Dartmoor Navigator
Well-Known Member
Andy -
SWR is about impedance matching the output stages of the transmitter to the antenna / coax cable which will vary from placement to placement. Even 'hand capacitance' will have an affect the outcome of an SWR reading as you handle parts of the set up. SWR (standing Wave Ratio) is about reflected signal (due to this impedance mismatch) reentering the coax / transceiver. On lareg output sets you can feel the nodal points where the waves cross, heating up.
The ground plane will affect this but it doesnt mean that a better ground plane will give a better SWR - it just means it will be a different impedance.
The more effective the ground plane then the better effective power that is utilised by the aether.
I hope this helps
SWR is about impedance matching the output stages of the transmitter to the antenna / coax cable which will vary from placement to placement. Even 'hand capacitance' will have an affect the outcome of an SWR reading as you handle parts of the set up. SWR (standing Wave Ratio) is about reflected signal (due to this impedance mismatch) reentering the coax / transceiver. On lareg output sets you can feel the nodal points where the waves cross, heating up.
The ground plane will affect this but it doesnt mean that a better ground plane will give a better SWR - it just means it will be a different impedance.
The more effective the ground plane then the better effective power that is utilised by the aether.
I hope this helps
Pikey
Dummy Ejection Facilitator..
tep too many peeps blame Alli for having poor counductivity but a properly fitted mount will work perfectly well 99% of the time.
Dartmoor Navigator
Well-Known Member
Yup - mine to.
I was once the field communications manager for a lot of expeditions and former tactical communications specialist - I really wouldn't get excited about my cb in Landy
blue beasty
Leaks an prone to bits dropping off
Ally is a good conductor but ally oxide int so any contact thats not cleaned or airtight will degrade.....think thats where the confusion arises
blue beasty
Leaks an prone to bits dropping off
Yup - mine to.
I was once the field communications manager for a lot of expeditions and former tactical communications specialist - I really wouldn't get excited about my cb in Landy
Thats great but if you've got a crap SWR reading you aint got a useable cb so for some its an issue
Dartmoor Navigator
Well-Known Member
Good points but it isnt just about the body work - the thing is earthed to the battery which is earthed to the chassis / engine / axles and every bit of copper wire running through the vehicle - more than enough to give an effective ground plane for a CB - your average 14 year old CBer in 1982 had a small whip mounted on a biscuit tin in the corner of the attic.
Adam1979
New Member
Good points but it isnt just about the body work - the thing is earthed to the battery which is earthed to the chassis / engine / axles and every bit of copper wire running through the vehicle - more than enough to give an effective ground plane for a CB - your average 14 year old CBer in 1982 had a small whip mounted on a biscuit tin in the corner of the attic.
They were the good old days. Brings back some memories that I had forgotten!!
Dartmoor Navigator
Well-Known Member
Yes - but the point I was emphasisng is that SWR and ground plane are not the same thing but have a mutual relationship. Sorry for my flippancy
Dartmoor Navigator
Well-Known Member
Andy Land
Well-Known Member
Yep ... I'll second that ... hours spent in the folks garage on my old AM rig with a car antenna mounted on the garden fence
blue beasty
Leaks an prone to bits dropping off
Good points but it isnt just about the body work - the thing is earthed to the battery which is earthed to the chassis / engine / axles and every bit of copper wire running through the vehicle - more than enough to give an effective ground plane for a CB - your average 14 year old CBer in 1982 had a small whip mounted on a biscuit tin in the corner of the attic.
I'm not saying it is just about body work and comments alone the lines of bung it on and forget about it are great coming from someone who really understands the tech......but if you dont and your swr is crap what do you do?
Mine was 3.5
I ran a separate earth from the base of the aerial and its now 3.....whats next....aerial trimming?
Dartmoor Navigator
Well-Known Member
I'm not saying it is just about body work and comments alone the lines of bung it on and forget about it are great coming from someone who really understands the tech......but if you dont and your swr is crap what do you do?
Mine was 3.5
Yup 3 and 3.5 is terrible. If there is no improvement then a longer or shorter antenna will solve it - you have a 50/50 chance in other words. Provided you have a good earth (try bonding it direct to the negative terminal as a temporary trail - while in the drive) I would hacksaw a mil at a time off and see what direction the SWR goes. Alternatively try a different antenna.
blue beasty
Leaks an prone to bits dropping off
Got a 6' springer.......making it longer might be tricky
Having said that there's about 30mm adjustment in the mounting so tis gonna be a part of my 'quality' time with the old gurl tommorrow
Pikey
Dummy Ejection Facilitator..
Got a 6' springer.......making it longer might be tricky
There is a bit of adjustment in the bit where the antenna enters the body of the spring. try that first
Dartmoor Navigator
Well-Known Member
Oooooooooooooops -YES
-Sorry I assume you had tried that adjustment - that's what it is for. Then nibble bits of the top end.
DEFENDER90-DAZ
New Member
Yep i remember having my first cb rigged up in my bedroom with the aerial on a roses tin
Them were the days "good buddy"
Them were the days "good buddy"
blue beasty
Leaks an prone to bits dropping off
Oooooooooooooops -YES
Yep, thats the plan....cheers chaps
Dartmoor Navigator
Well-Known Member
Yep i remember having my first cb rigged up in my bedroom with the aerial on a roses tin
Them were the days "good buddy"
I have no idea what you you are talking about. You wouldn't find me 'eyeballing' 'seatcovers' while 'square wheeled' in the local car park.................... hang on - sounds like a 1980's version of dogging
