1. CrossCountryWireless@groups.io
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Re: HF Active Loop Antenna v4 YouTube video now on web page

Chris Moulding
 

That's not a bad idea.

I've got three HF transceivers that could use one so I would have no problem testing a prototype.

One possibility rather than use the radio PTT line would be to use a RF switch circuit I developed a few years ago. This was for a possible version of the Multicoupler that had one transceiver port and four receiver outputs.  It worked well and I still use the prototype but we didn't put it into production.

If I use that circuit the switch box would need a 12 V supply but that could also be used to power a bias tee circuit for an active antenna on the receive antenna port.

I'll make a prototype next week.

Regards,

Chris
Re: HF Active Loop Antenna v4 YouTube video now on web page

Paul Picking
 

Enjoyed the video! New double loop antenna is very interesting. Would fit nicely on my modest tower between the 2 VHF/UHF verticals. David Cutter's idea of you designing and manufacturing the coax switch is also interesting.       .Paul WD8OJL


On Sat, Nov 19, 2022, 1:34 PM Simon <ohhellnotagain@...> wrote:
Yes that would sell well I expect, but would need external power..even the ftdx 10 has only one antenna port..a reason why i love my ftdx3000..3 antenna ports and a suberb rx.
Re: HF Active Loop Antenna v4 YouTube video now on web page

Simon
 

Yes that would sell well I expect, but would need external power..even the ftdx 10 has only one antenna port..a reason why i love my ftdx3000..3 antenna ports and a suberb rx.
Re: HF Active Loop Antenna v4 YouTube video now on web page

David Cutter
 

Hi Chris

 

I watched the video with interest. 

 

For folks who want to use a separate receive antenna with their transmitter, there is the problem of switching from one antenna to the other using an external coax switch of some kind or buy a radio with built-in second antenna capability.  There are lots of good radios out there without this facility and it would be a great benefit for them to have a relay operated switch from the PTT on the radio.  This only needs to be for receive signals and not required to switch transmitter power.  I wonder if you have considered manufacturing these in your usual polycarb box, the perfect companion it seems to me.

 

73 David G3UNA

 

From: CrossCountryWireless@groups.io <CrossCountryWireless@groups.io> On Behalf Of Chris Moulding
Sent: 19 November 2022 16:54
To: CrossCountryWireless@groups.io
Subject: [CrossCountryWireless] HF Active Loop Antenna v4 YouTube video now on web page

 

I've just added a YouTube video on the new loop antenna at the bottom of the web page: https://www.crosscountrywireless.net/active_loop_antenna.htm

It shows a quick table top review and demonstration.

I also answer questions asked on various Facebook groups about the antenna.

Regards,

Chris

HF Active Loop Antenna v4 YouTube video now on web page

Chris Moulding
 

I've just added a YouTube video on the new loop antenna at the bottom of the web page: https://www.crosscountrywireless.net/active_loop_antenna.htm

It shows a quick table top review and demonstration.

I also answer questions asked on various Facebook groups about the antenna.

Regards,

Chris
Re: Hi Chris and others..move almost happening, advice required please.

Simon
 

Hi Chris

Thanks for replying

Do you have any recommendations for how many extra windings on type 61 or is that for me to experiment with?

The fcp isolation transformer..it uses type 2..similar in principle, total isolation..will it work?

Thanks for help.

Ps new twin loop looks excellent, very well built and a good price for what you get! Hope it sells well as it should! I assume when used horizontally the usual rule applies, higher the better. (For low angle takeoff.) plus pole, if used horizontally, non metallic?

Simon
Re: HF Active Loop Antenna v4 released

Chris Moulding
 

One point I forgot to mention. If it's mounted horizontally it has to be in a RF quiet location as you cannot null the noise out like you can with vertical mounting.

Regards,

Chris
Re: HF Active Loop Antenna v4 released

Chris Moulding
 

Mounting the loop horizontally gives an omni-directional pattern.

The nulls are vertically up and down so it's not ideal for NVIS operation.

Mounting at a low height say 8 to 10 feet above ground gives a fairly high angle doughnut shaped pattern. I confirmed this in testing this morning. Strong signals heard from around Europe on 10 MHz and above.

Mounting at height say on a tower or high building will give a very low angle especially if it's several wavelengths high at the frequency of operation. A steel framed building will tend to act as a reflector behind the antenna and affect the antenna pattern.

