|
Greetings.? I am a frequent "lurker" and very infrequent "poster" to this forum, my interest is primarily MW.? I usually use a 1m diameter resonant loop and am puzzled as to why resonant loops seem to be out of favor with most of the group members.? The resonant peak provides both "free", noiseless gain to the signal of interest while also rejecting signals at frequencies other than resonance, eliminating the need for high second- and third-order intercept performance.? Granted the broadband loops that are much discussed on the forum can acquire broad swaths of the RF spectrum essentially simultaneously, is this a significant advantage given the fact that the frequency of the signal of interest is known?
?
Would someone please discuss the advantages of the broadband loop over a resonant one, have I missed something??
?
Thanks
?
JohnT
|
I make overnight recordings of the NDB band, 200-530KHz. I need a broadband response to do that.
Tony
AD0VC
toggle quoted message
Show quoted text
Greetings.? I am a frequent "lurker" and very infrequent "poster" to this forum, my interest is primarily MW.? I usually use a 1m diameter resonant loop and am puzzled as to why resonant loops seem to be out of favor with most of the group members.? The
resonant peak provides both "free", noiseless gain to the signal of interest while also rejecting signals at frequencies other than resonance, eliminating the need for high second- and third-order intercept performance.? Granted the broadband loops that are
much discussed on the forum can acquire broad swaths of the RF spectrum essentially simultaneously, is this a significant advantage given the fact that the frequency of the signal of interest is known?
?
Would someone please discuss the advantages of the broadband loop over a resonant one, have I missed something??
?
Thanks
?
JohnT
|
On Sat, Jan 25, 2025 at 08:17 AM, JohnT wrote:
I usually use a 1m diameter resonant loop and am puzzled as to why resonant loops seem to be out of favor with most of the group members.?
? Is this a multi turn 1M resonate loop? Do you have a tuning capacitor? What is the frequency range of your loop?
?
???????????????????????????????????????????????????????? Mikek
|
Yes, the frequencies of our targets may be known.? For loops my interests range from the Schumann Resonance around 7 Hz plus harmonics to roughly 2 to 4 MHz.? Tuned loops have an extremely high-Q.? For example, while using my 1-meter diameter tuned loop for transmit on 40-meters (7 MHz), my 2:1 SWR bandwidth is only some 6 to 8 kHz wide.? Beyond that on receive, I can easily detect its rapid response falloff. ??
Most of us are not after a single frequency as mentioned with the NDB band.? Even with AM BCB "DX'ing", a tuned loop would yield single-station tuning.? The loop would have to be re-resonated every 10 kHz (the AM BCB frequency spacing in the US).??
Dave - W?LEV?
Greetings.? I am a frequent "lurker" and very infrequent "poster" to this forum, my interest is primarily MW.? I usually use a 1m diameter resonant loop and am puzzled as to why resonant loops seem to be out of favor with most of the group members.? The resonant peak provides both "free", noiseless gain to the signal of interest while also rejecting signals at frequencies other than resonance, eliminating the need for high second- and third-order intercept performance.? Granted the broadband loops that are much discussed on the forum can acquire broad swaths of the RF spectrum essentially simultaneously, is this a significant advantage given the fact that the frequency of the signal of interest is known?
?
Would someone please discuss the advantages of the broadband loop over a resonant one, have I missed something??
?
Thanks
?
JohnT
|
In the past, many of us heard great MW DX with a tuned loop next to the receiver.? However, such a loop now would be likely to hear only local electrical noise from house wiring, wouldn't it?? That's pretty much all that mine can hear now.
If one has some property, it may be possible to put a tuned loop away from the house, but protected from the weather, and tuned with a varicap diode, which itself may affect loop Q.? But, then one loses the ability to turn the loop to null interfering stations on the chosen channel, which was another advantage of the indoor tuned loop.
