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Old 05-02-2017, 9:02 PM
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Default Are Antenna Tuners a Lie?

Wasn't sure where to post this so since I have a tuner
connected to my CB I figured here is good enough.

I'm curious to know if using an antenna tuner actually
makes a difference or is it just lie?
The only way I can elaborate is to use the following scenario.

Radio hooked up to an antenna with SWR meter in between.
The SWR comes back as 2.3:1.
Which means out of (random) 10 watts transmitted, 10 watts is
not going out or my antenna.
Now an antenna tuner is put in line. Everything adjusted and
now the SWR barely moves 1.05:1.
Question: Of the original 10 watts transmitted, (from the radio)
are all 10 watts leaving my antenna OR is the originally reflected
wattage being absorbed by the antenna tuner and therefore creating
the illusion of a perfect SWR match?
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Old 05-02-2017, 10:55 PM
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One thing the antenna tuner does is allow the radio to transmit into the questionable load without the power backing down due to SWR protection circuits and in some cases it can avoid damaging the radio. BTW, I've tried to purposely damage many radios by transmitting with no antenna and have never been successful.

In many cases and depending on the antenna match and feedline, the reflected power will get sent right back to the antenna where a portion of it will be radiated and a portion will be reflected back toward the tuner in an endless cycle. This adds to the overall radiated signal and if you have no feedline loss it will make up for some calculated loss due to high VSWR.

In most CB installations coax is the feedline and when coax is used under high VSWR conditions, the advertised loss goes way up and you can't make up for that. If a 50ft chunk of coax has say .5dB loss at CB, then if you feed an antenna with a really bad match you could have a couple more dB of loss on top of the VSWR mismatch loss.

Where you may have been able to reflect and radiate some of your reflected power if you had used a very low loss balanced line, the now very lossy coax will absorb an amount of reflected power going back toward the radio or tuner and it will absorb more again as it heads back to the antenna, and so on.

All the stuff in the last couple of paragraphs are independent of using an antenna tuner and a tuner will not get back any of the lost power from VSWR problems or from power absorbed in the coax. However, if you place the antenna tuner at the antenna lots of things happen and its all good. The radio and feedline both operate into a good match and you avoid the additional coax loss from operating under high VSWR. Any reflected power from the antenna has no feedline loss to the tuner so more of it will be sent back to the antenna with more radiated.

Otherwise tuners are not perfect and they do have some loss, which will vary with the tuner design and if its matching to a very high or very low impedance. I use tuners every day for HF antennas, mainly because my antennas cover many bands and without them life would be more diffacult. I am losing something by using them but it appears to be very small and the reward is I can have more fun with less hassle.
prcguy

Quote:
Originally Posted by SpugEddy View Post
Wasn't sure where to post this so since I have a tuner
connected to my CB I figured here is good enough.

I'm curious to know if using an antenna tuner actually
makes a difference or is it just lie?
The only way I can elaborate is to use the following scenario.

Radio hooked up to an antenna with SWR meter in between.
The SWR comes back as 2.3:1.
Which means out of (random) 10 watts transmitted, 10 watts is
not going out or my antenna.
Now an antenna tuner is put in line. Everything adjusted and
now the SWR barely moves 1.05:1.
Question: Of the original 10 watts transmitted, (from the radio)
are all 10 watts leaving my antenna OR is the originally reflected
wattage being absorbed by the antenna tuner and therefore creating
the illusion of a perfect SWR match?
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Old 05-03-2017, 11:31 AM
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Another way to think about it, is that "tuner" is a misnomer. It should be called "adapter", "converter", or "matcher".

it 'matches' the radio to the antenna system so that the radio won't be damaged by a mismatched antenna. And it matches by going to the lower state; so if your antenna system sucks or is not properly tuned for CB, you will have losses regardless of using a tuner or not; the tuner just stops that mismatch from harming your radio.

FWIW; I, too, have never hurt a cb when using it barefoot; when using an amp with a mismatched antenna is another story; so if you're using an amplifier; and a mismatched antenna, you need a tuner. If you want full power, you need a properly matched and tuned antenna
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Old 05-04-2017, 7:31 AM
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I know that tuning for SWRs is done by following the SWR meter gauge and adjusting the length of the antenna accordingly.

How do you tune via an antenna "tuner?"
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Old 05-04-2017, 8:27 AM
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If you didn't read prcguy's very good explanation, all the antenna tuner does is match the bad tune of the antenna / feed line to the output of the radio so the radio is not damaged.
An antenna tuner DOES NOT TUNE THE ANTENNA.

To get the most out of your antenna, You need to match the entire system to the radio.
There are no shortcuts.
I use an antenna tuner on my amateur gear to so I don't have an entire forest (only a small grove) and I don't mind that not all of the signal my transmitter sends down the feed line gets converted to ElectroMagnetic energy. If some is lost as heat, that is the price paid to not have to put up another antenna matched to the frequency I am using at the moment. I only need enough to make the contact and no more.

