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Re: Experimenting with Loop Antennas

 

Physicist here... beware.
?
mHz --> means millihertz,? ?10^-3 Hz
MHz --> means megahertz, 10^6 Hz?
mc? ?--> means nothing... only mc/s, i.e. megacycles per second is a measure of frequency
?
:-)
?
73? Alberto? I2PHD
P.S. My new software Argo V2, soon to be release, has a selectable resolution in frequency that can range down to 44.7 uHz. i.e. 44.7 millionths of a Hz...
So, not only geologists use units of measure below 1 Hz....
Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos

 

If the L-network is single ended - common mode for coax - the balun belongs BEFORE the network!?? The balun converts differential mode to common mode.? That's why it is termed a "balun:? Balanced (to) Unbalanced.

Dave - W?LEV


On Fri, Jan 24, 2025 at 2:11?AM biastee via <biastee=[email protected]> wrote:
?
On Sat, Oct 12, 2024 at 11:21 PM, <biastee@...> wrote:
On Mon, Sep 30, 2024 at 01:13 AM, Martin - Southwest UK wrote:
Understood about the switch, but I think the location of the balun is causing problems.
Hi Martin,
?
You are right. Placing the balun after the L-network causes problems. ? The simulator showed similar result, regardless of whether the balun is placed BEFORE or AFTER the L-section. This deceptive result arises because the simulator's ideal balun was capable of tolerating high Z, whereas the real balun requires ~50 ohm to work properly.
?
When the L-network's impedance is measured without the fabricated balun, it shows the expected trajectory, with a resonance at the modelled 30 MHz (black trace). However, after the balun is added, i.e. AFTER the L-section, the resonance mysteriously shifts down to 13 MHz (red trace).?
?
The problem can be rectified by moving the balun L2 to a position before the L-section. With the balun in the new position, the impedance locus is as modelled with a resonant at ~30 MHz.
?
Additionally, the previously measured LZ1AQ's gain peak at 22 MHz, also correctly shifts back to the modelled 30 MHz.
?
I have posted the corrected results at the link:
Critique welcomed!
?
?
?
On Sun, Jun 30, 2024 at 08:17 PM, Caaarlo wrote:

  • M0AYF Improved: Input Z is more HF-friendly for a 1m loop without the need for a matching network, but CMR, IP2, and IP3 seem to be a bit worse than the LZ1AQ.

?
@Caarlo
My measurement of the LZ1AQ (fig. 11 in above link) shows worse CMRR than M0AYF, especially at the lower HF range. I hypothesize the latter's improved CMRR is due to it using a common emitter resistor in the differential pair. Below link to M0AYF's CMRR graph:
?
A variation on the M0AYF's emitter resistor is PA0FRI using an inductor instead. The PA0FRI circuit is virtually identical, but his replacing the emitter resistor with an inductor results in poor CMRR at low frequencies due to the decreasing inductive reactance.

73, Leong, 9M2LCL (ex 9W2LC).



--
Dave - W?LEV
Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos

 

Hi Mike,
Thanks for correcting my mistaken assumption. I was thinking that the imbalance can increase 2nd harmonic generation (IP2), which in turn also increases IP3 because the latter also depends on the 2nd harmonic, as in 2f1 - f2 and 2f2 - f1. Or is my logic flawed?
?
I have also uploaded a graph comparing the CMRR of the three active loops.
/g/loopantennas/photo/300229/3878684
?
Referring to the graph linked above, I hypothesize M0AYF & PA0FRI have significantly higher CMRR than?LZ1AQ because the former two incorporates a shared emitter resistor and emitter inductor, respectively. In the PA0FRI, CMRR is poor at the lowest frequencies due to the decreasing inductive reactance (XL), but as the frequency increases, the XL also increases, hence resulting in it having the highest CMRR at the upper HF range. Although M0AYF's emitter resistor is constant over frequency, the parasitic cap shunting the resistor causes its CMRR to degrade gradually with frequency.
?
73, Leong, 9M2LCL (ex 9W2LC).
?
?
Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos

 




Locate Full Wilson Current Source in above reference (and simple singular transistor types aforementioned)

Paul
On Thursday, January 23, 2025 at 11:41:47 p.m. EST, vbifyz via groups.io <3ym3ym@...> wrote:


On Thu, Jan 23, 2025 at 07:11 PM, <biastee@...> wrote:
Imbalance between top and bottom sections affects IP2 (which I don't see in the measurements), and not so much IP3.
Otherwise, very good and thorough work.
?
73, Mike AF7KR
Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos

 






On Friday, January 24, 2025 at 06:28:02 a.m. EST, Paul V Birke via groups.io <nonlinear@...> wrote:


Always wondered what about R1 and R2 being replaced by separate current sources?

