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Antenna location causing high SWR
- Thread starter Daffypuck
- Start date
The whacking is when I take the truck through the car wash, so it’s not a continual thing.
Pretty much everyone uses the same setup with some minor variations. I have tested a few of their setups and found that they also have really high SWR as well, yet they always seem to hear better than me.
Ok, but have you checked SWR with that sleeve on and again with it off?
My thoughts on this are if the sleeve causes the SWR to rise - wonder if a different material with less "influence" can help with this.
It's why I asked about what the others do. IF they too use a sleeve - but you answered that in the next post...
Ok, then if everything else seem equal...the "seem to hear better than you..." argument comes up.
How is the noise level in what the CB "hears" when your in the truck - running down the road?
My thoughts on this are if the sleeve causes the SWR to rise - wonder if a different material with less "influence" can help with this.
It's why I asked about what the others do. IF they too use a sleeve - but you answered that in the next post...
Ok, then if everything else seem equal...the "seem to hear better than you..." argument comes up.
How is the noise level in what the CB "hears" when your in the truck - running down the road?
Oh, I see what you saying. No I haven’t done that yet. Gimme a few days and I’ll try that. You really think that sleeve will affect SWR? I was always under the impression that the actual radio signal emanates at the top of the antenna. So why would something further down in the shaft affect the tip?
Looks like a short candle inside a tin can to me. I mean that signal is going to bounce around between the cowling and the trailer, cancel a lot of itself out, and what's signal that's left is going to go straight up towards another galaxy. I have been wrong before but it was a misteak.
Well if you just undo the sleeve - then check SWR.
I worked at a shop that took in drivers that had older antennas that although could be replaced, the drivers chose to keep them, or buy another that we could color the whip with a sleeve of shrink wrap - we just had to "re-sleeve" them with shrink wrap in a particular color that matched the paint job on the truck.
In doing so - this also affected the SWR - some colors worked well and had little problem retuning - others and due to the condition of the antenna by itself just could not be saved and had to buy a separate one that even with the new color sleeve - were more touchy to SWR tuning.
There were some instances the new sleeve worked in restoring the original SWR the driver had obtained - the old sleeve was allowing in dirt and water entry - so simple alcohol wipe and dry to clean the wrap was what was needed - they saved some money this way because the antenna didn't need to be replaced, just cleaned up and re-sleeved.
Ok, to wrap this up ...
If you had done this sleeve when you put it up and then had to adjust the SWR when you mounted the antenna - it is not the ONLY reason for the change - but if removing it lowers the SWR to a better tolerable range - then we just have to find another easy way to protect the sleeve from the impacts. Simple Electrical tape or a layer of heat shrink tubing slid over and sized by length to just provide the protection length over those winds - not over a long length just enough to prevent the whip from getting scuffed open.
By the thickness alone I can see that the winds in that region of the antennas length can affect the "apparent" SWR you get.
They Only way to tell is to remove and recheck SWR then we just need to find a less influential material to protect that section. If the SWR is lower with that sleeve or it';s the best thing you've got, then there's not much we can do except hope for the best.
Keep the ferrule and the mount as clean as you can - even furniture polish to help repel water in the area of the mount goes a long way to preserving the SWR you have.
- if its changed, that is the answer - the plastic sleeve the antenna is shrink wrapped in - "bumps" the antennas apparent SWR because of the interaction with a non-conducting plastic sleeve, still affects the RF field those wraps of wire produce when you transmit.
I worked at a shop that took in drivers that had older antennas that although could be replaced, the drivers chose to keep them, or buy another that we could color the whip with a sleeve of shrink wrap - we just had to "re-sleeve" them with shrink wrap in a particular color that matched the paint job on the truck.
In doing so - this also affected the SWR - some colors worked well and had little problem retuning - others and due to the condition of the antenna by itself just could not be saved and had to buy a separate one that even with the new color sleeve - were more touchy to SWR tuning.
There were some instances the new sleeve worked in restoring the original SWR the driver had obtained - the old sleeve was allowing in dirt and water entry - so simple alcohol wipe and dry to clean the wrap was what was needed - they saved some money this way because the antenna didn't need to be replaced, just cleaned up and re-sleeved.
Ok, to wrap this up ...
