2 turn loop


David Cutter
 

I have not and I think there are far too many QRM signals, absolutely scores on the display and the general noise level is "quite high" though I haven't a figure for that. A noise antenna couldn't be pointed at any particular source, it's all encompassing, at least, that's the way it looks at the moment. We are just at the beginning of this journey, and I think we'll learn a lot. First port of call is to drive the rig from a battery and then pull the big switch. This is going to take a while: that precious commodity again.

David G3UNA

-----Original Message-----
From: CrossCountryWireless@groups.io <CrossCountryWireless@groups.io> On Behalf Of Simon
Sent: 14 November 2022 20:08
To: CrossCountryWireless@groups.io
Subject: Re: [CrossCountryWireless] 2 turn loop

Also David

Have you suggested to your friend about “ noise cancelling unit”
Ie an antenna phaser, trx/ rx antennas against a “ noise” antenna?

Chris.when you starting to make one?? You sell antenna amps/ loops etc to combat noise..a canceller would sell like hot cakes!!

Here below with pics gives an example of one in operation ( homebrew ) pics taken just now..pic 1 canceller off, pic 2 on..pic 3 bottom right is of my cancelling device ( 2 in 1 box, as run cancelling unit on main trx and rx antennas.)

Antenna is 40m dipole, run against a “ noise antenna”

S9 constant noise ( xmax smpsus etc) vs s2 with cancellation device in..
Dx signal drops 6-12db with on, but that is not of concern as still r5.



Simon


Chris Moulding
 

I did design a noise cancellation unit about three years ago. It worked rather well but at the time there appeared to be many of them available on the market.

The prototype is in the workshop somewhere so I'll try and find it tomorrow.

Regards,

Chris


Simon
 

Also David

Have you suggested to your friend about “ noise cancelling unit”
Ie an antenna phaser, trx/ rx antennas against a “ noise” antenna?

Chris.when you starting to make one?? You sell antenna amps/ loops etc to combat noise..a canceller would sell like hot cakes!!

Here below with pics gives an example of one in operation ( homebrew ) pics taken just now..pic 1 canceller off, pic 2 on..pic 3 bottom right is of my cancelling device ( 2 in 1 box, as run cancelling unit on main trx and rx antennas.)

Antenna is 40m dipole, run against a “ noise antenna”

S9 constant noise ( xmax smpsus etc) vs s2 with cancellation device in..
Dx signal drops 6-12db with on, but that is not of concern as still r5.



Simon


David Cutter
 

Hi Simon
Yes, indeed, that’s all understood, I think it’s more about practice, learning and expectations.  I’ll be trying bandwidth controls next time I’m in the chair.  

73 David 


On 14 Nov 2022, at 18:24, davidg3una@... wrote:

Hi Chris
As I suspected.  We’ve compared it to a low dipole and whereas I am used to noisey conditions he still finds it a challenge even with the new s/n ratio. The rf gain is limited somewhat and mutes / squelches at half way, unlike other radios. More things to try, we’re not finished yet, including just turning up the volume but that has its own issues .  

Thanks for the detailed info

David G3UNA 





On 14 Nov 2022, at 16:58, Chris Moulding <chrism@...> wrote:

Hi David,

The problem with using a multi-turn loop with a magnetic loop antenna is that it increases the total inductance of the loop.

This reduces the current flow in the loop compared to a single turn loop when used with a LAA++.

When the LAA++ was released I was getting many questions about what loop to use and I think I probably tried all possible loop options from a ferrite rod (useless when untuned) to a 5m square loop (no improvement over a 1 turn 1 m diameter loop on medium wave or HF but excellent below 100 kHz). I found that the 2 turn loop gave no noticeable improvement. A true A/B test would probably show a small loss.

Have you asked him why he wants more signal pickup?

Using one on 20m in the UK he is unlikely to be limited by amplifier noise. I had a report from a customer who used a LAA++ deep in the Australian outback and out there the external noise was lower than the amplifier noise. After that report I did some work to find a better ferrite and toroid winding option so the latest LAA++ have less input transformer loss and better isolation of the loop to prevent the loop element acting as an electric field antenna.

