ground planing CB high swr

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gstuart

gstuart

D3 Grandad
Full Member
Posts
30,893
Location
Kent
been trying to find out a solution for a higher than normal swr or just above 2.5

got it mounted on my spare wheel bracket , comes with rubber mounting

the aerial has a spring at the bottom , goes through the hole and uses rubber grommets that sit in between the top and bottom of the bracket

also have a quick release connecter on the aerial

have got a good earth point ,tested via a multimeter from the bracket to the bolts that hold the spare wheel carrier on

am going to run a wire from the bracket to the bolt of the carrier , but then thought about running a wire from the bolt then onto the main earth plug that sits behind the rear panel for a belt and braces idea

however I cant find out if the size of the wire will effect my ground planing and lower the swr by using a thicker or thinner wire

sorry to ask daft questions don't wish to cause damage to my new CB unit

have just got in plugged into my cig lighter at the moment , so I can test it

another daft question can I put my swr meter at the back between the aerial , so as i adjust the aerial via an Allen key , saving going backwards and forwards to the CB unit to see what the swr reading is

thks guys and sorry once again for asking
 
IMHO I would be tempted to start again with the wire (coax) etc, Sirio do a nice mount (link supplied), it includes the coax, and you can always make it longer with an extension lead (x2 PL259 plugs with coax in between).

Tidy the whole thing up, get a longer springer antenna etc eventually (bigger is always better) and it all should work ok with a less than 1.5 to 1 SWR with very little tuning. Sounds like your earths are good, so thats a good beginning..

Placing the SWR meter too close to the antenna can cause duff readings as it measures "Standing Waves" (RF coming back down the coax).

Link:

Sigma 3/8 'N' Type DV CB HAM Antenna Aerial Body wing Mount & Cable Kit | eBay

10-4 Rubber Duck :)
 
Longbolt said:
IMHO I would be tempted to start again with the wire (coax) etc, Sirio do a nice mount (link supplied), it includes the coax, and you can always make it longer with an extension lead (x2 PL259 plugs with coax in between).

Tidy the whole thing up, get a longer springer antenna etc eventually (bigger is always better) and it all should work ok with a less than 1.5 to 1 SWR with very little tuning. Sounds like your earths are good, so thats a good beginning..

Placing the SWR meter too close to the antenna can cause duff readings as it measures "Standing Waves" (RF coming back down the coax).

Link:

Sigma 3/8 'N' Type DV CB HAM Antenna Aerial Body wing Mount & Cable Kit | eBay

10-4 Rubber Duck :)
Click to expand...

thks mate

the lead and straight mount are brand new, the coaxial lead is a premade one with both the connectors already factory done

appreciate about the position of the swr meter , just saved me going backwards and forwards , lol , will try and position it so I can see from the back

will put a pic up of the aerials and mounts ive got as I took them back off
 
this is the first aerial
 

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second aerial

thinking of putting the bigger spring on the shorter aerial

or use the longer one , got a roof rack for the 3 door I need to put on and then fix the tip of the longer aerail onto to the roof rails
 

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this is the type of bracket I've got

hope it's ok using someone elses pic
 

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blue beasty said:
Having the spring of the antenna too close to a reflective plane can cause swr problems.
Click to expand...

maybe that's why it's giving me a high swr reading

will put on a groundplane wire on tommorow to see what I get

as its got the rubber grommets and stopping it earthing properly ??

this is the rubber grommets ,

have laid it out , the bracket is installed where I've put the gap
 

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gstuart said:
thks mate

the lead and straight mount are brand new, the coaxial lead is a premade one with both the connectors already factory done

appreciate about the position of the swr meter , just saved me going backwards and forwards , lol , will try and position it so I can see from the back

will put a pic up of the aerials and mounts ive got as I took them back off
Click to expand...

No worries, hope it may have been of even some help. Have never had any joy personally with snail mounts or 3/8's mounts in general. Always found the Sirio stuff was practically plug and play. The best solution being a nice big mag mount on the roof, or a hole drilled in the roof for max ground plane even better.

Something like this on the mag mount:

SIRIO HYPOWER 4000 with SIRIO MAG-145 MAGNETIC MOUNT (very strong) | eBay

Yea, i know, not practical for green laning...but plug this into a sidebander, sit on a hill and talk all over the place/world.

Used to love CB/11 meters, then a went and got a ham ticket...and it was no fun then!...lol!. Funny old world :)
 
Longbolt said:
No worries, hope it may have been of even some help. Have never had any joy personally with snail mounts or 3/8's mounts in general. Always found the Sirio stuff was practically plug and play. The best solution being a nice big mag mount on the roof, or a hole drilled in the roof for max ground plane even better.

Something like this on the mag mount:

SIRIO HYPOWER 4000 with SIRIO MAG-145 MAGNETIC MOUNT (very strong) | eBay

Yea, i know, not practical for green laning...but plug this into a sidebander, sit on a hill and talk all over the place/world.

Used to love CB/11 meters, then a went and got a ham ticket...and it was no fun then!...lol!. Funny old world :)
Click to expand...

oh, hope my post didn't come across as rude buddy ,

as ur not a mind reader thought it better to put pics up of what I had

put some pics up to show what mount I have

maybe the earthing wire from the aerial to the spare wheel wheel bolts , may help

is it better to use the biggest wire possible so it carries a better ground planning earth than a thin wire plse

thought if im able to get a good swr reading then see if it changes when I fix the tip onto the roof rails

did read that when in aerial is mounted it can use a roof etc as a way of getting better reception so thought if I attach the aerail to the roof rails it may improve the reception , unless im not understanding it correctly

only reason I've not fitted my roof rack yet is concerned about any noise from it ???


do apologise asking daft questions , just could not find about wire sizing of the earth anywhere , expect im not loking well enough , lol

thks again
 
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gstuart said:
oh, hope my post didn't come across as rude buddy ,

as ur not a mind reader thought it better to put pics up of what I had

put some pics up to show what mount I have

maybe the earthing wire from the aerial to the spare wheel wheel bolts , may help

is it better to use the biggest wire possible so it carries a better ground planning earth than a thin wire plse


do apoligise asking daft questions , just could not find about wire sizing of the earth anywhere , expect im not loking well enough , lol

thks again
Click to expand...

