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Re: LZ1AQ possible changes

 
Edited

On Sun, Feb 9, 2025 at 01:26 PM, Nils wrote:

a while ago there was a discussion in a german forum where forum member ArnoR proposed modifications to the original LZ1AQ circuit.

The modifications seemed plausible to me but as an electronic hobbyist with little knowledge (but a lot of passion!) I had difficulties understanding them.

A circuit (and later an updated version) was presented as an improvement over the original LZ1AQ design that i know has been in use for years (and has highly regarded updated versions published in this forum).?

Hi all,
i went through this german "mikrocontroller forum" thread from August 2021, where the threadopener ArnoR claimes, that the LZ1AQ circuit is "much too bad" and proposes a long list of modifications to improve the - in his view - flawed design. (See Nils' opening message of this topic).
?
ArnoR seems to be quite experienced in discrete transistor circuit design, but not explicitly experienced in RF. The? language he uses during the forum discussion reads, even by german cultural language standards, annoyingly rude and self absorbed. He expects to be encouraged in his views and opinions and seems not really interested in advise or a true discussion of technical facts others than his. The moment of truth comes in post 15.08.2021 18:13:
?
The poster "Heiner" is asking the question: "Are your ‘optimisations’ of the LZ1AQ circuit merely based on simulations, or measured in comparison and compared in real in practice under identical conditions?"
?
ArnoR's response: "These are simulations, just like LZ1AQ, whose data also originate only from simulations. And two circuits,? simulated under the same conditions are comparable, even if the models are not 100% correct.......The circuit simulator is an excellent tool for designing such things. Due to the lack of measurement equipment, however, I can only judge subjectively."
?
Let me conclude: The design flaws alleged by ArnoR with respect to the very early circuit diagram published by LZ1AQ, are solely based on his assumptions and simulations. He insinuates that LZ1AQ's experiences are also based on simulations only. ArnoR has obviously neither built nor tested or compared the amplifiers, nor had he the basic RF-test equipment available to do this, respectively big skills in RF-testing or practical dx-ing!?
?
It seems, ArnoR's remarks have remained an unvalidated theoretical exercise, I have not yet found any information that his proposed amplifier circuit was built or tested by anyone later.?
?
regards, fred
Re: My PA0FRI active loop receiving antenna

 

My evaluation of the PA0FRI preamp.
?
:-) Critiques welcome!
73, Leong, 9M2LCL, ex-9W2LC
Re: Further attempt to improve my LZ1AQ installation

 

Hi Chavdar,
Thank you for your response!


On Thu, Feb 13, 2025, 1:07?PM чавдар левков via <lz1aq=[email protected]> wrote:
Hi Simon,
In coplanar loops the currents from A and B are simply added. So if B is noisy then A+B will be also noisy.

Yes, that's what I assumed as well, thank you for confirming that!


This cable layout is more important? if you use loops in dipole mode. In loop mode it almost does not have an impact.
Why loop B is more noisy? I do not know but in near field region every meter matters! The height of the loop above ground is not very important in an open field with no obstacles but in your case .....?.

Yes, lower loop B is definitely physically closer to the place where I have all the computers, screens, etc. Makes sense!

Best Regards,
Simon
Re: Further attempt to improve my LZ1AQ installation

 

Hi Simon,
In coplanar loops the currents from A and B are simply added. So if B is noisy then A+B will be also noisy.
This cable layout is more important? if you use loops in dipole mode. In loop mode it almost does not have an impact.
Why loop B is more noisy? I do not know but in near field region every meter matters! The height of the loop above ground is not very important in an open field with no obstacles but in your case .....?.
Regards,
Chavdar lz1aq
Re: VLF question

 

Good evening Dave.? Regarding your statement?But be sure to introduce the break at the top of the loop.

I Just purchased some copper screen #80 mesh and plan to cut it into possibly?3" to 4" wide stripsand wind it on the pipe starting at the top and basically covering the box at the bottom.? I think that 80 mesh is a tight enough weave.

Fred
N4CLA

On Tue, Feb 11, 2025, 14:44 W0LEV via <davearea51a=[email protected]> wrote:
You could cover your PEX with a continuous layer of a good conductive material like copper mesh or copper (bronze) screen.? But be sure to introduce the break at the top of the loop.? I believe PEX is nonconductive.? With the screen or mesh, it should act much like using a copper tube.

