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Re: Coupling loop advice

 

If you look at the physics of the "shielded" loop, you will rapidly realize it is NOT SHIELDED from the induced currents!? That's the whole reason for the gap at the top high-Z point, opposite the feed point and according to the reference diagram: "This will not work".

The use of the term "shielded" certainly connotes the physical appearance of the loop, but from an EMAG standpoint, it is totally in error.

Dave - W?LEV

On Fri, Apr 25, 2025 at 11:25?PM V¨ªctor J. S¨¢nchez via <vjosesan=[email protected]> wrote:
Hi all and thanks for accept me in the group.
?
I'm building a magnetic loop antenna for TX and I slightly follow the instructions in and another sources. I've finished the main loop with the capacitor and its rotator and now I have to choose a coupling loop configuration. There are basically 2 variants: unshielded and shielded (aka Faraday loops). According to the link I've wrote I'd like to use the shielded F variant because it seems to be better cancelling E-fields in horizontal and vertical polarization. But there are some people that think both variants work the same.
?
I'm in doubt with this. Any advice or experience?
?
Thanks in advance. Regards.



--
Dave - W?LEV
Re: Coupling loop advice

 

I would agree with Simon. Use an unshielded coupling loop and place an effective common mode choke on the feedline, and also on any control cables.
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Regards,
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Martin
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On Sat, Apr 26, 2025 at 09:48 AM, Simon wrote:

Unshielded..been there done it..dont waste time on shielded. Its not the antenna, its just the coupling to the antenna which has already received any noise. A common mode choke in coax by antenna would be good though.
Re: HYBRID QUADRATURE JH-6-4 or equivalent

 

OK. . .
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90 degree hybrids with mulitoctave frequency are possible but this is the 21st century. . .
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Buy a dual channel SDR receiver with matching "IF signal handling" chains and create the 90 degree phase shift in the "digital" local oscillator.
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For that matter add a third antenna element and think about a quaternion signal detector with three LO's and three parallel if stages.
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Jim/VEZ
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Re: HYBRID QUADRATURE JH-6-4 or equivalent

 

An addition:
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As you can see from the phase plot the deviation from 90 deg is less than 5 deg for the range: 2.4 - 37 MHz. The design can be easily scaled to another frequency range.
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But note: there is no constant phase difference between the input and outputs. Only the two outputs maintain an approximately constant phase shift between them.
Re: HYBRID QUADRATURE JH-6-4 or equivalent

 

A few years ago, a similar topic appeared in another group: /g/SimSmith/topic/69302617?.
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Last year, Chris Smith NX0E shared his hybrid coupler design with me. He based his design on Bedrosian's article "Normalized Design of 90¡ã Phase-Difference Networks" .
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I have included two of Chris's articles from 1988 in the NX0E_hybrid coupler folder /g/loopantennas/files/NX0E_hybrid_coupler .
I have transferred Chris' idea to LTspice. You can find the LTspice file and the phase difference plot in that folder.
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Kind regards
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Piotr, SP2BPD
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Re: Coupling loop advice

 

Hi

Unshielded..been there done it..dont waste time on shielded. Its not the antenna, its just the coupling to the antenna which has already received any noise. A common mode choke in coax by antenna would be good though.

See bottom of my qrz page..Simon g0zen
Coupling loop advice

 

Hi all and thanks for accept me in the group.
?
I'm building a magnetic loop antenna for TX and I slightly follow the instructions in https://www.nonstopsystems.com/radio/frank_radio_antenna_magloop.htm and another sources. I've finished the main loop with the capacitor and its rotator and now I have to choose a coupling loop configuration. There are basically 2 variants: unshielded and shielded (aka Faraday loops). According to the link I've wrote I'd like to use the shielded F variant because it seems to be better cancelling E-fields in horizontal and vertical polarization. But there are some people that think both variants work the same.
?
I'm in doubt with this. Any advice or experience?
?
Thanks in advance. Regards.
Re: HYBRID QUADRATURE JH-6-4 or equivalent

 

I think it is feasible to chose component values that would produce a 90 degree phase shift at a given frequency, especially if this is somewhere close to resonance, and if you are only interested in one spot frequency, this could work.?
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However, the 90 degrees shift is only likely to be present over a relatively narrow bandwidth, and the change in phase either side would probably be fairly rapid.
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Regards,
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Martin
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On Tue, Apr 22, 2025 at 09:46 PM, hisami dejima wrote:

If the coil is 10uH and the capacitance between the windings is 4pF (2x2pF), it seems to behave as it should at about 25MHz.
Re: HYBRID QUADRATURE JH-6-4 or equivalent

 

Hi Martin and All
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Illustration of SCPQ-10.5 Datsheet.
I thought about the "or some other element" that Martin mentioned.
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Most simple one is capacitance between the coil.
I did a simple simulation in LTSPICE.
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If the coil is 10uH and the capacitance between the windings is 4pF (2x2pF), it seems to behave as it should at about 25MHz.
I added a 100pF capacitor and it seems to work as a splitter/combiner at 3.5MHz.
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It is a crude simulation, but if the 3dB loss is acceptable, it could be used as a mono-band 90 degree Hybrid.
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I put the two pictures and the LTSPICE source in text on my brog.
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tnx & 73, Hisami 7L4IOU
Re: HYBRID QUADRATURE JH-6-4 or equivalent

 

I will be interested to see how well that performs outside its specified frequency range.
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I suspect it would actually work OK down to at least 2MHz, but Mini-Circuits published specifications tend to be cautious.
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Regards,
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Martin
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On Tue, Apr 22, 2025 at 03:14 PM, Rolf Haenggi wrote:

I ?ordered the minicircuits JSPQ-65W+ for a new project.
Re: HYBRID QUADRATURE JH-6-4 or equivalent

 

¿ªÔÆÌåÓý

Hi

?

