Author Topic: Automatic Antenna Tuner for general SWL  (Read 2615 times)

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Offline cemelec

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Automatic Antenna Tuner for general SWL
« on: October 16, 2021, 06:54:12 am »
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
 

Offline radiolistener

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Re: Automatic Antenna Tuner for general SWL
« Reply #1 on: October 16, 2021, 07:00:50 am »
ATU is good, but you're needs to place it between antenna and feeder in order to get maximum effect.
 

Online A.Z.

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Re: Automatic Antenna Tuner for general SWL
« Reply #2 on: October 16, 2021, 07:12:19 am »
The mAT 180H is an automatic tuner, the buttons only serve to finely adjust tuning if needed, not to tune it

https://www.vibroplex.com/contents/en-us/d9173.html

that said, antenna matching in RX isn't really that important, so you may bypass the tuner if using the antenna for RX only

The point is, how are you going to connect the antenna to your rig ? For a base (not portable) installation I'd advise against bringing the antenna wire all the way to the shack, my suggestion is to hang your longwire as far and high as possible, feed it with an UnUn connected to a good counterpoise and followed by a good choke, then a run of coax all the way to the shack

EDIT:

for further details. see

https://www.eevblog.com/forum/rf-microwave/putting-up-a-random-wire-antenna/

« Last Edit: October 16, 2021, 07:24:57 am by A.Z. »
 

Offline radiolistener

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Re: Automatic Antenna Tuner for general SWL
« Reply #3 on: October 16, 2021, 07:41:04 am »
that said, antenna matching in RX isn't really that important, so you may bypass the tuner if using the antenna for RX only

it is important for a weak stations, but you're needs to use tuner at antenna side. Because RX input is already matched with the feeder, they both have about 50 Ω impedance. But antenna has different impedance, so this is where tuner is needed to pull a weak signal out of noise.

In addition, tuner plays a role of pre-selector, which also helps to receive signal in a noisy environment.
« Last Edit: October 16, 2021, 07:51:45 am by radiolistener »
 

Online A.Z.

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Re: Automatic Antenna Tuner for general SWL
« Reply #4 on: October 16, 2021, 07:56:58 am »
that said, antenna matching in RX isn't really that important, so you may bypass the tuner if using the antenna for RX only

it is important for a weak stations, but you're needs to use tuner at antenna side. Because RX input is already matched with the feeder, they both have about 50 Ω impedance. But antenna has different impedance, so this is where tuner is needed to pull a weak signal out of noise.

In addition, tuner plays a role of pre-selector, which also helps to receive signal in a noisy environment.

Agreed on the preselector, other than that...

https://kv5r.com/ham-radio/coax-loss-calculator/

:D
 

Online A.Z.

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Re: Automatic Antenna Tuner for general SWL
« Reply #5 on: October 16, 2021, 08:34:59 am »
Wait a second, the 7300 has an embedded antenna tuner

https://www.icomeurope.com/en/product/ic-7300/

why do you want a separate one ?
 

Offline cemelec

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Re: Automatic Antenna Tuner for general SWL
« Reply #6 on: October 16, 2021, 09:01:30 am »
Quote
Wait a second, the 7300 has an embedded antenna tuner

Yes, I know that, but will it cope with the somewhat crappy long wire antenna I initially intend to use until I sort out something decent? 

Why do some ATU's get sold on the basis that they work directly with 7300's? I'm not new to electronics, even receiver design,  but fairly new to transmitting.
« Last Edit: October 16, 2021, 09:05:45 am by cemelec »
 

Offline richard.cs

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Re: Automatic Antenna Tuner for general SWL
« Reply #7 on: October 16, 2021, 09:27:24 am »
In the HF bands the antenna and/or it's matching have to be pretty bad before they start to significantly degrade signal to noise ratio unless the receiver has unusually high input noise. This is because there's so much atmospheric noise being received on your antenna that it dominates over receiver input noise, and a poorly matched antenna that gives you weaker signal also gives you less noise. This generally means that you get little or no receive benefit from an ATU.

If you have strong local noise sources you start to benefit from an antenna with some directionality, but you can generally get away with a pretty poor antenna for HF receive. This is not the case in the higher bands where the external noise is less and the receiver noise floor dominates.
 

Offline radiolistener

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Re: Automatic Antenna Tuner for general SWL
« Reply #8 on: October 16, 2021, 09:35:50 am »
This generally means that you get little or no receive benefit from an ATU.