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Old 05-04-2017, 8:37 AM
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It's not a tuner per se it's a matcher as have been described above. A real antenna tuner has multiple coil winding's in a box that are switched in and out to add length to an antenna based on it's frequency. You find them on HF 2-30 mhz radios and some are self tuning others need to be tuned manually. In the marine service you can load up a stay cable on a sailboat or a long wire between masts.While I was in the military we had automatic tuners on our mobile HF radios that tuned a whip that was about 30 ft long.
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Old 05-04-2017, 4:16 PM
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Quote:
Originally Posted by DaveJacobsen View Post
Another way to think about it, is that "tuner" is a misnomer. It should be called "adapter", "converter", or "matcher".

it 'matches' the radio to the antenna system so that the radio won't be damaged by a mismatched antenna. And it matches by going to the lower state; so if your antenna system sucks or is not properly tuned for CB, you will have losses regardless of using a tuner or not; the tuner just stops that mismatch from harming your radio.

FWIW; I, too, have never hurt a cb when using it barefoot; when using an amp with a mismatched antenna is another story; so if you're using an amplifier; and a mismatched antenna, you need a tuner. If you want full power, you need a properly matched and tuned antenna
I agree its a Matcher not a Tuner as prcguy said it matches the antenna to the radio .....
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Old 05-04-2017, 4:56 PM
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So I guess my thinking was right.
It just creates the illusion of a perfect match
to protect your radio from damage due to
reflected power.
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Old 05-28-2017, 6:54 PM
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Well I can say this, with a missed matched system and a poorly tuned IMAX 2000 (I am not dropping it to tune it for the 3rd time this month) I was running at 1.8 to 2.1 VSWR. I am now using a buddies auto "tuner" and my VSWR is now 1.1 if any at all.

Plus, there is a significant difference of performance over running it mismatched the way it was with that high VSWR
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Old 05-28-2017, 6:59 PM
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Normally tuners really aren't needed on CB if properly tuned antenna and matched, Mainly since it isn't like you are changing bands.

The only reason I even am is that I just want to buy some time on having to drop the antenna again. (In other words, I am done fighting with it and will fix it at a later date)

Last edited by swen_out_west; 05-28-2017 at 7:05 PM..
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Old 05-28-2017, 7:28 PM
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You nailed it. There's some that think they should buy/use a tuner for their 11 meter rigs. But since it is only one band, what they need do is work on the antenna to get a really good swr. Now there are some CB antennas that are just plain trash and no matter what you do, they never have an swr below 2.5 or whatever.
I had a gizmotchy many years ago, and I could never get the swr below 3 or 4. So, since it was a good antenna (by the CB crowd back then) I bought a tuner and brought the match to a respectable reading.
Later on, I found out that the gizmotchy was from a ham that had it matched to 10 meters, hence my high readings on CB channels.
A tuner has it's place and time.
(By any chance, anybody know if the gizmotchy is still around and any good?)
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Old 05-28-2017, 7:44 PM
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All an antenna matcher does is allow you to 'match' or adjust the impedance of the antenna and coax feed to something more to the 'liking' of your transmitter. That said, if you are using decent coax and fairly short runs (say under 50 ft) a bit of a mismatch (2.5 or less) is unlikely to have much effect on range. most modern radios back down on output power when they sense a 'high' SWR and some of them do so at ridiculously low levels of SWR. SWR is not a measure of antenna system performance -it just tells how good of a match the antenna is to the radio. As an example a 50 ohm 'dummy' load will show a match of 1:1 but is not a very good antenna.

Any antenna other than a 9 foot whip or similar base has an 'antenna tuner' (or matching network) built in to provide matching. How well that works depends on a lot of factors.
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Old 05-28-2017, 9:22 PM
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Okay speaking from personal experience. I have a base station with a homebrew 11 meter antenna at my office.

It tuned perfectly at the antenna feedpoint, so I put it up. I ran some mini RG8 type coax I got from Ham Radio Outlet while I was in Anaheim, CA about six months ago. Its a fifty foot run. As groundplanes go, it tuned out perfectly as I said before. But there's loss and mismatch.

I got lucky and found a Zetagi antenna matcher. I think they call it a 27 (for 11 meter). I found it at a Goodwill store so lucky me it was 3 bucks. Since that time I have not been able to find a local distributor, as these come out of Italy. Anyway I digress. The matcher actually fixed my SWR problem and ironically matched the coax to the antenna, or more appropriately matched the radio to the coax and antenna.