Dave - W?LEV


On Tue, Feb 11, 2025 at 7:41?PM Martin - Southwest UK via <martin_ehrenfried=[email protected]> wrote:
I think the skin depth of the various conductor types you have suggested may be an influencing factor.
?
Some of the antenna articles on the website could be of interest.
?
?
Regards,
?
Martin
?
On Tue, Feb 11, 2025 at 06:13 PM, Fred Moore wrote:
would I have the same shielding as an the copper pipe loop?



--
Dave - W?LEV
Re: VLF question

 

I have experimented with various Loop on the Ground receive antennas, and the closer to the ground (or buried beneath it), the more the higher frequencies become attenuated.
?
?
When buried a few inches below the ground, signals on frequencies above about 2MHz become significantly attenuated.
?
If you could bury a suitably sized loop even deeper, I think it would work quite well on the VLF bands, and perhaps be less subject to external interference.
?
Regards,
?
Martin
?
On Thu, Feb 13, 2025 at 06:29 AM, Doug Reed wrote:

I'm more inclined to the simple "LOG- Loop On Ground" concept.
Re: VLF question

 

Regarding earth probe antennas, there is a Facebook page dedicated to them at <https://www.facebook.com/groups/earthprobes/>.?
Another link on the page at <https://www.rtl-sdr.com/building-an-underground-earth-probe-antenna-for-0-14-mhz-tx-rx/> references a 1935 article about a buried antenna for SWL.
A search for "buried antenna" gives numerous links and eventually I found links for Soviet and US military documents related to underground antennas used in Cold War communications systems.
I'm more inclined to the simple "LOG- Loop On Ground" concept.
73, Doug Reed, N0NAS.
Re: VLF question

 

Thank you
?
Further attempt to improve my LZ1AQ installation

 

I tried to follow recommendation from Chavdar's app note in regards to feed cable location (for vertical dual loop configuration). Here is a picture:
?
?
Although in the notes Chavdar recommends 1-2m offset for the cable behind the loop's plane. I only have ~60-70cm (2ft) due to some space restrictions.
?
I noticed that in Dipole mode I see about 5dB drop in AM BC station images in the lower 80m band. That's due to CM issues in dipole mode. Not sure if that was worth the hassle as loop mode is still superior in my noisy environment (semi-urban location).
?
I also noticed that top loop (Loop A) usually provides better s/n ratio compared to lower loop (loop B) and cross-parallel connection of both loops. I see that on most HF bands. Sometimes LoopA=A+B but usually I just use loopA. I was wondering if that's due to the cable that was hanging right across the lower loop. New cable placement improved things a bit but I still see LoopA normally being better or equal to A+B configuration. LoopB is still normally worse than other two configs (A, or A+B).
Next I may try to put more clip on ferrites along the portion of the cable that hangs below LoopB. Maybe mix31 and mix75 clip-ons combined on the length of 1-3m up to the point where cable comes to the wall. I already have a stack of two FT240-31 with ~6 turns of CAT before cable leaves the amplifier box and a stack of three FT240-31 with 6 turns before it enters control switch box. That actually helped a lot but I wanted to improve things even more.
?
I wonder if Loop A is better simply because it's higher in the air and further away from my "shack" that's 2-3m away from the antenna physically.
?
Also may try to place Yaesu GS-050 mast bearing a bit lower. Right now it sits right below the lower loop. Wonder if that can create any un-balance issues.
?
Regards,
Simon
KM6MUL
?
Re: File upload: Rotable FLAG-antenna

 

Hi Fred,
Thanks! I wonder what difference will UTP vs S/FTP make? I use S/FTP
cat8 (24awg) patch cable for my LZ1AQ (original AAA-1). I know that at
antenna side cable shield is not connected to common GND to keep line
symmetrical (relative to GND) and for less CM issues. Same should be
applied for other antennas if shielded CAT is used (shield not
connected on one side, most likely antenna side)...
Regards,
Simon

On Tue, Feb 11, 2025 at 9:57?PM Fred M via groups.io
<dl4zao@...> wrote:

On Tue, Feb 11, 2025 at 04:17 PM, Warren Dean / NI5L wrote:

Would there be any problem feeding the antenna and pre-amp with CAT-6 cable?

No, there would be no problem, this a a proven technique. Te original LZ1AQ AAA-1C active loop is using twisted pair Ethernet cable as feedline, power supply line and control line..

