Topics

Availability of Mag Loop and other stuff...

Jack Purdum
 

Alan:

The results right now are modeled using the usual Pacific66 app. However, we do plan "real" tests in an attempt to get some useful data. Our reference antenna will likely be an 80-10M EFHW which we both use. Al also has a vertical that we might test against. However, the EFHW is always available; not so with the vertical.

We read in a paper that someone added a ground plane and said it "made a difference", whatever the hell that means. Anyway, because of that, we want to try it and see if it does have an impact. We have already noticed that the shape of the feed loop makes a difference, as does its position in the vertical plane. The effect is small, but real.

Al and I have talked about this a lot, and our feeling is to publish the results of the "Double-Double" as a construction article. (I want to call it the "Luggable Double-Double" but Al's not happy with that.) There are controllers out there (Loftur Jonasson) so my feeling is that will be kept for the book only. Also, it will be somewhat unique in that we hope to add a TFT display that shows the SWR in realtime as a plot. We have arranged to have all of the projects' PCB's available at a reasonable price.

Al and I are writing the book in a strange way. We are going to finish it before signing with a publisher. The reason is because I know the time pressures that editors put on authors with respect to deadlines and we want to get this right rather than to market fast. Our TOC has 18 chapters, of which the first 4 are really setting up the software for the Arduino, Teensy, STM32, and ESP32 µC's and giving the beginning reader enough C instruction to read our code (and shoot themselves in the foot a few times?) We see 12 projects in the book, some of which (e.g., the ML) are two chapters--construction and software. Some are "end products" (e.g., the ML, a different antenna tuner, CW messenger, CW decoder, CW Tutor) while others are test equipment (e.g., programmable power supply, AC voltmeter, signal generator). The last chapter is on using what you've built to troubleshoot a receiver. We think it will be a very unusual, but useful, book. Our goal is to have it done by the fall. We currently have 9 chapters done.

Long answer to a short question...


Jack, W8TEE


On Saturday, June 1, 2019, 12:01:46 PM EDT, Alan de G1FXB via Groups.Io <g1fxb@...> wrote:


Hi Jack,

Sounds like you are on to something special with 90% and even the 40% are impressive figures.
(Noted that they are modelled?? efficiencies at this point in time, here's hoping with can you can achieve something approaching in practical tests.)
To what reference antenna (also at the same modelled height to compare like for like) ?

Interested in your comment the trials of a counterpoise,
Previous papers indicate loop type antennas were considered a free space antenna requiring no ground plane / radials
I guess it's the feed / matching & counterpoise is where the magic happens?

As it's using an auto tuner is the write-up destined for your new book is there an ETA, or another perhaps magazine article release?

(One gotcha about some of the previous, (not your) small "miracle" antenna's.
Check it's actual the antenna doing the radiating and not the feed line, or counterpoise even the mounting pole has being known to be "accidentality" hot with RF.
(However disguised, generally any antenna employing a braid breaker / balun in the coax away from what they make you believe is the feed point or suggested feeder or support lengths perhaps warrants a second look.))


regards Alan

On 31/05/2019 18:45, Jack Purdum via Groups.Io wrote:
We are also trying to assess other factors, too, such as a counterpoise and its affect on performance. We may find that these "other factors" play no significant role in the antenna's performance. Still, learning that something doesn't matter is as helpful as learning what does matter.

Jack, W8TEE

ajparent1/KB1GMX
 

Jack,

the biggest issue is the 80-10 EFHW has a terrible pattern, broadside at 80m and by 20M
its a 4 lobe pattern with 10m its practically endfire.

That creates issues and questions for comparison as the EFHW is then rarely aimed at
the receiving station and hence you do not have a known comparison.

Generally when testing loops a loop of known performance are used but testing at HF is
never easy as the near field is at least 5 to 10 wavelengths or more and ground quality
dependent.  You want that distance to be able to see the total field.   The easiest rig
for that kind of testing is two fiberglass boats on calm salt water (an almost near
perfect ground plane).  Of course that does not include RF sources and calibrated
receivers and accurate GPS.

Allison

Alan de G1FXB
 

Thanks Jack,

Long answers are good and indicate your willingness for full disclosure.

(Manufactures antenna specifications tend to be BS generators?
Second only to the HiFi industry.??
Remember the kids in the mid 1980's with their "Ghetto Blasters" advertised with 780 Watts of stereo music power, and all from 8X D cell batteries.
In fairness some of the manufactures provided revised figures when used on mains power, nearly a KW.
Man those things must have being efficient, and all through a skinny power cord....)

I couldn't find on the pacciffic66 site what they reference their figures to, on that initial page at least?
hopefully it's something real and not against some theoretical property.
One of which, the proper name escapes me at this time.
(my numbers for instance :-)
6ft of wire whether straight or coiled is a larger percentage nearer a useful wavelength ie: 1/4wave?? at say 28MHz (approx 8ft) than the same 6ft of wire to 14MHz
I interpret this to It's a simple expression of comparison of physical length to wavelength, nothing to do with the antenna efficiency and devoid of losses in the matching networks that are necessary, etc, etc.
Even if it's a real antenna they are referencing it to, it in it's self could be a compromised reference gives great headline numbers.
Check the fine print!

Suggestion:- At least do the theoretical model of what ever you choose to use as the loop reference antenna against a full size centre fed dipole at identical heights, even if not a real world test.
Granted it's monoband & optimally performs mounted half wavelength above the ground but it's a good indicator & reference, and as cheap & simple?? to construct as it gets.
if you don't like what you see in the comparison it's between you and your conscience.
You can cripple it's performance and justifiably conclude an XYZ antenna, is greatly more efficient than?? a halfwave dipole when mounted at 15ft agl for example.... :-)

Saw the reports of doing A/B comparisons, however quick the changeover there is always the element of doubt as to propagation.
the ideal is simultaneous TX to both antennas in the same lot but far enough not to interact is the goal.
In the real world two antennas one each in the same town is good enough. What's a mile over a propagation distance of say 6,000??
everyone has their preferred mode, be it CW, WSPR the latest digimode.???? Reality it doesn't matter?
The requirement is for as many & widespread coverage of receiving stations as possible??
That said, QRP-Labs kits are cheap enough to utilise two, and compare like for like WSPR time slots to each of your and AL's callsigns allocated to each different antenna?


regards Alan

On 01/06/2019 17:27, Jack Purdum via Groups.Io wrote:
Alan:

The results right now are modeled using the usual Pacific66 app. However, we do plan "real" tests in an attempt to get some useful data. Our reference antenna will likely be an 80-10M EFHW which we both use. Al also has a vertical that we might test against. However, the EFHW is always available; not so with the vertical.

We read in a paper that someone added a ground plane and said it "made a difference", whatever the hell that means. Anyway, because of that, we want to try it and see if it does have an impact. We have already noticed that the shape of the feed loop makes a difference, as does its position in the vertical plane. The effect is small, but real.

Al and I have talked about this a lot, and our feeling is to publish the results of the "Double-Double" as a construction article. (I want to call it the "Luggable Double-Double" but Al's not happy with that.) There are controllers out there (Loftur Jonasson) so my feeling is that will be kept for the book only. Also, it will be somewhat unique in that we hope to add a TFT display that shows the SWR in realtime as a plot. We have arranged to have all of the projects' PCB's available at a reasonable price.