When I tune tuner for magnetic loop antenna at short wave, I hear very strong difference between tuned and untuned tuner.

The same thing happens with ferrite antenna, there is very strong difference when it is tuned or untuned.

The effect of antenna matching for receiver will depends on antenna bandwidth.
« Last Edit: October 16, 2021, 09:49:06 am by radiolistener »
 

Online A.Z.

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Re: Automatic Antenna Tuner for general SWL
« Reply #9 on: October 16, 2021, 12:33:08 pm »
Quote
Wait a second, the 7300 has an embedded antenna tuner

Yes, I know that, but will it cope with the somewhat crappy long wire antenna I initially intend to use until I sort out something decent? 

Why do some ATU's get sold on the basis that they work directly with 7300's? I'm not new to electronics, even receiver design,  but fairly new to transmitting.

there was an old saying about rigs and antennas which sounded like "one for the rig, 99 for the antenna", now, while that's pretty extreme, it's right

So, my suggestion is to start by setting up your antenna and feedline properly and then decide if you want an external ATU or not

So, I suggest you is to reread my post, and in particular, the link about the "random" wire antennas, set up yours properly and then move on from there; notice that, for listening you may consider the idea of using a separate antenna, for example

http://www.kk5jy.net/LoG/

http://www.kk5jy.net/rx-loop/

in such a case you may consider the idea of investing into an automatic antenna switch, so that you won't transmit by mistake with the rx antenna, at that point you'll be able to add to the rx antenna whatever preselector or LNA you want

But first of all, set up properly your main rx/tx antenna :)

EDIT

as for the tuner, it is COMPATIBLE with the 7300 along other Icom rigs, but this does not mean that the 7300 needs it, but I'd better invest some money into some FT240-43 toroids, and some lenght of good coax cable (from direct experience the "Messi & Paoloni" one would be a good pick

« Last Edit: October 16, 2021, 03:00:36 pm by A.Z. »
 
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Offline HB9EVI

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Re: Automatic Antenna Tuner for general SWL
« Reply #10 on: October 16, 2021, 04:50:20 pm »
in RX the only thing that really matters is the signal to noise ratio; impedance matching is secondary.
if you want to use your long wire (how long is it actually?), it makes sense to use an automatic tuner at the feed point; the internal tuner is not very useful;

also the matching area of internal tuners normally are in a range of 3:1; specially on the longer bands, you'll have lower impedance than the tuner can handle due to simple fact that even 'long wire ham antennas' are still too short and too low above ground for the wavelenght to reach a higher radiation resistance
 

Online A.Z.

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Re: Automatic Antenna Tuner for general SWL
« Reply #11 on: October 16, 2021, 05:02:14 pm »
The basic idea, when it comes to "random" wire antennas, that is end fed wires which aren't resonant, aren't a 1/2 wave on some band and aren't multples of an 1/2 wave (those are EFHW or longwires), is to choose a non resonant lenght on all the bands of interest so that impedance won't be too low (near a 1/4 wave) or too high (near a 1/2 wave), at that point, using a 9:1 UnUn we bring the impedance down to a value which will allow a reasonable coupling with a coax and then, use an ATU to make our TX happy, that's it.

for further details, please see

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

« Last Edit: October 16, 2021, 05:12:04 pm by A.Z. »
 

Offline geggi1

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Re: Automatic Antenna Tuner for general SWL
« Reply #12 on: October 16, 2021, 06:21:19 pm »
If you are using a long/random wire antenna you should use a a longwire tuner like the Icom AH-3, AH-4 or some other tuner of a similar kind.
A long/random wire antenna will have a high impedance feed-point typically in the range of 1000 Ohm or more. These tuners are made for taking the high impedance feed-point impedance down to somewhere close to 50 Ohm giving you a SWR of about 1:1.

Some of these long-wire tuners have several hundred memories sometimes over 1000 and will not loose the settings at a power down, either by battery backup or some kind of static memory.

Get one tuner (with CI-V) of this kind ang get a local Ham come over to you and tune up your antenna on several spots on each ham band.
The tuner will tuner your antenna when you change frequency.
 

Online A.Z.