Simple FET ones or Full Wilson with matching transistors (THAT Corp sells chip with 4 matched HF transistors)

Would be worth a try even if just running a model to see any serious positive effect.

best Paul

On Thursday, January 23, 2025 at 11:41:47 p.m. EST, vbifyz via groups.io <3ym3ym@...> wrote:


On Thu, Jan 23, 2025 at 07:11 PM, <biastee@...> wrote:
Imbalance between top and bottom sections affects IP2 (which I don't see in the measurements), and not so much IP3.
Otherwise, very good and thorough work.
?
73, Mike AF7KR
Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos

 

Always wondered what about R1 and R2 being replaced by separate current sources?

Simple FET ones or Full Wilson with matching transistors (THAT Corp sells chip with 4 matched HF transistors)

Would be worth a try even if just running a model to see any serious positive effect.

best Paul

On Thursday, January 23, 2025 at 11:41:47 p.m. EST, vbifyz via groups.io <3ym3ym@...> wrote:


On Thu, Jan 23, 2025 at 07:11 PM, <biastee@...> wrote:
Imbalance between top and bottom sections affects IP2 (which I don't see in the measurements), and not so much IP3.
Otherwise, very good and thorough work.
?
73, Mike AF7KR
Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos

 

On Thu, Jan 23, 2025 at 07:11 PM, <biastee@...> wrote:
Imbalance between top and bottom sections affects IP2 (which I don't see in the measurements), and not so much IP3.
Otherwise, very good and thorough work.
?
73, Mike AF7KR
Re: Steve ugly-build LZ1AQ using MPS2222 sweeps uploaded to Photos

 

?
On Sat, Oct 12, 2024 at 11:21 PM, <biastee@...> wrote:
On Mon, Sep 30, 2024 at 01:13 AM, Martin - Southwest UK wrote:
Understood about the switch, but I think the location of the balun is causing problems.
Hi Martin,
?
You are right. Placing the balun after the L-network causes problems. ? The simulator showed similar result, regardless of whether the balun is placed BEFORE or AFTER the L-section. This deceptive result arises because the simulator's ideal balun was capable of tolerating high Z, whereas the real balun requires ~50 ohm to work properly.
?
When the L-network's impedance is measured without the fabricated balun, it shows the expected trajectory, with a resonance at the modelled 30 MHz (black trace). However, after the balun is added, i.e. AFTER the L-section, the resonance mysteriously shifts down to 13 MHz (red trace).?
?
The problem can be rectified by moving the balun L2 to a position before the L-section. With the balun in the new position, the impedance locus is as modelled with a resonant at ~30 MHz.
?
Additionally, the previously measured LZ1AQ's gain peak at 22 MHz, also correctly shifts back to the modelled 30 MHz.
?
I have posted the corrected results at the link:
https://sites.google.com/site/randomwok/Home/electronic-projects/aerials/lz1aq-active-loop-performance-evaluation
Critique welcomed!
?
?
?
On Sun, Jun 30, 2024 at 08:17 PM, Caaarlo wrote:

  • M0AYF Improved: Input Z is more HF-friendly for a 1m loop without the need for a matching network, but CMR, IP2, and IP3 seem to be a bit worse than the LZ1AQ.

?
@Caarlo
My measurement of the LZ1AQ (fig. 11 in above link) shows worse CMRR than M0AYF, especially at the lower HF range. I hypothesize the latter's improved CMRR is due to it using a common emitter resistor in the differential pair. Below link to M0AYF's CMRR graph:
?
A variation on the M0AYF's emitter resistor is PA0FRI using an inductor instead. The PA0FRI circuit is virtually identical, but his replacing the emitter resistor with an inductor results in poor CMRR at low frequencies due to the decreasing inductive reactance.

73, Leong, 9M2LCL (ex 9W2LC).

Re: Experimenting with Loop Antennas

 

mhz? I mean to type 188,495,559.20579 rad/s (left handed approximation) but got tired typing.
?
Please edit the "mhz" for me and replace it with "mc".?
?
Only geologists know about "milli Hertz" amplifiers which use long length projected light beams for stable amplification.
?
Take that, you physicist, you!
?
Maxwell-Boltzmann forever!
?
"k" ??
?
VEZ/Jim
?
Re: Experimenting with Loop Antennas

 

On Wed, Jan 22, 2025 at 07:22 PM, W0LEV wrote:
Regarding the amplifier:? It's like using a crystal set to receive solar emissions.? Yes, get a better amp.
The wellgood amplifier Roland uses is a well proven Amp with noiseless transformer feedback. It is a clone of the Wellbrook ALA1530N. There is no reason to question the sensitivity and noise figure or to blame the amplifier.
?
regards
Fred
Re: Experimenting with Loop Antennas

 

A couple of observations.
1.) Why is your amplifier box so high on the mast?
2.) The leads from the bottoms of the loops seem longer than necessary. I'd make them as short and straight as possible.
3.) I understand that you're trying to lower the inductance as much as practical, and separation is one way, but 660 mm is a LOT. It seems that your construction may be solid, it may be fine.
--
Phil, K0TWA
Re: Experimenting with Loop Antennas

Roland
 

On Wed, Jan 22, 2025 at 08:11 PM, Simon wrote:
Roland..get a better amplifier..you are putting lots of effort into the loop which is being wasted.
Nothing is wasted. I call it learning
Re: Experimenting with Loop Antennas

 

Regarding the amplifier:? It's like using a crystal set to receive solar emissions.? Yes, get a better amp.