Al and I are writing the book in a strange way. We are going to finish it before signing with a publisher. The reason is because I know the time pressures that editors put on authors with respect to deadlines and we want to get this right rather than to market fast. Our TOC has 18 chapters, of which the first 4 are really setting up the software for the Arduino, Teensy, STM32, and ESP32 ??C's and giving the beginning reader enough C instruction to read our code (and shoot themselves in the foot a few times?) We see 12 projects in the book, some of which (e.g., the ML) are two chapters--construction and software. Some are "end products" (e.g., the ML, a different antenna tuner, CW messenger, CW decoder, CW Tutor) while others are test equipment (e.g., programmable power supply, AC voltmeter, signal generator). The last chapter is on using what you've built to troubleshoot a receiver. We think it will be a very unusual, but useful, book. Our goal is to have it done by the fall. We currently have 9 chapters done.

Long answer to a short question...


Jack, W8TEE


On Saturday, June 1, 2019, 12:01:46 PM EDT, Alan de G1FXB via Groups.Io <g1fxb@...> wrote:


Hi Jack,

Sounds like you are on to something special with 90% and even the 40% are impressive figures.
(Noted that they are modelled?? efficiencies at this point in time, here's hoping with can you can achieve something approaching in practical tests.)
To what reference antenna (also at the same modelled height to compare like for like) ?

Interested in your comment the trials of a counterpoise,
Previous papers indicate loop type antennas were considered a free space antenna requiring no ground plane / radials
I guess it's the feed / matching & counterpoise is where the magic happens?

As it's using an auto tuner is the write-up destined for your new book is there an ETA, or another perhaps magazine article release?

(One gotcha about some of the previous, (not your) small "miracle" antenna's.
Check it's actual the antenna doing the radiating and not the feed line, or counterpoise even the mounting pole has being known to be "accidentality" hot with RF.
(However disguised, generally any antenna employing a braid breaker / balun in the coax away from what they make you believe is the feed point or suggested feeder or support lengths perhaps warrants a second look.))


regards Alan

On 31/05/2019 18:45, Jack Purdum via Groups.Io wrote:
We are also trying to assess other factors, too, such as a counterpoise and its affect on performance. We may find that these "other factors" play no significant role in the antenna's performance. Still, learning that something doesn't matter is as helpful as learning what does matter.

Jack, W8TEE

Jack Purdum
 

If I were writing a treatise on mag loop antennas, I might worry about simultaneous transmissions and similar exogenous factors, but we're not. Chances are, we will do some simple tests using CW, SSB, and probably FT8 or FT4. We will transmit for a period of time, switch antennas and see what happens. We will be collecting data from WSPR and the beacons, but it is all constrained by the time we have to do such things. Our goal is not to probe the physics of the ML, but rather to provide enough information to those who are interested to decide if it's worth the effort to build a ML. One of our club members is using a dipole on 40M and uses thumb tacks to hold it to the ceiling, bending around 90º corners, yet he's still making contacts. All he wants to know is if he can put one out on his balcony any make contacts with it on 20M.

The good news is that I believe that the construction article we plan should be sufficiently robust that you can build one, too. Then the ball's in your court and you can do the depth of testing you mention. I simply don't have enough grains of sand left in the hourglass to worry about it that much.

Jack, W8TEE

On Saturday, June 1, 2019, 4:45:46 PM EDT, Alan de G1FXB via Groups.Io <g1fxb@...> wrote:


Thanks Jack,

Long answers are good and indicate your willingness for full disclosure.

(Manufactures antenna specifications tend to be BS generators?
Second only to the HiFi industry.??
Remember the kids in the mid 1980's with their "Ghetto Blasters" advertised with 780 Watts of stereo music power, and all from 8X D cell batteries.
In fairness some of the manufactures provided revised figures when used on mains power, nearly a KW.
Man those things must have being efficient, and all through a skinny power cord....)

I couldn't find on the pacciffic66 site what they reference their figures to, on that initial page at least?
hopefully it's something real and not against some theoretical property.
One of which, the proper name escapes me at this time.
(my numbers for instance :-)
6ft of wire whether straight or coiled is a larger percentage nearer a useful wavelength ie: 1/4wave?? at say 28MHz (approx 8ft) than the same 6ft of wire to 14MHz
I interpret this to It's a simple expression of comparison of physical length to wavelength, nothing to do with the antenna efficiency and devoid of losses in the matching networks that are necessary, etc, etc.
Even if it's a real antenna they are referencing it to, it in it's self could be a compromised reference gives great headline numbers.
Check the fine print!

Suggestion:- At least do the theoretical model of what ever you choose to use as the loop reference antenna against a full size centre fed dipole at identical heights, even if not a real world test.
Granted it's monoband & optimally performs mounted half wavelength above the ground but it's a good indicator & reference, and as cheap & simple?? to construct as it gets.
if you don't like what you see in the comparison it's between you and your conscience.
You can cripple it's performance and justifiably conclude an XYZ antenna, is greatly more efficient than?? a halfwave dipole when mounted at 15ft agl for example.... :-)

Saw the reports of doing A/B comparisons, however quick the changeover there is always the element of doubt as to propagation.
the ideal is simultaneous TX to both antennas in the same lot but far enough not to interact is the goal.
In the real world two antennas one each in the same town is good enough. What's a mile over a propagation distance of say 6,000??
everyone has their preferred mode, be it CW, WSPR the latest digimode.???? Reality it doesn't matter?
The requirement is for as many & widespread coverage of receiving stations as possible??
That said, QRP-Labs kits are cheap enough to utilise two, and compare like for like WSPR time slots to each of your and AL's callsigns allocated to each different antenna?


regards Alan

On 01/06/2019 17:27, Jack Purdum via Groups.Io wrote:
Alan:

The results right now are modeled using the usual Pacific66 app. However, we do plan "real" tests in an attempt to get some useful data. Our reference antenna will likely be an 80-10M EFHW which we both use. Al also has a vertical that we might test against. However, the EFHW is always available; not so with the vertical.

We read in a paper that someone added a ground plane and said it "made a difference", whatever the hell that means. Anyway, because of that, we want to try it and see if it does have an impact. We have already noticed that the shape of the feed loop makes a difference, as does its position in the vertical plane. The effect is small, but real.

Al and I have talked about this a lot, and our feeling is to publish the results of the "Double-Double" as a construction article. (I want to call it the "Luggable Double-Double" but Al's not happy with that.) There are controllers out there (Loftur Jonasson) so my feeling is that will be kept for the book only. Also, it will be somewhat unique in that we hope to add a TFT display that shows the SWR in realtime as a plot. We have arranged to have all of the projects' PCB's available at a reasonable price.

Al and I are writing the book in a strange way. We are going to finish it before signing with a publisher. The reason is because I know the time pressures that editors put on authors with respect to deadlines and we want to get this right rather than to market fast. Our TOC has 18 chapters, of which the first 4 are really setting up the software for the Arduino, Teensy, STM32, and ESP32 ??C's and giving the beginning reader enough C instruction to read our code (and shoot themselves in the foot a few times?) We see 12 projects in the book, some of which (e.g., the ML) are two chapters--construction and software. Some are "end products" (e.g., the ML, a different antenna tuner, CW messenger, CW decoder, CW Tutor) while others are test equipment (e.g., programmable power supply, AC voltmeter, signal generator). The last chapter is on using what you've built to troubleshoot a receiver. We think it will be a very unusual, but useful, book. Our goal is to have it done by the fall. We currently have 9 chapters done.

Long answer to a short question...