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Re: Automatic Antenna Tuner for general SWL
« Reply #13 on: October 16, 2021, 07:17:22 pm »
that's ONLY true if you bring the wire straight to the tuner w/o using an UnUn (and choke !) to connect the wire to yor rig, again, been there, done that and knowing what I'm talking about

EDIT

while nothing forbids it, most examples of end fed antennas show the wire going down (from whatever height) straight to the ATU, now, that works, sure, but it's FAR from an optimal setup; the latter would mean having a REMOTE tuner connected to the wire (and CONTERPOISE, in real life an end fed NEEDS it !)

was I saying ? Oh yes, the feedpoint of a random, ok, try using a modeling software and check what. happens when you RAISE the feedpoint and use a good counterpoise, for example, a vèrtical wire, coming down from the feedpoint to ground. and connected to (say) two radials in inverted T config
« Last Edit: October 16, 2021, 07:44:15 pm by A.Z. »
 

Offline radiolistener

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Re: Automatic Antenna Tuner for general SWL
« Reply #14 on: October 16, 2021, 08:11:39 pm »
Using ATU near transceiver is a bad choice, this is not effective way. It leads to a lot of losses in the feeder. Such configuration can be used when adding tuner at antenna feed point is very complicated or even impossible.

With integrated ATU or with tuner placed near transceiver you're using significant part of your transceiver power for heating the feeder and ATU, this part of power does not enter the antenna and just lost.

And this is why ATU integrated into transceiver in many cases are useless.

But there is also compromise option exists, you can put ATU in the middle of feeder. As short as you can to antenna feed point. Such configuration allows to reduce losses in the feeder and improve antenna efficiency. Of course such tuner needs to be automatic, because it will be placed far away from the operator. Usually such a tuner is placed on the roof to be close to antenna.

Aslo, ATU integrated into transceiver has a limited tuning range. This is why external tuner still may be required if your antenna with feeder requires very high L or C for matching or if it has very high or very low resistance.

Note, that if your antenna is not matched with feeder, impedance on antenna terminals is not the same as impedance of antenna connected through feeder. In such case feeder works as impedance transformer and it's input impedance will depends on feeder length. So, you can't tune your tuner near the transceiver and then move it to antenna side, you will needs to retune it at antenna side.
« Last Edit: October 16, 2021, 08:40:17 pm by radiolistener »
 

Online A.Z.

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Re: Automatic Antenna Tuner for general SWL
« Reply #15 on: October 16, 2021, 09:40:17 pm »
sigh...

https://svarc.us/swr-the-persistent-myth/

and I think it's time to stop those myths
 
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Offline radiolistener

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Re: Automatic Antenna Tuner for general SWL
« Reply #16 on: October 16, 2021, 11:41:26 pm »
and I think it's time to stop those myths

What myths you're talking about?

Power loss in the feeder is not a myth. This is a property of transmission line and you can find the value of that power loss in the coax cable datasheet.


For example here is my measurements for 20 meters of Chinese RG316 which I bought on aliexpress, taken from 1 kHz to 90 MHz (see attachment). It is pretty close to RG316 datasheet specification.

As you can see, it has pretty significant loss. And that loss will be multiplied for each time wave travels back and forth through the cable between your ATU and antenna before it will be consumed by antenna. It will happens when you use ATU on transceiver side instead of antenna side.

On the contrary, when you use ATU on antenna side, that loss happens just once, because there is no reflected waves in the feeder. And wave travels back and forth between tuner and antenna with no needs to loss something on a long feeder.


VSWR cannot show you all details. In order to see details, you're needs to understand what is going on in the feeder, tuner and antenna.

This is the typical myth that VSWR at some section can show you total efficiency of your feeder-tuner-antenna system. No, it can't.

For example someone can replace your antenna at the end of feeder with 50 Ω dummy load and you will not be able to detect it with SWR meter. It will show you SWR about 1, but it doesn't means that 100 % of power is transferred to your antenna. Because your antenna is completely disconnected and all power is dissipated into heat on a dummy load   :D

If your tuner allows wide range tuning, you can just disconnect antenna from tuner and tune it to have VSWR about 1 in the cable between transmitter and tuner. But it doesn't means that you transmit all power with 100% efficiency. It didn't transmitted at all and dissipated into heat inside your tuner.

This is because your SWR meter connected between transmitter and tuner show you just VSWR in the feeder between transmitter and tuner, but it don't show you VSWR between tuner and antenna. It don't show you losses in the feeder. And it don't show you how much power is radiated by antenna, how much is dissipated into heat in antenna and how much is dissipated into heat by some object in the near field of antenna.

Another example, you can connect long enough coax cable with open end to your transmitter and get VSWR=1.0 on SWR meter connected between transmitter and coax cable. Because all power is consumed by coax cable and dissipated into heat.

This is why it's better to not focus on the VSWR value, but taking all things into account. Include things which happens in the feeder, tuner and antenna.

