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 Atu do they really work

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Andybron
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Call Sign : 26-CT-989
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Join date : 2020-01-13
QTH or Location : Clacton on sea essex
Equipment Used : CRT ss9900 with solarcon aerial
Age : 52

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PostSubject: Atu do they really work    Atu do they really work  Icon_minitimeWed Jan 15, 2020 3:12 am

Hi all,probably a daft question but I ain’t one to be shy 🤣🤣if you have say a yaesu ft450 with a built in atu if I was mobile with a solocon on a small 6ft pole would this atu work on 11 metres ssb?? So basically if you have a bad Swr does it automatically bring it down to a stable say 1.3????
Cheers guys 👍👍
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GaryWilson
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Call Sign : 26-CT-1836 Ham 2E0GGQ
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QTH or Location : London
Equipment Used : Radios & Wires & Stuff!
Age : 55

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PostSubject: Re: Atu do they really work    Atu do they really work  Icon_minitimeWed Jan 15, 2020 6:36 am

Hi Andy.

Yes the tuner on the 450d works very well. It will tune a mismatch of 3 and under.

You should be aware that these radios won't do 11 meters as standard a mod is required to do that, also on a single band 11 meters you shouldn't need a tuner the antenna will work better if it's properly tuned.

Really all a ATU is doing is presenting a 50 Ohm load to the radio to make sure that the radio isn't harmed.

73's Gary.
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Andybron
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PostSubject: Re: Atu do they really work    Atu do they really work  Icon_minitimeWed Jan 15, 2020 6:42 am

GaryWilson wrote:
Hi Andy.

Yes the tuner on the 450d works very well. It will tune a mismatch of 3 and under.

You should be aware that these radios won't do 11 meters as standard a mod is required to do that, also on a single band 11 meters you shouldn't need a tuner the antenna will work better if it's properly tuned.

Really all a ATU is doing is presenting a 50 Ohm load to the radio to make sure that the radio isn't harmed.

73's Gary.  
Ok Gary thankyou loads for that feedback is much appreciated👍Going to stick with the solorcon I think as used to have one and was so easy to tune Smile
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Northern Crusader
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PostSubject: Re: Atu do they really work    Atu do they really work  Icon_minitimeWed Jan 15, 2020 11:53 am

You shouldn't need to touch the tuning rings at all for either the Antron A99 or Imax 2000 out of the box. Don't worry if the SWR isn't 1:1, as long as it's below around 1.5-1.6:1 it'll be fine. Even 2:1 isn't the end of the world as long as you're not using an amp.
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43CT016
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PostSubject: Re: Atu do they really work    Atu do they really work  Icon_minitimeSat Jan 18, 2020 5:02 am

"Tuner" is a name that is somewhat misleading....what these devices do is match the impedance from the radio to the feedline and antenna, allowing you to transmit full power and still keep the radio happy. They don't tune the antenna to a different resonant frequency if it's off, but they provide what is known as a conjugate match, which takes into account the components of complex impedance and not just the often talked about 50 ohm. This is still over simplifying things, BTW.

However, a perfect impedance match does not mean the antenna is effectively radiating, which is what you really want, and even a low SWR does not guarantee that.  Always remember, a dummy load will give you a 1:1 SWR, but it's not known to be an effective radiator.  Wink

So ultimately, it is better to have an antenna tuned to, and hence resonant on, your frequency...and for single band radios like CB with not a huge separation between top and bottom frequency, you shouldn't really need one unless the antenna is of such narrow bandwidth it can't cope with top and bottom frequency at a suitable SWR.


Last edited by 43CT016 on Thu Jun 11, 2020 1:28 am; edited 1 time in total
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The DB
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PostSubject: Re: Atu do they really work    Atu do they really work  Icon_minitimeSat Jan 18, 2020 8:26 am

There is a freely available .pdf out there called "Another look at Reflections". If you want to know what is really going on I recommend that as a starting point...


The DB
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Victor
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PostSubject: Re: Atu do they really work    Atu do they really work  Icon_minitimeSat Jan 18, 2020 9:50 am

Ouch!
No offence to "The DB" but that document should come with a government health warning Very Happy

I personally wouldn't recommend it as a "starting point".

If you want to know infinite details, with maths and charts, it's quite a good read and echoed in other documents on the same subject. If maths, charts and detailed explanations isn't your thing you'll be lucky if you skim read it Wink

For simple monoband operation, much like CB transmission, the old rig/coax/tuned antenna/SWR method works perfectly well. As attested by many decades of CB operation, local and DX.

Many radio amateurs use the same method but with a veritable antenna farm, one for each band Wink

The in depth stuff starts becoming interesting if you want one antenna to cover the whole lot of HF frequencies. Then you can knock yourself out with ladder line, long bits of wire and matchers Smile


Andy's original question was well answered by Gary Wilson.



_________________
Theory means that we know everything, but nothing works.
Practice means that everything works, but we don't know why.
Often, however, theory is closely related to practice.
It means nothing works and nobody knows why ...
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The DB
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PostSubject: Re: Atu do they really work    Atu do they really work  Icon_minitimeSat Jan 18, 2020 10:42 am

How strange, it was a starting point for me...  Heavy math? Have you read said document? The first equation isn't until page 16 and in a 68 page document there is a total of 15 equations... Seriously, as far as documents written by engineers the math presented as as easy as you can get and still explain what is being talked about. Its not anywhere near calculus level or anything. Only algebra, and some (very limited) trigonometry. And you don't need to know the math to understand what is written in the document. Several sections don't include any math at all.

I agree that with single band operation, an antenna designed to work for said band is the best way to go.  There is actually a technical name for keeping everything at the same impedance. In spite of a vast majority of people using such a setup and even thinking its the only way you can go, no one seems to know this name...

That being said, when it comes to an "antenna tuner", to say they only hide a high impedance to protect a radio as Gary and others said above is not actually accurate.  There is far more going on with said devices, that was my only point and said document talks about it in in much more depth so I recommended it for those that actually want to know more...


The DB
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Victor
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Call Sign : 26-CT-3228 Ham M7VIC
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PostSubject: Re: Atu do they really work    Atu do they really work  Icon_minitimeSat Jan 18, 2020 11:11 am

No one is knocking your mathematic abilities, so I apologise if this is how you read this, but I definitely wouldn't recommend said document as a starting point for many.
For some, the first equation or even a simple fraction is enough to switch them off, in which case it's useless to them.

I didn't mention 'heavy math', and yes, I have read the document and many others like it a long time ago.
As I said, interesting stuff Smile

For some, your recommendation will be useful and for others not so. It's just a case of addressing a wide range of abilities that people have so that they can find solutions.


All the best,
Victor


_________________
Theory means that we know everything, but nothing works.
Practice means that everything works, but we don't know why.
Often, however, theory is closely related to practice.
It means nothing works and nobody knows why ...
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