Jack, W8TEE


On Saturday, June 1, 2019, 12:01:46 PM EDT, Alan de G1FXB via Groups.Io <g1fxb@...> wrote:


Hi Jack,

Sounds like you are on to something special with 90% and even the 40% are impressive figures.
(Noted that they are modelled?? efficiencies at this point in time, here's hoping with can you can achieve something approaching in practical tests.)
To what reference antenna (also at the same modelled height to compare like for like) ?

Interested in your comment the trials of a counterpoise,
Previous papers indicate loop type antennas were considered a free space antenna requiring no ground plane / radials
I guess it's the feed / matching & counterpoise is where the magic happens?

As it's using an auto tuner is the write-up destined for your new book is there an ETA, or another perhaps magazine article release?

(One gotcha about some of the previous, (not your) small "miracle" antenna's.
Check it's actual the antenna doing the radiating and not the feed line, or counterpoise even the mounting pole has being known to be "accidentality" hot with RF.
(However disguised, generally any antenna employing a braid breaker / balun in the coax away from what they make you believe is the feed point or suggested feeder or support lengths perhaps warrants a second look.))


regards Alan

On 31/05/2019 18:45, Jack Purdum via Groups.Io wrote:
We are also trying to assess other factors, too, such as a counterpoise and its affect on performance. We may find that these "other factors" play no significant role in the antenna's performance. Still, learning that something doesn't matter is as helpful as learning what does matter.

Jack, W8TEE

Jack Purdum
 

Good grief, guys, this is a hobby for me. Allison, are you really trying to be helpful here, or simply showing that you have a lot of RF experience? Perhaps the best solution is to do no testing and simply say we made contacts with it and leave it at that. Pretty hard to criticize the methodology when there's no information given. We have an EFHW available to us for testing, so that's what we're using. Also, there are a lot of hams out there using EFHW antennas so any testing we do with it will have meaning to them even if it does have a crappy radiation pattern for testing. If it's not ideal, so be it. My chances of renting two fiberglass crafts to sit on the Great Salt Lake loaded with a boat-load of equipment and antennas are about zero. Someone else with deeper pockets than I have will have to do that testing.

The good news is that if we do write an article on our ML experience, no one has to read it.

Jack, W8TEE



On Saturday, June 1, 2019, 4:17:30 PM EDT, ajparent1/KB1GMX <kb1gmx@...> wrote:


Jack,

the biggest issue is the 80-10 EFHW has a terrible pattern, broadside at 80m and by 20M
its a 4 lobe pattern with 10m its practically endfire.

That creates issues and questions for comparison as the EFHW is then rarely aimed at
the receiving station and hence you do not have a known comparison.

Generally when testing loops a loop of known performance are used but testing at HF is
never easy as the near field is at least 5 to 10 wavelengths or more and ground quality
dependent.  You want that distance to be able to see the total field.   The easiest rig
for that kind of testing is two fiberglass boats on calm salt water (an almost near
perfect ground plane).  Of course that does not include RF sources and calibrated
receivers and accurate GPS.

Allison

jim
 

Ha ...or one boat and one helicopter ...easy-peasy

Jim

On Saturday, June 1, 2019, 8:17:29 PM UTC, ajparent1/KB1GMX <kb1gmx@...> wrote:


Jack,

the biggest issue is the 80-10 EFHW has a terrible pattern, broadside at 80m and by 20M
its a 4 lobe pattern with 10m its practically endfire.

That creates issues and questions for comparison as the EFHW is then rarely aimed at
the receiving station and hence you do not have a known comparison.

Generally when testing loops a loop of known performance are used but testing at HF is
never easy as the near field is at least 5 to 10 wavelengths or more and ground quality
dependent.  You want that distance to be able to see the total field.   The easiest rig
for that kind of testing is two fiberglass boats on calm salt water (an almost near
perfect ground plane).  Of course that does not include RF sources and calibrated
receivers and accurate GPS.

Allison

Tom, wb6b
 

On Sat, Jun 1, 2019 at 07:54 PM, jim wrote:
Ha ...or one boat and one helicopter ...easy-peasy
Of maybe a drone.

https://www.radioworld.com/tech-and-gear/using-drones-for-signal-measurements

Tom, wb6b

Arv Evans
 

Jack

Since your loop is small it could be rotated and a remote receiver and antenna
used to derive a signal strength pattern.  This could be automated if you use a
stepper motor rotator and automated logging of the signal levels at various angles. 
Then you came up with the idea of counterpoises and possibly ruined it all because
rotating a counterpoise might be difficult at best.

I share Allison's thoughts that near-fields should be avoided because it could lead
to inaccurate results.  Have you considered using one of the many on-line remote
receivers for your tests.  This could get outside the near-field situation. 

Arv
_._


On Sat, Jun 1, 2019 at 8:17 PM Jack Purdum via Groups.Io <jjpurdum=yahoo.com@groups.io> wrote:
Good grief, guys, this is a hobby for me. Allison, are you really trying to be helpful here, or simply showing that you have a lot of RF experience? Perhaps the best solution is to do no testing and simply say we made contacts with it and leave it at that. Pretty hard to criticize the methodology when there's no information given. We have an EFHW available to us for testing, so that's what we're using. Also, there are a lot of hams out there using EFHW antennas so any testing we do with it will have meaning to them even if it does have a crappy radiation pattern for testing. If it's not ideal, so be it. My chances of renting two fiberglass crafts to sit on the Great Salt Lake loaded with a boat-load of equipment and antennas are about zero. Someone else with deeper pockets than I have will have to do that testing.

The good news is that if we do write an article on our ML experience, no one has to read it.

Jack, W8TEE



On Saturday, June 1, 2019, 4:17:30 PM EDT, ajparent1/KB1GMX <kb1gmx@...> wrote:


Jack,

the biggest issue is the 80-10 EFHW has a terrible pattern, broadside at 80m and by 20M
its a 4 lobe pattern with 10m its practically endfire.

That creates issues and questions for comparison as the EFHW is then rarely aimed at
the receiving station and hence you do not have a known comparison.

Generally when testing loops a loop of known performance are used but testing at HF is
never easy as the near field is at least 5 to 10 wavelengths or more and ground quality
dependent.  You want that distance to be able to see the total field.   The easiest rig
for that kind of testing is two fiberglass boats on calm salt water (an almost near
perfect ground plane).  Of course that does not include RF sources and calibrated
receivers and accurate GPS.

Allison

Donald
 

Jack, ham radio is a hobby for me, too. Please keep up your experiments and post anything you care to share. As a renter, magnetic loops interest me, and *your* experiments will improve the probability of *my success*.

Donald, KB5PWL

On 6/1/2019 9:16 PM, Jack Purdum via Groups.Io wrote:
Good grief, guys, this is a hobby for me. Allison, are you really trying to be helpful here, or simply showing that you have a lot of RF experience? Perhaps the best solution is to do no testing and simply say we made contacts with it and leave it at that. Pretty hard to criticize the methodology when there's no information given. We have an EFHW available to us for testing, so that's what we're using. Also, there are a lot of hams out there using EFHW antennas so any testing we do with it will have meaning to them even if it does have a crappy radiation pattern for testing. If it's not ideal, so be it. My chances of renting two fiberglass crafts to sit on the Great Salt Lake loaded with a boat-load of equipment and antennas are about zero. Someone else with deeper pockets than I have will have to do that testing.

The good news is that if we do write an article on our ML experience, no one has to read it.