« Last Edit: October 17, 2021, 12:58:49 am by radiolistener »
 

Online A.Z.

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Re: Automatic Antenna Tuner for general SWL
« Reply #17 on: October 17, 2021, 07:52:08 am »
and I think it's time to stop those myths

What myths you're talking about?
.....
For example here is my measurements for 20 meters of Chinese RG316 which I bought
.....

I was referring to that paper about the SWR myths I posted, as for RG316, it's ok for short pigtail cables, but using a long run of RG316 to feed an antenna is a very bad idea; for RX only better using RG6, for TX too, go for at least RG8
« Last Edit: October 17, 2021, 06:37:11 pm by A.Z. »
 

Online A.Z.

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Re: Automatic Antenna Tuner for general SWL
« Reply #18 on: October 18, 2021, 09:53:10 am »
Quote
Wait a second, the 7300 has an embedded antenna tuner

Yes, I know that, but will it cope with the somewhat crappy long wire antenna I initially intend to use until I sort out something decent? 


That's your main problem  :) instead of throwing money into an external ATU, use it to improve your antenna, buy some length of decent coax cable, by or build a 9:1 UnUn and a 1:1 choke and put up your antenna "in the clear", connecting it (and a counterpoise wire !!) to the UnUn + choke  and feeding it with coax going all the way to your transceiver, then the trick is cutting your antenna wire so that it will NOT resonate on any ham band so that the internal ATU, with the help of the 9:1 UnUn at the antenna feedpoint, will be able to find a match; to sum it up

Find a length in this table which will fit your available space

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

for example a 70ft wire will allow you to cover all bands from 80 to 10 meters (if you have more space, pick a longer length from the table, e.g. 85ft) , add another piece of wire with a length of about 1/4 to 1/3 of the antenna length which will be dropped down as the counterpoise, next, build a 9:1 UnUn like the one described here

http://vk6ysf.com/unun_9-1_v2.htm

but use an FT240-43 toroid core and wind 9 turns, next build a choke like the one described here

http://vk6ysf.com/balun_guanella_current_1-1.htm

use another FT240-43 core for it, and wind 17 turns using a piece of RG-174 coax, at that point connect the output of the 9:1 UnUn to the input of the choke and host both into a box with a connector for the coax and binding posts and eyelets for the antenna wire and counterpoise, plus an eyelet to suspend the box

all the above will cost you much less than the external ATU and the result will work MUCH better than your current "arranged" antenna connected to an external ATU, it's the antenna which radiates/receives, the ATU won't improve a crappy antenna ! Remember again, invest more in your antenna system (everything from the antenna to the rig) than in other components, without a good antenna even a gazillion dollars rig will have crappy performances

HTH

Forgot, if you don't want to build your UnUn and Choke but prefer sheeting out money to buy them, you may pick (just an example) those

https://palomar-engineers.com/ferrite-application-experts-2/Bullet-50-450-9-1-HF-Unun-1-8-61-MHz-500-Watts-End-Fed-Antennas-p74356620

https://palomar-engineers.com/antenna-products/baluns-and-ununs/1-8-30-mhz-balunsununs/11-toroid-baluns/CUBE-Feed-Line-Choke-Unun-5KW-1-8-61-MHz-20-38-dB-Common-Mode-Rejection-Static-Bleeder-Ground-Option-p74536617







« Last Edit: October 18, 2021, 10:10:03 am by A.Z. »
 
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Offline cemelec

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Re: Automatic Antenna Tuner for general SWL
« Reply #19 on: October 18, 2021, 01:55:44 pm »
A.Z. thank you for your detailed and informative posts, they are very helpful.

I'd pretty much decided to go the way you suggest, but one question: Isn't the 1:1 choke supposed to go as near to the transceiver as possible?
I have seen that suggested in various places: i.e long wire > 9:1 unun > coax > choke >coax > radio

I may or may not wind my own (I've wound small ones for Rx only) but the commercial ones are not too expensive and by the time you get your toroids, boxes, connectors the savings are not huge.
I'll try the 7300's own ATU first, and see how it goes. 80m - 10m would be fine for me.
My next step might be a collapsible 10m mast, they seem quite interesting, but that's for another day
 

Online A.Z.

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Re: Automatic Antenna Tuner for general SWL
« Reply #20 on: October 18, 2021, 02:13:54 pm »
A.Z. thank you for your detailed and informative posts, they are very helpful.