"Ethernet cables are designed to handle frequencies that coincide nicely with most of the interesting amateur radio bands, and their insertion losses not much worse than RG58. The twisted pairs are also a balanced system that’s good at rejecting common mode noise. Cat 6 cable also has four pairs of conductors, allowing you to feed multiple antennas with one cable, or to distribute power to amplifiers and switches along with antenna feeds."

Video:



regards, Fred
Re: VLF question

 

A mate of mine also builds DSP-based cave radios ,operating at around 87kHz, which is a coomnly used frequency for such purposes.
?
The antennas are tuned loops
?
Regards,
?
Martin
?
On Wed, Feb 12, 2025 at 12:01 PM, Fred Moore wrote:

Martin, great history document
Re: File upload: Rotable FLAG-antenna

 

Thanks for that, Fred. I am definitely going to use CAT6 for the loop. We shall see how it works out.
?
73
Warren / NI5L
Re: VLF question

 

Martin, great history document. Who would have thought that buried wire could actually have worked that well.

Thanks for the history lesson.

Fred

N4cla


On Wed, Feb 12, 2025, 06:17 Martin - Southwest UK via <martin_ehrenfried=[email protected]> wrote:

I think the issues is how much contribution there is from the ground path vs, the interconnecting wire laid on the surface.
?
Earth probes and amplifiers were extensively used during trench warfare in WWI, in order to eavesdrop on field telephones, that at the time used the earth as a return path for the single wire phone line. Twin wire was then introduced, and latterly the Fullerphone, with increasing development to further improve security.
?
?
The earth itself is a lossy dielectric medium, but at VLF it's mainly resistive, the ground conductivity, and underlying geology having a major effect on propagation.
?
50 or 60Hz mains "hum" and harmonics are a major issue, and extensive filtering is required to reduce their level.
?
There has been some amateur experimentation at around 8kHz, and transatlantic communications, at a very low data rate has been achieved.
?
Some interesting historical notes on underground VLF antennas, including loops, can be found here.
?
?
Regards,
?
Martin
?
?
On Wed, Feb 12, 2025 at 09:54 AM, John E. Burgar wrote:
I have been meaning to try an earth probe antenna here for over a year. I wanted to make one about 500' long with each end terminated by 8' copper coated ground rods.
Re: VLF question

 

I think the issues is how much contribution there is from the ground path vs, the interconnecting wire laid on the surface.
?
Earth probes and amplifiers were extensively used during trench warfare in WWI, in order to eavesdrop on field telephones, that at the time used the earth as a return path for the single wire phone line. Twin wire was then introduced, and latterly the Fullerphone, with increasing development to further improve security.
?
?
The earth itself is a lossy dielectric medium, but at VLF it's mainly resistive, the ground conductivity, and underlying geology having a major effect on propagation.
?
50 or 60Hz mains "hum" and harmonics are a major issue, and extensive filtering is required to reduce their level.
?
There has been some amateur experimentation at around 8kHz, and transatlantic communications, at a very low data rate has been achieved.
?
Some interesting historical notes on underground VLF antennas, including loops, can be found here.
?
http://www.rexresearch.com/rogers/1rogers.htm#wx319
?
Regards,
?
Martin
?
?
On Wed, Feb 12, 2025 at 09:54 AM, John E. Burgar wrote:

I have been meaning to try an earth probe antenna here for over a year. I wanted to make one about 500' long with each end terminated by 8' copper coated ground rods.
Re: VLF question

 



On Tuesday, February 11, 2025 at 09:20:29 PM PST, Gedas via groups.io <w8bya@...> wrote:


I have been meaning to try an earth probe antenna here for over a year. I wanted to make one about 500' long with each end terminated by 8' copper coated ground rods.

When you think about it, in practice, it sort of resembles (to me) a weird folded dipole of sorts.? A somewhat folded dipole where the "top dipole wire" is running along on the ground surface while the bottom dipole is a complex form comprised of the two copper rods driven in the ground and whatever conductivity exists between them via the soil. I might be wrong but my gut tells me that the top dipole, the wire laying on the ground contributes quite a bit to the antennas characteristics.
Gedas, W8BYA EN70JT
Light travels faster than sound.....
This is why some people appear bright until you hear them speak.
On 2/11/2025 11:24 PM, Facility 406 wrote:

On 2/11/2025 11:55, Everett N4CY via groups.io wrote:
What would happen if you put two ground rods in the ground, spaced 25' to 50' apart and use an amplifier?

