Antenna matcherboxs??

[Billybob]

Hi Guys,

Ive reacently came across a box with a few old SWR/power meters and odd boxes with knobs on.
All claiming to have some thing or other to do with CB radios.

Ive reacently put a post on the Tech help page about a old single knob SWR/Power meter witch I neded help on how to use, witch Stampmann came to the rescue with a really simple instructions

Amongst this bunch of various stuff, I came across a antenna macher box.
This Little box Only has two knobs and the two PL295 connecters.

Ive seen these kinda things knocking about, bud never really knew much about them or how to use them!

Am I right in thinking they are an aid, or something to do with tuning an antenna for a better SWR or something like?

Again, I would appreciate any light on why and how you would use these matchers or on how they work?

Billybob..*

[stampman]

they fool the cb into tthinking the antenna is a perfect match ok if you are useing 100 wattts waste of time if you are uesing 4 watts

[Billybob]

I got ya!

Don't think I need it, the highiest SWR reading I get On my 10 meter S9 is about 1.5 on around 15-20 watts.

So how would you use it, in regards of in line fitting and tune?
I would like to know, just in case 1 day you never know. Plus I do like to have a mess now-n-again

Is it as simple as that SWR/Power meter you help me with the other day?

Thanks again Stampman..
Billybob..*

[stampman]

GOES BETWEEN THE ANTENNA AND SWR METER

[disgwylfa]

As stamp says, it goes between the antenna and the SWR meter and, if it's one of the "two SO259 Sockets and Two Knobs - nothing else" type they're generally really simple to use. You, supposedly, turn one knob until you get the lowest SWR reading that you can, then you do the same with the other knob. Then back to the first knob to check there's no more improvement to be had.

It 'fools' the CB into beliveing it has an exceptionally good SWR but, obiovusly, there's no change to the actual performance of the aerial. So the only benefit is that if you're using a mismatched aerial, it won't (shouldn't) blow your Finals and fry the rig. With a CB it's always a better idea to fix the SWR and get a good, proper antenna match.

If you're using some home-brew cobweb antenna, or a multi-element beam, or some other exotica then getting the SWR adjusted isn't a case of moving the tip, or winding the coil, so a Matcher is the only way to go. They're also used by Ham enthusiasts who have a whole bunch of different bands on their transcievers so they could, for example, use a matcher to allow the same antenna to be used for 10 meters and 12 meters (and 11mtr too, if they're naughty Ham operators!).

Hope that's added to your store of (probably useless) radio knowledge

[Billybob]

Ok,
So the two are labled 'TUNE' and 'LOAD'.
So Im Tuneing down first as low as it will go, then turn on the LOAD knob to see if I can the needle lower!
Is this correct.
Sorry if Im being a bit thick. Its just that ive never really messed with these things, now Im intrigued!

Billybob..*

[stampman]

you got it

[Billybob]

Nice 1,
Am I right in thinking that it cant all be roses!
I guess some of the output power is sacrificed in having to load this gadget, in order to allow this tune to happen!
Billybob..*

[disgwylfa]

You're losing / have lost the power already. Any mismatched antenna is inefficient and therefore loses power.

What the Matcher does is prevent that mismatched power being reflected back into the transciever and (worst case) frying your finals.

Here's a sort of example. . . .
Using really inappropriate numbers (in reality the numbers are much smaller):
- Let's say you have the perfect antenna - SWR is 1.0:1 - so 100% of the output power of your rig, 4 watts, is going to the antenna and is off out into the world carrying your signal.
- Now let's say you have an off spec aerial. Your SWR is really high so some signal is reflected back. Let's say 25% is reflected (That'd be a MONSTER SWR reading by the way).
Firstr of all you're now only transmitting with 3 watts. Secondly, that 25% (1 watt) is heading back into your radio where it has nowhere to go . .hence the fried finals.
But, with the matcher in place, it "soaks up" that reflected 1 watt before it gets back to your delicate and expensive radio parts.

I can't remember the figures off the top of my head, but in reality a SWR reading of 2:1 is still about 90%. So to lose 25% would be a HUGELY mismatched aerial.

I'm sure someone on here will provide an accurate definition of what a SWR of 2:1 is....

[Billybob]

Oh I get ya, I understand now!

So really Its the last dance, a radio safe guard buffer if you like, should you not being able to get that reflection down!

But your still left with a limp wristed signal because the antenna still not tuned correctly!

Thanks for spelling out for me disgwylfa, and also stampman.

Ive learnt something new today.

There are two other little black gadget boxes here I would like the down low on but I might start another post, so folks can find it and follow up on should they want to...

Thanks again guys
' Ive just noticed ive upgraded to Official CB NUT 'is that good or bad '

[stampman]

good