Automatic Antenna Tuner for general SWL

[A.Z.]

and, without quoting the remainder of your post, and aside adding confusion to chaos, what's your suggestion for an antenna setup to be used for both rx and tx ? A tuned loop ?

I said above - use tuner on antenna side. At feeding point. In order to exclude feeder from matching circuit.

Magnetic loop is a bad choice for TX, due to high Q it has high losses and extreme high field strength near it (which is not safe for your health).

totally out of topic

[radiolistener]

totally out of topic

This is a subject of topic. Topic starter asked if a tuner can help for RX.
Yes, it can, but it needs to be placed at antenna side. Not on receiver side.
The internal tuner integrated into transceiver is useless for RX.

[A.Z.]

just to sum it up; start by setting up a proper installed antenna, given your current set up. skip (at least for the moment) balanced feeders, and put up a decent feeder (coax) with unun and choke, that will cost you less than that "automatic ATU" and, since at the end of the day, it's the antenna the thing which works, the result will be better than the one obtained by wasting money buying an ATU connected to s piece of wire

then. money is yours, so you are free to waste it as you like better, in such a case you may invest into an ATU and use a light bulb as your antenna.

[radiolistener]

that will cost you less than that "automatic ATU"

It depends on the use case. For example, if you're using a lot of different bands, it may be worth to use remote controlled ATU at antenna side instead of a bunch of dedicated matching circuits for each band with remote control unit to switch between them.

[A.Z.]

dedicated ... what ?

[radiolistener]

dedicated ... what ?

matching circuit for each required frequency band (with fixed tune).

[richard.cs]

And unless you tune the loop antenna itself no antenna tunner will correct it after the fact.

You can match it with tuner on receiver side, but high losses in the feeder will make it useless.

Shortened magnetic loop antenna needs Q factor about 1000-2000.
10 meters RG316 has insertion loss about 1 dB on 14 MHz.

As you can see it will be just impossible to get even Q=10 with so high loss per cycle in the cable.


This is why the tuner should be placed on antenna side.

I mean yes, with an electrically-small, magnetic loop but that is a very extreme case. With many other (nearly all other) antenna types the ratio of reactance to radiation resistance is far less and you end up with a matching circuit with a Q of perhaps 3 to 10. In that case matching at the "wrong" end of the feeder becomes much more acceptable. Yes, the losses are higher than matching at the antenna, and yes you may need a better feed cable to partially-mitigate that, but you have to balance this against the advantages of an indoor matching arrangement. i.e. accessible for manual tuning, not needing to be weatherproofed, etc.

Combine with the fact that for listening in the HF bands specifically you can throw away many dB of signal and not care. See https://upload.wikimedia.org/wikipedia/commons/9/93/Atmosphericnoise.PNG - at 14 MHz you can waste 20 dB in a bad feeder and/or with a mismatched antenna and not significantly affect your signal to noise ratio provided your receiver front end noise is modest. Agreed you can't get away with something like a magnetic loop without tuning, but a random wire of significant length doesn't need tuning for receive. A fixed 9:1 in impedance as others have suggested will get close enough, and if you loose 10 dB of received signal it doesn't matter because you've also lost 10 dB of received noise and you're still safely clear of your receiver noise floor.

Transmit is another issue entirely. You care about losses more because generating much more RF than you need is a pain, but it's still not absolute. You can still choose to trade a few dB of losses (generate a few dB more RF) for some other engineering gain such as easier maintenance by putting the matching the wrong end.

[borjam]

And unless you tune the loop antenna itself no antenna tunner will correct it after the fact.

You can match it with tuner on receiver side, but high losses in the feeder will make it useless.

and, without quoting the remainder of your post, and aside adding confusion to chaos, what's your suggestion for an antenna setup to be used for both rx and tx ? A tuned loop ?

I have a MFJ 1788 loop and it is excellent. Loops are not as inefficient as models predict and it is quite simple to prove it. Where does the energy go? I have been transmitting with mine and a thermal camera doesn't show any heating at all.

For SWL they are cumbersome because you would need to be retuning whenever you change the frequency. But there is a plus to it as it helps reject off frequency interference which might cause problems for receivers with a poor front-end.

And there are also receive only broadband loops like the Wellbrooks. The received signal level is lower than, say, a dipole, but the signal to noise ratio is significantly better.