If you had done this sleeve when you put it up and then had to adjust the SWR when you mounted the antenna - it is not the ONLY reason for the change - but if removing it lowers the SWR to a better tolerable range - then we just have to find another easy way to protect the sleeve from the impacts. Simple Electrical tape or a layer of heat shrink tubing slid over and sized by length to just provide the protection length over those winds - not over a long length just enough to prevent the whip from getting scuffed open.
By the thickness alone I can see that the winds in that region of the antennas length can affect the "apparent" SWR you get.
They Only way to tell is to remove and recheck SWR then we just need to find a less influential material to protect that section. If the SWR is lower with that sleeve or it';s the best thing you've got, then there's not much we can do except hope for the best.
Keep the ferrule and the mount as clean as you can - even furniture polish to help repel water in the area of the mount goes a long way to preserving the SWR you have.
there's too much extraneous metal in the near field of the antenna creating capacitive coupling to the antenna itself. as the antenna is electrically shortened the swr will be lower on the uppermost frequencies and higher on the lower frequencies, indicating that the antenna is too short. that piece of vertically oriented flat metal where the bracket is attached rising up above the mount or the base of the antenna in such close proximity to each other is also exacerbating the situation. it's an extremely poor mounting location.
Ok, I moved the antenna to try and get it as far away from the truck and the trailer. Retested the SWR and got it down to 1.8 on 40 and 1.6 on 1. Then took the sheath I had on it off and the SWR dropped to 1.5 on both 40 and 1. I think that’s the best I’m gonna get with this set up. Curious, does a lower SWR actually help with TX and RX signal? Thanks for yalls help.
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Hate to beat a dead horse but even if the SWR is acceptable, pulling a dry van or reefer your antenna is basically in a metal reflect-o-box. Mirror mounting will get some free space around it and would have to improve things, even if the SWR isn't perfect. Plenty of manufactured mirror mounts out there or fab what you need if possible. Betting you'd see better results in the long term.
73 and keep that dirty side down Driver.......
73 and keep that dirty side down Driver.......
No, that mount location is not going to work, puts the antenna right at the trailer.
Noticed your transponder / GPS / Satellite thingy is on the main brace - can you segue the mirror mount to that other side?
The sleeve since you took it off, yes would help receive and TX but only by marginal "recovery" - you're better off mounting the antenna away from that whole mess you have back there - I know you might not be able to - but the antenna right now, can interfere with that trailer and you may even lose the antenna and radio.
This is a tough call, for in many cases you need as radio talk to the "shacks" that guide you in and out of the docks and bays so they use CB - but you're in a position where if you have to run it - can't you put it on a mirror mount towards the front?
If you can't then restore what you had - it was probably better there then where it's at now, unless you can slide your cab''s drive tandems back all the way - which some weights stations might pull you off to the side for if they see its trailer is too far to the rear.
If your running Refer - the problem is worsened by the AC unit just behind the whip and it will get smacked by the wind whack and that's for starters...
You might need to put everything back to where you had it - too much lean on the whip to any good if they keep you parked because they feel you're unsafe.
Just leave the sleeve off and see what can be done with some quick wraps of electrical tape to keep the scuffing down.
Noticed your transponder / GPS / Satellite thingy is on the main brace - can you segue the mirror mount to that other side?
The sleeve since you took it off, yes would help receive and TX but only by marginal "recovery" - you're better off mounting the antenna away from that whole mess you have back there - I know you might not be able to - but the antenna right now, can interfere with that trailer and you may even lose the antenna and radio.
This is a tough call, for in many cases you need as radio talk to the "shacks" that guide you in and out of the docks and bays so they use CB - but you're in a position where if you have to run it - can't you put it on a mirror mount towards the front?
If you can't then restore what you had - it was probably better there then where it's at now, unless you can slide your cab''s drive tandems back all the way - which some weights stations might pull you off to the side for if they see its trailer is too far to the rear.
If your running Refer - the problem is worsened by the AC unit just behind the whip and it will get smacked by the wind whack and that's for starters...
You might need to put everything back to where you had it - too much lean on the whip to any good if they keep you parked because they feel you're unsafe.
Just leave the sleeve off and see what can be done with some quick wraps of electrical tape to keep the scuffing down.
Daffy,
I still have the Firestiks I had mirror mounted for years (4 footers and 7 footers on drivers side mirror). Never broke one. The 4 footers are over a decade old. Don't let that worry stop you. The 7 footers withstood some fairly strong winds but never snapped. I did always make sure to keep them ice-free. Ice will definitely take them out.
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