Correct way to swr a SSB

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original45
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Correct way to swr a SSB

Post by original45 » 01 Jun 2018, 09:48

I'm fairly familiar with how to swr a regular cb radio but havnt had experience in swr of a ssb radio.

I have looked on the net and read some info also but wish to be clear and accurate whilst doing it right.
So few questions and some input required please if you don't mind.

I have a president Linc mk 1 to use now

I will be using the Antron 99 ,I believe the frequency average of the Antron should be wide enough ,is this correct.
Standard antron without the 5/8 fire stick up grade which I believe reduces standard antennas coverage ? .
So is my antenna wideband enough firstly as standard.

What mode should I used whilst swr of the radio is undertaken a.m f.m ?.
Where is best to start in frequencies to swr .

Should I swr the antenna with radio output power set at lowest level first.

Should I use the radios built in meter or use my known to be accurate cb swr meter I can put inline.

If their is anything I having considered please advise me so I may do things correctly please.

Thank you in advance.

108EH002
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Re: Correct way to swr a SSB

Post by 108EH002 » 01 Jun 2018, 10:44

Best place to tune any CB antenna is 27.500,as it is roughly in the middle of the frequencies that you are wanting the antenna to work.
Best mode is Fm for checking the swr,better using an external meter in my opinion,but always check on radio being used if it has a built in swr meter aswell just to double check.Usually the built in swr meter on some Cb's is close enough but some might need recalibrated,as the swr on my Imax was 1 to 1 on mk1 Lincoln,but 1.2 to 1 on a digital readout on another radios built in swr meter.
Can check swr with power at 4w,and your A99 should have enough bandwidth either side of the CB band's that it shouldnt be an issue.Hope this helps you original45.
Last edited by 108EH002 on 01 Jun 2018, 15:15, edited 1 time in total.
You can talk worldwide on CB radio aswell,
rsgb are too far up their own @rses to admit it,
many freebanders just happen to know otherwise.

27.781.25 Fm
27.555 Usb
27.385 Lsb
27.315 Fm
27.275 Usb
27.025 Am

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ch25
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Re: Correct way to swr a SSB

Post by ch25 » 01 Jun 2018, 11:24

Only correct way is FM or CW
original45 wrote:
01 Jun 2018, 09:48
What mode should I used whilst swr of the radio is undertaken a.m f.m ?.
Where is best to start in frequencies to swr .
I would start with middle frequency of bandwidth you want to use.
Antron is wideband, so not much tuning there.
original45 wrote:
01 Jun 2018, 09:48
Should I swr the antenna with radio output power set at lowest level first.
SWR is power independent. I wouldn't go lower that 4W.
original45 wrote:
01 Jun 2018, 09:48
Should I use the radios built in meter or use my known to be accurate cb swr meter I can put inline.
Internal meter is junk. Use accurate external meter.
original45 wrote:
01 Jun 2018, 09:48
If their is anything I having considered please advise me so I may do things correctly please.
Use trusted external meter and do not forget to use 1/2 wave (180 degrees) or it's multiplication coax to measure SWR.
Also make choke balun under antenna feed point.
Bottom line, replace with decent aluminium antenna, it will improve a lot.
Chris
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The Collector
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Re: Correct way to swr a SSB

Post by The Collector » 01 Jun 2018, 13:26

Try and SWR it on SSB just for fun ;)

original45
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Re: Correct way to swr a SSB

Post by original45 » 01 Jun 2018, 13:36

Thank you all.
Chris I'm guessing here only ,but because it's a half wave and you mention mathematical length of the coax is some form of counterpoise ? .

A quick measure of my rg 213 it measures 38 foot and 9".

Will I need to reduce this to a 36 foot length then..

Balun I have a 4" ground drain pipe cut ready as a former .
Would guess 5 turns ,does this sound right.

Now I know if I swr it on ssb the needle will bounce up n down like a rabbit lol.

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ch25
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Re: Correct way to swr a SSB

Post by ch25 » 01 Jun 2018, 13:56

Electrical length.
Half wave - 180 degrees or multiplication make coax transparent for your measurement device. Other lengths will act as impedance transformer, so reading will be affected by coax.
You could even use 75 Ohm sat coax, will work perfectly, it's cheap and low loss :) I use sat coax for my rx antennas, hundreds of meters, low loss.
If you want to go deeper look at https://ac6la.com/tldetails1.html
Very useful piece of software.
Chris
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original45
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Re: Correct way to swr a SSB

Post by original45 » 01 Jun 2018, 15:01

Thanks Chris ,that link is far too technical for my understanding however I will try and grasp it.

Interesting you mention 75ohm coax for satellite.
I have read this before that it's loss is far less than 50 and the only reason 50 was generally excepted as the radio coax was because of the higher power handling over 100 watts of 50 ohm.

I have seen several posts on net on how many hams use the 70 ohm coax .
I will bear this in mind Chris for future reference especially on making a wire antenna latter at some point.

A exact measurement of my coax is 38 feet 9" as I just had some help to measure exactly.
Add another 3" in total if you include two pl plugs.

Sureshot , I will start on 27,555 as you suggest and then check either end of frequency.
Thank you again.

108EH002
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Re: Correct way to swr a SSB

Post by 108EH002 » 01 Jun 2018, 15:11

Should have been = hope this helps original 45,was reading a thread by sureshot at same time elsewhere {bnghd} and some even tune on 27.485 just to be closer to the middle of the legal 80 channels.
You can talk worldwide on CB radio aswell,
rsgb are too far up their own @rses to admit it,
many freebanders just happen to know otherwise.