Jack, W8TEE



On Saturday, June 1, 2019, 4:17:30 PM EDT, ajparent1/KB1GMX <kb1gmx@...> wrote:


Jack,

the biggest issue is the 80-10 EFHW has a terrible pattern, broadside at 80m and by 20M
its a 4 lobe pattern with 10m its practically endfire.

That creates issues and questions for comparison as the EFHW is then rarely aimed at
the receiving station and hence you do not have a known comparison.

Generally when testing loops a loop of known performance are used but testing at HF is
never easy as the near field is at least 5 to 10 wavelengths or more and ground quality
dependent.  You want that distance to be able to see the total field.   The easiest rig
for that kind of testing is two fiberglass boats on calm salt water (an almost near
perfect ground plane).  Of course that does not include RF sources and calibrated
receivers and accurate GPS.

Allison

Alan de G1FXB
 

Hi Jack,
It's a hobby to me as well, Constrained by finite time and money.
There are many miracle claims, just using cheap & simple gets overlooked.
Your reference the realworld ingenuity of to your friends use of the dipole was what I was trying to portray,


Not to dissuade you,
The suggestions just were a way to get best results, fewest doubts in half the time?
Wish you luck and I look forward to seeing the write-up, and it warrants building over a traditional STL.



regards Alan

On 02/06/2019 03:02, Jack Purdum via Groups.Io wrote:
If I were writing a treatise on mag loop antennas, I might worry about simultaneous transmissions and similar exogenous factors, but we're not. Chances are, we will do some simple tests using CW, SSB, and probably FT8 or FT4. We will transmit for a period of time, switch antennas and see what happens. We will be collecting data from WSPR and the beacons, but it is all constrained by the time we have to do such things. Our goal is not to probe the physics of the ML, but rather to provide enough information to those who are interested to decide if it's worth the effort to build a ML. One of our club members is using a dipole on 40M and uses thumb tacks to hold it to the ceiling, bending around 90?? corners, yet he's still making contacts. All he wants to know is if he can put one out on his balcony any make contacts with it on 20M.

The good news is that I believe that the construction article we plan should be sufficiently robust that you can build one, too. Then the ball's in your court and you can do the depth of testing you mention. I simply don't have enough grains of sand left in the hourglass to worry about it that much.

Jack, W8TEE

On Saturday, June 1, 2019, 4:45:46 PM EDT, Alan de G1FXB via Groups.Io <g1fxb@...> wrote:


Thanks Jack,

Long answers are good and indicate your willingness for full disclosure.

(Manufactures antenna specifications tend to be BS generators?
Second only to the HiFi industry.??
Remember the kids in the mid 1980's with their "Ghetto Blasters" advertised with 780 Watts of stereo music power, and all from 8X D cell batteries.
In fairness some of the manufactures provided revised figures when used on mains power, nearly a KW.
Man those things must have being efficient, and all through a skinny power cord....)

I couldn't find on the pacciffic66 site what they reference their figures to, on that initial page at least?
hopefully it's something real and not against some theoretical property.
One of which, the proper name escapes me at this time.
(my numbers for instance :-)
6ft of wire whether straight or coiled is a larger percentage nearer a useful wavelength ie: 1/4wave?? at say 28MHz (approx 8ft) than the same 6ft of wire to 14MHz
I interpret this to It's a simple expression of comparison of physical length to wavelength, nothing to do with the antenna efficiency and devoid of losses in the matching networks that are necessary, etc, etc.
Even if it's a real antenna they are referencing it to, it in it's self could be a compromised reference gives great headline numbers.
Check the fine print!

Suggestion:- At least do the theoretical model of what ever you choose to use as the loop reference antenna against a full size centre fed dipole at identical heights, even if not a real world test.
Granted it's monoband & optimally performs mounted half wavelength above the ground but it's a good indicator & reference, and as cheap & simple?? to construct as it gets.
if you don't like what you see in the comparison it's between you and your conscience.
You can cripple it's performance and justifiably conclude an XYZ antenna, is greatly more efficient than?? a halfwave dipole when mounted at 15ft agl for example.... :-)

Saw the reports of doing A/B comparisons, however quick the changeover there is always the element of doubt as to propagation.
the ideal is simultaneous TX to both antennas in the same lot but far enough not to interact is the goal.
In the real world two antennas one each in the same town is good enough. What's a mile over a propagation distance of say 6,000??
everyone has their preferred mode, be it CW, WSPR the latest digimode.???? Reality it doesn't matter?
The requirement is for as many & widespread coverage of receiving stations as possible??
That said, QRP-Labs kits are cheap enough to utilise two, and compare like for like WSPR time slots to each of your and AL's callsigns allocated to each different antenna?


regards Alan

On 01/06/2019 17:27, Jack Purdum via Groups.Io wrote:
Alan:

The results right now are modeled using the usual Pacific66 app. However, we do plan "real" tests in an attempt to get some useful data. Our reference antenna will likely be an 80-10M EFHW which we both use. Al also has a vertical that we might test against. However, the EFHW is always available; not so with the vertical.

We read in a paper that someone added a ground plane and said it "made a difference", whatever the hell that means. Anyway, because of that, we want to try it and see if it does have an impact. We have already noticed that the shape of the feed loop makes a difference, as does its position in the vertical plane. The effect is small, but real.

Al and I have talked about this a lot, and our feeling is to publish the results of the "Double-Double" as a construction article. (I want to call it the "Luggable Double-Double" but Al's not happy with that.) There are controllers out there (Loftur Jonasson) so my feeling is that will be kept for the book only. Also, it will be somewhat unique in that we hope to add a TFT display that shows the SWR in realtime as a plot. We have arranged to have all of the projects' PCB's available at a reasonable price.

Al and I are writing the book in a strange way. We are going to finish it before signing with a publisher. The reason is because I know the time pressures that editors put on authors with respect to deadlines and we want to get this right rather than to market fast. Our TOC has 18 chapters, of which the first 4 are really setting up the software for the Arduino, Teensy, STM32, and ESP32 ??C's and giving the beginning reader enough C instruction to read our code (and shoot themselves in the foot a few times?) We see 12 projects in the book, some of which (e.g., the ML) are two chapters--construction and software. Some are "end products" (e.g., the ML, a different antenna tuner, CW messenger, CW decoder, CW Tutor) while others are test equipment (e.g., programmable power supply, AC voltmeter, signal generator). The last chapter is on using what you've built to troubleshoot a receiver. We think it will be a very unusual, but useful, book. Our goal is to have it done by the fall. We currently have 9 chapters done.

Long answer to a short question...


Jack, W8TEE


On Saturday, June 1, 2019, 12:01:46 PM EDT, Alan de G1FXB via Groups.Io <g1fxb@...> wrote:


Hi Jack,

Sounds like you are on to something special with 90% and even the 40% are impressive figures.
(Noted that they are modelled?? efficiencies at this point in time, here's hoping with can you can achieve something approaching in practical tests.)
To what reference antenna (also at the same modelled height to compare like for like) ?

Interested in your comment the trials of a counterpoise,
Previous papers indicate loop type antennas were considered a free space antenna requiring no ground plane / radials
I guess it's the feed / matching & counterpoise is where the magic happens?

As it's using an auto tuner is the write-up destined for your new book is there an ETA, or another perhaps magazine article release?

