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Re: Measuring S11 or frequency range of an active SRL
Thank you Mike!
I found an article about measuring the difference of the mounting height of SMLs using existing signals from 77 kHz to 28 MHz here:
Would you pls. point me to the LZ1AQ setup with test transmitter in the far field?
Could I perhaps also use my NanoVNA for this purpose (then S21) by connecting the SML to one (receiving) port and a small coil to the other VNA port (transmitting)?
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Re: Measuring S11 or frequency range of an active SRL
Hi Dirk,
They way I have done it in the past whilst trying to optimise loop and loop amplifier setups, was to place a small loop (as small as possible) within the main loop, and feed the small loop via a 3dB attenuator (to keep the signal source happy) and then sweep the overall loop response.
Although this is not the same as the far field response, it does seem to produce a very close approximation to the actual performance.
This is the sort of plot you can obtain.
Regards,
Martin
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Re: Measuring S11 or frequency range of an active SRL
The proper way would be to set up a calibrated test transmitter in the far field zone and sweep its frequency. You can read how LZ1AQ did it on his website.
The gain (or more correctly, antenna factor) variation across the wide range will be way more than 3dB, more like 30dB. But it is still an interesting experiment.
73, Mike AF7KR
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Measuring S11 or frequency range of an active SRL
Perhaps a silly question:
What is the best way to measure the frequency range of an active SRL?
I have built a 1m diameter loop with 10mm^2 copper with a NE592 amplifier.
First tests show, that it works good from VLF to middle VHF.
But I would like to measure the frequency range (-3dB).
I have no very special equipment. What I could use: a NanoVNA, a signal generator from 10 kHz to 30 MHz (no sweeping function), some SDR receivers ...
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Re: STLcalc: the missing Linux update message attachments
Joe, ? Let me add my five cents to your explanation. Any small antennas when their sizes ?( either the loop antenna perimeter or the length of dipole antenna ) are physically small, say ten times of wavelength of interest, are considered electrically small antennas ( loop ?or dipole antennas ) which ?have low radiation resistance ?and non-compensated reactance. These factors shall be taken in account regardless you deal with a broadband or narrowband antenna. However, for narrowband antenna is much easier to match up or compensate for reactance and ¡°resistiveness¡± caused by antenna. ? Regards, ? Raphael ? ? ?
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From: [email protected] < [email protected]> On Behalf Of VE7VXO Sent: Tuesday, November 8, 2022 7:45 PM To: [email protected]Subject: Re: [loopantennas] 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
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
Hello VE7VXO.
I have a doubt regarding the losses you mention, which, I understand, are on the transmission with this type of antennas.
But, this type of losses like the ones you mention in point 1 and point 2, (failures in loop connections, dielectric losses, etc.) also affect the reception performance?
?
I always had this doubt, in practice it seems that it does not affect (at least not in a perceptible way).
?
Thanks in advance.
Federico LW7DFM
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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
Take a look at my project here: /g/loopantennas/files/AF7KR%20projects/Two%20turn%20shielded%20loopIt is 100% shielded and 100% balanced (which may make some difference in null depth, but I didn't notice any). I am more interested in HF, and this loop rolls off above 3MHz, so I didn't play with it much. 1m diameter works very well on AM BCB, may work fine on LW too. The cable is RG-6Q. The preamp is LZ1AQ clone. 73, Mike AF7KR
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Re: searching for a passive receiving shielded loop for medium wave broadcast band
Oh, yes..... I also have a 1-Meter diameter of 0.5" copper tubing loop which is tuned and I occasionally use it for transmitting during the peak of lightning season.? The Q is extremely high.? 2:1 SWR bandwidth on 40-Meters is about 5 to 6 kHz!? I could potentially run a spark transmitter to that loop without ever violating energy outside the band!!??
Dave - W?LEV
Shielded untuned loops are easy to build and far less expensive than buying one ready-made.? I have two which I built:? 1)? A 2-Meter diameter 2" copper pipe with three internal turns and 2) A 0.5-Meter diameter 0.5" copper tubing with five internal turns which I use for DFing.? The nulls are extremely sharp on the small loop!? The larger loop is mounted up on the hillside just to our east and is used pretty much for VLF/ELF receive.
Again, really simple to build.? Just pay attention to symmetry.
Dave - W?LEV?
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:
- ??
- Youtube: N1KPR
- Youtube: Ham Radio Doctor
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 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
- ??
- Youtube: N1KPR
- Youtube: Ham Radio Doctor
Engineering, where enigma meets paradox
On Sunday, November 6, 2022 at 04:47:58 AM EST, rinus nienhuis via <dridotcom3= [email protected]> wrote:
searching for a passive? receiving shielded loop for medium wave broadcast band
have somebody a design?
thanks in advance
rinus
--
Dave - W?LEV
Just Let Darwin Work
-- Dave - W?LEV
Just Let Darwin Work
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Re: searching for a passive receiving shielded loop for medium wave broadcast band
Shielded untuned loops are easy to build and far less expensive than buying one ready-made.? I have two which I built:? 1)? A 2-Meter diameter 2" copper pipe with three internal turns and 2) A 0.5-Meter diameter 0.5" copper tubing with five internal turns which I use for DFing.? The nulls are extremely sharp on the small loop!? The larger loop is mounted up on the hillside just to our east and is used pretty much for VLF/ELF receive.
Again, really simple to build.? Just pay attention to symmetry.
Dave - W?LEV?
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:
- ??
- Youtube: N1KPR
- Youtube: Ham Radio Doctor
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 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
- ??
- Youtube: N1KPR
- Youtube: Ham Radio Doctor
Engineering, where enigma meets paradox
On Sunday, November 6, 2022 at 04:47:58 AM EST, rinus nienhuis via <dridotcom3= [email protected]> wrote:
searching for a passive? receiving shielded loop for medium wave broadcast band
have somebody a design?
thanks in advance
rinus
-- Dave - W?LEV
Just Let Darwin Work
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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:
- ??
- Youtube: N1KPR
- Youtube: Ham Radio Doctor
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
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
- ??
- Youtube: N1KPR
- Youtube: Ham Radio Doctor
Engineering, where enigma meets paradox
On Sunday, November 6, 2022 at 04:47:58 AM EST, rinus nienhuis via <dridotcom3= [email protected]> 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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Re: searching for a passive receiving shielded loop for medium wave broadcast band
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
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
- ??
- Youtube: N1KPR
- Youtube: Ham Radio Doctor
Engineering, where enigma meets paradox
On Sunday, November 6, 2022 at 04:47:58 AM EST, rinus nienhuis via <dridotcom3= [email protected]> 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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Re: searching for a passive receiving shielded loop for medium wave broadcast band
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Re: searching for a passive receiving shielded loop for medium wave broadcast band
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Re: searching for a passive receiving shielded loop for medium wave broadcast band
Great Bob
where can i find it?
Regards
rinus
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Re: FW: [loopantennas] Optimizing Small Untuned Loop Antennas
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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: FW: [loopantennas] Optimizing Small Untuned Loop Antennas
Jef, the link does not work.? Is there another way to view the article?? ?Dave? K2ZU
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Dirk
VE7VXO
Bob, N1KPR
Steven Greenfield AE7HD