[borjam]

And unless you tune the loop antenna itself no antenna tunner will correct it after the fact.

You can match it with tuner on receiver side, but high losses in the feeder will make it useless.

[/quote]
Which was my point.

It is important to understand the difference between adapting the impedance of an antenna to a feeder and actually tuning an antenna. The term "antenna tuner" is not especially accurate.

Imagine you have a Yagi for, say, 7 MHz. You can make it work for 10 MHz by changing the length of its elements (and their spacing) which would mean you are tuning the antenna. Or you can match it to your coax using a "tuner". Will the result be equivalent? Not at all. Energy will be wasted as heat unless you really tune the antenna itself.

[borjam]

totally out of topic

This is a subject of topic. Topic starter asked if a tuner can help for RX.
Yes, it can, but it needs to be placed at antenna side. Not on receiver side.
The internal tuner integrated into transceiver is useless for RX.

Any impedance mismatch will induce losses. So, obviously, a proper match between antenna and feeder will improve reception.

However, bear in mind that the reason why SWR is kept low for transmission is, in the first place, to protect the transmitter circuit from reflected energy. A SWR of 3:1 means a power loss of about 25% which, in dB, is almost negligible. But the transmitter may have a really hard time to cope with that and the protection circuits will reduce power further. Or some final stages can just break.

So, imagine you have a a SWL antenna with a SWR of, say, 6.0:1. The loss is 50%, which means 3 dB. Is 3 dB such a dramatic loss? Given the HF band noise it's not a deal breaker.

[A.Z.]

I have an ICOM IC-7300 which I am currently using for listening to the amateur bands but also general HF listening

Trying to sum it up, skip the idea of the external ATU and use the 7300 built-in one

Set up the antenna as shown in this image (no artwork !)



keep the ropes between the antenna and the two supports long enough to allow for a spacing of 50cm to 1m (or more), the antenna wire doesn't need to be horizontal, it may be sloping; use a pulley at the far end support and connect that end of the support rope to a weight (it may even be a brick) so that, if the antenna is loaded by wind or ice, the rope will be free to slide and the antenna wire won't break, that's a very old trick, but it still works; optionally you may add a second pulley to the other side of the antenna, that would allow you to lower the whole antenna for manteinance if/when needed, lay the counterpoise down as shown, the counterpoise wire may also be laid down on ground if needed, for the ropes pick some good UV and weather resistant one, the so called "paracord" may fit

At the "near" end of the antenna connect a 9:1 UnUn, following it, connect an 1:1 choke, either directly after the UnUn or just before the coax enters the building, the coax will then go to an ATU or, if your rig has an embedded ATU, directly to the rig, use decent quality coax (I suggest using RG8 at least) and good connectors, stay far away from "chinese" UnUns, Chokes and coax cable, they usually suck !

As for the length of the main antenna wire (the horizontal one in the pic), select it from here

https://udel.edu/~mm/ham/randomWire/

picking the longer length which will fit your available space (70ft is the minumum to cover 80-10, 135ft is the minimum for 160-10), try keeping the antenna in a straight line, if possible; if not you may run the wire at some angle (at/above 100°) either/both horizontally and/or vertically.

[edit]

whatever you'll decide, please, PLEASE, do NOT use that piece of wire you are calling "longwire" to transmit... and then say bad words at that poor IC7300

[radiolistener]

Set up the antenna as shown in this image (no artwork !)

Your setup is okay, but I would suggest to avoid unbalanced antenna and use classic dipole with center feed point. It helps to reduce interference from home equipment. RF choke can reduce it for unbalanced antenna, but don't eliminate.

[A.Z.]

forgot, "cemelek", if you're still here, after the chaos and noise someone tried to generate, please keep us up to date about your antenna setup for TX and RX

[cdev]

There is no such thing. Knobs work fine for receive preselectors or antenna matching. Since it doiesn't transmit.

You can use an unun and an untuned wire of a number of different random, nonreasonant lengths to get the SWR low enough so you dont need a tuner. (this works with a 9:1 unun and a 43 foot wire. (posted before reading the whole post, I am basically suggesting what AZ suggested here. If you avoid the resonant lengths you avoid the impedance extremes its hard to tune out with a transmatch..