Others have mentioned the necessity of a wide band loop for SDR recordings, but if one can live with a single tuned channel, is there any advantage to a tuned over an untuned loop?? That is, can something be heard on one but not the other?? ?I did try a remotely tuned Kiwa loop vs. a Flag antenna on trans-Arctic signals here, and didn't find any advantage, but the testing was not exhaustive.? ?Something more to add to the list, I guess.
best wishes,
Nick
?
On Sat, 25 Jan 2025 08:17:14 -0800, "JohnT via groups.io" <jtstein46@...> wrote:
?
Greetings.? I am a frequent "lurker" and very infrequent "poster" to this forum, my interest is primarily MW.? I usually use a 1m diameter resonant loop and am puzzled as to why resonant loops seem to be out of favor with most of the group members.? The resonant peak provides both "free", noiseless gain to the signal of interest while also rejecting signals at frequencies other than resonance, eliminating the need for high second- and third-order intercept performance.? Granted the broadband loops that are much discussed on the forum can acquire broad swaths of the RF spectrum essentially simultaneously, is this a significant advantage given the fact that the frequency of the signal of interest is known?
?
Would someone please discuss the advantages of the broadband loop over a resonant one, have I missed something??
?
Thanks
?
JohnT
|
After many hours of experimentation I settled on a tuned loop for the family room entertainment feed; news, traffic and weather. I'm using an old W-J 8711 demo/loaner unit that's quite beat up, but works as expected. As I mentioned in an earlier post, I have recorded signal strengths from either an 80-meter vertical or the 160-meter wire at 35 feet. So I can gauge from the known antennas and the known AM b'casters as to what levels I should need to get. The tuned loop is about 35 feet from the house and was on a cheap rotator (now broken) and feeding a bias-tee to a variactor (BB112). With the 330uH loop and the diode tuning I can cover 500kHz thru 2MHz. I generally have the loop toward NYC which is directly SW from here. To reorient the loop I use an "Armstrong rotator." That means I need to go outside and turn it myself. East for New Haven and RI, NNE for Hartford/Boston and the SW for NYC The tuned loop feeds me a much better diet that the Mobius or other homebrew loops. As was mentioned, the tuned loop is limited as to what the diode can cover to resonate the 330uH loop. In the evening, I switch to the Pixel Pro for International stuff, also on a cheap rotator (this one still works). My point is that the tuned loop is about 18dB below the 160 wire and about 22-24dB below the vertical 80, but with significantly less noise. With a preamp (LNA) I can boost the loops up to the Ham antenna's strength. But, that gets to be a feel-good situation, since the QRN/QRM is also amplified.
Added note: A good DSP Noise Reduction device (I use BHI) can make life a lot more enjoyable, especially for long-term listening.
gud sigs to all, 73,
Bob, N1KPR
-
- Youtube: N1KPR
- Youtube: Ham Radio Doctor
Engineering, where enigma meets paradox
On Saturday, January 25, 2025 at 01:24:59 PM EST, Nick Hall-Patch <nhp@...> wrote:
In the past, many of us heard great MW DX with a tuned loop next to the receiver.? However, such a loop now would be likely to hear only local electrical noise from house wiring, wouldn't it?? That's pretty much all that mine can hear now.
If one has some property, it may be possible to put a tuned loop away from the house, but protected from the weather, and tuned with a varicap diode, which itself may affect loop Q.? But, then one loses the ability to turn the loop to null interfering stations on the chosen channel, which was another advantage of the indoor tuned loop.
Others have mentioned the necessity of a wide band loop for SDR recordings, but if one can live with a single tuned channel, is there any advantage to a tuned over an untuned loop?? That is, can something be heard on one but not the other?? ?I did try a remotely tuned Kiwa loop vs. a Flag antenna on trans-Arctic signals here, and didn't find any advantage, but the testing was not exhaustive.? ?Something more to add to the list, I guess.
best wishes,
Nick
?
On Sat, 25 Jan 2025 08:17:14 -0800, "JohnT via groups.io" <jtstein46@...> wrote:
?
