Bob, N1KPR <rwbetts@...> added folder /Broadcast loop - passive
The following files and folders have been uploaded to
the Files area of the [email protected] group.
By: Bob, N1KPR <rwbetts@...>
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searching for a passive receiving shielded loop for medium wave broadcast band
searching for a passive? receiving shielded loop for medium wave broadcast band
have somebody a design?
thanks in advance
rinus
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STLcalc v2.0.5x available
There's more that I want to add to the v2.0.6 update than just the Q calculation fix, mostly related to a configuration panel, plus some additional refinements to improve accuracy.
Rather than wait until the update to v2.0.6, I have corrected the Q calculation in the current version and added an 'x' to the version number. The Dropbox URLs shown on my QRZ.com page () are still good, and only the "executable" file (folder for macOS) needs to be updated.
If you want to try the program, but have not acquired it yet, download the ZIPped package, extract the files, and follow the README instructions.
If you have previously done the installation, do the ZIP download again, but you need only replace the executable file/folder for your system.
When you run the updated program the banner should show STLcalc (v2.0.5x) for <your system>. If you don't see the 'x' it means you're still accessing the original version.
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STLcalc program correction - missing attachments
I guess they're stripping attachments. The two pictures I referenced are now in my Dropbox:
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STLcalc program correction
Thanks to Roger for pointing out the review by Owen Duffy. I have been a fan of his work for a long time and it saddens me that I messed up one item in the recent updates to my program. For a long time I have done parallel development of the program to compare formulas, window layouts, and other aspects of the program design. I left in a factor of 2 in the denominator of the Q calculation that should have been taken out. (Unfortunately it's in the ARRL formula in all recent Antenna Book coverage of small loops.)
An update to version 2.0.6 is in progress.In it I'm adding a menu item to allow configuration of loss resistance values for the tuning capacitor, joints that are soldered or welded, and connections. I have some small values hard-coded in the calculations already, but they are currently my guesses for best conditions, with the expectation that the user will add loss values in the Additional Loss field if they have better estimates of measured values.
The attached picture STLcalc2.0.6_test shows a run (with the corrected Q calculation) using the loop values in Duffy's "Reconciling W5QJR's loop formulas" paper.? The second picture, STLcalc_comparison, is a table I just prepared to show how the program compares to the Hart and Duffy (NEC) results presented in the paper. There is fairly close agreement between NEC and STLcalc now, although there is still room for improvement:
- I may need to add in the ground loss calculation if users need to install loops closer to ground than the suggested one loop physical diameter to the loop center. I have added a loss resistance estimate of 110 mOhms to align with Duffy's loop description.
- The inductance value is a little higher than either of the others, but I'm not sure of the veracity of either of them. My reactance value may or may not account for the self capacitance effect - investigation needed.
- My Q value is a little high, but will be affected by any possible inductance/reactance calculation changes.
- Both BW and peak voltage calculations are affected by Q, but seem to be reasonable. I report peak voltage because that's what damages capacitors if too high, not RMS.
This program is soon to be put on GitHub to enable anyone to offer suggestions, corrections, and possibly programming assistance. I want this to be open sourced so that it can be fixed quickly if errors are found. Today's feedback is an example of that. I'll put the corrected versions of the "executable" bundles for the Windows, Linux, and macOS platforms in my Dropbox as soon as I finish the programing I'm doing now on the configuration option. These will be identified as STLcalc v2.0.6 entries on my QRZ page ().
73,
Gus Hansen
KB0YH
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Re: STLcalc: the missing Linux update message attachments
Owen Duffy has made numerous posts about loop antennas on his site and has developed several loop calculators.? He recently wrote a review of STLcalc 2.05 .
Roger
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Over the past several days I have been asked by some users of my STLcalc program why I have not responded to a rather snarky email to the loopantennas reflector from Jim, AA5CT. For the same reason I don't participate in any popular social media. They're time sinks with the additional unfortunate attribute of producing lots of heat, but little or no light.
Simply put, anyone who receives a reasonable and thoughtful response and uses it as an opportunity for an ad hominem attack deserves to be ignored. Hence forth any AA5CT correspondence will be redirected to /dev/null (Unix talk for the cosmic black hole).