You can tune the SWR significantly lower with a Z-match, of S-match (which both are fairly easy to make. Z-match can tune most unbalanced loads. S-match is particularly good for balanced antennae.. even loops.. (it is itself a sort of loop electrically, which is why I like it) Radiolistener would I suspect likely like it with his dipole.. )

I have an ICOM IC-7300 which I am currently using for listening to the amateur bands but also general HF listening

In about 2 weeks I expect to gain my amateur radio foundation license and have been looking to get an automatic antenna tuner for my long wire antenna, for example the mAT-180H or similar.

How does this cope (or not cope) with non amateur frequencies, as you can't use the tune function?
 
The mAT-180H  has manual L/C up & down buttons, but that seems a bit slow and tedious. I realise that the memory functions wont work either without RF going into the box.

Is there an ATU which is more suitable, or should I consider bypassing the ATU when in listening only mode and revert to my receive only ATU, which is very quick and easy to use but has no power handling capability.

Thanks

  I dont understend, do you mean for receive? You would do fne with a Unun, which decouples your antenna and improves reception across the bands.. Get one of the new NanoVNAs and build your own collection of tuners. Thats a lot of fun. Another fun tuner thats good for receive because its got a sharp peak, it has a high Q is an S-match which is especially good for balanced antennas. It -like the Z-match also has a modest parts count.  If you are working QRP it can be built for almost nothing.   You can get toroids from mini-kits.

[A.Z.]

You can use an unun and an untuned wire of a number of different random, nonreasonant lengths to get the SWR low enough so you dont need a tuner. (this works with a 9:1 unun and a 43 foot wire. (posted before reading the whole post, I am basically suggesting what AZ suggested here. If you avoid the resonant lengths you avoid the impedance extremes its hard to tune out with a transmatch..

That was exactly my point, the OP (cemelec) wrote he owns an IC7300 and will have his license in some time, he also stated he has a "piece of wire" he has been using for RX only (with his 7300, I suppose) and asked how to use that "piece of wire" as an antenna, now, given that he seems to want go for an endfed, I suggested him to put up a random wire antenna but do so "the right way" since plugging that piece of wire to the center of the coax connector and trying to transmit with the 7300 won't be exactly a good idea 

You can tune the SWR significantly lower with a Z-match, of S-match (which both are fairly easy to make. Z-match can tune most unbalanced loads. S-match is particularly good for balanced antennae.. even loops.. (it is itself a sort of loop electrically, which is why I like it)

an endfed isn't exactly a balanced antenna and the IC7300 has an embedded matching unit, so if the endfed is properly setup (as I described in a previous post), the tuner of the 7300 should be able to deal with it; that said, for an endfed I'd probably go for an "L" match (not willing to start a debate about antenna matching units, mind me !), that one in my experience (if properly built) can match quite a good range of impedances and has lower losses than other matching networks, a coarse example of such a circuit can be seen in the attached image

[cemelec]

Again thanks everyone, and to A.Z. for his input

I came across this:
INRAD RX7300 RX
https://www.nevadaradio.co.uk/product/inrad-rx7300/


Basically on the IC-7300 it switches between a receive antenna and a transmit antenna.
As I'm interested in non amateur bands as well, I could use the cheap (no power handling) manual antenna matching unit I already have on a separate less demanding antenna than my future Tx antenna.
Just a thought

[A.Z.]

Basically on the IC-7300 it switches between a receive antenna and a transmit antenna.
As I'm interested in non amateur bands as well, I could use the cheap (no power handling) manual antenna matching unit I already have on a separate less demanding antenna than my future Tx antenna.
Just a thought

The mod is nice, sure, but I believe that before thinking to two separate antennas you'd better improve your current antenna since that will improve its receiving performance too, then you may consider the modification and, in turn, consider which rx only antenna will fit/match your requirements. But again, start by setting up your "main" antenna correctly.

[edit]

To be even more clear, your current setup with the wire going all the way inside the house and to the receiver isn't good neither for receiving nor for transmitting, you're bringing part of the antenna inside, this means that in reception it will pick up all the noise from the house appliances (switching PSUs, plasma TVs and then more), while in transmission it will also radiate INSIDE which will cause a number of problems.