(One gotcha about some of the previous, (not your) small "miracle" antenna's.
Check it's actual the antenna doing the radiating and not the feed line, or counterpoise even the mounting pole has being known to be "accidentality" hot with RF.
(However disguised, generally any antenna employing a braid breaker / balun in the coax away from what they make you believe is the feed point or suggested feeder or support lengths perhaps warrants a second look.))


regards Alan

On 31/05/2019 18:45, Jack Purdum via Groups.Io wrote:
We are also trying to assess other factors, too, such as a counterpoise and its affect on performance. We may find that these "other factors" play no significant role in the antenna's performance. Still, learning that something doesn't matter is as helpful as learning what does matter.

Jack, W8TEE

ajparent1/KB1GMX
 

Jack,

Not showing off, no one is paying for it.  However when someone claims a loop
that 1-2db below a EFHW (or a dipole) that's pretty close to saying my 10 year
old Tacoma can win at Indy.  In short, not likely or the Indy cars had an unusual
handicap, like no fuel and must be pushed by pit crew.   Reality is that the EFHW
is pointed in some random direction relative to the station and the loop is aimed
though its 3db beam width is likely far wider than the EFHW or a standard dipole
at reasonable height.  That makes its aim very wide where a 80-10 EFHW on
40M will at best have a pattern with a beam width that is narrow as its 1
wavelength long.   I can claim and prove my square loop on 6M at 7ft is better
than my portable 6M full wave length rectaangle loop at 25ft  by pointing the
edge of the loop to the station at distance as the front to side is easily 20db
down.  For that I'm at least the same horizontal polarization.  The square loop
under that condition is about 14db better however if the big loop is aligned its
4 db worse.  In short that proves the big loop does really work and also proves
the omnidiriectional square loop is superior when omnidirectional coverage
is required.

In short comparing it to any antenna without some form of controls and claiming
performance is at best meaningless.    A valid compare is a full size vertical with
elevated radials as it will have known gain and similar takeoff angles.

Loops are cool antennas but they are small antennas and they nominally will be
negative gain compared to any dipole.  Its the nature of antenna compromise.

Fyi: the testing part is to show how difficult it is to get meaningful real world
test data with any accuracy at HF because of distances and even local
surface propagation.   Modeled is of value but care must be taken to use a 
model that works with small loops and real grounds (NEC4.2 engine).

As to helpful.  Yes I want people to realize the limits of small antennas and
the claims sometimes made that are against all modeled data and practical
theory never minding prior works done to verify the models.  To that I see a
lot of suppliers and articles for loops making claims like this is the new
better sliced bread.  

I use loops and I do apply them as they have characteristics that make
them useful.  First being they are self contained antennas. The other
feature is the nulls and their insensitivity to close in electrostatic fields.
Its what they are good at even when they are full sized 1lambda loops.

Allison

ajparent1/KB1GMX
 

Arv,

The problem of online RX or for that fact QRSS and WSPR sites is antenna alignment.
If you antenna is not "aimed" that way the result is it could have been a long path or worse
"off the side".  They do help with "have you been heard" and allows estimating propagation 
in a given direction but comparing A and B antennas requires care for both aim and
time of comparison as propagation is a transient thing.

MY 0.02$ on hobby, it is!  However taking peoples money with inaccurate or
extravagant claims should not be a hobby, though it is often a vocation people
pursue.  When people want to enjoy the hobby and are limited in time and budget
accuracy and good explanation is helpful.  When one expends time and money
on a course of action or material its desirable to understand what the outcome
may be or the limitations.

So every time a new antenna fad hits we have this.  Loops are indeed useful.
They are compact, self contained, and in some cases can help with local noise.
The yabut is they are very narrow band if they are as efficient as possible and
that leads to remote tuning as they are touchy and requiring SWR monitoring.
Being small antennas they are still low gain and therefor not the ultimate radiator. 
However the idea that I can get a loop and conquer the world from my garden
is loaded for disappointment as even the cheapest loop cost hundreds of
dollars and they most expensive ones are not that much better.  I've looked at
commercial loops and they are in the range of 199$ to well over 500$  that is
a lot of money to get an antenna that may be only passable or worse that it
can't work indoors in a building with metallic handicaps (stucco with wire, metal
framing, aluminum siding,  and foil backed insulation).  You have to keep it a
reasonable distance away from the radio so RF problems do not result.

As to building ones own, a good design wants a vacuum variable and they
are NOT cheap.  Air variables of the dual rotor forma can work ok but still
if you have to buy one they are costly.  Also the cap used determines max
power and tuning range as it had to withstand very high voltages even
at QRP levels.

That said if your junk box can full the need its interesting to experiment with Loops.


Allison

Jack Purdum
 

Allison:

I'm really only reporting the data that we had from the RBN reports. Your position seems to be that, because we didn't control all exogenous factors, the reports are meaningless...that no report is better than what we did report. I don't want to "claim" anything...that makes it sound like I'm selling something, which I'm not. I don't think anyone expects a shorten antenna to perform exactly like its full wave counterpart.

The best I can afford to do is report what I find with what I have. To me, something is better than nothing.

Jack, W8TEE

On Sunday, June 2, 2019, 11:39:10 AM EDT, ajparent1/KB1GMX <kb1gmx@...> wrote:


Jack,

Not showing off, no one is paying for it.  However when someone claims a loop
that 1-2db below a EFHW (or a dipole) that's pretty close to saying my 10 year
old Tacoma can win at Indy.  In short, not likely or the Indy cars had an unusual
handicap, like no fuel and must be pushed by pit crew.   Reality is that the EFHW
is pointed in some random direction relative to the station and the loop is aimed
though its 3db beam width is likely far wider than the EFHW or a standard dipole
at reasonable height.  That makes its aim very wide where a 80-10 EFHW on
40M will at best have a pattern with a beam width that is narrow as its 1
wavelength long.   I can claim and prove my square loop on 6M at 7ft is better
than my portable 6M full wave length rectaangle loop at 25ft  by pointing the
edge of the loop to the station at distance as the front to side is easily 20db
down.  For that I'm at least the same horizontal polarization.  The square loop
under that condition is about 14db better however if the big loop is aligned its
4 db worse.  In short that proves the big loop does really work and also proves
the omnidiriectional square loop is superior when omnidirectional coverage
is required.

In short comparing it to any antenna without some form of controls and claiming
performance is at best meaningless.    A valid compare is a full size vertical with
elevated radials as it will have known gain and similar takeoff angles.

Loops are cool antennas but they are small antennas and they nominally will be
negative gain compared to any dipole.  Its the nature of antenna compromise.

Fyi: the testing part is to show how difficult it is to get meaningful real world
test data with any accuracy at HF because of distances and even local
surface propagation.   Modeled is of value but care must be taken to use a 
model that works with small loops and real grounds (NEC4.2 engine).

As to helpful.  Yes I want people to realize the limits of small antennas and
the claims sometimes made that are against all modeled data and practical
theory never minding prior works done to verify the models.  To that I see a
lot of suppliers and articles for loops making claims like this is the new
better sliced bread.  

I use loops and I do apply them as they have characteristics that make
them useful.  First being they are self contained antennas. The other
feature is the nulls and their insensitivity to close in electrostatic fields.
Its what they are good at even when they are full sized 1lambda loops.

Allison

Jack Purdum
 

"However taking peoples money with inaccurate or extravagant claims should not be a hobby, though it is often a vocation people pursue."

Taking people's money? I'm not selling anything. My real goal is to get people constrained by HOA's or spouses back on the air.

