swr meter.....

[exosteve]

asuming I havent killed my radio by trying without one.
is this 400332239015 what i need.
and is it just a tester or do you leave it in permenantly?
cheers steve

[briggie]

yep , looks ok , you will need a patch lead from your cb to the meter ...... it has 2 pl 259 plugs on it , connect an aerial to the socket marked aerial , and your cb to the other , then read my guide in the cb section .

its always a good idea to leave your swr meter in situ .

running without a swr meter in line wont neccesarily damage your radio , but transmitting without an aerial will , heres hoping its ok .

all the best .

pete

[briggie]

swr stands for standing wave ratio and is a measure of the reflected power ,ideaaly this should be as low as possible to prevent damage to your radio .... a figure of up to 1-1.5 is acceptable providing you do not use any power boosters .


to measure the swr you will need a swr meter , this connects between your aerial and radio by means of a patch lead , change the cb channel to channel 1 and ensure the switch marked fwd /ref is on fwd .....press the ptt button on the microphone .. adjust the needle reading by means of the calibration switch/knob untill the needle is reading right at the end of the scale ( not over ) .... release the microphone ..... then switch the switch marked fwd/ref to ref ..... and press the microphone again ..... this is now your swr reading and should be as low as possible ....... do the same on channel 40 also .

[Fez_uk]

Don't worry you won't have damaged it. All the newer CB radios will protect the radio from damage if the swr is too high or antenna not connected by reducing the power.

Means you won't transmit as far though. So still worth checking it, But don't loose any sleep over it.

[Lazy-Ferret]

Just as a matter of interest, why do you say "leave the SWR meter in situ"? I was always told to take it out once set up, as it actually attenuated the output power by a significant amount, especially when you only have 4w to start with.

Just interested in the reasoning

[Fez_uk]

I think it's so you can check it more often and see if theres a problem quicker.

I've always thought your meant to leave it out too

[jims-terrano]

Briggie is quite right in an ideal situation to leave the SWR meter in circuit. However in a mobile situation it is less practical to do this, best way is to check the SWR from time to time if it is not practical to leave SWR meter connected.
There will be losses of the RF Energy but if the connections to the plugs are correct this should be pretty low.
Yes 4watts is quite a low power but as the saying goes "it aint what you've got it's how you use it". This is so true with radio, more power does not always mean you'll get further. The better your antenna, co-ax (aerial wire) and connections the more of your power will be released from the antenna.
As said modern radios are more tolerant of higher SWR's and will either lower the power output or shutdown to save the radio.
SWR stands for Standing Wave Ratio, it is the radio waves that come out of your radio, they go through the co-ax and to the antenna. If they do not fit the antenna they get reflected back down the co-ax to the radio where they can cause damage. Of course the more power you have the more the likelyhood of damage. Imagine the antenna to be a hole at the end of the co-ax, this hole can be adjusted or made larger or smaller. So the radio waves produced by your radio are one size, if the hole is not the correct size the radio waves can't get out and bounce back down the co-ax to the radio.

People who already have knowledge of this will be cringing at my explanation but I'm trying to explain it in very simple terms.

PL259 this is the commercial name of the screw on plug that is used to connect the co-ax to the radio or antenna connections. When fitted to the co-ax a PL259 should be nice and tight with good electrical connections. Over time the co-ax moves and eventually the electrical connection breaks down. This is likely to happen to the patch lead and eventually the aerial cable too, more so in a mobile situation. A Patch Lead is the short cable between the radio and SWR Meter.

So over time the SWR will change, usually by the cable connection being degraded or the antenna becoming degraded. Even placing the magnetic mount of the antenna in a different place. Weather will effect it too, wet or dry. Placing objects near the antenna or even the co-ax will change the SWR.

So to sum up you don't need more power just an efficient antenna system. Look after the antenna system and check the SWR from time to time.

Sorry for rambling on but all being well you will have an understanding of what it is all about.

[edgerton19]

Fit meter, adjust antenna then remove the meter in a mobile situation. Refit and test from time to time.
Leaving meter out in normal operation reduces the number of RF connections between the antanna and the radio and should improve the reliability of the system.
If VSWR is less than 3:1 most of your power will be entering the antenna and the cable losses will not be too high.
People worry about being less than 1.5:1 but don't worry if its slighly higher. The CAA for instance allow up to 3:1 across the VHF aircraft band on an approved installation.
Most radios are protected against open and short circuit antennas.

[briggie]

Originally Posted by Lazy-Ferret

Just as a matter of interest, why do you say "leave the SWR meter in situ"? I was always told to take it out once set up, as it actually attenuated the output power by a significant amount, especially when you only have 4w to start with.