You're welcome, just trying to help

Quote
I'd pretty much decided to go the way you suggest, but one question: Isn't the 1:1 choke supposed to go as near to the transceiver as possible?
I have seen that suggested in various places: i.e long wire > 9:1 unun > coax > choke >coax > radio

It may be put near the rig too, but my suggestion if possible, is to place one choke near the antenna and a second one near the transceiver, then adding more chokes will NOT hurt  :)

[edit]

the point is that, even with a good counterpoise, an endfed antenna will still "try" to use the coax as part of the radiating system, and sincerely, I'd try avoiding that, so, placing the choke near the antenna AND connecting a decent counterpoise will help, then, if you want adding more chokes along the feedline and near the rig, won't hurt; but now that I think at it... didn't you get your license ? Once upon a time that meant passing an exam, and the latter involved some basic stuff. including CM currents... but maybe nowadays things changed and I'm just an old fart ...

Quote
I may or may not wind my own (I've wound small ones for Rx only) but the commercial ones are not too expensive and by the time you get your toroids, boxes, connectors the savings are not huge.

two or three FT240-43, the winding wire (for the UnUn) and RG-174 coax (for the chokes), plus the box and the other stuff won't cost so much, commercial decent/good UnUns and chokes would cost much more, assuming you aren't going to buy CRAPPY chinese stuff which will cause problems instead of solving them, that is  :)

[edit]

and then, willing to go for "buy" (SIGH ... where is the ham spite today ?) the unun and choke from "palomar" (again, NOT promoting them, just. an example) won't cost you more than the ATU, and then connecting the ATU to a poor piece of wire brought directly INSIDE the shack won't offer you the same results of a properly set up antenna, even if it's a humble "random" wire

Quote
I'll try the 7300's own ATU first, and see how it goes. 80m - 10m would be fine for me.

With the current antenna, w/o a good setup ? Well, good luck with that ! But remember, the "problem" is not the 7300, it's the ANTENNA and adding an external ATU to the combo will still resuilt in a CRAPPY antenna and a waste of money (to buy the external ATU), again, skip the idea and start by setting up the antenna as needed, that's the ANTENNA which radiates and receives, if it's crap then adding tuners, preamps or linears will just mean wasting money without solving the problem

[edit]

Forgot, the antenna is an "end fed" one, but don't call it "long wire"; a long wire antenna is at least one full wavelength long (or multiple of a wavelength), an EFHW is an endfed with a length of 1/2 wave at the lower desired frequency, a "random" is an endfed calculated so that it will NOT be a multiple of 1/2 wave on any of the desired frequencies and that it will be near/above 1/4 wave at the lower desired operating frequency, so please, avoid calling it "long wire", it's a mistake

« Last Edit: October 18, 2021, 05:57:07 pm by A.Z. »
 

Online borjam

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Re: Automatic Antenna Tuner for general SWL
« Reply #21 on: October 18, 2021, 02:57:11 pm »
This generally means that you get little or no receive benefit from an ATU.

When I tune tuner for magnetic loop antenna at short wave, I hear very strong difference between tuned and untuned tuner.

The same thing happens with ferrite antenna, there is very strong difference when it is tuned or untuned.

The effect of antenna matching for receiver will depends on antenna bandwidth.

That's an entirely different question. Loop antennas (and a ferrite antenna is also a loop) are extremely narrow band tuned elements. So, tuned loops are actually a corner case.

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

« Last Edit: October 18, 2021, 02:58:52 pm by borjam »
 

Offline radiolistener

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Re: Automatic Antenna Tuner for general SWL
« Reply #22 on: October 18, 2021, 06:38:29 pm »
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.


If your antenna with feeder and tuner works bad for TX, it will also works the same bad for RX.

Note that in RX mode your gain is limited with thermal noise on 50 Ω of receiver input, so you cannot use gain to compensate weak signal attenuation due to antenna mismatch.
« Last Edit: October 18, 2021, 07:02:37 pm by radiolistener »
 

Online A.Z.

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Re: Automatic Antenna Tuner for general SWL
« Reply #23 on: October 18, 2021, 07:02:10 pm »
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 ?
« Last Edit: October 18, 2021, 07:04:23 pm by A.Z. »
 

Offline radiolistener

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Re: Automatic Antenna Tuner for general SWL
« Reply #24 on: October 18, 2021, 07:07:47 pm »
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, magnetic loop has more losses on heating and extreme high field strength near it (which is not safe for your health).
« Last Edit: October 18, 2021, 07:19:40 pm by radiolistener »
 


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