Jack, W8TEE


On Sunday, June 2, 2019, 12:10:18 PM EDT, ajparent1/KB1GMX <kb1gmx@...> wrote:


Arv,

The problem of online RX or for that fact QRSS and WSPR sites is antenna alignment.
If you antenna is not "aimed" that way the result is it could have been a long path or worse
"off the side".  They do help with "have you been heard" and allows estimating propagation 
in a given direction but comparing A and B antennas requires care for both aim and
time of comparison as propagation is a transient thing.

MY 0.02$ on hobby, it is!  However taking peoples money with inaccurate or
extravagant claims should not be a hobby, though it is often a vocation people
pursue.  When people want to enjoy the hobby and are limited in time and budget
accuracy and good explanation is helpful.  When one expends time and money
on a course of action or material its desirable to understand what the outcome
may be or the limitations.

So every time a new antenna fad hits we have this.  Loops are indeed useful.
They are compact, self contained, and in some cases can help with local noise.
The yabut is they are very narrow band if they are as efficient as possible and
that leads to remote tuning as they are touchy and requiring SWR monitoring.
Being small antennas they are still low gain and therefor not the ultimate radiator. 
However the idea that I can get a loop and conquer the world from my garden
is loaded for disappointment as even the cheapest loop cost hundreds of
dollars and they most expensive ones are not that much better.  I've looked at
commercial loops and they are in the range of 199$ to well over 500$  that is
a lot of money to get an antenna that may be only passable or worse that it
can't work indoors in a building with metallic handicaps (stucco with wire, metal
framing, aluminum siding,  and foil backed insulation).  You have to keep it a
reasonable distance away from the radio so RF problems do not result.

As to building ones own, a good design wants a vacuum variable and they
are NOT cheap.  Air variables of the dual rotor forma can work ok but still
if you have to buy one they are costly.  Also the cap used determines max
power and tuning range as it had to withstand very high voltages even
at QRP levels.

That said if your junk box can full the need its interesting to experiment with Loops.


Allison

Ian Reeve
 

Spent some time with a low budget may loop made from straight pieces of thick aluminium strip bolted in a hexagon shape with a remote tune function fed by a separate coax cable from a 12v supply.Deliberately designed to add a little resistance to the "loop" to reduce the spacing on the variable tuning capacitor,it worked.Hanging it from a tree branch it proved to receive signals two s points below my half size windom.Transmit showed a similar pattern.No efficiency figures for either antenna,just receive and transmit reports.The transceiver used a k3 at 100 watts at the input to the power/swr meter.There are some very fancy loops around at equally fancy prices but it seems to me a loop of copper pipe( 6 or 8mm diameter central heating radiator supply) of 1 meter overall diameter would be a good starting point.I understand that the lest resistance in the loop is paramount and therefore a massive voltage will be across the tuning capacitor which ideally needs to be of the vacuum sort.Either way the loop is resonant over a very narrow band and a being directional,useful to reduce troublesome qrm.As to efficiency,I will leave the calculations to the folks who know.


From: BITX20@groups.io <BITX20@groups.io> on behalf of Jack Purdum via Groups.Io <jjpurdum@...>
Sent: Sunday, June 2, 2019 5:35:38 PM
To: BITX20@groups.io
Subject: Re: [BITX20] Availability of Mag Loop and other stuff...
 
"However taking peoples money with inaccurate or extravagant claims should not be a hobby, though it is often a vocation people pursue."

Taking people's money? I'm not selling anything. My real goal is to get people constrained by HOA's or spouses back on the air.

Jack, W8TEE


On Sunday, June 2, 2019, 12:10:18 PM EDT, ajparent1/KB1GMX <kb1gmx@...> wrote:


Arv,

The problem of online RX or for that fact QRSS and WSPR sites is antenna alignment.
If you antenna is not "aimed" that way the result is it could have been a long path or worse
"off the side".  They do help with "have you been heard" and allows estimating propagation 
in a given direction but comparing A and B antennas requires care for both aim and
time of comparison as propagation is a transient thing.

MY 0.02$ on hobby, it is!  However taking peoples money with inaccurate or
extravagant claims should not be a hobby, though it is often a vocation people
pursue.  When people want to enjoy the hobby and are limited in time and budget
accuracy and good explanation is helpful.  When one expends time and money
on a course of action or material its desirable to understand what the outcome
may be or the limitations.

So every time a new antenna fad hits we have this.  Loops are indeed useful.
They are compact, self contained, and in some cases can help with local noise.
The yabut is they are very narrow band if they are as efficient as possible and
that leads to remote tuning as they are touchy and requiring SWR monitoring.
Being small antennas they are still low gain and therefor not the ultimate radiator. 
However the idea that I can get a loop and conquer the world from my garden
is loaded for disappointment as even the cheapest loop cost hundreds of
dollars and they most expensive ones are not that much better.  I've looked at
commercial loops and they are in the range of 199$ to well over 500$  that is
a lot of money to get an antenna that may be only passable or worse that it
can't work indoors in a building with metallic handicaps (stucco with wire, metal
framing, aluminum siding,  and foil backed insulation).  You have to keep it a
reasonable distance away from the radio so RF problems do not result.

As to building ones own, a good design wants a vacuum variable and they
are NOT cheap.  Air variables of the dual rotor forma can work ok but still
if you have to buy one they are costly.  Also the cap used determines max
power and tuning range as it had to withstand very high voltages even
at QRP levels.

That said if your junk box can full the need its interesting to experiment with Loops.


Allison

Arv Evans
 

Antenna measurements are for the most part relative to some measured reference signal between
the antenna being tested and the remote reception point.  Antenna at the remote reception point
would seem to be immaterial as long as it does not change characteristics during the tests.  In most
antenna test ranges it is the device being tested that is rotated with the received signal at a fixed
point being measured.  This allows measurement and documentation of signal levels at various
angles of radiation.  Rotating or moving the receiving site is not necessary and would probably
invalidate the measurements. 

Small loop antennas are interesting for another reason.  They can be mounted and measured in
either horizontal or vertical position relative to the local ground plane, or at any angle in between. 
This gives one an idea of which propagation angle might be more advantageous, but only an
idea of that.  Propagation at later dates may totally invalidate any reference measurements that
have been made and published. 

My 2 pence worth. 

Arv
_._


On Sun, Jun 2, 2019 at 9:39 AM ajparent1/KB1GMX <kb1gmx@...> wrote:
Jack,

Not showing off, no one is paying for it.  However when someone claims a loop
that 1-2db below a EFHW (or a dipole) that's pretty close to saying my 10 year
old Tacoma can win at Indy.  In short, not likely or the Indy cars had an unusual
handicap, like no fuel and must be pushed by pit crew.   Reality is that the EFHW
is pointed in some random direction relative to the station and the loop is aimed
though its 3db beam width is likely far wider than the EFHW or a standard dipole
at reasonable height.  That makes its aim very wide where a 80-10 EFHW on
40M will at best have a pattern with a beam width that is narrow as its 1
wavelength long.   I can claim and prove my square loop on 6M at 7ft is better
than my portable 6M full wave length rectaangle loop at 25ft  by pointing the
edge of the loop to the station at distance as the front to side is easily 20db
down.  For that I'm at least the same horizontal polarization.  The square loop
under that condition is about 14db better however if the big loop is aligned its
4 db worse.  In short that proves the big loop does really work and also proves
the omnidiriectional square loop is superior when omnidirectional coverage
is required.

In short comparing it to any antenna without some form of controls and claiming
performance is at best meaningless.    A valid compare is a full size vertical with
elevated radials as it will have known gain and similar takeoff angles.

