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Re: STLcalc: the missing Linux update message attachments
Hi Frederico
The losses impact the antenna's efficiency which is a reciprocal thing ie it affects both TX and RX, however on RX we often use very low efficiency antennas, especially when we want a broad band antenna, if it is small it is automatically inefficient (if it is broad band), but the thing is modern recievers have excess gain for HF especially the low end of HF so we can disregard the efficiency problem for RX as long as noise level increases when the antenna is connected.? Of course a highly efficient antenna will always bring stronger signals but you get the point. Best regards...Joe |
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Re: STLcalc: the missing Linux update message attachments
"Here is a discussion where the Kraus equation has been found to be incorrect in yielding the loop feedpoint Z."?? - quoting AA5CT
Kraus calculation is not wrong.? The poster has made an unfortunate error.? Respectfully, it is naive to think that since a transformer can be made to obtain a 50 ohm match with a given turns ratio, that the resulting resistance reflected across the transformer (in this case roughtly 22 ohms) is therefore the radiation resistance of the antenna.? The impedance at the match point is a combination of things and if resonant it is still the combination of many sources of resistance all rolled together as an apparent match resistance.? So, to list these, and this is probably not an exhaustive list, they include; 1. Construction losses: ie mechanical connections on the loop conductor and to the tuning capacitor, dielectric losses in the capacitor, core and conductor losses in the transformer, radiator conductor loss which is determined by material type and skin depth at the operating frequency. etc. etc. 2. Losses from energy coupled into lossy earth and nearby lossy conductors in the near field of the antenna.? This can easily be observed and I have seen it with earth which goes from thaw to frozen and back to thaw where the resonant match changed due to freezing and returned to the previous value in spring. Proof? for anyone who suggests that so called magnetic loops are not subject to ground losses, that the truth is otherwise. Similarly, if you use collapsible poles to raise/lower the antenna the match and therefore turns ratio needed will be seen to change.? This is ground loss rolled into the match. 3. Radiation resistance.? This is a function of the enclosed area of the loop and can be mathematically calculated and is independent of the feed method and point along the antenna which is chosen for feeding energy into the antenna which was claimed in error by Ben Eddington G0CWT |
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Re: searching for a passive receiving shielded loop for medium wave broadcast band
Hi Fred; It's non-resonant so it acts like the secondary of an air-core transformer. I had a 48" version for LOWFER work (136 and 472 KHz), but really couldn't see enough signal gain to account for the bigger size. Also monitored Cutler (Maine)signals around 24KHz here in Connecticut (W-J8711). I'm currently using an old Rockwell-Collins RDF 650 Aircraft receiver for LOWFER 472. One of the projects is here:
Engineering, where enigma meets paradox
On Monday, November 7, 2022 at 11:01:51 AM EST, Fred Moore <n40cla@...> wrote:
Good morning Bob, Do you possibly have the same design for 100khz - 500khz?? Basically I think the only difference would be the wire length and maybe the loop diameter.? Thanks Fred - N4CLA On Sun, Nov 6, 2022, 11:58 Bob, N1KPR via <rwbetts=[email protected]> wrote:
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Re: FW: [loopantennas] Optimizing Small Untuned Loop Antennas
On Thu, Nov 3, 2022 at 07:45 AM, Jef Verborgt, Contractor, Code 6138 wrote:
.Remove the underscore at the end and it works. ? -- Steve Greenfield AE7HD |
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Re: searching for a passive receiving shielded loop for medium wave broadcast band
I uploaded a triple shield passive loop that is a common monitor antenna for b'cast stations. I use it with a 15-20dB preamp for home entertainment. That gives a signal strength equal to my 160-meter dipole but much quieter. Great for AM DXing. Bob, N1KPR
Engineering, where enigma meets paradox
On Sunday, November 6, 2022 at 04:47:58 AM EST, rinus nienhuis via groups.io <dridotcom3@...> wrote:
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. |
VE7VXO
Bob, N1KPR
Steven Greenfield AE7HD
Augie "Gus" Hansen