Why is my SWR always changing????

[07dodgeram5.9]

Hey guys I got a Wilson 4 ft on the top of my flatbed headache rack all my connections are right and tight good ground bed is grounded to the chassis but that damn SWR changes I notice cause my receive is different all the time some days I have to turn gain up farther to hear anything some days I have to turn it down cause it's blaring and I noticed my swr is different when that happens I always check it on 1 and 40 it never goes over 1.5 but some days it's like 1.2 on both other days it's 1.5 on 40 and 1.2 on 1 and vice verse

What's going on?
It's not the radio cause it does it on all 4 of them I been working on all Cobras

 

[07dodgeram5.9]

Hey guys I got a Wilson 4 ft on the top of my flatbed headache rack all my connections are right and tight good ground bed is grounded to the chassis but that damn SWR changes I notice cause my receive is different all the time some days I have to turn gain up farther to hear anything some days I have to turn it down cause it's blaring and I noticed my swr is different when that happens I always check it on 1 and 40 it never goes over 1.5 but some days it's like 1.2 on both other days it's 1.5 on 40 and 1.2 on 1 and vice verse

What's going on?
It's not the radio cause it does it on all 4 of them I been working on all Cobras

I do have a spring on it could that be causing the issue?

 

[RatsoW8]

That's a negligible swr variation with a mobile setup. Nothing I'd worry about antenna wise anyway. If your receive volume is all over the place for no good reason you may have an issue there.

 

[Captain Kilowatt]

Agreed with RatsoW8. That variance in SWR is not enough to even be noticeable on receive. Sounds like either you better check it closer or there is another factor at play.

 

[The DB]

I've seen SWR spike up by about 0.3 because a car passed over 30 feet away when my VNA was scanning my antenna on my SUV. I have also seen spikes in SWR because birds fly by the antenna when running such scans. Changing SWR in a mobile environment is not anything new, and is always happening weather you realize it or not. The antenna is reacting to the changing environment, which is constantly changing when your vehicle is moving anyway. The small change you seem to be concerned about is normal, and if it wasn't happening I would be concerned about the antenna system anyway. Such small changes in SWR don't have any noticeable difference anyway, actually you wouldn't notice even much larger changes, such as going from a perfect match to a 2:1, so your .2 or .3 SWR change is beyond negligible. SWR has very little to do with how well an antenna works.

There are also other factors that can affect your receive, depending on environmental occurrences that affect wide areas at any given time, and that is before you add in the man made stuff that will also have an effect. Ever hear of the solar cycle? That alone can affect the amount of static you get based on what is happening with said cycle. Putting a CB at a certain setting, and expecting nothing to require a change to said setting ever is unrealistic, there is to much changing for that to happen. There are times when some settings will be stable for a long time, possibly even a year or two (generally at the lower point of a solar cycle) but that is as good as it gets.

You are correct about one thing, the radios are not the cause of SWR found on an external SWR meter, but that is because the meter can only measure SWR on its antenna side. A radio will never, in and of itself, cause a high SWR reading on an external SWR meter, and if a radio ever seems to do this then there is something else wrong with the antenna system.


The DB

 

[Captain Kilowatt]

FWIW I had an HF antenna that matched perfectly on 20m. It was mounted on my trunk lid. The SWR went thru the roof everytime I closed the trunk and my rx was affected but would go great as soon as I popped the remote trunk release even though the lid was not raised. Now THAT was a REAL head scratcher. I couldn't just drive around with the trunk not latched. Several feet of grounding straps later all was good in the world again. Mobile antennas can be funny at times. If your receive is being affected then you have something else wfong other than a minor change in SWR.

 

[Captain Kilowatt]

Then there was the time I spent ALL DAY tuning my 80m mobile antenna. Went to try it out that night and the SWR was crazy. My wife's car was parked alongside mine when I tuned the antenna but she had now left for a night shift. All day wasted because of a brain fart.

 

[07dodgeram5.9]

I do appolojize I am still very wet behind the ears in this hobby as you could say, I should have named this post something different any ways thanks for your input I was just trying to diagnose this issue and I found two different issues that seemed at the time may have been hand and hand but as most of y'all have said they aren't I don't think I have an issue with antenna thanks again for the info

 

[07dodgeram5.9]

I

swr That's a negligible variation with a mobile setup. Nothing I'd worry about antenna wise anyway. If your receive volume is all over the place for no good reason you may have an issue there.

I understand swr is affected constantly while in motion by anything that obstructs the signal but I park in the same place with the same surroundings and it still is different I even park within inches of the exact same spot most of the time and swr is different I have heard about the solar rays causing issues haven't read much into it but I will

 

[07dodgeram5.9]

Agreed with RatsoW8. That variance in SWR is not enough to even be noticeable on receive. Sounds like either you better check it closer or there is another factor at play.

Thanks I didn't know that small amount wouldn't affect signal that much it just seems like I receive better the lower the swr

 

[07dodgeram5.9]

FWIW I had an HF antenna that matched perfectly on 20m. It was mounted on my trunk lid. The SWR went thru the roof everytime I closed the trunk and my rx was affected but would go great as soon as I popped the remote trunk release even though the lid was not raised. Now THAT was a REAL head scratcher. I couldn't just drive around with the trunk not latched. Several feet of grounding straps later all was good in the world again. Mobile antennas can be funny at times. If your receive is being affected then you have something else wfong other than a minor change in SWR.

Well I can understand that the ground plane some how went slim to none while the lid was fully latched probably only grounding through the rest of the car with two bolt holes that are painted... Thanks for the Info any input is appreciated!

 

[Captain Kilowatt]

Well I can understand that the ground plane some how went slim to none while the lid was fully latched probably only grounding through the rest of the car with two bolt holes that are painted... Thanks for the Info any input is appreciated!

It was poor contact through the trunk lid hinges. Somehow the lock was providing enough pressure to alter the stress on the hinges and make poor contact. As soon as the lid was popped up even just enough to clear the lock things went good. It would have bee MUCH easier to find if it was the other way around. LOL

 

[Captain Kilowatt]

To be noticeable on receive the SWR must usually go well into the red and then you can detect a difference in your receiver. I have seen almost no difference between a perfect match and a 3:1.

 

[midnight special]

are you using an external swr meter? and i know this is crazy but had to deal with a newbie over it,,, he complained that one day it would quiet and he would turn volume up and said then it would blare and he would have to turn it down,,,,turned out it was just going from nonskip conditions to skip condition,, he didnt understand it yet,,,,

 

[Road Squawker]

... one day it would quiet and he would turn volume up and said then it would blare and he would have to turn it down,,,,,,,

Yep, deep and rapid QSB