Greetings.? I am a frequent "lurker" and very infrequent "poster" to this forum, my interest is primarily MW.? I usually use a 1m diameter resonant loop and am puzzled as to why resonant loops seem to be out of favor with most of the group members.? The resonant peak provides both "free", noiseless gain to the signal of interest while also rejecting signals at frequencies other than resonance, eliminating the need for high second- and third-order intercept performance.? Granted the broadband loops that are much discussed on the forum can acquire broad swaths of the RF spectrum essentially simultaneously, is this a significant advantage given the fact that the frequency of the signal of interest is known?
?
Would someone please discuss the advantages of the broadband loop over a resonant one, have I missed something??
?
Thanks
?
JohnT
|
With receive antennas, Signal To Noise is the important factor, and not absolute signal strength.
?
However, it's very easy to be fooled into thinking that a weaker signal has a subjectively better Signal to Noise Ratio than a stronger signal, because the background noise drops below our hearing "threshold", or may be masked by "smoother" sounding internal noise from the receiver itself.
?
It's a psychoacoustic phenomenon, which can be emulated by increasing attenuation ahead of a receiver.
?
In an urban environment, it's most likely that the local noise floor will be the limiting factor, and you won't notice any difference between a narrowband passive tuned loop, or a similar sized broadband active loop. It's only when you get out into the countryside, with a very low noise floor, that you may observe some differences, but even then a decent broadband active loop will most likely be adequate.
?
Regards,
?
Martin
?
?
On Sat, Jan 25, 2025 at 06:58 PM, Bob, N1KPR wrote:
My point is that the tuned loop is about 18dB below the 160 wire and about 22-24dB below the vertical 80, but with significantly less noise
|
Hi Bob, I like
messing with tuned loops as well. It was with Bertha (my first
multi-turn tuned loop) that I was able to hear my first LWBC
transmissions after several years of trying with numerous full
sized V's and verticals.
One thing that you mentioned that sparked my attention was your
use of a dsp noise canceller. My only experience with them has
been the canned NR on box rigs like the FT-1000, etc. I never did
find any settings that I thought I could tolerate longer than a
few minutes and I never really thought they did much good other
than make the audio sould like it coming from outer space. Do you
by chance have a short video demonstrating the effectiveness of
your NR in action?? If not even a 2-3 minute cell phone video
uploaded to YT or to Google drive, dropbox etc. Would love to see
an effective noise canceller/reducer in action esp during distant
lightning strikes at night.? 73
Gedas, W8BYA EN70JT
Light travels faster than sound.....
This is why some people appear bright until you hear them speak.
On 1/25/2025 1:58 PM, Bob, N1KPR via
groups.io wrote:
toggle quoted message
Show quoted text
After many hours of
experimentation I settled on a tuned loop for the family
room entertainment feed; news, traffic and weather.
I'm using an old W-J 8711
demo/loaner unit that's quite beat up, but works as
expected. As I mentioned in an earlier post, I have recorded
signal strengths from either an 80-meter vertical or the
160-meter wire at 35 feet. So I can gauge from the known
antennas and the known AM b'casters as to what levels I
should need to get. The tuned loop is about 35 feet from the
house and was on a cheap rotator (now broken) and feeding a
bias-tee to a variactor (BB112). With the 330uH loop and the
diode tuning I can cover 500kHz thru 2MHz. I generally have
the loop toward NYC which is directly SW from here. To
reorient the loop I use an "Armstrong rotator." That means I
need to go outside and turn it myself. East for New Haven
and RI, NNE for Hartford/Boston and the SW for NYC
The tuned loop feeds me a
much better diet that the Mobius or other homebrew loops. As
was mentioned, the tuned loop is limited as to what the
diode can cover to resonate the 330uH loop.
In the evening, I switch to
the Pixel Pro for International stuff, also on a cheap
rotator (this one still works).
