Tom, Here is another link for you
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@...
?
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
|
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@...
?
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
|
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@...
toggle quoted message
Show quoted text
On Feb 12, 2025, at 2:13?AM, Fred Moore via groups.io <n40cla@...> 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: File upload: Rotable FLAG-antenna
That's exactly what I intend to do.? :)
?
73
|
Look at the W1VLF YouTube channel. He has several different loops of different sizes and materials. For example a 9' x 9' loop made from hardware cloth:
?
?
On the shielded loop shielding the windings from the electric field I'm not so sure. We are talking about electromagnetic waves which are both E and H. Unless Maxwell is wrong a changing magnetic field generates an electric field (and vice-versa), so I'm not sure how you can sort one from the other. Here is a good page that talks about receiving loops. Summary is that the shield helps balance the loop and thus makes it less susceptible to common mode noise:
?
?
--
===================================================================
Mike M
|
Just for the heck of it I asked AI if the ground rods would work and this is what it came back with.
?
Everett N4CY
?
Yes, it is possible to detect VLF (Very Low Frequency) signals using two rods in the ground connected to a preamplifier. This setup essentially forms a simple dipole antenna2. The rods act as the receiving elements, and the preamplifier boosts the weak signals received by the rods.
However, there are a few considerations to keep in mind:
-
Signal-to-Noise Ratio (S/N): VLF signals are often weak and can be easily drowned out by noise. A good preamplifier with a high dynamic range can help improve the S/N ratio1.
-
Ground Conductivity: The effectiveness of the rods can depend on the ground conductivity where they are placed.
-
Interference: Avoid areas with high electromagnetic interference, such as power lines or electronic devices.
Would you like more detailed information on how to set this up, or any specific aspects you're curious about?
https://physicsopenlab.org/2020/05/03/loop-antenna-for-very-low-frequency/
In a message dated 2/11/2025 1:41:32 PM Central Standard Time, martin_ehrenfried@... writes:
?
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 VLF.IT 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?
|
What would happen if you put two ground rods in the ground, spaced 25' to 50' apart and use an amplifier?
?
Everett
In a message dated 2/11/2025 1:51:11 PM Central Standard Time, 1rfsam@... writes:
?
Or that one:
?
On Tue, Feb 11, 2025 at 11:49?AM rfsam via groups.io
<1rfsam@...> wrote:
>
> There are also PEX lines with aluminum layer between plastic layers.
> Could be a proper candidate for shielded loop?
> Like that
> Not cheap though.
> Simon
>
> On Tue, Feb 11, 2025 at 11:44?AM W0LEV via groups.io
> <davearea51a@...> 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 groups.io <martin_ehrenfried@...> 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 VLF.IT 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
> >
> >
> >
>
>
>
>
>
?
?
?
?
|
Or that one: On Tue, Feb 11, 2025 at 11:49?AM rfsam via groups.io <1rfsam@...> wrote:
There are also PEX lines with aluminum layer between plastic layers.
Could be a proper candidate for shielded loop?
Like that
Not cheap though.
Simon
On Tue, Feb 11, 2025 at 11:44?AM W0LEV via groups.io
<davearea51a@...> 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 groups.io <martin_ehrenfried@...> 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 VLF.IT 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
|
There are also PEX lines with aluminum layer between plastic layers. Could be a proper candidate for shielded loop? Like that Not cheap though. Simon On Tue, Feb 11, 2025 at 11:44?AM W0LEV via groups.io <davearea51a@...> 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 groups.io <martin_ehrenfried@...> 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 VLF.IT 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
|
Hi Martin, What are your thoughts on shielded loops (broadband amplified or resonated with the cap) - do they really work or it's not worth the hassle? Thank you, Simon On Tue, Feb 11, 2025 at 11:41?AM Martin - Southwest UK via groups.io <martin_ehrenfried@...> 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 VLF.IT 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?
|
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?
|
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 VLF.IT website could be of interest.
?
http://www.vlf.it/
?
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?
|
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: File upload: Rotable FLAG-antenna
Hi Warren!
Don't really know. But why not try and find out?
/Hans
Hans,
?
Would there be any problem feeding the antenna and pre-amp with CAT-6 cable?
?
I read an article by a Canadian fellow that CAT 6 is better than coax because:
?
The twisted pairs are naturally balanced and according to him, less prone to common mode problems
The characteristic impedance is 100 ohms
The multiple twisted pairs offer 4 different possibilities of use. i.e. power for the pre-amp, antenna lead(s), T/R protection switch, etc.
?
I am seriously looking at this antenna for 160 meters as I have a small lot and cannot use a proper 160 meter receive antenna.
?
73
Warren / NI5L
?
|
Re: File upload: Rotable FLAG-antenna
Hans,
?
Would there be any problem feeding the antenna and pre-amp with CAT-6 cable?
?
I read an article by a Canadian fellow that CAT 6 is better than coax because:
?
The twisted pairs are naturally balanced and according to him, less prone to common mode problems
The characteristic impedance is 100 ohms
The multiple twisted pairs offer 4 different possibilities of use. i.e. power for the pre-amp, antenna lead(s), T/R protection switch, etc.
?
I am seriously looking at this antenna for 160 meters as I have a small lot and cannot use a proper 160 meter receive antenna.
?
73
Warren / NI5L
?
|
Re: File upload: Rotable FLAG-antenna
Hi Hans.
?
Can you verify this is actually the case: "In a passive splitter, there is a 6dB signal loss on each output and you may want to compensate for this loss, using a 6dB buffer amplifier."
?
A broadband resistive 'splitter' (not used much in practice today) may result in 6 dB loss, but a broadband CATV type transformer style results closer to 3 dB (half power) loss.
?
Thanks for the pdf too.
?
de Jim AA5CT
?
|
Re: File upload: Rotable FLAG-antenna
?
Regards,
?
Martin
?
On Tue, Feb 11, 2025 at 09:10 AM, Mike Usher wrote:
toggle quoted message
Show quoted text
I would be very interested but I can't find the file.
|
Re: Entry Level SDR recommendations
When it comes to ease of use, I recommend web-888 which integrates most of the codecs.
It is based on openweb-rx and can work independently from the computer. As long as there is a browser device, such as mobile phones and Macs, it can be used directly.
Here are some devices that can be accessed directly as an experience
https://www.rx-888.com/web/rx.html
|
Re: File upload: Rotable FLAG-antenna
|
Re: File upload: Rotable FLAG-antenna
Hello Mike,
look on this Website. PDF is under FLAG Antennas.( The growing FLAG Antenna)
https://www.dxinfo.se/
|
Warren Dean / NI5L
Everett N4CY
Hans Ostnell