Thanks for the private expressions of support and concern.
Gus Hansen
KB0YH
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Re: Optimizing Small Untuned Loop Antennas
Start of reading Gentry’s paper from page 26 to understand the matching technique proposed. Talking about the radiation efficiency for small antennas the value is low and there is no improvement method unless an antenna preamplifier is used. Only can be improved the mismatch factor caused by Unequal impedances of antenna and the input of your selected amplifier. Regards,
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On Nov 3, 2022, at 10:39 PM, vbifyz <3ym3ym@...> wrote:
?Although Gentry uses the term "matching", I don't see his method optimizing the power transfer or achieving the impedance matching on either end of the network.
It only generates the desired frequency response, with no regard to efficiency.
Unless I am missing something obvious.
73, Mike AF7KR.
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Re: FW: [loopantennas] Optimizing Small Untuned Loop Antennas
Although Gentry uses the term "matching", I don't see his method optimizing the power transfer or achieving the impedance matching on either end of the network.
It only generates the desired frequency response, with no regard to efficiency.
Unless I am missing something obvious.
73, Mike AF7KR.
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Re: FW: [loopantennas] Optimizing Small Untuned Loop Antennas
All,
For an illustrative purpose you may read De Gentry's work about the broadband matching of a loop antenna but the calculated by him filter elements you cannot use because he designed his filters for two extreme conditions either the source and load impedance are 50 ohm or source impedance is 0 ohms and load impedance 50 ohms.
Your small unshielded loop antennas will not have these source impedances, say for a specified bandwidth from 1.6 to 28.75 MHz.
Also, the terminals of your loop antenna probably will be connected to RF transformer, so with VNA you should measure the transformed loop antenna impedance defining the active and reactive components of this impedance in order to use them for further calculation the elements of, say, 5th order Chebyshev BPF with a specified ripple of 3 dB or less in the specified passband.
Regards,
Raphael
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-----Original Message----- From: [email protected] < [email protected]> On Behalf Of Michael.2E0IHW via groups.io Sent: Thursday, November 3, 2022 11:28 AM To: [email protected]Subject: Re: FW: [loopantennas] Optimizing Small Untuned Loop Antennas Thank for the response, Jef. I will follow that link ! Michael 2E0IHW On 03/11/2022 15:16, Jef Verborgt, Contractor, Code 6138 via groups.io wrote: Good morning Michael,
If you google the thesis about" broadband matching of a loop antenna
by De Gentry" you will get a lot of actual filters with values for
the parts and a performance curve for the particular filter. It does
take very little time to build one filter and see for yourself the
results. Understanding the calculations is a bit more difficult but
the practical examples of actual filters should get you going.
Jef
Michael.2E0IHW via groups.io
Sent: Thursday, November 3, 2022 10:57 AM
To: [email protected]
Subject: Re: FW: [loopantennas] Optimizing Small Untuned Loop Antennas
Some of us, maybe only me, would just like to know what works best
and how to build it ...
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Re: FW: [loopantennas] Optimizing Small Untuned Loop Antennas
Thank for the response, Jef.
I will follow that link !
Michael 2E0IHW
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Show quoted text
On 03/11/2022 15:16, Jef Verborgt, Contractor, Code 6138 via groups.io wrote: Good morning Michael,
If you google the thesis about" broadband matching of a loop antenna by De
Gentry" you will get a lot of actual filters with values for the parts and a
performance curve for the particular filter. It does take very little time to
build one filter and see for yourself the results. Understanding the
calculations is a bit more difficult but the practical examples of actual
filters should get you going.
Jef
Michael.2E0IHW via groups.io
Sent: Thursday, November 3, 2022 10:57 AM
To: [email protected]
Subject: Re: FW: [loopantennas] Optimizing Small Untuned Loop Antennas
Some of us, maybe only me, would just like to know what works best and how to
build it ...
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Re: FW: [loopantennas] Optimizing Small Untuned Loop Antennas
Good morning Michael,
If you google the thesis about" broadband matching of a loop antenna by De
Gentry" you will get a lot of actual filters with values for the parts and a
performance curve for the particular filter. It does take very little time to
build one filter and see for yourself the results. Understanding the
calculations is a bit more difficult but the practical examples of actual
filters should get you going.