My point is that the tuned
loop is about 18dB below the 160 wire and about 22-24dB
below the vertical 80, but with significantly less noise.
With a preamp (LNA) I can boost the loops up to the Ham
antenna's strength. But, that gets to be a feel-good
situation, since the QRN/QRM is also amplified.
Added note: A good DSP
Noise Reduction device (I use BHI) can make life a lot more
enjoyable, especially for long-term listening.
gud sigs to all,
73,
Bob, N1KPR
-
- Youtube: N1KPR
- Youtube: Ham Radio Doctor
Engineering, where enigma meets paradox
On Saturday, January 25, 2025 at 01:24:59 PM EST, Nick
Hall-Patch <nhp@...> wrote:
In the past, many
of us heard great MW DX with a tuned loop next to the
receiver.? However, such a loop now would be likely to
hear only local electrical noise from house wiring,
wouldn't it?? That's pretty much all that mine can
hear now.
If one has some property, it may be possible to put a
tuned loop away from the house, but protected from the
weather, and tuned with a varicap diode, which itself
may affect loop Q.? But, then one loses the ability to
turn the loop to null interfering stations on the
chosen channel, which was another advantage of the
indoor tuned loop.
Others have mentioned the necessity of a wide band
loop for SDR recordings, but if one can live with a
single tuned channel, is there any advantage to a
tuned over an untuned loop?? That is, can something be
heard on one but not the other?? ?I did try a remotely
tuned Kiwa loop vs. a Flag antenna on trans-Arctic
signals here, and didn't find any advantage, but the
testing was not exhaustive.? ?Something more to add to
the list, I guess.
best wishes,
Nick
?
On Sat, 25 Jan 2025 08:17:14 -0800, "JohnT via
groups.io" <jtstein46@...>
wrote:
?
Greetings.? I am a frequent "lurker" and very
infrequent "poster" to this forum, my interest is
primarily MW.? I usually use a 1m diameter resonant
loop and am puzzled as to why resonant loops seem to
be out of favor with most of the group members.? The
resonant peak provides both "free", noiseless gain
to the signal of interest while also rejecting
signals at frequencies other than resonance,
eliminating the need for high second- and
third-order intercept performance.? Granted the
broadband loops that are much discussed on the forum
can acquire broad swaths of the RF spectrum
essentially simultaneously, is this a significant
advantage given the fact that the frequency of the
signal of interest is known?
?
Would someone please discuss the advantages of
the broadband loop over a resonant one, have I
missed something??
?
Thanks
?
JohnT
|
Bob,
?
One of the major reasons to use a Broadband Loop vs a Tuned Loop, is that most people these day are using SDR? Receivers, with some being able to see up to 24MHz of bandwidth, at one time. Using a Tune Loop would greatly restrict the visible signals.
?
Everett N4CY
In a message dated 1/25/2025 1:34:57 PM Central Standard Time, w8bya@... writes:
?
Hi Bob, I like messing with tuned loops as well. It was with Bertha (my first multi-turn tuned loop) that I was able to hear my first LWBC transmissions after several years of trying with numerous full sized V's and verticals.
One thing that you mentioned that sparked my attention was your use of a dsp noise canceller. My only experience with them has been the canned NR on box rigs like the FT-1000, etc. I never did find any settings that I thought I could tolerate longer than a few minutes and I never really thought they did much good other than make the audio sould like it coming from outer space. Do you by chance have a short video demonstrating the effectiveness of your NR in action?? If not even a 2-3 minute cell phone video uploaded to YT or to Google drive, dropbox etc. Would love to see an effective noise canceller/reducer in action esp during distant lightning strikes at night.? 73
Gedas, W8BYA EN70JT
Light travels faster than sound.....
This is why some people appear bright until you hear them speak.
On 1/25/2025 1:58 PM, Bob, N1KPR via groups.io wrote:
After many hours of experimentation I settled on a tuned loop for the family room entertainment feed; news, traffic and weather.