So, start by installing your antenna properly (and I already described that), then once you'll have that fixed you may consider ways to improve the setup, but doing that now and pretending that buying some "magic" piece of stuff will turn your piece of wire into a good antenna will just result in a waste of time and money

[cdev]

Basically on the IC-7300 it switches between a receive antenna and a transmit antenna.
As I'm interested in non amateur bands as well, I could use the cheap (no power handling) manual antenna matching unit I already have on a separate less demanding antenna than my future Tx antenna.
Just a thought

The mod is nice, sure, but I believe that before thinking to two separate antennas you'd better improve your current antenna since that will improve its receiving performance too, then you may consider the modification and, in turn, consider which rx only antenna will fit/match your requirements. But again, start by setting up your "main" antenna correctly.

[edit]

A computer and monitor ad associated cables emits a surprising amount of broadband noise on virtually the entire RF spectrum. This is easy to demonstrate. For this reason, its virtually a requirement that the first part of the transmission line consist of a coaxial cable enclosed feedline leading to a broadband balun with a ground or at least counterpoise of soe kind. Without this you are guaranteed to pick up that noise. It would not hurt the be generous with ferrite noise suppression materials on the transceiver side of the transition so as to decouple the receiver and the house and its power system from the antenna and especially its ground. Otherwise the power system becomes the RF ground and its a very very very noisy one here at my QTH. Even though I have the (required by code) two hefty ground stakes(copper plated metal, and copper clamp)  and 6 awg (at least)  thick grounding wires. If I take my portable HF radio (Sangean) anywhere near this grounding setup a wave of RF hash just overpowers the receiver. It says loud and clear "This is not the RF ground you are looking for" Couldnt be clearer..

OTOH a unun works much better when it has a real ground, preferably a grounding stake physically isolated from the house by earth, preferably moist soil.. (more conductive)  . Again it makes a dramatic difference in noise.. Dry earth much less so.
AZ is right..

"your current setup with the wire going all the way inside the house and to the receiver isn't likely good either for receiving nor for transmitting, you're bringing part of the antenna inside, this means that in reception it will pick up all the noise from the house appliances (switching PSUs, plasma TVs and then more), while in transmission it will also radiate INSIDE which will cause a number of problems."

I'm going to try to illustrate this with some hopefully helpful photos that makes what I suspect you might be able to use and build cheap, now, clearer..

The second photo is of an elecraft commercial it thats easyto replicate and very useful to have.. the schematic is identical to the image * TwoInOne-balun-toroid-version.jpg The switch is super useful and the balun works all the way up through six meters just like the IC7300.

These switchable balus are super useful indoors and generally when you have several choices (switchable) the one with the loudest signl is likely to also be giving you the lowest SWR. Then the rigs tuner will get you the rest of the way, we hope. I would use low power, whenever there was any doubt. RF power transistors are expensive, often.

Its amazing the useful things you can make out of what my wife sometimes calls "junk"

To make a 9:1 un-un (to match a single long wire antenna close enough in SWR to 50 ohms to be tuned by an in-rig tuner.. you just need some (two) big old cheap ferrite material beads, two.. and a few feet of twisted wire, enough to run a triple stand of wire through the two beads maybe a dozen times. Treat it like a binocular core. This will give you the electrical equivalent of a 9:1 balun wrapped on a toroid binocular core.. very easy to build if you like me possess LOTS of split beads. Select two identical ones to make your "binocular core" mimic a commercial binocular core..Emulate the winding of the classic 9:1 unun. Again make sure you ground the part you are supposed to ground. You could use two more split beads top help isolate your feedline. At its ends. But that is not necessary IF it is grounded properly. It just may make a bit of a reduction in that noise picked up on the last bit of the feed line.

These are some "interesting" (to me) HF impedance transformations, that I thought might have wide appeal. One of these (airbaluns.gif) can be constructed without any magnetic cores at all (but it probably works better made with two of the "Ukrainian" ferrite rods from ebay or other magnetics. (You can make almost anything out of those split bead cores in a pinch).

This was made by Pa0fri , its from his site on the S-match. (balanced antenna tuner) It has a sharp peak so its useful for HF receive more so than baluns, generally. It will match your antenna and also preselect.  Very helpful for use with RTLSDR/upconverter combinations. (high vulnerability to out of band interference, so preselection is more important than with a more selective receiver. )

[A.Z.]

Cdev ... my name is Andrew, in case you wonder, then I totally agree, FIRST set up the WHOLE antenna system and THEN reason about ways to improve it