Jef
toggle quoted message
Show quoted text
-----Original Message----- From: [email protected] < [email protected]> On Behalf Of Michael.2E0IHW via groups.io Sent: Thursday, November 3, 2022 10:57 AM To: [email protected]Subject: Re: FW: [loopantennas] Optimizing Small Untuned Loop Antennas Some of us, maybe only me, would just like to know what works best and how to build it ... Ouch, Michael ...Can you give an example of a passive network that can match a small loop to a 50Ohm load across a wide band? Chris Trask's 2008 paper"Wideband Loop Antenna Matching" is a good
starting point.
rks
The implementation is rather more difficult than the theory.
Regards,
Martin
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Re: FW: [loopantennas] Optimizing Small Untuned Loop Antennas
Some of us,? maybe only me, would just like to know what works best and how to build it ...
Ouch,
Michael
...Can you give an example of a passive network that can match a small loop to a 50Ohm load across a wide band?
toggle quoted message
Show quoted text
Chris Trask's 2008 paper"Wideband Loop Antenna Matching" is a good starting point.
The implementation is rather more difficult than the theory.
Regards,
Martin
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Re: FW: [loopantennas] Optimizing Small Untuned Loop Antennas
For those of you that are interested in matching a small wideband loop antenna there is an interesting article ( actually a thesis ) from 1966. The paper describes the use of a low pass filter that is easy to copy and will give you the advantages and short comings of this approach. You can ?google:” Broadband impedance matching of a loop antenna by De Gentry”. ? . ? Best regards, ? Jef _,_._,_
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Re: FW: [loopantennas] Optimizing Small Untuned Loop Antennas
On Thu, Nov 3, 2022 at 05:10 AM, vbifyz wrote:
Can you give an example of a passive network that can match a small loop to a 50Ohm load across a wide band?
Chris Trask's 2008 paper "Wideband Loop Antenna Matching" is a good starting point.
The implementation is rather more difficult than the theory.
Regards,
Martin
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Re: Optimizing Small Untuned Loop Antennas
Mike, I do not want to sound rude but there are many sources in technical literature where you can find how to calculate elements of broadband filters based on the source and load impedance and required bandwidth.?
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On Nov 3, 2022, at 7:33 AM, Martin via groups.io <martin_ehrenfried@...> wrote:
?On Wed, Nov 2, 2022 at 05:27 PM, Raphael Wasserman wrote:
I assume that by efficiency you mean radiation efficiency, yes. This value is a ratio that is better than zero but less than 1 ( the ratio ?of the radiation resistance to total resistance of antenna losses that includes the radiation resistance plus the ohmic losses of antenna, ?K= R rad/ R rad + R loss ).
Hi Raphael, Thanks for your reply and comments. I need to spend some time reviewing them in order to better understand the points you are making. I think my main problem is differentiating between the use of the terms, radiation efficiency (as you describe), and total antenna efficiency, which includes mismatch losses. Unfortunately these (and other similar terms) tend to be interchanged with each other, especially in on-line postings, and I think this has added to the confusion. As mismatch losses are frequently the major contributor to 'real life' antenna efficiency, it does make me wonder if the percentage values we frequently see in loop calculators refer to radiation efficiency, or total antenna efficiency. Regards, Martin
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Re: Optimizing Small Untuned Loop Antennas
On Wed, Nov 2, 2022 at 05:27 PM, Raphael Wasserman wrote:
I assume that by efficiency you mean radiation efficiency, yes. This value is a ratio that is better than zero but less than 1 ( the ratio ?of the radiation resistance to total resistance of antenna losses that includes the radiation resistance plus the ohmic losses of antenna, ?K= R rad/ R rad + R loss ).
Hi Raphael, Thanks for your reply and comments. I need to spend some time reviewing them in order to better understand the points you are making. I think my main problem is differentiating between the use of the terms, radiation efficiency (as you describe), and total antenna efficiency, which includes mismatch losses. Unfortunately these (and other similar terms) tend to be interchanged with each other, especially in on-line postings, and I think this has added to the confusion. As mismatch losses are frequently the major contributor to 'real life' antenna efficiency, it does make me wonder if the percentage values we frequently see in loop calculators refer to radiation efficiency, or total antenna efficiency. Regards, Martin
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Re: FW: [loopantennas] Optimizing Small Untuned Loop Antennas
Hi Raphael,
This sounds very interesting. Can you give an example of a passive network that can match a small loop to a 50Ohm load across a wide band?