Dave - W?LEV


On Wed, Jan 22, 2025 at 7:12?PM Simon via <ohhellnotagain=[email protected]> wrote:
Hi Dave

Come on, obs a typo..

Also re giving noise floor relating to s reading on radio.
Yes I agree abit iffy, but good enough for the reference I was trying to give..ie. If live in urban noise noise area, then attempting to get a few db extra out of? loop is pretty pointless..( you wont notice any difference in real world.)
Been there done that, waste of time..HOWEVER now live in very rf quiet area a different story.

Roland..get a better amplifier..you are putting lots of effort into the loop which is being wasted.

If it works a pic of my old London rx loop..( before used crossed parallel¡¯s.)



Regards..







--
Dave - W?LEV
Re: Experimenting with Loop Antennas

 

Hi Dave

Come on, obs a typo..

Also re giving noise floor relating to s reading on radio.
Yes I agree abit iffy, but good enough for the reference I was trying to give..ie. If live in urban noise noise area, then attempting to get a few db extra out of loop is pretty pointless..( you wont notice any difference in real world.)
Been there done that, waste of time..HOWEVER now live in very rf quiet area a different story.

Roland..get a better amplifier..you are putting lots of effort into the loop which is being wasted.

If it works a pic of my old London rx loop..( before used crossed parallel¡¯s.)



Regards..
Re: Experimenting with Loop Antennas

 

30 mhz?? That's in the realm of acoustic earthquake signatures!? Possibly you mean 30 MHz indicating MEGAHERTZ?

Dave - W?LEV


On Wed, Jan 22, 2025 at 6:13?PM James Redding WA9VEZ via <wa9vez=[email protected]> wrote:
Try the ITU standard:
?
?
It shows almost every radio frequency below 30 mhz as impaired.
?
i.e. Ambient noise energy above the Maxwell-Boltzmann thermal noise limit.
?
JIm/vez



--
Dave - W?LEV
Re: Experimenting with Loop Antennas

 

Try the ITU standard:
?
?
It shows almost every radio frequency below 30 mhz as impaired.
?
i.e. Ambient noise energy above the Maxwell-Boltzmann thermal noise limit.
?
JIm/vez
Re: Experimenting with Loop Antennas

 

Cross connecting the cables will result in a lower value of inductance (due to mutual inductance), but you will also get cancellation of the received signals due to the phase reversal.
?
?
To avoid this, when cross connected, the coils need to be in separate planes to prevent mutual coupling, which is why LZ1AQ uses a different layout.
?
Regards,
?
Martin
?
On Wed, Jan 22, 2025 at 02:07 PM, Roland wrote:

Cross-connecting results in the lowest loop inductance
Re: Experimenting with Loop Antennas

Roland
 

It's too bad it's not possible to edit a posting.
?
Correction:?
The inductance of a cable length of 200mm (?6mm2) is 0.17 ¦Ì±á.
Re: Experimenting with Loop Antennas

Roland
 

I have experimented with loop spacing and connector cable lengths and measured inductance.
?

1 Loop measured at loop cable terminals

2.37 ¦Ì±á (according to mag loop calc. 2.45 ¦Ì±á)

?

Loop spacing 500mm cable length 430mm - all 4 cables (parallel) connected to LCR45

1.65 ¦Ì±á

?

?Loop spacing 500mm cable length 390mm - all 4 cables (parallel) connected to LCR45

1.56 ¦Ì±á

?

Loop spacing 300mm cable length 200mm - all 4 cables (parallel) connected to LCR45

1.55 ¦Ì±á

?

If I cross-connect the (200mm) cables like so /g/loopantennas/photo/300189/3878181 I get 1.08 ¦Ì±á! Cross-connecting results in the lowest loop inductance. The inductance of a cable length of 200m (?16mm2) is 0.17 ¦Ì±á.

?
Re: Experimenting with Loop Antennas

 

On Wed, Jan 22, 2025 at 09:42 AM, Simon wrote:
Low noise floor is to be found in a rural location. Ie I have s0 ( sometimes s1) noise on a full size 40m vertical
Unfortunately S-Figure values of a non-calibrated receiver are not very meaningful. Better specify the voltage at 50 Ohms in dB?V or power in dBm. Some of the better SDR (e. G. Perseus, SDR-Play devices etc.) show quite accurate input level values.
?
Regards, Fred
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