Jump to content

CB Radio's


Recommended Posts

I bought a CB set to go in the Lightweight this week off Ebay (proving that you should never go on there when bored!). It has come complete with a SWR meter and all the cables that go with it.

Problem is, what the hell is a SWR Meter - and what do I do with it?

Any suggestions as to where I could attach the CB would be useful too as my dashboard (or lack of) is covered with randomly scattered switches!

Link to comment
Share on other sites

The VSWR (voltage standing wave ratio) meter, is a simple way of testing the tuning of the antenna and feeder.

But once you have the system working, you must remove it. It's a source of interferance, so having it in the line all the time is not a lot of help.

What you are trying to do, is look for the best forward power and the lowest returned power. This means that most of the energy is being radiated from the antenna, which is what you want.

Best place for any antenna is the middle of a large metal surface. But the offside front wing of a Rover is good enough in most cases. Don't add extra cable to the antenna to "tune" it. All you do reduce the amount of power to the antenna due to losses in the cable. Solder ALL connections were at all posible.

Link to comment
Share on other sites

CB radios, SWR meters, mag mounts that brings back memories from when I was young sticking up aerials at my parents house - some of them very big and ugly, god knows how i got away with it.

Regards the licence - Is it only people who have held a licence for over a certain period of time that dont now need one or has the licence been scrapped.

Link to comment
Share on other sites

Thanks guys.

 

ArtistsRifles, thanks for the link - even I understood that!

 

79Lightweight, I'm in Folkestone, Kent - still can't work out where to attach the damn thing at the moment but if anyone is nearby would love to meet up and talk MV's!

 

OOEC25, I believe that the CB license is not needed after 6th Dec 2006.

Link to comment
Share on other sites

And don't forget to remove it once the aerial is tuned !! :-) :-)

 

Oh yeah - try and locate the aerial as far from anyones head as possible, one of the demo's used by our Sigs troop was to hold a bit of paper near the aerial on a Landie and hit the PTT switch - paper would burst into flame as those aerials radiate a lot of energy!!

Link to comment
Share on other sites

HE HE bet you wish you never asked, :evil: :evil: :evil:

 

Lots of my mates who were into CB went on to ham radio, and I must confess they do lose me a bit, think i am some what bedazzled by the Fairisle tank tops and the sandals :schocked: :whistle:

 

10-4 there g/buddy this the crackerjack(alias HF) catch you on the sunny side of the flip flop...

 

That shows a mis-spent youth :whistle: :-D

 

 

Hardyferret :tup: :banana: :banana: :yay:

Link to comment
Share on other sites

Because all I need it for is keeping in touch with the rest of the convoy and contacting the heir to my debts once he's disappeared off into stall-land at W&P! :-D

 

You know what it's like - they wander off to get an ice cream and you don't see them again all day (which is sometimes a blessing!)

 

 

Link to comment
Share on other sites

[

OOEC25, I believe that the CB license is not needed after 6th Dec 2006.

 

 

thanks Lightweight

 

i have never actually used mine in my Ferret because at £15 per year (the cost when i first enquired) i had only paid £40 for the entire set up and thought it a waste of money when i would only use it infreqently in my MV. sdtand by for a lot of use now then

:banana:

Link to comment
Share on other sites

When you are receiving radio signals, the more antenna you throw up, the better.

 

When transmitting however, you need the antenna to be as near to a quarter wave-length (or just below) as possible. However, because the antenna length is more or less fixed (Larkspur: 8' of rods for VHF, 12' for HF; Clansman: 2m of rods VHF - I cannot now remember seeing 3m of rods for HF but that could just be me), you will need an electronic device attached to the antenna. On Larkspur this was an ATU - Antenna Tuning Unit. On Clansman VHF it was a TUAAM: Tuning Unit Automatic Antenna Matching. ISTR on Clansman HF it was ARFAT: Adaptor, Radio Frequency, Antenna Tuning. This device would electronically optimise the signal to match the antenna.

 

On Larkspur you actually had to send a signal whilst manually tuning the ATU to get the biggest possible deflection on the meter. ISTR on Clansman VHF there was a "Tuning" position on the face of the set which did the same thing automatically without actually transmitting. A whole squadron retuning and transmitting to adjust the Larkspur antenna tuning was a godsend to enemy direction-finders.

 

The rod lengths stated above were deliberately derived to match the quarter wavelength of the sets.

 

Note that if you carried a millimeter too much rod, the ATU would try to transmit and the next quarter-wavelength up, ie half a wavelength and it would be terribly out of tune. The only realistic way to do that in practice would be to carry 12' of rod in a VHF antenna base.

 

As a Control Signaller, I was taught a formula to derive the actual length of antenna required. Useful when we set up dipoles on the HF sets in static locations. After I left the cavalry and recce, I went to a REME Armoured Workshop where we spent a week in a location and worked on the Divisional HF Logistic Net rather than the VHF Command Nets. A dipole was the norm. As the expert, I did permanent night radio stags, so that I could change the frequency, the dipole lengths to match the frequency and all the codes at midnight.

 

One night, bored out of my skull, I plotted a graph by first principles of frquency against 1/4 wavelength for the whole frequency range of the UK/VRC321 and laminated it to the command vehicle wall where the coax left the vehicle to go to the antenna mast.

 

For those that care, the command vehicle was a hand-converted Bedford RL Machy Wagon (well it was a REME workhop: they were the people to do the conversion).

 

Getting fed up of this now so I'll stop.

 

;o)

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...