I'd have to dig out some old books, but I think the Germans were doing that, minus the amp at the time, in the 1860's.? I seem to recall a section in one of my radio books from around 1906 having a decent writeup on it.? It wasn't called radio yet, but was known as wireless at the time, and detected intentional signals, but it was the beginning.

For several decades, probes with amplifiers were the go-to.? Probes ranged from screwdrivers stuck in the dirt in gardens, to 1m rods tens of meters apart.? Several years ago, I asked about two probes, one about 200' deep, the other, about 500', 1/2 mile apart.? No response.? I no longer have access to both of those probes.? I also had the idea of a 1/2 mile loop, and up to a dozen turns a half mile around each.? I may still play with that.

Here is some probe info:



If you can find references to the old ELF/ULF forum that was on Yahoo, it was almost entirely discussing probes.

This one may parallel it:

/g/VLF

If not, people at the above forum may have info.

Kurt







Re: File upload: Rotable FLAG-antenna

 

On Tue, Feb 11, 2025 at 04:17 PM, Warren Dean / NI5L wrote:
Would there be any problem feeding the antenna and pre-amp with CAT-6 cable?
No, there would be no problem, this a a proven technique. Te original LZ1AQ AAA-1C? active loop is using twisted pair Ethernet cable as feedline, power supply line and control line..
?
"Ethernet cables are designed to handle frequencies that coincide nicely with most of the interesting amateur radio bands, and their insertion losses not much worse than RG58. The twisted pairs are also a balanced system that’s good at rejecting common mode noise. Cat 6 cable also has four pairs of conductors, allowing you to feed multiple antennas with one cable, or to distribute power to amplifiers and switches along with antenna feeds."
?
Video:
?
?
regards, Fred
Re: VLF question

 

开云体育

I have been meaning to try an earth probe antenna here for over a year. I wanted to make one about 500' long with each end terminated by 8' copper coated ground rods.

When you think about it, in practice, it sort of resembles (to me) a weird folded dipole of sorts.? A somewhat folded dipole where the "top dipole wire" is running along on the ground surface while the bottom dipole is a complex form comprised of the two copper rods driven in the ground and whatever conductivity exists between them via the soil. I might be wrong but my gut tells me that the top dipole, the wire laying on the ground contributes quite a bit to the antennas characteristics.
Gedas, W8BYA EN70JT
Light travels faster than sound.....
This is why some people appear bright until you hear them speak.
On 2/11/2025 11:24 PM, Facility 406 wrote:

On 2/11/2025 11:55, Everett N4CY via groups.io wrote:
What would happen if you put two ground rods in the ground, spaced 25' to 50' apart and use an amplifier?

I'd have to dig out some old books, but I think the Germans were doing that, minus the amp at the time, in the 1860's.? I seem to recall a section in one of my radio books from around 1906 having a decent writeup on it.? It wasn't called radio yet, but was known as wireless at the time, and detected intentional signals, but it was the beginning.

For several decades, probes with amplifiers were the go-to.? Probes ranged from screwdrivers stuck in the dirt in gardens, to 1m rods tens of meters apart.? Several years ago, I asked about two probes, one about 200' deep, the other, about 500', 1/2 mile apart.? No response.? I no longer have access to both of those probes.? I also had the idea of a 1/2 mile loop, and up to a dozen turns a half mile around each.? I may still play with that.

Here is some probe info:



If you can find references to the old ELF/ULF forum that was on Yahoo, it was almost entirely discussing probes.

This one may parallel it:

/g/VLF

If not, people at the above forum may have info.

Kurt







Re: VLF question

 

On 2/11/2025 11:55, Everett N4CY via groups.io wrote:
What would happen if you put two ground rods in the ground, spaced 25' to 50' apart and use an amplifier?
I'd have to dig out some old books, but I think the Germans were doing that, minus the amp at the time, in the 1860's. I seem to recall a section in one of my radio books from around 1906 having a decent writeup on it. It wasn't called radio yet, but was known as wireless at the time, and detected intentional signals, but it was the beginning.

For several decades, probes with amplifiers were the go-to. Probes ranged from screwdrivers stuck in the dirt in gardens, to 1m rods tens of meters apart. Several years ago, I asked about two probes, one about 200' deep, the other, about 500', 1/2 mile apart. No response. I no longer have access to both of those probes. I also had the idea of a 1/2 mile loop, and up to a dozen turns a half mile around each. I may still play with that.

