inline as it is just going to be iffy rolling down our great highways and byways..But at least I know where the issue was..

I yanked off a jumper yesterday for same reason. There’s just not a good way to add in-line devices without — sooner or later — experiencing a fault.

The transceiver coax RF filter — when I can do so — attached via hard connectors seems to work okay, but they have to be HQ ($$) and the whole contraption has to be secured against motion as can be done.

In this case, versus a meter, it’s a performance gain which pays. With latest radios one sets a HIGH SWR limit as a back-up to daily checks.

Yesterday I hit the 3.0 limit. Yanked jumper and was back to 1.2 @ 20 and 1.4 @ 1 & 40.

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