Even matching on 2 amateur bands with the same network would be of great practical interest.
73, Mike AF7KR
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FW: [loopantennas] Optimizing Small Untuned Loop Antennas
Hi Martin, ? The second part of our discussion – the ?mismatch loss that gets defined differently as: ? t (tau) = 4 ( R rad + R loss ) x R load/ | Z antenna + Z load |^2 ? Here we have an option for a single frequency of interest, for example conjugate the reactance of antenna with the ?load then we will deal only with active resistances ??????????????????????R rad, R loss ?and R load and the mismatch equation will be different: ? t= 4 ( R rad +R loss ) x R load / ( R rad + R loss + R load ) ^ 2, assuming that R rad << R loss for small antennas, we will get ? t= 4 R load x R loss/ (R loss +R load )^2 and using RF transformer to achieve a condition R loss = R load then we will achieve ?for a single frequency of interest t =1 – complete matching condition. ? This matching example can be practically achieved only at one frequency not for a broadband application ! In a broadband case ?( from LF to SW ) shall be used a high order band pass filters or other type of filtering network between the antenna and the load and more complex calculations are involved in this case. ? Raphael ? ?
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From: wassermanr46@... <wassermanr46@...> Sent: Wednesday, November 2, 2022 1:28 PM To: [email protected]Subject: RE: [loopantennas] Optimizing Small Untuned Loop Antennas ? I hope I did not create more confusion… ? ? Hi Raphael,
Can you confirm the following statements, in order to improve my understanding of some basic concepts.
I assume that by efficiency you mean radiation efficiency, yes. This value is a ratio that is better than zero but less than 1 ( the ratio ?of the radiation resistance to total resistance of antenna losses that includes the radiation resistance plus the ohmic losses of antenna, ?K= R rad/ R rad + R loss ). For any small passive antennas either loop or dipoles to compensate the low radiation efficiency and subsequent the ?antenna gain are used antenna amplifiers.
The Radiation resistance does not change between a tuned and un-tuned loop of the same dimensions and construction. The radiation resistance is given by R rad.= 31200 x (NxA / wavelength of interest^2) ^2
N – number of turns, A=pi x ( D/2)^2 ,where D is diameter of loop. See all my corrections in red (RW). Increasing the number of turns on a loop will increase its Radiation Resistance, but this will “ be offset by increased losses” ? ( there shall be involved calculations/estimates for both the radiation resistance and ohmic losses of antenna to drive a proper conclusion for the radiation efficiency value. Increasing the number of turns on loop will increase its Radiation Resistance as well as the? ohmic losses of the loop antenna. There is other formula to estimate the ohmic loss of loop antenna: R l = Rhf x ( Rp x l /Rhf +1 ), where Rhf = l/p x Rs – high-frequency resistance , where l=length of loop wire, p=perimeter of the wire’s cross-section and Rs- surface resistance due to the skin-effect In turn, ?Rs= sqrt ( pi x f x m/ s ), where f – frequency of interest, m ( mu ) - magnetic? permeability and s (sigma ) – wire material conductivity Rp – resistance increase due to proximity effect, this should be considered for multiturn loop antennas (RW).
The difference in radiation efficiency between a tuned and untuned loop, is simply due to mismatch losses, as all other losses must remain the same between t
Radiation efficiency would be the same as the total antenna efficiency if there was no loss due to impedance mismatch ?? Impedance mismatch is between antenna and its load ( load could be the input of antenna amplifier or receiver input ) and it has nothing to do with the radiation efficiency. By Improvement of impedance mismatch gets optimized the signal power transfer from antenna to the load. In order to improve the radiation efficiency should ?either be used a full size antenna or (in case of active antenna ) antenna amplifier ( for radio ?receiving applications ) ? ? If a narrow band matching network is added to an untuned antenna, in order to minimise mismatch losses at a specific frequency (effectively becoming a tuned antenna), the radiation efficiency is improved.
