CB hints and tips......

Yorkshire Andy
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Re: CB hints and tips......

Post by Yorkshire Andy » Fri Aug 07, 2015 8:39 pm

Any tips on swr reduction?

I've moved the antenna up and down and still no change

Using a thunder ant and mag mount

Got CH 40 to about 1.8 but

Ch1 is just scraping 2.5

?

Cheers in advance
If your roughing it, Your doing it wrong ;)

Lack of planning on your part doesn't make it an emergency on mine

HBP
Posts: 135
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Location: Area 51

Re: CB hints and tips......

Post by HBP » Sat Aug 08, 2015 7:04 am

I have never had a lot of luck with mag mounts and always ended up with a mount that's got some electrical connection to the vehicle.

A few ideas:
Move the mag mount
Make a choke in the coax close to the antenna by coiling it up. http://www.k3dav.com/rfchokecoil.htm
Trim the coax a bit and fit a new plug
Try a hatch or mirror mount depending on the vehicle you have.

Hamradioop
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Location: Area 1: north wessex

Re: CB hints and tips......

Post by Hamradioop » Sat Aug 08, 2015 11:24 am

With over a Megaherz of frequency span I would do one of two things tune for low SWR on the centre of the span or tune to my favourite channel. Mag mounts can be a real challenge to cut for frequency. a boot lip or hatch mount may be a better option and will not damage the car as much. and will give a better earth.
Got CH 40 to about 1.8 but

Ch1 is just scraping 2.5
this indicates your radiating element is on the short side. the other way round indicates it is on the long side. You could also insert an amu in line between the radio and the antenna but it will introduce losses.
AMU= Aerial Matching unit also known as a transmatch, match box etc.

ImageTM-999 swr/power meter & Matcher

A very popular antenna tuner for CB for up to 100W.

The meter will give direct reading of either swr or power, the power scale being selectable from either 10W or 100W.

The matcher can be switched on or off.

Frequency: 26-28MHz
Max Power: 100W
“A nation of sheep will beget a government of wolves.” ― Edward R. Murrow
"Remember Politicians are like babies diapers they both need changing often for the very same reason" - Mark Twain
If voting changed anything, they'd make it illegal.

Yorkshire Andy
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Joined: Thu Oct 03, 2013 4:06 pm

Re: CB hints and tips......

Post by Yorkshire Andy » Sun Aug 09, 2015 11:24 am

Thanks turns out i made a school boy error and errm got a bit carried away with my mates cordless grinder and cut it off when I needed to raise it :oops:

Need a new whip antenna and will try again..
Local shops been good and lent me a rigid base loaded antenna just to make sure its not the mag mount and its spot on getting about 1 on both ch1 and ch40

Got a nice big loom pulled to the battery yesterday with waterproof fuse holder close to the battery just need to mount the unit now
If your roughing it, Your doing it wrong ;)

Lack of planning on your part doesn't make it an emergency on mine

Yorkshire Andy
Posts: 3971
Joined: Thu Oct 03, 2013 4:06 pm

Re: CB hints and tips......

Post by Yorkshire Andy » Sun Aug 09, 2015 11:10 pm

just been playing managed to pick up a conversation oneside of which was a minimum of 16 miles away :D
If your roughing it, Your doing it wrong ;)

Lack of planning on your part doesn't make it an emergency on mine

Wulfshead
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Location: Area 4

Re: CB hints and tips......

Post by Wulfshead » Mon Aug 10, 2015 5:35 pm

Andy,
I may get told different but I also made the same mistake with my 1/4 wave ground plane antenna.
What I did was use an electric cable connector and screwed some antenna rod into the top. I was then able to re-cut to gain a better SWR match.
I did cut about 40mm of the element that was to short so I had enough new rod to play with, got a good SWR also.

Wulfshead
Area 4 Coordinator

For the strength of the pack is the wolf, and the strength of the wolf is the pack

Hamradioop
Posts: 2089
Joined: Sun Jan 20, 2013 11:21 am
Location: Area 1: north wessex

Re: CB hints and tips......

Post by Hamradioop » Tue Aug 11, 2015 8:50 am

Same rule with Aerials as wood measure twice cut once.
“A nation of sheep will beget a government of wolves.” ― Edward R. Murrow
"Remember Politicians are like babies diapers they both need changing often for the very same reason" - Mark Twain
If voting changed anything, they'd make it illegal.

Yorkshire Andy
Posts: 3971
Joined: Thu Oct 03, 2013 4:06 pm

Re: CB hints and tips......

Post by Yorkshire Andy » Wed Aug 12, 2015 4:19 pm

Ive got it something like now with it about 2.0 on ch1 and 1.5 on ch40..... with a whip but cant get any better

http://www.thunderpole.co.uk/large-cb-a ... bitor.html



yet with this one:

http://www.thunderpole.co.uk/large-cb-a ... yager.html


gives sub 1 readings on both channels (using the same mag mount )
If your roughing it, Your doing it wrong ;)

Lack of planning on your part doesn't make it an emergency on mine

HBP
Posts: 135
Joined: Wed Apr 29, 2015 7:33 pm
Location: Area 51

Re: CB hints and tips......

Post by HBP » Wed Aug 12, 2015 7:54 pm

You have 2 very different loading coils on those antennas. The one that gives a better swr may well be better designed and as it can't move it will be more electrically stable.

Basically, one is probably a better antenna than the other.

A quarter wave whip for cb (11m band) would be approx 2.75m long. Adding a loading coil makes it appear electrically longer than it is so is always a compromise.

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dangerman
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Location: Liverpool

Re: CB hints and tips......

Post by dangerman » Wed Aug 12, 2015 8:21 pm

What kind of range is a set up like this capable of? How many people are likely available to communicate with?

I worry about CB because I hardly know anyone who uses it. And I know they're only short range.
I love motorcycles like a fat guy loves cake. I also love cake.

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