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Author Topic: "Antenna Tuners" Misleading Name for pro  (Read 6678 times)
KB3MMX
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Posts: 132




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« on: October 31, 2007, 05:52:43 PM »

Does anyone notice how some Hams refer to the antenna tuner, tuning the "ANTENNA" down to a flat swr or low swr?

 I often laugh at this BC it is thought that the antenna is actually tuned. The antenna might still stink but the Transciever finals are happy!!
 I also commonly hear, "Oh, it tuned up great", that is another apparent test to how "good" the antenna is.  LOL!!
 Does anyone else sit and listen shaking their head when they hear this type of stuff?......LOL
 It would be nice to hear "Antenna TUNERS" called a Transmatch more often instead of such a misleading name, regarding actual antenna tuning.


--Chuck  
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NA0AA
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Posts: 1043




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« Reply #1 on: October 31, 2007, 07:07:28 PM »

Agreed, but if you use Transmatch most people give you a blank stare.  They get even more wierd when you mention an Antenna Coupler [Those are the things that SGC makes].

Transmatch is a more accurate description to be sure.
AFAIK, only the SteppIR has a true antenna TUNER....
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AA4PB
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Posts: 12641




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« Reply #2 on: November 01, 2007, 05:26:26 AM »

It's all terminology - antenna "tuner", "coupler", "transmatch" or whatever you want to call it. They all do exactly the same thing - they transform whatever impedance (reactance and resistance) is presented at the terminals to 50 ohms resistive. You might say that a tuner located at the transmitter tunes the whole antenna system (antenna plus feed line) to resonance since it cancels out the reactance presented at its terminals.

The important thing is to understand that the device placed at the transmitter does NOT reduce the SWR on the feed line between the device and the antenna nor does it reduce the loss on that feed line. It only affects the SWR between the device and the transmitter. If you place the device at the antenna then it lowers the SWR on the whole feed line. If you place it 2-feet from the transmitter then it lowers the SWR on that 2-foot of feed line.
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SSB
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Posts: 1




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« Reply #3 on: November 01, 2007, 06:15:02 AM »

Antenna tuners DO tune antennas.  Those that say it doesn't don't know how tuners work to change the phase of current with respect to voltage across the antenna terminals.

If antenna tuners don't tune then please explain in detail how antennas radiate with a tuner connected that is removed from the antenna and the antenna that won't radiate without the tuner connected.

Alex...
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K8KAS
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Posts: 569




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« Reply #4 on: November 01, 2007, 06:25:55 AM »

Big Deal!
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KB9CRY
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Posts: 4284


WWW

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« Reply #5 on: November 01, 2007, 06:34:39 AM »

how antennas radiate with a tuner connected that is removed from the antenna

The tuner converts a mismatch between the antenna's real impedance the rig's required/design max impedance of 50 ohms.  Presenting a 50 ohm match for the rig allows the rig to put out full output (less matching losses lost as heat in the tuner itself) into the antenna.  This power inputted into the antenna then radiates per the design of the antenna.



and the antenna that won't radiate without the tuner connected

It's not that is won't radiate, it's just that if you connect your rig, which again is designed to output full power into a perfect 50 ohm load, to a mismatched antenna, the rig will not output full power.  Most modern solid state rigs will actually fold back the power output automatically to prevent damage to the rig.  With a large mismatch most rigs will just shut down and you'll have no power out.

Does this make more sense now?
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SSB
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Posts: 1




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« Reply #6 on: November 01, 2007, 06:47:25 AM »

Read Lorrain and Carsons "Electromagnetic Fields and Waves" and you will see the ridiculous nonsense that permeates technical discussions on eHam.


Alex.....
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WW5AA
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Posts: 2088




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« Reply #7 on: November 01, 2007, 07:53:11 AM »

I agree Alex...A lot of rocket scientists on this thread.

73, de Lindy
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WW5AA
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Posts: 2088




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« Reply #8 on: November 01, 2007, 09:44:04 AM »

It does not matter what you call it or what type it is. It is a common misconception that high standing wave ratio (SWR) in and of itself causes loss. This is not the case. An antenna with a high SWR when properly configured with an ATU could have only a few percent additional losses compared to a perfectly resonant antenna. The ATU essentially redirects the reflected energy back along the feed line and antenna path. The additional losses come from the inherent losses within the feed line and antenna itself. SWR causes feed line losses to be multiplied. Low loss feed line would have minimal loss when tuned with an ATU whereas a "lossy" feed line/antenna combination of the same SWR could have significant loss. OK, so here goes my usual comment:  TX antennas do not care. RX antennas do.

