It Amazes me..

So many people use a "tuner"

However so few people know how to use it or why to use it.

The reason to use a tuner is if your antenna is not resonate on a particular frequency.
If this is the case then using a tuner will enable ones radio to see a low swr where otherwise a higher swr would be seen by ones radio..
So your radio will be happy and its finals safe....
This will not persay enable your radio to transmit extremely well when the tuner has to "ajust"
what the radio sees for an swr (because in so needing to "ajust" the swr to make radio happy means the antenna is not particularly resonate on that frequency.

So what does that mean
Ok you have room for a single antenna but are trying to get it to work across several frequency bands....but as was said earlier...it is possible to get a coke can to show you radio a desirable swr so that it will transmit at full power and not "worry" about damaging-destroying its finals..

So what really is a "tuner" good for..
is simple

if you are using say a multiband antenna or even a single band antenna
say if it a rather far run from your radio to the antenna
so using a 50 ohm coax-feedline would incur a lot of loss (thereby greatly reducing your antennas ability to talk and recieve at a good distance)
So instead of coax one desides to use say 300 ohm open wire-ladder line (for extreme low loss of signal)..

Now here is where a tuner truely works as it is designed for our radios need to see 50 ohms
So now the tuner will match the feedline 300 ohm and bring it to 50 ohm matching for our radio....now we obtained extreme low loss with open wire feedline and still able to show 50 ohm and low swr to the radio......but because the antenna is extremely resonant on the frequency you are on....and since the radio now sees also the 50 ohms it needs as well as low swr....now everything works great...so nearly all you power goes to radiate on your desired frequency-band..

So in conclusion..
if your antenna is well designed for the frequency you desire and or need to use..
then using a tuner to over come either poor feedline and or unmatched ohms is what most tuners are truely designed for

i bet at least 70% of people using tuners are Not using them Properly

I have a tuner and have had it for years..
I also have never used it..
For my antennas are designed properly to radiate effectively on the frequency's i use
Also my coax-feedlines are in exellent shape

there is another use for a tuner
is a way to use a tuner to help you hear a bit better
to help pull contacts out of the qrm (although i have not needed to use it for that)

anyways
that is my 2 cents

It Amazes me..

So many people use a "tuner"

However so few people know how to use it or why to use it.

The reason to use a tuner is if your antenna is not resonate on a particular frequency.
If this is the case then using a tuner will enable ones radio to see a low swr where otherwise a higher swr would be seen by ones radio..
So your radio will be happy and its finals safe....
This will not persay enable your radio to transmit extremely well when the tuner has to "ajust"
what the radio sees for an swr (because in so needing to "ajust" the swr to make radio happy means the antenna is not particularly resonate on that frequency.

So what does that mean
Ok you have room for a single antenna but are trying to get it to work across several frequency bands....but as was said earlier...it is possible to get a coke can to show you radio a desirable swr so that it will transmit at full power and not "worry" about damaging-destroying its finals..

So what really is a "tuner" good for..
is simple

if you are using say a multiband antenna or even a single band antenna
say if it a rather far run from your radio to the antenna
so using a 50 ohm coax-feedline would incur a lot of loss (thereby greatly reducing your antennas ability to talk and recieve at a good distance)
So instead of coax one desides to use say 300 ohm open wire-ladder line (for extreme low loss of signal)..

Now here is where a tuner truely works as it is designed for our radios need to see 50 ohms
So now the tuner will match the feedline 300 ohm and bring it to 50 ohm matching for our radio....now we obtained extreme low loss with open wire feedline and still able to show 50 ohm and low swr to the radio......but because the antenna is extremely resonant on the frequency you are on....and since the radio now sees also the 50 ohms it needs as well as low swr....now everything works great...so nearly all you power goes to radiate on your desired frequency-band..