Regards,

Chris
Re: VLF/LF/HF Active Vertical Antenna Base Unit

Mark Lucas
 

Following up on the antenna, both the feeder cable as well as the cable from the choke to the amp check good.  I did test for a few days with a new cable going directly to the amp.  Has the same issue but still intermittent.  I did clean the BNC sockets with small amount of contact cleaner.  The base unit goes immediately every time tested to around 11.18 volts and there is 11.17 or so measured at the amp end of the cable.  I'm now wondering if the problem could be in the amp.  Being as it doesn't occur every power cycle, it's been frustrating trying to pinpoint.   I'll keep a watch to see if the issue becomes more frequent.  Thanks much for your help.  Now on to looking at your new loop antenna...
Re: Receiving SAQ

Chris Moulding
 

Hi Gerard,

Good to hear about you receiving SAQ with the VLF Loop Amplifier.

For those on the forum who haven't heard about SAQ it's a VLF radio transmitter in Sweden that went live in 1924 using an Alexanderson alternator to generate the RF power. It's now a working museum that comes on air a few times a year.

i once heard one of the Christmas Eve transmissions a few years ago. I was impressed by the quality of the CW signal from a keyed alternator!

The web page of the museum is: https://alexander.n.se/en/

Regards,

Chris
Receiving SAQ

PA3BCB
 

My compliments to CCW:
Today I once again received the historic Alexanderson VLF transmitter SAQ in Grimeton Sweden on 17.2 kHz very well, with snr > 30 dB.
Antenna was a triangular wire loop of 5.4 meters circumference to a CCW VLF loop amplifier, running 30 meters of RG58/U coax to an Airspy Discovery. On the input of the Discovery for safety a 6 dB attenuator. SDR application was SDR Console v3.1
My location is in grid square JO33.
Regards,
Gerard PA3BCB
Re: HF Active Loop Antenna v4 released

martinbradford2001
 

Sounds good, Chris. 

I really don't want to get involved in rotators at the moment, so I would be interested in mounting it horizontal for an omnidirectional pattern. As you know already, I'm using your LAA++ amplifier with a 1m loop vertically oriented and another passive 1m vertical loop at right angles. That works remarkably well, but I'm always looking for improvements - would be interested in how this new loop is likely to perform oriented horizontally and something like eight or ten feet above the ground...

Martin (G8FXC)
Re: HF Active Loop Antenna v4 released

Chris Moulding
 

Comparison tests with my 1 m diameter test loop using  LDF-4-50 show that signal levels are a few dB down but the signal to noise ratio is significantly improved.

The nulls on the double loop are remarkable around 50 to 60 dB down. Most other loops fill the nulls with noise picked up by the loop acting as an electric field antenna.

i usually use a 5m vertical with a High Z Antenna Amplifier as a reference "sanity check" at the workshop. The double loop is the only loop design to beat it so far.

I'll see if I can run a comparison test on the video.

Regards,

Chris
Re: HF Active Loop Antenna v4 released

martinbradford2001
 

Very interesting! Any idea how to expect it to compare with the LAA++ on a 1m loop as a low noise RX antenna?

Martin (G8FXC)
HF Active Loop Antenna v4 released

Chris Moulding
 

We have just started building the first production batch of the HF Active Loop Antenna v4. They will be ready for shipping in about a week.

The antenna uses a small double loop 350 mm or 14" in diameter.

it uses a variant of our Loop Antenna Amplifier ++ with sharp RF filtering to limit the frequency response to 500 kHz to 55 MHz.

The small size of the loop and the input transformer design are designed to prevent the loop element acting as an electric field antenna. This antenna acts as a true magnetic loop with very deep nulls for direction finding or noise rejection.

Due to the small size it's ideal for use as a portable antenna and will easily store away in a car. From the size you can see why during development it was called the "Pizza box loop"!

Later this week I'll make a video in the workshop to demonstrate the loop. If we get a dry day I'll take one out to make a video of some testing in the field.

I've got to thank the members of the forum for inspiring the development of this loop antenna. When we released the Loop Antenna Amplifier we had so many questions about loop types that I ran a project to try as wide a range of loop designs as possible, This small double loop design with a very low self-inductance was comparable to much bigger loops at medium wave and HF.

The web page for the new antenna is https://www.crosscountrywireless.net/active_loop_antenna.htm

Regards,

Chris
Re: 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
Re: 2 turn loop

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
Re: 2 turn loop

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
Re: 2 turn loop

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
Re: 2 turn loop

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
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