I'm using an old W-J 8711 demo/loaner unit that's quite beat up, but works as expected. As I mentioned in an earlier post, I have recorded signal strengths from either an 80-meter vertical or the 160-meter wire at 35 feet. So I can gauge from the known antennas and the known AM b'casters as to what levels I should need to get. The tuned loop is about 35 feet from the house and was on a cheap rotator (now broken) and feeding a bias-tee to a variactor (BB112). With the 330uH loop and the diode tuning I can cover 500kHz thru 2MHz. I generally have the loop toward NYC which is directly SW from here. To reorient the loop I use an "Armstrong rotator." That means I need to go outside and turn it myself. East for New Haven and RI, NNE for Hartford/Boston and the SW for NYC
The tuned loop feeds me a much better diet that the Mobius or other homebrew loops. As was mentioned, the tuned loop is limited as to what the diode can cover to resonate the 330uH loop.
In the evening, I switch to the Pixel Pro for International stuff, also on a cheap rotator (this one still works).
My point is that the tuned loop is about 18dB below the 160 wire and about 22-24dB below the vertical 80, but with significantly less noise. With a preamp (LNA) I can boost the loops up to the Ham antenna's strength. But, that gets to be a feel-good situation, since the QRN/QRM is also amplified.
?
Added note: A good DSP Noise Reduction device (I use BHI) can make life a lot more enjoyable, especially for long-term listening.
?
?
gud sigs to all,
73,
Bob, N1KPR
?
?
?
?
?
?
-
- Youtube: N1KPR
- Youtube: Ham Radio Doctor
?
Engineering, where enigma meets paradox
?
?
On Saturday, January 25, 2025 at 01:24:59 PM EST, Nick Hall-Patch <nhp@...> wrote: ?
?
In the past, many of us heard great MW DX with a tuned loop next to the receiver.? However, such a loop now would be likely to hear only local electrical noise from house wiring, wouldn't it?? That's pretty much all that mine can hear now. If one has some property, it may be possible to put a tuned loop away from the house, but protected from the weather, and tuned with a varicap diode, which itself may affect loop Q.? But, then one loses the ability to turn the loop to null interfering stations on the chosen channel, which was another advantage of the indoor tuned loop. Others have mentioned the necessity of a wide band loop for SDR recordings, but if one can live with a single tuned channel, is there any advantage to a tuned over an untuned loop?? That is, can something be heard on one but not the other?? ?I did try a remotely tuned Kiwa loop vs. a Flag antenna on trans-Arctic signals here, and didn't find any advantage, but the testing was not exhaustive.? ?Something more to add to the list, I guess. best wishes, Nick ? On Sat, 25 Jan 2025 08:17:14 -0800, "JohnT via groups.io" <jtstein46@...> wrote: ?
Greetings.? I am a frequent "lurker" and very infrequent "poster" to this forum, my interest is primarily MW.? I usually use a 1m diameter resonant loop and am puzzled as to why resonant loops seem to be out of favor with most of the group members.? The resonant peak provides both "free", noiseless gain to the signal of interest while also rejecting signals at frequencies other than resonance, eliminating the need for high second- and third-order intercept performance.? Granted the broadband loops that are much discussed on the forum can acquire broad swaths of the RF spectrum essentially simultaneously, is this a significant advantage given the fact that the frequency of the signal of interest is known?
?
Would someone please discuss the advantages of the broadband loop over a resonant one, have I missed something??
?
Thanks
?
JohnT
?
|
I'll try to get something recorded for my youtube channel. It'll be a few days since I'm still recovering from a few surgeries.
I'll use <ham radio doctor> channel. 73, Bob
-
- Youtube: N1KPR
- Youtube: Ham Radio Doctor
Engineering, where enigma meets paradox
On Saturday, January 25, 2025 at 02:59:41 PM EST, Everett N4CY via groups.io <everettsharp@...> wrote:
Bob,
?