So in conclusion..
if your antenna is well designed for the frequency you desire and or need to use..
then using a tuner to over come either poor feedline and or unmatched ohms is what most tuners are truely designed for

i bet at least 70% of people using tuners are Not using them Properly

I have a tuner and have had it for years..
I also have never used it..
For my antennas are designed properly to radiate effectively on the frequency's i use
Also my coax-feedlines are in exellent shape

there is another use for a tuner
is a way to use a tuner to help you hear a bit better
to help pull contacts out of the qrm (although i have not needed to use it for that)

anyways
that is my 2 cents

KingCobra_CDX882,
I'm sorry, but you're mistaken. The only thing a tuner does is match impedances between whatever is on either side of it. That has nothing to do with resonance.
- 'Doc

i know has nothing to do with resonance
people use it often thinking an atenna not resonating well on a frequency
can be fixed by a tuner
simply because a tuner shows a radio a good swr

Right, but a tuner can make a non-resonant antenna -usable-, which is sort of the point. While resonance is a nice thing to have, it certainly isn't always the 'best' alternative. If a non-resonant antenna puts a signal where you want it to go, and if using a tuner makes that signal stronger than what it would be otherwise, then a tuner is a pretty handy little 'do-dad' to have. But it isn't a miracle worker, just handy.
- 'Doc

I dis-agree

A antenna is either properly resident on a frequency or it isn't

A tuner may get a radio to be happy
but not persay enable any more power to radiate on a antenna that suffers from poor swr (residence on a given frequency).

is still best to be sure the antenna is fully resident on the frequency(s) you want to use it for

multiband antennas still are supposed to have reaonable swr over several bands

The problem with resonance is that an antenna is only resonant on one frequency. It can maybe be sort of resonant on a range of frequencies, but very seldom over a wide range. By definition, resonance is the absence of reactances. Even so, when at resonance, an antenna's input impedance is almost never very close to what the average transmitter wants to see, about 50 ohms, without some sort of impedance matching being done. That impedance matching for a single band antenna is usually some fixed device. For most multi-band antennas, there's an impedance matching device and then the lengths, or positioning of 'traps', is selected so that that matching device can be used for all of the covered bands. The measured lengths are not what would normally be called resonant, but combined with the matching device and trap, the resulting length would exhibit no reactances making the thing resonant. One example of such a thingy is the tuner and whip combination produced by 'SGC', where the tuner is at the base of the antenna. What 'SGC' doesn't advertise is that the further away from the frequency that whip would normally be resonant on, the worse the efficiency of the thingy is. Where the whip is something close to one of the 'typical' lengths thought resonant (1/4, 1/2, 5/8 wave), it does work fairly well. On bands where the whip is extremely electrically short, you can shout further than the resulting signal will go (an exaggeration, but not much of one).
The biggest draw back for tuners is the feed line between tuner and antenna. If that feed line has much loss, or is subject to deterioration because of the resulting voltages from the SWR, it ain't the best situation in the world. If you don't have to worry about the feed line being destroyed by high SWR, then it can work very well indeed, in terms of radiated signal getting to where you want it because of non-resonant antenna lengths. That doesn't mean that always using a tuner is the best possible means of doing things, but it does mean that in certain circumstances it will mean making an inappropriate antenna usable. Which is basically the point of this thread. It doesn't say anything about how appropriate any particular length of antenna is, some are just not going to be very good (usually too short).
- 'Doc