To explain it is kind of difficult. Everyone else seems to have given you a good explanation. So here's the gap filler. Your radio is set for 50 ohm matching. In theory if you have a 50 ohm radio, 50 ohm coax, and a 50 ohm antenna, then everything matches and you should have very little signal loss and your SWR's if they are not dead-even should be close. But, nature isn't perfect. No matter how close they try and make coax 50 ohms, it isn't. Depending on a bunch of variables including technical velocity factors and such gobbeldy gook that is great for math geeks and those familiar with geometry, trigonometry and the standard model and special model of physics, its all Chinese and so you have to take my word for it here. Coax no matter how perfectly made will have an impedance value of say 34 to 36 ohms. So ... you get some loss. Some coax is more lossy than other coax. So there's a gap. And that gap between that 50 ohm antenna and 50 ohm radio is your SWR value that is the amount of energy going through the center conductor and returning back in the form of RF energy or heat through RF ground. You can't transmit out without it back firing to your unit. The idea is to get as much out as comes back on an even number. When more comes back to your unit, the hotter your transistor gets because now its mismatched, and it de-tunes. The hotter it gets the more detuned it gets and its possible to blow your finals. In the old days it was easy to blow your finals. Today's transistors are designed to take a load of abuse. But you can still damage them and detune them.

So what is the matcher? Its two variable capacitors to ground. Some are single capacitors to ground. It appears to short but in reality it bounces your signal back up to the radiating element instead of into your radio. In a way it tunes to resonance and in a way it doesn't. So its both a tuner and a matcher, but in reality its just a matcher.

A capacitor stores and discharges energy across either air or a membrane; and depending on which direction its going and how much, it will do a fine job of balancing your RF out to your RF back if you have the right one. What does not get emitted out, just bounces back and forth away from your radio, as the others said. No risk of detuning your finals.

If you do find a Zetagi I will say they're good for standard radios. I don't think they're rated for a lot of power but its an inexpensive item and works well for low power which is what I use it for. I am getting another one for my mobile radio because I have a stubborn antenna situation without any easy solutions.
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Old 05-28-2017, 10:01 PM
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Well, after reading this "Thread", I guess my contribution will be off-topic. My best SWR and CB transmit/receive results have been obtained using a (about) 1 foot high (mounted on vehicle roof top) antenna with a threaded collar (about 1/4 way up the antenna). Rotating the collar moves it up and down on the antenna. Used with a SWR meter, I dial in the best reading, and then wrap a wad of chewed gum around the collar to fix its location. It's been on three trucks (36 yrs), so I don't have a memory of brand or purchase location. In my mind, the "collar" is an "antenna tuner".
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Old 05-30-2017, 3:48 AM
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Quote:
Originally Posted by rwier View Post
I dial in the best reading, and then wrap a wad of chewed gum around the collar to fix its location. .
What kind of gum do you use?
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Old 06-07-2017, 11:01 PM
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Default Is this a Base Loaded Antenna?

Allied and Lafayette used to make a "Shorty" which was a base-loaded antenna and you tuned it by rotating the coil and moving the whip up and down. Is this what you're talking about? That was about, oh 40 years ago? Or is this a center-loaded whip that let you move the coil up and down the bottom part of the whip?


Quote:
Originally Posted by rwier View Post
Well, after reading this "Thread", I guess my contribution will be off-topic. My best SWR and CB transmit/receive results have been obtained using a (about) 1 foot high (mounted on vehicle roof top) antenna with a threaded collar (about 1/4 way up the antenna). Rotating the collar moves it up and down on the antenna. Used with a SWR meter, I dial in the best reading, and then wrap a wad of chewed gum around the collar to fix its location. It's been on three trucks (36 yrs), so I don't have a memory of brand or purchase location. In my mind, the "collar" is an "antenna tuner".
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Old 06-08-2017, 11:07 AM
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That would be a "tuneable antenna" and not an antenna tuner. It would have to work with other antennas to be an antenna tuner as discussed in this thread.
prcguy

Quote:
Originally Posted by rwier View Post
Well, after reading this "Thread", I guess my contribution will be off-topic. My best SWR and CB transmit/receive results have been obtained using a (about) 1 foot high (mounted on vehicle roof top) antenna with a threaded collar (about 1/4 way up the antenna). Rotating the collar moves it up and down on the antenna. Used with a SWR meter, I dial in the best reading, and then wrap a wad of chewed gum around the collar to fix its location. It's been on three trucks (36 yrs), so I don't have a memory of brand or purchase location. In my mind, the "collar" is an "antenna tuner".
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Old 06-08-2017, 4:10 PM
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Quote:
Originally Posted by forkeye View Post
Allied and Lafayette used to make a "Shorty" which was a base-loaded antenna and you tuned it by rotating the coil and moving the whip up and down. Is this what you're talking about? That was about, oh 40 years ago? Or is this a center-loaded whip that let you move the coil up and down the bottom part of the whip?
The only thing that moves is the collar. The collar appears to be simple metal cylinder about 1 1/2" long with an inside diameter of about 1/2", which is the same as the diameter of the antenna (not a "whip"). The collar itself is only about 1/8" thick and appears homogenous in nature (not a coil). The range of motion of the collar (up/down by rotation) is only about an inch.
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Old 06-08-2017, 4:15 PM
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Quote:
Originally Posted by prcguy View Post
That would be a "tuneable antenna" and not an antenna tuner.....
Of course. I was referring to the collar only ("..... the "collar" is an "antenna tuner" ...")
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Old 06-08-2017, 4:23 PM
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No it isn't. An antenna tuner is a device that goes between the feedline and the antenna, not a part of the antenna itself.
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