Ham Radio - Do antenna tuners help with shortwave listening?

As a tuning device--matching to conjugate impedance- a tuner does nothing to the signal to noise ratio from the antenna.

If you use it--rather poorly I might add-- to reject PIM from out of band strong signals, then I recommend you get a better receiver to start with.

The reasons are neither 'complex' nor 'multifacted' We understand heterodyning and nonlinear overload very well. These are separate conditions and issues from conjugate matching.

There is no meat left on this bone.

73
Chip W1YW

 

i use my atu as a noise attenuator. does nothing to improve signal strength

 

Hi Chip.

I agree, if using your antenna “tuner” to help with problems that arise from strong out of band signals works (to some extent - as it can, depending as you mentioned on the tuner’s design) one would do well to get a better receiver.

But having a crappy front end is one of those factors (separate from SWR or the use of the tuner as an impedance matching device) to which I am alluding.

That a tuner works at all to improve signal discernment (which it sometimes does) is the interesting phenomenon.

Yes, it is misguided to suggest this has much if anything to do with SWR in most cases (as has also been mentioned, it can have something to do with SWR if the mismatch is extreme), but the phenomenon remains wonderfully complex, and the conversation interesting.

(I know, in addition to getting a decent receiver the SWL would be well-served to put up a decent antenna … )

Seems there is yet some meat left on these bones and I’m enjoying the conversation.

And honestly, very much enjoying your contributions.



Vy 73,

Steve, W0AZ

 

Thanks Jim and Kevin. Great visual and explanation of impedance matching with different frequencies and one "set" antenna length. May the Good Lord Bless You both and Your Families this Christmas and throughout 2022. Lawrence (VA7LTX) and Jeanette (VA7JTX) in Richmond BC Canada.

 

I think Chip, we listen to you because of your undoubted intelligence. Regarding antennae your knowledge I would suggest is unsurpassed. I, and I am sure many others are extremely grateful you take time out to respond to these questions that arise and explain the answers for us. Thank you.
I’ll take this opportunity to wish you and your Family a very happy holiday season and send my best wishes for the New Year, 73 Pad.

 

Best to all for a safe new year in these very troubling times!

 

I too wish everyone the best for the Holidays and a safe New Year!

Chip, I am not speaking to the "theory" of why a tuner should have no effect on a received signal. I am simply relating what I see. Maybe a better receiver would also make a difference. My observation was using an Anan 7000DLE MkII "receiver" and a Palstar AT2K tuner. The tuner made the difference between usable and unusable on 160 and better and best on 80 meters.

No offense was taken! When "theory" is contrasted by actual results, it always makes for an interesting discussion!

73 -- Larry W8ER

 

Of course tuning the antenna helps with SWL.

Why else would the majority of the analog / tube-type receivers have an antenna tuner and an S-meter? To get the highest signal strength and then use the other circuits for noise reduction, rf gain, etc.

 

Larry,

You are correct--and no one said otherwise: You can use a tuner for rejection, but if you use the tuner to reject a BC signal, the LC setting of the tuner will not be anywhere near a conjugate match at your 160M frequency.

This video is about conjugate matching with a tuner to get a better signal to noise from the antenna.

I am not familair with the Anan (I presume it is an SDR): do you have the ability to control the (effective) IF filters on RX? If so, they should be capable of significant out of band rejection. They will function much better than using a tuner for rejection.

Have a great XMAS and HNY!

73
Chip W1YW

 

Would An antenna, like A loop have less noise and better RF signal response ???
Unlike my Traped Vertical Antenna...

 

Loops (mag loops) are very high Q. That means that the tuner on the loop adds or subtracts reactance to take the loop into resonance at the TX/RX port. (it also 'steps up' the resistance').At that frequency the loop works well, and acts very much like a passband filter, rejecting out of passband noise/signals, if indeed, they are overloading and or adding heterodyning products.(As W8ER, Larry, notes, that is common on 160m because, in part, the nearness of AM BCB.)

In general, electrically small antennas are narrow band when tuned to resonance with a tuner, so they are great at rejecting signals out of passband. Flag antennas on 160M are an example. But the signal at the conjugate is not stronger than the noise -- because of the match. There may be less heterodyning and overloading, because of the hi Q rejection. To wit: when you tune to conjugate, the SWR at the rejecting signal frequency goes UP, so its intensity goes DOWN. You can reverse the issue and find the tuner setting that gives the highest SWR for the rejecting signal frequency--that maximizes the rejection.

Although we never think this way in ham radio, antennas are resonators: RLC circuits (or have an equivalent). So notions of filtering apply. A good rule of thumb is that the smaller the antenna is in wavelengths, the narower its passband when made to resonate (there are exceptions...)Look at an antenna as a radiating RLC circuit....

I am sure others can contribute more, even better, info than me on these points. Again: rejection is a different dealie than matching...

73
Chip W1YW

 

Back in the early 1980's I had a Kenwood R-1000. The antenna was a 140 foot end fed wire. I had allot of overload intermod because the front end of the receiver had low dynamic range. I tried an MFJ-949 antenna tuner just for the heck of it and it did nothing for the intermod.

I then bought a Grove TUN 5 preselector and it knocked out all of overload intermod. It also seemed to peak the signal some. I still use it on an old Kenwood R-2000 (another receiver with a poor front end) and a coincidently a 140 foot end fed wire.

If you have a small modern receiver like a Sangean ATS-818, ATS-909X2, Tecsun PL-880, etc. and want to use big antennas you need a preselector. Unfortunately there are no modern portables that can be hooked directly to a big antenna.

 

Not a direct answer to the tuner question, but a suggestion on where to learn more about sources of received noise and solving part of the received noise issue. Some received noise is local common mode noise and often can be eliminated with transmission line chokes, reducing the total noise delivered to your receiver. Jim Brown provides information on building your own choke(s) relatively economically.

Check out K9YC, Jim Brown's web site for tips on how to improve received signals at: http://audiosystemsgroup.com/publish.htm

More Specifically: Build Contesting Scores by Killing Receive Noise Jim Brown K9YC at: http://audiosystemsgroup.com/KillingReceiveNoise.pdf This is an application note I (Jim, K9YC) wrote for National Contest Journal (an ARRL publication)
and Jim's presentation slides: http://audiosystemsgroup.com/KillingRXNoiseVisalia.pdf for my (Jim, K9YC) talk at the 2017 Visalia DX Convention. NEW! May 2017

Antennas designed for low noise receive applications can also help and should be considered depending on your needs and situation (loops, shielded loops, beverage, and others are potential candidates). A good reference is the ARRL Antenna Book (available from the ARRL and in many public libraries and often librarians are looking for suggestions regarding acquisitions if you don't find it in the collection).

Bill AF6AE

 

As an ex SWL for many years before being licenced in 1981 ,i always used a tuner with my SW reciever . It had no fancy gain controls or anything. I just tuned to get the highest signal on the meter. Still do this today before i tune to TX as it is then more or less there. And i do prefer a manual tuner than these hit or miss auto ATU's .I do own an auto ATU that i take portable mainly as it weighs nothing in the backpack

 

If I'm not mistaken, Zack, @W1VT, uses a flag antenna for his 160 meter exploits and he's just a stone throw distance from WRYM 840. WPOP 1410 isn't too much farther away from him, too. His 160M stats are impressive.