Loops are cool antennas but they are small antennas and they nominally will be
negative gain compared to any dipole.  Its the nature of antenna compromise.

Fyi: the testing part is to show how difficult it is to get meaningful real world
test data with any accuracy at HF because of distances and even local
surface propagation.   Modeled is of value but care must be taken to use a 
model that works with small loops and real grounds (NEC4.2 engine).

As to helpful.  Yes I want people to realize the limits of small antennas and
the claims sometimes made that are against all modeled data and practical
theory never minding prior works done to verify the models.  To that I see a
lot of suppliers and articles for loops making claims like this is the new
better sliced bread.  

I use loops and I do apply them as they have characteristics that make
them useful.  First being they are self contained antennas. The other
feature is the nulls and their insensitivity to close in electrostatic fields.
Its what they are good at even when they are full sized 1lambda loops.

Allison

Ian Reeve
 

Hi Arv,  Very useful information and so useful that they can be used any orientation,they are a option but as my amateur radio course tutor says....you need as much wire in the sky as you can get....as a stating point to good Hf receive.


From: BITX20@groups.io <BITX20@groups.io> on behalf of Arv Evans <arvid.evans@...>
Sent: Sunday, June 2, 2019 6:19:39 PM
To: BITX20@groups.io
Subject: Re: [BITX20] Availability of Mag Loop and other stuff...
 
Antenna measurements are for the most part relative to some measured reference signal between
the antenna being tested and the remote reception point.  Antenna at the remote reception point
would seem to be immaterial as long as it does not change characteristics during the tests.  In most
antenna test ranges it is the device being tested that is rotated with the received signal at a fixed
point being measured.  This allows measurement and documentation of signal levels at various
angles of radiation.  Rotating or moving the receiving site is not necessary and would probably
invalidate the measurements. 

Small loop antennas are interesting for another reason.  They can be mounted and measured in
either horizontal or vertical position relative to the local ground plane, or at any angle in between. 
This gives one an idea of which propagation angle might be more advantageous, but only an
idea of that.  Propagation at later dates may totally invalidate any reference measurements that
have been made and published. 

My 2 pence worth. 

Arv
_._


On Sun, Jun 2, 2019 at 9:39 AM ajparent1/KB1GMX <kb1gmx@...> wrote:
Jack,

Not showing off, no one is paying for it.  However when someone claims a loop
that 1-2db below a EFHW (or a dipole) that's pretty close to saying my 10 year
old Tacoma can win at Indy.  In short, not likely or the Indy cars had an unusual
handicap, like no fuel and must be pushed by pit crew.   Reality is that the EFHW
is pointed in some random direction relative to the station and the loop is aimed
though its 3db beam width is likely far wider than the EFHW or a standard dipole
at reasonable height.  That makes its aim very wide where a 80-10 EFHW on
40M will at best have a pattern with a beam width that is narrow as its 1
wavelength long.   I can claim and prove my square loop on 6M at 7ft is better
than my portable 6M full wave length rectaangle loop at 25ft  by pointing the
edge of the loop to the station at distance as the front to side is easily 20db
down.  For that I'm at least the same horizontal polarization.  The square loop
under that condition is about 14db better however if the big loop is aligned its
4 db worse.  In short that proves the big loop does really work and also proves
the omnidiriectional square loop is superior when omnidirectional coverage
is required.

In short comparing it to any antenna without some form of controls and claiming
performance is at best meaningless.    A valid compare is a full size vertical with
elevated radials as it will have known gain and similar takeoff angles.

Loops are cool antennas but they are small antennas and they nominally will be
negative gain compared to any dipole.  Its the nature of antenna compromise.

Fyi: the testing part is to show how difficult it is to get meaningful real world
test data with any accuracy at HF because of distances and even local
surface propagation.   Modeled is of value but care must be taken to use a 
model that works with small loops and real grounds (NEC4.2 engine).

As to helpful.  Yes I want people to realize the limits of small antennas and
the claims sometimes made that are against all modeled data and practical
theory never minding prior works done to verify the models.  To that I see a
lot of suppliers and articles for loops making claims like this is the new
better sliced bread.  

I use loops and I do apply them as they have characteristics that make
them useful.  First being they are self contained antennas. The other
feature is the nulls and their insensitivity to close in electrostatic fields.
Its what they are good at even when they are full sized 1lambda loops.

Allison

Arv Evans
 

Ian

As much wire in the air as is physically possible is a good approach, as long as one has
many acres of open space to work with.  Loop antennas are effective enough for those of
us with HOA restrictions to get on the air, even if we have to hide the antenna in the attic. 
Loop antenna efficiency does increase with increasing size.  Size versus efficiency is a
trade-off that we sometimes have to live with. 

Small loops can be rotated in a small space and can even be rotated from vertical to
horizontal orientation, and anywhere in between.  Doing that with a 7 wavelength rhombic
antenna on 80 meters may be a little difficult.  8-)

Arv
_._


On Sun, Jun 2, 2019 at 11:34 AM Ian Reeve <ian.radioworkshop@...> wrote:
Hi Arv,  Very useful information and so useful that they can be used any orientation,they are a option but as my amateur radio course tutor says....you need as much wire in the sky as you can get....as a stating point to good Hf receive.


From: BITX20@groups.io <BITX20@groups.io> on behalf of Arv Evans <arvid.evans@...>
Sent: Sunday, June 2, 2019 6:19:39 PM
To: BITX20@groups.io
Subject: Re: [BITX20] Availability of Mag Loop and other stuff...
 
Antenna measurements are for the most part relative to some measured reference signal between
the antenna being tested and the remote reception point.  Antenna at the remote reception point
would seem to be immaterial as long as it does not change characteristics during the tests.  In most
antenna test ranges it is the device being tested that is rotated with the received signal at a fixed
point being measured.  This allows measurement and documentation of signal levels at various
angles of radiation.  Rotating or moving the receiving site is not necessary and would probably
invalidate the measurements. 

Small loop antennas are interesting for another reason.  They can be mounted and measured in
either horizontal or vertical position relative to the local ground plane, or at any angle in between. 
This gives one an idea of which propagation angle might be more advantageous, but only an
idea of that.  Propagation at later dates may totally invalidate any reference measurements that
have been made and published. 

My 2 pence worth. 

Arv
_._


On Sun, Jun 2, 2019 at 9:39 AM ajparent1/KB1GMX <kb1gmx@...> wrote:
Jack,

Not showing off, no one is paying for it.  However when someone claims a loop
that 1-2db below a EFHW (or a dipole) that's pretty close to saying my 10 year
old Tacoma can win at Indy.  In short, not likely or the Indy cars had an unusual
handicap, like no fuel and must be pushed by pit crew.   Reality is that the EFHW
is pointed in some random direction relative to the station and the loop is aimed
though its 3db beam width is likely far wider than the EFHW or a standard dipole
at reasonable height.  That makes its aim very wide where a 80-10 EFHW on
40M will at best have a pattern with a beam width that is narrow as its 1
wavelength long.   I can claim and prove my square loop on 6M at 7ft is better
than my portable 6M full wave length rectaangle loop at 25ft  by pointing the
edge of the loop to the station at distance as the front to side is easily 20db
down.  For that I'm at least the same horizontal polarization.  The square loop
under that condition is about 14db better however if the big loop is aligned its
4 db worse.  In short that proves the big loop does really work and also proves
the omnidiriectional square loop is superior when omnidirectional coverage
is required.