Just interested in the reasoning

my reasoning is so you are aware of any problem as it happens , not after the event so to speak

[briggie]

Originally Posted by jims-terrano

Briggie is quite right in an ideal situation to leave the SWR meter in circuit. However in a mobile situation it is less practical to do this, best way is to check the SWR from time to time if it is not practical to leave SWR meter connected.
There will be losses of the RF Energy but if the connections to the plugs are correct this should be pretty low.
Yes 4watts is quite a low power but as the saying goes "it aint what you've got it's how you use it". This is so true with radio, more power does not always mean you'll get further. The better your antenna, co-ax (aerial wire) and connections the more of your power will be released from the antenna.
As said modern radios are more tolerant of higher SWR's and will either lower the power output or shutdown to save the radio.
SWR stands for Standing Wave Ratio, it is the radio waves that come out of your radio, they go through the co-ax and to the antenna. If they do not fit the antenna they get reflected back down the co-ax to the radio where they can cause damage. Of course the more power you have the more the likelyhood of damage. Imagine the antenna to be a hole at the end of the co-ax, this hole can be adjusted or made larger or smaller. So the radio waves produced by your radio are one size, if the hole is not the correct size the radio waves can't get out and bounce back down the co-ax to the radio.

People who already have knowledge of this will be cringing at my explanation but I'm trying to explain it in very simple terms.

PL259 this is the commercial name of the screw on plug that is used to connect the co-ax to the radio or antenna connections. When fitted to the co-ax a PL259 should be nice and tight with good electrical connections. Over time the co-ax moves and eventually the electrical connection breaks down. This is likely to happen to the patch lead and eventually the aerial cable too, more so in a mobile situation. A Patch Lead is the short cable between the radio and SWR Meter.

So over time the SWR will change, usually by the cable connection being degraded or the antenna becoming degraded. Even placing the magnetic mount of the antenna in a different place. Weather will effect it too, wet or dry. Placing objects near the antenna or even the co-ax will change the SWR.

So to sum up you don't need more power just an efficient antenna system. Look after the antenna system and check the SWR from time to time.

Sorry for rambling on but all being well you will have an understanding of what it is all about.

[Lazy-Ferret]

Originally Posted by briggie

my reasoning is so you are aware of any problem as it happens , not after the event so to speak

Fair enough... Just wondered, as there are so many opinions that differ, so wanted to hear another side, so to speak.

When I did my RAE course, the guy who ran it, was a real stickler for as little in the way of connectors and gubbings between the transmitter and the aerial, so as far as he was concerned, you had just 2 connectors, one at the radio end, one at the aerial, and even then, he liked long wire stuff and actually would join the wires straight to the coax with solder and heat shrink.

[exosteve]

I feel like im at college im learning so much.
cheers peeps.

[briggie]

Originally Posted by Lazy-Ferret

Fair enough... Just wondered, as there are so many opinions that differ, so wanted to hear another side, so to speak.

When I did my RAE course, the guy who ran it, was a real stickler for as little in the way of connectors and gubbings between the transmitter and the aerial, so as far as he was concerned, you had just 2 connectors, one at the radio end, one at the aerial, and even then, he liked long wire stuff and actually would join the wires straight to the coax with solder and heat shrink.

you pays your money and you takes your choice my friend , im a firm believer in prevention is better than the cure ,most radio hams are aware of how to check swr correctly and how to rectify any abnormalities , or they should be lol , novice cb users aren't always aware of correct set up and operating procedure , so my personal belief is its far better to monitor the swr all the time ...... or at the very least check it everytime before tx ........ just my personal view ...... obviously people will disagree .....

[exosteve]

Originally Posted by briggie

you pays your money and you takes your choice my friend , im a firm believer in prevention is better than the cure ,most radio hams are aware of how to check swr correctly and how to rectify any abnormalities , or they should be lol , novice cb users aren't always aware of correct set up and operating procedure , so my personal belief is its far better to monitor the swr all the time ...... or at the very least check it everytime before tx ........ just my personal view ...... obviously people will disagree .....

I want to constantly monitor everything on my only one vehicle so its staying in situ.
I dont think I will ever be in a situation where I will need to broadcast too far.
just a few miles will do.

[solarman216]

do not know if CB has got any better but when it was not legal the average distance was around 1 to 2 miles many times a lot less than that, if I made contact with a truck travelling in the opposite direction at 50 mph then we literately only had time to say hello where you going goodbye, and a burner made no difference at all, other than if I stuck my hand out the window and touched the aerial while transmitting it hurt, that was a DV27 base loaded as far as I remember, reckoned to be the best at the time, some of the Italians were running 1500 watt base stations and could be heard in the UK on skip but it was in and out, lovely days, Rick