One of the major reasons to use a Broadband Loop vs a Tuned Loop, is that most people these day are using SDR? Receivers, with some being able to see up to 24MHz of bandwidth, at one time. Using a Tune Loop would greatly restrict the visible signals.
?
Everett N4CY
In a message dated 1/25/2025 1:34:57 PM Central Standard Time, w8bya@... writes:
?
Hi Bob, I like messing with tuned loops as well. It was with Bertha (my first multi-turn tuned loop) that I was able to hear my first LWBC transmissions after several years of trying with numerous full sized V's and verticals.
One thing that you mentioned that sparked my attention was your use of a dsp noise canceller. My only experience with them has been the canned NR on box rigs like the FT-1000, etc. I never did find any settings that I thought I could tolerate longer than a few minutes and I never really thought they did much good other than make the audio sould like it coming from outer space. Do you by chance have a short video demonstrating the effectiveness of your NR in action?? If not even a 2-3 minute cell phone video uploaded to YT or to Google drive, dropbox etc. Would love to see an effective noise canceller/reducer in action esp during distant lightning strikes at night.? 73
Gedas, W8BYA EN70JT
Light travels faster than sound.....
This is why some people appear bright until you hear them speak.
On 1/25/2025 1:58 PM, Bob, N1KPR via groups.io wrote:
After many hours of experimentation I settled on a tuned loop for the family room entertainment feed; news, traffic and weather.
I'm using an old W-J 8711 demo/loaner unit that's quite beat up, but works as expected. As I mentioned in an earlier post, I have recorded signal strengths from either an 80-meter vertical or the 160-meter wire at 35 feet. So I can gauge from the known antennas and the known AM b'casters as to what levels I should need to get. The tuned loop is about 35 feet from the house and was on a cheap rotator (now broken) and feeding a bias-tee to a variactor (BB112). With the 330uH loop and the diode tuning I can cover 500kHz thru 2MHz. I generally have the loop toward NYC which is directly SW from here. To reorient the loop I use an "Armstrong rotator." That means I need to go outside and turn it myself. East for New Haven and RI, NNE for Hartford/Boston and the SW for NYC
The tuned loop feeds me a much better diet that the Mobius or other homebrew loops. As was mentioned, the tuned loop is limited as to what the diode can cover to resonate the 330uH loop.
In the evening, I switch to the Pixel Pro for International stuff, also on a cheap rotator (this one still works).
My point is that the tuned loop is about 18dB below the 160 wire and about 22-24dB below the vertical 80, but with significantly less noise. With a preamp (LNA) I can boost the loops up to the Ham antenna's strength. But, that gets to be a feel-good situation, since the QRN/QRM is also amplified.
?
Added note: A good DSP Noise Reduction device (I use BHI) can make life a lot more enjoyable, especially for long-term listening.
?
?
gud sigs to all,
73,
Bob, N1KPR
?
?
?
?
?
?
-
- Youtube: N1KPR
- Youtube: Ham Radio Doctor
?
Engineering, where enigma meets paradox
?
?
On Saturday, January 25, 2025 at 01:24:59 PM EST, Nick Hall-Patch <nhp@...> wrote: ?
?
In the past, many of us heard great MW DX with a tuned loop next to the receiver.? However, such a loop now would be likely to hear only local electrical noise from house wiring, wouldn't it?? That's pretty much all that mine can hear now. If one has some property, it may be possible to put a tuned loop away from the house, but protected from the weather, and tuned with a varicap diode, which itself may affect loop Q.? But, then one loses the ability to turn the loop to null interfering stations on the chosen channel, which was another advantage of the indoor tuned loop. Others have mentioned the necessity of a wide band loop for SDR recordings, but if one can live with a single tuned channel, is there any advantage to a tuned over an untuned loop?? That is, can something be heard on one but not the other?? ?I did try a remotely tuned Kiwa loop vs. a Flag antenna on trans-Arctic signals here, and didn't find any advantage, but the testing was not exhaustive.? ?Something more to add to the list, I guess. best wishes, Nick ? On Sat, 25 Jan 2025 08:17:14 -0800, "JohnT via groups.io" <jtstein46@...> wrote: ?