In short comparing it to any antenna without some form of controls and claiming
performance is at best meaningless.    A valid compare is a full size vertical with
elevated radials as it will have known gain and similar takeoff angles.

Loops are cool antennas but they are small antennas and they nominally will be
negative gain compared to any dipole.  Its the nature of antenna compromise.

Fyi: the testing part is to show how difficult it is to get meaningful real world
test data with any accuracy at HF because of distances and even local
surface propagation.   Modeled is of value but care must be taken to use a 
model that works with small loops and real grounds (NEC4.2 engine).

As to helpful.  Yes I want people to realize the limits of small antennas and
the claims sometimes made that are against all modeled data and practical
theory never minding prior works done to verify the models.  To that I see a
lot of suppliers and articles for loops making claims like this is the new
better sliced bread.  

I use loops and I do apply them as they have characteristics that make
them useful.  First being they are self contained antennas. The other
feature is the nulls and their insensitivity to close in electrostatic fields.
Its what they are good at even when they are full sized 1lambda loops.

Allison

iz oos
 

Maybe it would be easier to test if made for the 2m band and compare with a ground plane and a dipole at different heights.
It is interesting the link https://www.lnrprecision.com/store/W4OP-Loop-Antenna-p69633466 which deals with the efficiency of commercial small loops. If you can really obtain a small loop with a 50% efficiency I would be really interested to know more about it.


Il 02/giu/2019 19:20, "Arv Evans" <arvid.evans@...> ha scritto:
Antenna measurements are for the most part relative to some measured reference signal between
the antenna being tested and the remote reception point.  Antenna at the remote reception point
would seem to be immaterial as long as it does not change characteristics during the tests.  In most
antenna test ranges it is the device being tested that is rotated with the received signal at a fixed
point being measured.  This allows measurement and documentation of signal levels at various
angles of radiation.  Rotating or moving the receiving site is not necessary and would probably
invalidate the measurements. 

Small loop antennas are interesting for another reason.  They can be mounted and measured in
either horizontal or vertical position relative to the local ground plane, or at any angle in between. 
This gives one an idea of which propagation angle might be more advantageous, but only an
idea of that.  Propagation at later dates may totally invalidate any reference measurements that
have been made and published. 

My 2 pence worth. 

Arv
_._


On Sun, Jun 2, 2019 at 9:39 AM ajparent1/KB1GMX <kb1gmx@...> wrote:
Jack,

Not showing off, no one is paying for it.  However when someone claims a loop
that 1-2db below a EFHW (or a dipole) that's pretty close to saying my 10 year
old Tacoma can win at Indy.  In short, not likely or the Indy cars had an unusual
handicap, like no fuel and must be pushed by pit crew.   Reality is that the EFHW
is pointed in some random direction relative to the station and the loop is aimed
though its 3db beam width is likely far wider than the EFHW or a standard dipole
at reasonable height.  That makes its aim very wide where a 80-10 EFHW on
40M will at best have a pattern with a beam width that is narrow as its 1
wavelength long.   I can claim and prove my square loop on 6M at 7ft is better
than my portable 6M full wave length rectaangle loop at 25ft  by pointing the
edge of the loop to the station at distance as the front to side is easily 20db
down.  For that I'm at least the same horizontal polarization.  The square loop
under that condition is about 14db better however if the big loop is aligned its
4 db worse.  In short that proves the big loop does really work and also proves
the omnidiriectional square loop is superior when omnidirectional coverage
is required.

In short comparing it to any antenna without some form of controls and claiming
performance is at best meaningless.    A valid compare is a full size vertical with
elevated radials as it will have known gain and similar takeoff angles.

Loops are cool antennas but they are small antennas and they nominally will be
negative gain compared to any dipole.  Its the nature of antenna compromise.

Fyi: the testing part is to show how difficult it is to get meaningful real world
test data with any accuracy at HF because of distances and even local
surface propagation.   Modeled is of value but care must be taken to use a 
model that works with small loops and real grounds (NEC4.2 engine).

As to helpful.  Yes I want people to realize the limits of small antennas and
the claims sometimes made that are against all modeled data and practical
theory never minding prior works done to verify the models.  To that I see a
lot of suppliers and articles for loops making claims like this is the new
better sliced bread.  

I use loops and I do apply them as they have characteristics that make
them useful.  First being they are self contained antennas. The other
feature is the nulls and their insensitivity to close in electrostatic fields.
Its what they are good at even when they are full sized 1lambda loops.

Allison

ajparent1/KB1GMX
 

Jack,

Not aimed at you personally that was a general comment on some of the other loop vendors
that came from nowhere.  After all at this point you not selling anything.  If you telling people
how to do it [book] that's experimental electronics and encouraged.  

As to getting HOA/restricted people back on the air a loop is a possible choice but far from
the only one.  It has potential for a quick trip to the park, hill or other areas where ambient
electrical noise is much lower and its desirable to have minimal setup time.   Usually the
limitation is lack of imagination and maybe understanding of antennas in general.  Antennas
do not have to look like antennas and they can be reasonably efficient with a small amount
of work.  The key element is to look at the box and not be limited by it.  The biggest thing I
see is everyone wants every band even the inactive ones.  Two maybe three bands with a
reasonable antenna is far easier and more likely to be enjoyed.  

And being 10db down from a "good" antenna is not a crime.  I've worked a lot of DX from the
mobile on 40M QRP SSB with a center loaded 8ft whip.  Efficient?  No they are legendary for
being terrible as in easily 10db or more down from a full size vertical.  However the mobile is not
unlike the HOA, we just add it has to work at 80mph and clear a 12.6ft bridge (we have
low ones here!) when mounted on a truck more than 4ft above the road with a crappy
ground (counterpoise maybe?).  

As to commentary on exogenous factors, when you quote dB and people look at it without
understanding or knowledge of those factors it can look better than it is.  Fact is and I
already said that you cannot control the external factors as it would cost dearly, having
done it for MIL applications and budget.

Also I think it was Arv that suggested scaling it for low VHF and that can be done to show if
correlation holds true but its a lot of work to make a scale model and  test it against a vertical
dipole. 

I've done that and it can be close (usually +-1db) and the amount of room needed is a back
yard without metal fences or aluminum siding as reflections will make you nuts. Reflections
can make for errors as in higher or lower gain that should be expected.   The test is RF
source to a vertical dipole and a second dipole at a distance of 10-20M at 2m will do ok
and you get a RX measurement that will be the reference.  Dipoles vertical or horizontal if
resonant are predictable in gain and behavior.  A pair of ELK log periodic antennas would
work well for this, they just have to be the same.  I've used 4 element yagis for 2m and
432 as test antennas as they are simple and easy to make.  In any case directional
antennas  make for fewer issues with weak signals and reflections.    Now substitute the
antenna under test and  get new reading.   How to get an accurate reading is easy, on the
TX side use maybe 20dbm (100mw) and an attenuator to radiate a signal to the RX and
then use the attenuator as adjust the signal to S9. install new antenna at the RX end and after
recording the attenuator before then adjust it for S9 again.  The difference is gain or loss.
A SA can make that easier but any detector can do the job if sensitive enough and has
selectivity to avoid offending signals.  I've used a AD8703 for that with an input tuned
circuit [bandpass] added to keep it from hearing FM broadcast stations.    Don't try this
at HF you will go insane or expend much treasure and going end to end to read or
adjust will wear you out.

Allison