Ham Radio - Do antenna tuners help with shortwave listening?

As an SWL (receiving only) If you only tuned to get the highest signal on the meter how do you know you wouldn't have gotten the same meter reading without the tuner in line?

So why have the tuner at all?

If anything I've always read that tuners for SWL should be a little detuned, if anything, so as to improve signal to noise ratio. But certainly not to peak that in rush of background noise.

 

Some can, depending on your definition of portable. I use a ‘big antenna’ with my Eton Field radio and (with the appropriate adapter) my Eton Elite Executive with great results. They both have external antenna inputs (F connector on the Field and 1/8” on the Executive).

 

5 pages of comments to answer a single question.
Radio on, yup, hit tune button on SW band. Yup, it’s better. Test complete.

 

I have a better suggestion: since you equate VOLUME with BETTER, then just turn up the audio VOLUME control.

Yup.

Louder audio on the speakers means better signal copy....

Nope.

Th answer to the question is'no', and it is embarrassing for the amateur radio service when we don't acknowledge reality. There has certainly been plenty of facts presented here in the '5 pages'.

Conjugate matching with a tuner does not improve the antenna signal to noise ratio.

Period.

73
Chip W1YW

 

But he DIDN'T equate volume with better.

 

A tuned antenna resonates on the frequency of interest, and depending on the antenna system Q; does not resonate on frequencies outside of the "pass-band".
A random length or non-resonant wire receives much better if an antenna tuner is employed.
If the antenna is already close to resonance, and the sinal is already reasonably strong; the AGC circuit is already reducing receiver input, and no difference will be noticed.

 

That is incorrect.

A tuned antenna resonates at a variety of frequencies. For example, a dipole resonates like a picket fence as you go up in frequency.

ALL antennas used by hams are non-resonant off the frequency of resonance. So if my antenna resonates at 14200 KHz It is non-resonant at 14080 KHz, for example. ALL antenna are non resonant. SOME resonate at a specific frequency within a desired band.

Tuners exist for transmitters, because modern TX's cannot tolerate high SWR at the final PA transistors, and pull back power accordingly--so they don't blow.

A tuner is incapable of improving the signal to noise ratio of the antenna at the frequency of interest. Its job is to match, through conjugation, the characteristic impedence required at the RX port (in this OP case). If one chooses to use a tuner to get worse mismatch (higher SWR) at selected out-of-passband signal frequencies, then there is a modest amount of attenuation to heterodyning and or overload. Please see the prior posts: this has already been discussed. But that has nothing to do with matching at the frequency of interest--which is the purpose of a tuner.

Resonance has nothing to do with signal to noise from the antenna. It is defined as the frequenc(ies) where the reactance is zero.

73
Chip W1YW

 

It appears that the "signal in space" concept is largely overlooked by radio amateurs.

Using this point-of-view, the signal/noise ratio is determined by the signal field strength divided with the noise field strength, which in turn determines the RF signal/noise ratio.

No "tuning arrangements" can change this, as long as the ambient noise picked up by the antenna exceeds the thermal noise generated in the receiver with some margin. On the HF bands, this is almost always the case.

"Tuners" may help in two circumstances;

1. The antenna is so electrically small that the receiver input impedance will short-circuit its output voltage
   
   
2. The receiver system is operated in an "high-RF environment" where strong emissions on adjacent frequencies may overload the receiver. Here, the added selectivity from a "tuner" can improve the performance

73/
Karl-Arne
SM0AOM

 

All previously stated.

The point you are missing is that the video asserts that conjugate matching improves the SINR of the antenna--which thus perpetuates incorrect and misleading info, as we have seen here.

73
Chip W1YW

 

The assertion in the video that the impedance matching provided by an antenna tuner improves the signal to noise ratio is, except in very rare extreme cases (as previously discussed), incorrect.

But the conversation had, early on, broadened considerably to include the observation that the use of a tuner sometimes does improve signal discernment and to ask why this is sometimes the case and discuss possible reasons.

In my reading of this thread few continue to support the video’s primary assertion, but the broadened discussion remains both unresolved and interesting.

I’d like to hear more about it.

 

Partly true. A given length of conductor will resonate at many different frequencies. There is one fundamental resonant frequency and many overtone frequencies. If you watch your waterfall display as you use a manual tuner, you will often see a band of frequencies (quite wide) being favored as you change the capacitor settings. True, the less favored freqencies will not practically improve your S/N ratio in your received audio, since there is so much noise out there that is on your resonant and harmonic frequencies.
Resonance is real folks, but as Chip said, often we use tuners as transformers to match transmitter impedence to the impedence of our antenna/feedline system to satisify the transmitter design characteristics. My experience is that I have had much better results when operating a wire that is near a resonant length, and somehow fed at a point where the resonant wire impedence point matches or transforms to the feedline impedence.
http://laarrl.org/pdfs/upthecoax4.pdf

 

Looks like yer antenna works ACROSSED (or is it "acrosst") a wide range of frequencies.

 

Signal strength and SWR are unlikely to play a part in this discussion, but there are circumstances where an antenna tuner will help with receive,
and this is related to the dynamic range of the receiver and the front end of that receiver / bandpass filters and the environment where the radio is being used.

Receivers with poor bandpass filters and marginal dynamic range may benefit from using a tuner.
[You can also use a pre-selector for the receiver to obtain similar results].

If you have an older receiver, or live in an area where you are near out-of-band strong signals [AM or SW broadcast stations, for example] a tuner / pre-selector may provide significant improvement.

Finally as active hams know, operating multi-station multi-op [think Field Day] almost always requires a bandpass filter of some type to get optimal performance from a receiver.

 

A good test would simply be to set up a non-resonant dipole for say 20m. Place a tuner in line, tune the antenna for best match and then have a fellow ham tx on WSPR repeatedly with the tuner in bypass and with the tuner active.
Compare SNR measurement as recorded by whichever WSPR software you use, tabulate and compare.
Obviously, there are some variables which we cannot control, however, this would be a good enough test to evaluate SNR difference as it is a quantifiable output by the software.