27.781.25 Fm
27.555 Usb
27.385 Lsb
27.315 Fm
27.275 Usb
27.025 Am

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andrew013
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Re: Correct way to swr a SSB

Post by andrew013 » 01 Jun 2018, 16:29

forget the length of coax , just use what you need there are people out there who belive cutting an inch off your coax will lower or raise the swr , FOOLS swr the antenna as close to the ariel as poss i swr from the base of ariel as i get someone to key the radio up for me when im up the ladders , job done if you then stick a swr meter at radio end and it changes its due to the coax , but ariel swr will still be the same
as for using an ally twig instead of a fibreglass one is again rubbish nothing wrong what so ever with a fibreglass ariel
on air,tyne&wear,northumberland,durham,holy island,eu120+eu124 and anywhere from gateshead/north wales
scrap uk 40 give cbers L/M/Hcalling on 27.355/555 usb qsy 27.015 lsb/410 usb cb radio is for life not just for profits
i do cb radio not 11mtres,countrys worked 2015 with imax 2000 72

original45
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Re: Correct way to swr a SSB

Post by original45 » 01 Jun 2018, 16:55

Thank you both I will carry on and do so as advised best.

Much appreciate all the advices and clearing up any mis understandings .

Again I am very glad I asked what seem simple questions for those with the experience and knowledge . And again I learn something that will serve me well in future .
Thank you.

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ch25
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Re: Correct way to swr a SSB

Post by ch25 » 01 Jun 2018, 17:00

andrew013 wrote:
01 Jun 2018, 16:29
forget the length of coax , just use what you need there are people out there who belive cutting an inch off your coax will lower or raise the swr , FOOLS swr the antenna as close to the ariel as poss i swr from the base of ariel as i get someone to key the radio up for me when im up the ladders , job done if you then stick a swr meter at radio end and it changes its due to the coax , but ariel swr will still be the same
as for using an ally twig instead of a fibreglass one is again rubbish nothing wrong what so ever with a fibreglass ariel
Forgot to take ur pills lately? Calm down. Try to understand what was written earlier.
No one told him to cut coax to adjust swr. What was told it is no need to climb a ladder since law of physics are well known since a really long time. Try sometimes, won't hurt.
Chris.
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Re: Correct way to swr a SSB

Post by Transwarp » 02 Jun 2018, 09:43

"It's worse then that it's physics Jim" :lol:
"Did video really kill the radio star?"

original45
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Re: Correct way to swr a SSB

Post by original45 » 02 Jun 2018, 16:10

Couple more questions please if you don't mind.

Should I insulate the Antrons base from its mounting pole .

As I understand its self contained and grounded by the coax into radio ?.

And lastly if I can explain myself correctly.
I intend to swr the antenna about 12feet of ground on pole.
It will need to be bought down to ajust swr as needid.
Now once I get hopefully the lowest swr reading in the centre of frequencies
Then regardless of its erected position the SWR can't be lowered any further by adjustment .
Any increase in swr must be to do with obstructions or environment coax and such ?.

Thank you again.

108EH002
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Re: Correct way to swr a SSB

Post by 108EH002 » 02 Jun 2018, 19:35

1 = No need to insulate base of A99 in my opinion.

2 = If it was my antenna I would put the 2 swr rings in the middle,and this should be close enough for the CB frequencies that you want to use.
You can talk worldwide on CB radio aswell,
rsgb are too far up their own @rses to admit it,
many freebanders just happen to know otherwise.

27.781.25 Fm
27.555 Usb
27.385 Lsb
27.315 Fm
27.275 Usb
27.025 Am

wa10
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Re: Correct way to swr a SSB

Post by wa10 » 03 Jun 2018, 00:13

There is no reason to cut coax to any particular length to measure vswr, that's an old cb myth,

it is IMPOSSIBLE to fool a vswr meter, fools the meter is another cb myth,

antennas don't have a vswr, they have a feedpoint impedance that terminates the coax,
whenever that impedance does not match the characteristic impedance of the coax you have a vswr inside the coax that is not 1:1,

much of what you read about antennas & vswr on cb forums is mythology, why bother with what is really going on when a few words of fiction is so much easier to understand,

if you know the length of your coax and the attenuation of the coax per unit length you can calculate the vswr at the antenna end of the coax regardless of where you put the meter,

yes impedance seen at the input end of the coax changes in a cyclic fashion with coax length mirrored at 1/2wave multiples & inverted at odd 1/4wave multiples whenever the load does not match the characteristic impedance of the coax used but vswr should not change with coax length other than a gradual reduction in reading the further from the load/antenna you place the meter due to loss in the coax,

when vswr does change significantly with small changes in coax length like adding/ cutting a few feet you have common mode current on the outside of the coax braid, this is common with no radial endfeds like a99 & imax,

the common mode impedance is seen in parallel with the load and does change vswr not just the vswr reading, cutting 1/2wave multiples won't stop that,

using 1/2wave multiples only makes the coax impedance transparent so you can measure the feed-point impedance (not vswr) some distance from the antenna and only when you have no common mode on the coax braid & the load is none reactive,

only the operator can be fooled, you are certainly not fooling the vswr meter but some people misunderstand what is actually going on and make up their own laws of physics to fit what they observe,

the only time you need to cut specific lengths is when you are making phasing harnesses or using coax as an impedance transformer,

anybody wanting the truth from respected sources should read walt maxwells "reflections" & "another look at reflections"

or "vswr meters make you stupid"

or mfj analyser user manual

or bird technologies white sheets

or tellewave white sheets

to isolate or not isolate the a99 from a conductive mast is a can of worms im not opening right now, too much to go into at this time of night but you could read w8ji's article on imax 2000 & other endfed verticals as a starter if interested.
Last edited by wa10 on 03 Jun 2018, 02:42, edited 1 time in total.

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