Nothing taken as rude at all, or daft questions :)

Frankly (and i am probably being rude this side), your mount is not up to the job. Have seen the bayonet/multi washer stuff on many installations, especially trucks, and it doesn't seem to 100% do the job.

Have always much preferred internal mount insulation (IE center pin). I want to see a fair amount if insulation before the antenna gets anywhere near the ground plane as beasty says.

Experiment and have fun with it either way...just don't blow the final transistors on your rig/CB :)

Edit: thick coax is not really needed on a low power installation/earth. Good 50 Ohm is all you need (RG58), the big stuff comes into its own on base stations for high power set ups. You can also get some thin low loss coax, but again, not worth it for normal 4 watt set ups IMHO.

Top tip: give the people at "Thunderpole" a ring... they know sh1t loads about car installations (I don't work for them)
 
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Longbolt said:
Nothing taken as rude at all, or daft questions :)

Frankly (and i am probably being rude this side), your mount is not up to the job. Have seen the bayonet/multi washer stuff on many installations, especially trucks, and it doesn't seem to 100% do the job.

Have always much preferred internal mount insulation (IE center pin). I want to see a fair amount if insulation before the antenna gets anywhere near the ground plane as beasty says.

Experiment and have fun with it either way...just don't blow the final transistors on your rig/CB :)

Edit: thick coax is not really needed on a low power installation/earth. Good 50 Ohm is all you need (RG58), the big stuff comes into its own on base stations for high power set ups. You can also get some thin low loss coax, but again, not worth it for normal 4 watt set ups IMHO.

Top tip: give the people at "Thunderpole" a ring... they know sh1t loads about car installations (I don't work for them)
Click to expand...

cheers mate

getting abit confused, doesn't take much

the thick wire I meant when I get a bit of wire, then put o clamps on each end, then put one underneath the aerial fixing and take the other end to the bolt on the spare wheel mount

ref the rubber seals, do they need to be either side of the metal mount or u want the aerial to touch the metal bracket , so sorry for asking , lol

have I got them in the wrong sequence plse

like u say maybe I need some better mounts , but would prefer to keep it on the spare wheel bracket , can drill it out to accept a bigger one if that helps

funny enough I bought all my bits off thunderpole and explained my set up , have got a tti tcb 900 as its got a very small depth for dashboards
 
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gstuart said:
cheers mate

getting abit confused, doesn't take much

the thick wire I meant when I get a bit of wire, then put o clamps on each end, then put one underneath the aerial fixing and take the other end to the bolt on the spare wheel mount

ref the rubber seals, do they need to be either side of the metal mount or u want the aerial to touch the metal bracket , so sorry for asking , lol

like u say maybe I need some better mounts , but would prefer to keep it on the spare wheel bracket , can drill it out to accept a bigger one if that helps

funny enough I bought all my bits off thunderpole and explained my set up , have got a tti tcb 900 as its got a very small depth for dashboards
Click to expand...

The base of the antenna should not touch metal, the whole thing should be properly insulated. Think of the whip itself being the "live", and the negative/braid of the coax going to earth. You shouldn't need gash wires going all over the place, the existing spare wheel mount should be enough, There is plenty of metal.

Am sorry i mentioned Thunderpole now, as they have clearly dropped the ball. I know its confusing me old mate, but it's just like normal electronics really + and -.

I wish i could just come over and sort it for you. That sounds clever assed i know.

Have to sleep now, will pick it up tomorrow if someone else doesn't help.

Warning!!..this is an addictive hobby radio! :)
 
Longbolt said:
The base of the antenna should not touch metal, the whole thing should be properly insulated. Think of the whip itself being the "live", and the negative/braid of the coax going to earth. You shouldn't need gash wires going all over the place, the existing spare wheel mount should be enough, There is plenty of metal.

Am sorry i mentioned Thunderpole now, as they have clearly dropped the ball. I know its confusing me old mate, but it's just like normal electronics really + and -.

I wish i could just come over and sort it for you. That sounds clever assed i know.

Have to sleep now, will pick it up tomorrow if someone else doesn't help.

Warning!!..this is an addictive hobby radio! :)
Click to expand...

thks buddy

maybe I should just wait till the lz event,lol

am putting the kettle on and thks again for the help

speak later
 
put a pic up

have just put a knife there , is this where the metal bracket should go

thks again
 

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There should be no continuity between the antenna and the knife/wheel mount. Think of it as a live wire, and the mount/knife is the earth.

You should get a circuit/continuity between the knife/mount and the screw bit on the mount/outer bit of the PL259 plug (earth).

Short antennas are also usually fairly inefficient/crap. Size really does matter in the world of radio. :)

Catch you later.
 
one of the easiest ways of testing "earth" is to take you negative wire out of the plug and then switch the radio on with the antenna connected and if it does switch on then you have a good "earth" but never ever transmit this way ,if you have the Freelander face lift I have noticed on several of them that the rear door does not seem as though it has a good earth, run a piece of wire from the antenna mount and thread it through and connect it to the earth point behind the boot side panel drivers side (in the UK).
and do not do your standing wave ratio or SWR near to a house or any buildings as you will get reflect of the building. you get all this advise when you have spent nearly 50 years into ham radio.
 
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