Again, the radiation efficiency will not be improved ( follow through all equations that estimate miscellaneous antenna active losses and radiation resistance as well ) but the impedance matching will improve the signal power transfer to the load.
The Q factor (and therefore bandwidth) of the matched antenna is an indicator of the radiation efficiency. Q-factor is not an indicator of antenna radiation efficiency but an indicator of antenna gain indirect improvement because the gain is a function of radiation efficiency and Q-factor as two undependable values that effect antenna gain.
This older thread my be of relevance regarding Antenna Factor.
/g/loopantennas/topic/70230511
Specifically the link to
Regards,
Martin
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Re: Optimizing Small Untuned Loop Antennas
I hope I did not create more confusion… ?
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From: [email protected] < [email protected]> On Behalf Of Martin via groups.io Sent: Wednesday, November 2, 2022 6:39 AM To: [email protected]Subject: Re: [loopantennas] Optimizing Small Untuned Loop Antennas ? Hi Raphael,
Can you confirm the following statements, in order to improve my understanding of some basic concepts.
I assume that by efficiency you mean radiation efficiency, yes. This value is a ratio that is better than zero but less than 1 ( the ratio ?of the radiation resistance to total resistance of antenna losses that includes the radiation resistance plus the ohmic losses of antenna, ?K= R rad/ R rad + R loss ). For any small passive antennas either loop or dipoles to compensate the low radiation efficiency and subsequent the ?antenna gain are used antenna amplifiers.
The Radiation resistance does not change between a tuned and un-tuned loop of the same dimensions and construction. The radiation resistance is given by R rad.= 31200 x (NxA / wavelength of interest^2) ^2
N – number of turns, A=pi x ( D/2)^2 ,where D is diameter of loop. See all my corrections in red (RW). Increasing the number of turns on a loop will increase its Radiation Resistance, but this will “ be offset by increased losses” ? ( there shall be involved calculations/estimates for both the radiation resistance and ohmic losses of antenna to drive a proper conclusion for the radiation efficiency value. Increasing the number of turns on loop will increase its Radiation Resistance as well as the? ohmic losses of the loop antenna. There is other formula to estimate the ohmic loss of loop antenna: R l = Rhf x ( Rp x l /Rhf +1 ), where Rhf = l/p x Rs – high-frequency resistance , where l=length of loop wire, p=perimeter of the wire’s cross-section and Rs- surface resistance due to the skin-effect In turn, ?Rs= sqrt ( pi x f x m/ s ), where f – frequency of interest, m ( mu ) - magnetic? permeability and s (sigma ) – wire material conductivity Rp – resistance increase due to proximity effect, this should be considered for multiturn loop antennas (RW).
The difference in radiation efficiency between a tuned and untuned loop, is simply due to mismatch losses, as all other losses must remain the same between t
Radiation efficiency would be the same as the total antenna efficiency if there was no loss due to impedance mismatch ?? Impedance mismatch is between antenna and its load ( load could be the input of antenna amplifier or receiver input ) and it has nothing to do with the radiation efficiency. By Improvement of impedance mismatch gets optimized the signal power transfer from antenna to the load. In order to improve the radiation efficiency should ?either be used a full size antenna or (in case of active antenna ) antenna amplifier ( for radio ?receiving applications ) ? ? If a narrow band matching network is added to an untuned antenna, in order to minimise mismatch losses at a specific frequency (effectively becoming a tuned antenna), the radiation efficiency is improved.
Again, the radiation efficiency will not be improved ( follow through all equations that estimate miscellaneous antenna active losses and radiation resistance as well ) but the impedance matching will improve the signal power transfer to the load.
The Q factor (and therefore bandwidth) of the matched antenna is an indicator of the radiation efficiency. Q-factor is not an indicator of antenna radiation efficiency but an indicator of antenna gain indirect improvement because the gain is a function of radiation efficiency and Q-factor as two undependable values that effect antenna gain.
This older thread my be of relevance regarding Antenna Factor.
/g/loopantennas/topic/70230511
Specifically the link to
Regards,
Martin
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Augie "Gus" Hansen
Roger Need