73, de Lindy



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KB9CRY
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« Reply #9 on: November 01, 2007, 10:37:41 AM »

I agree with you guys on your discussion concerning high SWR and loss of power associated with that and the antenna and such......however.......

Do we all agree that if the SWR presented at the rig (especially modern solid state units) is above a designed threshold, that these rigs are designed to fold back and reduce power?  

So one could say that there is a "loss" in power from the antenna (caused by less power out of the rig) that wouldn't occur if the SWR were better (be that by a resonant antenna or a tuner).

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WB2WIK
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« Reply #10 on: November 01, 2007, 03:18:24 PM »

A resonant antenna needn't have a low VSWR.

Consider a full-wave, center-fed dipole.  VSWR when fed with 50 Ohm coax is typically 40:1 or higher.

But it's still perfectly resonant.

WB2WIK/6
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AA4PB
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Posts: 12641




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« Reply #11 on: November 02, 2007, 11:53:52 AM »

Resonance means only one thing: at that frequency there is no inductive or capacitive reactance, only resistance. The voltage and current are in phase. It has nothing to do with VSWR nor minimizing loss, nor efficiency, nor the ability of the antenna to raditate the power applied to it.

We get confused because many antennas are designed such that at their resonant frequency they happen to present a 50 ohm load, minimizing the VSWR on 50 ohm coax. That's due to the antenna design rather than some "magic" about resonance. Antennas can be designed to present almost any impedance you'd like at resonance.
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K7KBN
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Posts: 2754




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« Reply #12 on: November 03, 2007, 07:49:29 AM »

The "tuner" in the shack thinks that everything connected to its output -- the coax, the remote antenna switch, the mismatched antenna and everything else -- is the "antenna".  Not just that yagi with the 4.6:1 SWR.  You will probably be able to find a setting which allows the transmitter to deliver full power to this perceived "antenna", but much of that power will be used to heat electrical connections and components.
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73
Pat K7KBN
CWO4 USNR Ret.
G3RZP
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Posts: 4325




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« Reply #13 on: November 03, 2007, 02:47:37 PM »

If antennas don't radiate unless they're resonant, how come the random length antennas used on ships and aircraft work - likewise slot antennas at HF on aircraft? The natural resonant frequency of the antenna cannot be affected by the the matching network, but the impedance presented to the transmitter can and is, made to be that which the tx wishes to see - usually, but not necessarily, 50 ohms.

My work involves small antennas implanted in the human body. They're ceratinly nowhere near resonant, but we use impedance transformation to get them to offer a suitable load to the final device. Then they look as if they're resonant : I suppose you could say the whole system is resonant, but the antenna certainly isn't. But at the output device, the load V and I are in phase.
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AE5EH
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Posts: 47




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« Reply #14 on: November 05, 2007, 07:21:46 AM »

"Read Lorrain and Carsons "Electromagnetic Fields and Waves" and you will see the ridiculous nonsense that permeates technical discussions on eHam.


Alex....."

Hey Alex,

I hear you guy. I feel that way sometimes myself. Folks including myself don't know what we don't know. I sure don't know it all, and I constantly remind myself of that. But I will say (for what it may be worth) that through the years, in almost all things I do technical, that I have always learned the most, the quickest, and what I learn sticks with me better, by doing and investigating on my own (if that makes any sense at all) and not wasting my time senselessly debating things just for the sake of debating. And, I'm not saying you are.

Please forgive the long blah, blah, post if you can. I generally don't makem' or readem'. I still like these forums but I for me they have yielded very little technical information about ham radio, and more information on peoples nature in general in the way they interact and react from at least behind a computer.

I also realize ham radio would be nothing without the people behind the mics', the keys, and anything else they use within their privileges while they are on the air.
 
Thus said, I still dig ham radio and I need to get back in the books, my test equipment, and my gear and quench my thirst for technical knowledge about the hobby.

Best of 73's

de ae5eh
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