Greetings.? I am a frequent "lurker" and very infrequent "poster" to this forum, my interest is primarily MW.? I usually use a 1m diameter resonant loop and am puzzled as to why resonant loops seem to be out of favor with most of the group members.? The resonant peak provides both "free", noiseless gain to the signal of interest while also rejecting signals at frequencies other than resonance, eliminating the need for high second- and third-order intercept performance.? Granted the broadband loops that are much discussed on the forum can acquire broad swaths of the RF spectrum essentially simultaneously, is this a significant advantage given the fact that the frequency of the signal of interest is known?
?
Would someone please discuss the advantages of the broadband loop over a resonant one, have I missed something??
?
Thanks
?
JohnT
?
|
Reply to Mikek:
?
I use an 11 turn flat (pancake) wound loop to chase broadcast-band Dx in the US. ?The loop tunes from about 700 hHz to a little over 1600 kHz. A small silver mica cap can be switched in to tune down to 500 kHz. ?A single turn coupling loop diameter about 5” feeds the receiver through shielded twisted pair.?
|
Great, but it's narrow banded!? Again, my interests in loops range from below the submarine comms. (Schumann Resonance) through 160-meters.??
I have a tuned loop for 40, 30, and 20-meters, but here at 5800-feet elevation, even a 2.5 kV variable capacitor for resonating the loop arcs with even 50-watts.? Using a standard 365 pF BC variable is totally out of the question.? I finally had to buy a vacuum capacitor rated for 15 kV to operate at 100-watts comfortably.? Yes, it's an overkill.? And again, the 2 : 1 bandwidth on that 1-meter diameter tuned loop is 3 to 5 kHz wide.? To resonate my 2-meter "shielded" loop made of 2-inch OD copper pipe (hexagonal) out on the eastern hogback at the Schumann Resonance presents quite a challenge and each harmonic of the nominal 7 Hz fundamental would just further complicate the logistics. ? This also applies to all the submarine comm. frequencies.? No thanks to resonated loops for my applications.
EXAMPLE:? Assume 10-?H inductance for that 2-meter "shielded" loop the nominal Schuman Resonance frequency of 7 Hz.
10 ?H at 7 Hz = + j 440 ?Ohms ? ? ?? Yes, that's MICRO-ohms!!
To resonate with a capacitor, that would require a capacitor of? 51.7 FARADS.? That's FARADS, NOT MILLIFarads and NOT MICROFarads!? Yea......sure......I don't think so.......?
And take a submarine comm. frequency of nominally 20 kHz:
10 ?H at 20 kHz = 1.26 Ohms
To resonate with a capacitor, that would require a capacitor of 6.32 ?F.? Well, at least that' within reason. ?
Dave - W?LEV
?
Reply to Mikek:
?
I use an 11 turn flat (pancake) wound loop to chase broadcast-band Dx in the US.? The loop tunes from about 700 hHz to a little over 1600 kHz. A small silver mica cap can be switched in to tune down to 500 kHz.? A single turn coupling loop diameter about 5” feeds the receiver through shielded twisted pair.?
|
I live within long walking distance of the Homebush Bay, Sydney medium wave transmitter site. The signal strengths are high. With wideband antenna systems, the radio exhibits desensitization. A tuned loop antenna effectively acts as a tuned circuit or RF pre-selector. The higher the circuit 'Q factor', the narrower the 3 dB bandwidth when the variable capacitor is tuned to resonance.
?
It is easy to desense my radio by aiming the loop towards the local MW TX antenna site. Imagine how higher the desense would be if a wideband antenna was aimed at the local TX antenna site.
?