Here is some probe info:



If you can find references to the old ELF/ULF forum that was on Yahoo, it was almost entirely discussing probes.

This one may parallel it:

/g/VLF

If not, people at the above forum may have info.

Kurt
Re: VLF question

 

Tom, Here is another link for you


On Tue, Feb 11, 2025 at 10:18?PM Fred Moore via <n40cla=[email protected]> wrote:
Good Evening Tom.

Here is one of them
? This is an open wire loop with no shielding for obvious?reasons because of its physical?size.

Here is another VLF antenna using a Ferrite Rod

There was a third one I recently found but can't seem to locate it at the moment.? The one with the ferrite rod ought to give you some idea of the shielding and I hope the reason for the shielding. Basically the shield reduces the electrical field and lets the magnetic field in the box.? When I find it I will?pass it along.

Fred
N4cla


On Tue, Feb 11, 2025 at 8:49?PM Tom ANderson via <SDR_Radio=[email protected]> wrote:
Fred,
Can you list the web sites that talk about this type of antenna?? I have never heard of the gap that you mention nor the shielding.

I am familiar with loop antenna but this seems very different then a normal loop?

Thank you
Tom

?

?

Tom Anderson

SDR_Radio@...





On Feb 12, 2025, at 2:13?AM, Fred Moore via <n40cla=[email protected]> wrote:

?
I am thinking of making a VLF loop out of a 10 ft piece of PEX pipe with many turns of wire inside the PEX and a plastic junction box on the bottom.? I have read several articles about doing the same thing with copper pipe as the shield and making a gap in the top center of the pipe. The purpose of the gap is to shield the windings from electrical noise and allowing the magnetic waves inside the pipe.?

There are several?articles on how to shield VLF antennas ie; Ferrite Rods, from electrical noise.? Making copper pipe loops and metal electrical boxes at the bottom and cutting a gap in the pipe at the top is basically the same as shielding the Ferrite Rod with aluminum and leaving an air gap for the magnetic waves.? Pex is a different animal as if you cut a gap in the top of a PEX loop, you lose the round loop. So my question is this.? What if I keep the round loop attached to the plastic electrical box and shield the entire round loop with #80 copper mesh and not the box, would I have the same shielding as an the copper pipe loop?

Fred
N4CLA
Re: VLF question

 

Good Evening Tom.

Here is one of them
? This is an open wire loop with no shielding for obvious?reasons because of its physical?size.

Here is another VLF antenna using a Ferrite Rod

There was a third one I recently found but can't seem to locate it at the moment.? The one with the ferrite rod ought to give you some idea of the shielding and I hope the reason for the shielding. Basically the shield reduces the electrical field and lets the magnetic field in the box.? When I find it I will?pass it along.

Fred
N4cla


On Tue, Feb 11, 2025 at 8:49?PM Tom ANderson via <SDR_Radio=[email protected]> wrote:
Fred,
Can you list the web sites that talk about this type of antenna?? I have never heard of the gap that you mention nor the shielding.

I am familiar with loop antenna but this seems very different then a normal loop?

Thank you
Tom

?

?

Tom Anderson

SDR_Radio@...





On Feb 12, 2025, at 2:13?AM, Fred Moore via <n40cla=[email protected]> wrote:

?
I am thinking of making a VLF loop out of a 10 ft piece of PEX pipe with many turns of wire inside the PEX and a plastic junction box on the bottom.? I have read several articles about doing the same thing with copper pipe as the shield and making a gap in the top center of the pipe. The purpose of the gap is to shield the windings from electrical noise and allowing the magnetic waves inside the pipe.?

There are several?articles on how to shield VLF antennas ie; Ferrite Rods, from electrical noise.? Making copper pipe loops and metal electrical boxes at the bottom and cutting a gap in the pipe at the top is basically the same as shielding the Ferrite Rod with aluminum and leaving an air gap for the magnetic waves.? Pex is a different animal as if you cut a gap in the top of a PEX loop, you lose the round loop. So my question is this.? What if I keep the round loop attached to the plastic electrical box and shield the entire round loop with #80 copper mesh and not the box, would I have the same shielding as an the copper pipe loop?

Fred
N4CLA
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