Doc has some good info there. First do not get hung up on the word "resonant". Probably 99% of the people that use that word use it in the wrong context. Like Doc said it simply means having no reactance. Most people think it means having an impedance of 50 ohms. I have seen that over and over again in antenna posts. I have an antenna that is resonant on one band but presents an impedance of about 5 ohms,that means an SWR of 10:1. The tuner allows me to use it and allows my TX to deliver full power into the feedline. The absolute best place for any antenna tuner is directly at the antenna feedpoint. I use a Yaesu FC-40 auto-tuner in the mobile and the tuner is mounted on the rear hatch door of my Ford Escape with about 1 foot of heavy braid connecting it to the antenna base. This braid is very well insulated as the RF voltage can on some freqs. be several hundred volts or even more. The use of coax in this case presents two problems. First is break down voltage rating and the other is capacity. With a very low impedance like one would see with an 8 foot whip on 80m, the coax capacitance appears in parallel with the low impedance and effectivly shunts the RF to ground thereby making a bad performing antenna even worse. Commercial AM broadcast stations have an antenna tuning unit (ATU) at the base of each tower transforming whatever the tower impedance is to a normal 50 ohms and then use 50 ohm cable back to the TX building where it is fed from a phaser or power divider. The ATU is NEVER at the TX end of the cable for the above mentioned reasons.

"I'm sorry, but you're mistaken. The only thing a tuner does is match impedances between whatever is on either side of it. That has nothing to do with resonance."

no he isn't mistaken, you are. Impedance = Resistance + Reactance. the "tuner", whether used at the antenna or the transmitter exhibits the ability to cancel reactance. a pre-existing mismatch coupled with another calculated mismatch provides the "conjugate" match and since impedance consists of both resistance and reactance and the absence of reactance determines resonance it is you who is in error.

"That said if you were to take a reading at the antenna you would find that the swr was through the roof and your radiation efficency was a fraction of what a properly tuned antenna for a particular frequecy would be."

the radiation efficiency of the antenna has nothing to do with swr.

swr on the line between the antenna and transmatch* is determined ONLY by the matching
conditions at the load, and is not changed or "brought down" by the matching device. "low
swr" obtained by using the device indicates only the mismatch remaining between the input
impedance of the transmatch and impedance of the line from the transmitter.

*designed for use between the transmitter output and line input.

__________________
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You are right, as far as you went. But that's only if the tuner is at the antenna's input. If it isn't, such as at the transmitter end, then the feed line also becomes part of that impedance mismatch, not just the antenna. That's where the 'problem' occurs, if the feed line isn't 'SWR-resistant'. Coax as a feed line is not 'SWR-resistant' by any means. It can be damaged quite easily by a combination of high SWR and too much power for that particular circumstance (that power doesn't have to be high, even a few watts can do the damage).

You're also right about the efficiency of an antenna not being dependent on SWR. But, if presented with a high SWR a transmitter tends not to produce it's full output. The antenna can only radiate what power gets to it, so if there is reduced power getting there, then the antenna's radiation efficiency will -appear- less than a properly matched exact same antenna. My mistake, should have said antenna system (antenna and feed line), and where the tuner was located. Oops, sorry 'bout that.

SWR on the feed line being determined by the load's input impedance. True, if the feed line and transmitter's output impedance are reasonably close. You can also 'transform' that mismatch by using a suitable length of coaxial feed line as the 'tuner'. The draw back to that is that coax was never designed, or intended, to do that transformation. Coax IS affected by SWR, and not to the betterment of it's self. Meaning that it will degrade, change it's characteristics, basically 'eats' it's self up. I wouldn't say that was a very good thing to do.

You're also right about what a transmatch/tuner is doing, changing the apparent SWR that the transmitter see. It doesn't change the actual SWR of the antenna system. And like I said, there are other feed lines besides coax, that reduce that 'loss' because they are just not affected by SWR as much. They can't be used in all circumstances without a -lot- of trouble because of their own particular characteristics.

Taking another 'step', the losses associated with tuners is almost always less than that when using a coaxial feed line as the 'tuner'. The exception being when a tuner/transmatch is used in a circumstance where it's ratings are exceeded (holds true for anything, not just tuners).

Knowing why coaxial cable was invented to start with is helpful. It wasn't because it did the job better than anything else. It was because it made a radio installation in vehicles much easier. Same for 'standardizing' transmitter impedance outputs at 50 ohms. Not cuz it was 'best', it just made other things easier.
- 'Doc