I built a Gary DeBock design 9-turn 40 inch (100 cm) side length PVC box loop. The tuning capacitor is standard 360 pf. The tank coil wire diameter is similar to what Gary recommends in the article PDF (link below). The loop works well at my suburban house location. The loop would work even better at a rural location, or coastal site overlooking the sea. Adding an RF amplifier is not necessary, partly because the total composite QRN and QRM at 525-1710 KHz is high. I use a Sangean PR-D3 radio which is largely modelled on a Crane CC 2E. The RF noise figure of the internal DSP chip is usually RF noise-limited at MW.?
?
I also use a smaller 26 inch (65 cm) diameter PVC 'hula-hoop' tunable C-LOOP-HDXXLTAM HD series loop manufactured by PK Antennas, Melbourne. The SNR on the smaller loop is similar to the larger 40 inch diameter loop. This means that the loop antenna overall diameter can be small enough to fit on a standard kitchen benchtop. This is where I do most long distance MW listening. When especially interesting signals appear, the 40 inch diameter loop is used.?
?
Thanks,
?
Todd.
?
?
?
?
|
I like tuned loop antennas for AM BCB as well as for NDB chasing. I have a 45 inch on a side box 8 turn loop wound with
#12 magnet wire and also use it as a crystal radio set. A good tuning capacitor is essential. I recently was given a Comet vacuum variable
8 to 1000pf capacitor and it is great for tuning the loop. Very sharp tuning and no need for a vernier. Better Q than my air variables for the BCB band as the tuning peak is sharper and the signal is stronger.
?
?I am glad it was free. They are expensive capacitors!
|
I have made several similar loops for BCB and NDB work. I wind the loop to about 330uH and use a BB112 Variactor to? resonate it, fed from a 0-10V Bias-Tee (indoors) . Very sharp / hi-Q and nothing expensive.
Here's the circuit, but with a different model loop using ferrite. Both the 1-meter loop and the rod loop work nicely with the BB112 circuitry.
Bob, N1KPR
-
- Youtube: N1KPR
- Youtube: Ham Radio Doctor
Engineering, where enigma meets paradox
On Saturday, March 8, 2025 at 02:48:51 PM EST, VLF Dilletante via groups.io <brownpiggin@...> wrote:
I like tuned loop antennas for AM BCB as well as for NDB chasing. I have a 45 inch on a side box 8 turn loop wound with
#12 magnet wire and also use it as a crystal radio set. A good tuning capacitor is essential. I recently was given a Comet vacuum variable
8 to 1000pf capacitor and it is great for tuning the loop. Very sharp tuning and no need for a vernier. Better Q than my air variables for the BCB band as the tuning peak is sharper and the signal is stronger.
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?I am glad it was free. They are expensive capacitors!
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This subject was extensively covered and commented on a few months ago.? I'd suggest you check the archives.
Personally, I don't want to tune the loop every time I chase something else.? They are extremely high-Q and tuning is required at BCB and HF frequencies for even a couple of 10 kHz.? No thanks.? My untuned loops work just fine!? I do have a single tuned 1-meter diameter loop I occasionally use for RCV and XMT on 40 and 20-meters during lightning season.? But on 40 the 2 : 1 bandwidth is roughly 6 kHz.? I don't use it too often.
Dave - W?LEV
On Sat, Mar 8, 2025 at 7:48?PM VLF Dilletante via <brownpiggin= [email protected]> wrote: I like tuned loop antennas for AM BCB as well as for NDB chasing. I have a 45 inch on a side box 8 turn loop wound with
#12 magnet wire and also use it as a crystal radio set. A good tuning capacitor is essential. I recently was given a Comet vacuum variable
8 to 1000pf capacitor and it is great for tuning the loop. Very sharp tuning and no need for a vernier. Better Q than my air variables for the BCB band as the tuning peak is sharper and the signal is stronger.
?
?I am glad it was free. They are expensive capacitors!
|
Bob, N1KPR
Everett N4CY