I suspect that he's comparing the signal level seen on his transmit antenna with that of the loop.  The total signal measured with his transmit antenna will also include the extra unwanted noise. Using the loop the wanted signal level should be similar but the noise level will be reduced which will lower the total signal measurement.

As long as he is limited by the external noise floor don't worry about the signal levels. Tell him to turn the RF gain up if he wants so that he gives everyone S9!

Regards,

Chris


David Cutter
 

Hi Chris
As I suspected.  We’ve compared it to a low dipole and whereas I am used to noisey conditions he still finds it a challenge even with the new s/n ratio. The rf gain is limited somewhat and mutes / squelches at half way, unlike other radios. More things to try, we’re not finished yet, including just turning up the volume but that has its own issues .  

Thanks for the detailed info

David G3UNA 





On 14 Nov 2022, at 16:58, Chris Moulding <chrism@...> wrote:

Hi David,

The problem with using a multi-turn loop with a magnetic loop antenna is that it increases the total inductance of the loop.

This reduces the current flow in the loop compared to a single turn loop when used with a LAA++.

When the LAA++ was released I was getting many questions about what loop to use and I think I probably tried all possible loop options from a ferrite rod (useless when untuned) to a 5m square loop (no improvement over a 1 turn 1 m diameter loop on medium wave or HF but excellent below 100 kHz). I found that the 2 turn loop gave no noticeable improvement. A true A/B test would probably show a small loss.

Have you asked him why he wants more signal pickup?

Using one on 20m in the UK he is unlikely to be limited by amplifier noise. I had a report from a customer who used a LAA++ deep in the Australian outback and out there the external noise was lower than the amplifier noise. After that report I did some work to find a better ferrite and toroid winding option so the latest LAA++ have less input transformer loss and better isolation of the loop to prevent the loop element acting as an electric field antenna.

I suspect that he's comparing the signal level seen on his transmit antenna with that of the loop.  The total signal measured with his transmit antenna will also include the extra unwanted noise. Using the loop the wanted signal level should be similar but the noise level will be reduced which will lower the total signal measurement.

As long as he is limited by the external noise floor don't worry about the signal levels. Tell him to turn the RF gain up if he wants so that he gives everyone S9!

Regards,

Chris


Simon
 

Hi Dave

Chris is spot on!

Explain to him the whole point of rx antennas is to get better s/n.. if that means no signal is above s3 so be it..just lie on signal reports..
At the end of the day if the loop allows one to hear stations that otherwise are in noise it is working well doing its job.

But you know all this..

Simon


Chris Moulding
 

Hi David,

The problem with using a multi-turn loop with a magnetic loop antenna is that it increases the total inductance of the loop.

This reduces the current flow in the loop compared to a single turn loop when used with a LAA++.

When the LAA++ was released I was getting many questions about what loop to use and I think I probably tried all possible loop options from a ferrite rod (useless when untuned) to a 5m square loop (no improvement over a 1 turn 1 m diameter loop on medium wave or HF but excellent below 100 kHz). I found that the 2 turn loop gave no noticeable improvement. A true A/B test would probably show a small loss.

Have you asked him why he wants more signal pickup?

Using one on 20m in the UK he is unlikely to be limited by amplifier noise. I had a report from a customer who used a LAA++ deep in the Australian outback and out there the external noise was lower than the amplifier noise. After that report I did some work to find a better ferrite and toroid winding option so the latest LAA++ have less input transformer loss and better isolation of the loop to prevent the loop element acting as an electric field antenna.

I suspect that he's comparing the signal level seen on his transmit antenna with that of the loop.  The total signal measured with his transmit antenna will also include the extra unwanted noise. Using the loop the wanted signal level should be similar but the noise level will be reduced which will lower the total signal measurement.

As long as he is limited by the external noise floor don't worry about the signal levels. Tell him to turn the RF gain up if he wants so that he gives everyone S9!

Regards,

Chris


David Cutter
 

A friend has installed a loop ++ amplifier on a bicycle wheel and is getting some success combatting local noise, but wants more signal pickup (he is using a IC7300 with second pre-amp).  I've seen 2-turn loops used on *tuned* loops for low power transmit, so I would like to know if this idea would improve receive sensitivity with the LA ++ over a single turn loop.  He is primarily interested in 20m. 

73 David G3UNA