I ?ordered the minicircuits JSPQ-65W+ for a new project.

?

73, Rolf

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RX:?? ?SIR-2115, G69/31DDC, PERSEUS, ?SIGNALHOUND, AFEDRI, GRX-LAN¡­¡­

ANT: T2FD, G5RV, ALA 1530/100, GA3005, ?X-ONE, DISCONE

SW:? ?go2signals Software Suite

Logs:

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From: [email protected] <[email protected]> On Behalf Of hisami dejima via groups.io
Sent: Monday, April 21, 2025 11:04 AM
To: [email protected]
Subject: [loopantennas] HYBRID QUADRATURE JH-6-4 or equivalent

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Hi All,

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I came across "The R&S HE-015 active antenna" by chance.

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In the pictures there, the combiner seems to be "anzac JH-6-4".

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I have some home brewed Small Loop, Active Dipole and Mini Whips,?
so I would like to try combine them.

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The key component JH-6-4 is also listed on DigiKey, but price is exorbitant!

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the datasheet here

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Does anyone know what the JH-6-4 or equivalent is made of or how it works?

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I imagine it is probably a device like this.

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What do you think?

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tnx & 73, Hisami 7L4IOU
Re: HYBRID QUADRATURE JH-6-4 or equivalent

 
Edited

Yes Martin.
With a 90 deg. Phaseshift the directional pattern of the E-plane of the dipoles then rotates with the period of the Signal by 360 degrees. Thus the average horizontal rms Rotation ist quasi omnidirectional. Orthogonal to the E-plane the polarisation ist circular.
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reference: Kraus/Marhefka "Antennas and wave propagation 4th ed" Chapter 15-7.
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regards, Fred
Re: HYBRID QUADRATURE JH-6-4 or equivalent

 

Hi Fred,
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Rick did also say to include a 1/4 wave transmission line in one leg, in order to introduce a 90 degree phase shift at that specific frequency.
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This method is typically used in coaxial phasing harness, for VHF & UHF frequencies.
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Regards,
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Martin
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On Tue, Apr 22, 2025 at 10:55 AM, Fred M wrote:

are you sure, Rick?
Re: HYBRID QUADRATURE JH-6-4 or equivalent

 

On Mon, Apr 21, 2025 at 06:37 PM, Richard \(Rick\) Karlquist \(N6RK\) wrote:
1.? If you work at a narrow band of frequencies, you can simply use a 0 or 180 degree hybrid combiner to feed the two loops
are you sure, Rick?
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As far as i know: if you combine two orthogonal dipoles ( X-dipole) via an 180¡ã coupler you only achieve a +45¡ã oder a -45¡ã Skew of the E-Plane directional pattern of the dipoles. But not an horizontally polarised omnidirectional pattern.
?
?
regards, Fred
Re: HYBRID QUADRATURE JH-6-4 or equivalent

 

Typical, I found the book title just after I'd pressed send. It's a bit pricey new, so I'd try and borrow a copy, via your local library (remember those).
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"Lumped Element Quadrature Hybrids" by David Andrews
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Regards,
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Martin
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On Tue, Apr 22, 2025 at 09:15 AM, Martin - Southwest UK wrote:

There is also an excellent book devoted to the subject,
Re: HYBRID QUADRATURE JH-6-4 or equivalent

 

You may also wish to look out for an article entitled "How to design wide band RF quadrature networks" Page 5, QEX, November 1982, published by The American Radio Relay League.
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Another source is "The theory and design of lumped element quadrature hybrids"? which can be downloaded at
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There is also an excellent book devoted to the subject, which I think was written by the same person, and based on his Phd, but I can't find the details at the moment.
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Regards,
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Martin
Re: HYBRID QUADRATURE JH-6-4 or equivalent

 

Hi Hisami,
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All 90 degree hybrids tend to be relatively narrowband devices. However, you can extend this by adding more phase shift sections, with their corner frequencies offset by suitable amounts. The more sections that are cascaded, the more difficult it becomes to align, and the losses also start to mount up.
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I also have an Anzac JH-10-4 20-140MHz 90 degree hybrid, which is a lot more complicated, and incorporates 6 transformers, plus other inductors and capacitors.
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The CSA hybrid I posted is adequate for use across the majority of the short wave spectrum, but it is not good enough for professional beam-forming in military / radar / astronomy, or lab grade use.
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The Mini-Circuits hybrid is most likely intended for use in the IF path of a superheterodyne receiver / transmitter, where it will be operating at a fixed centre frequency. The circuit in the data sheet is just an electrical representation, to indicate which ports are DC coupled, and what impedance is present. I don't think it is the actual circuit, unless the transformer coupling, or some other element, has somehow been "manipulated" to generate the required phase shift, which I think is highly unlikely.
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Regards,
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Martin
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On Tue, Apr 22, 2025 at 12:24 AM, hisami dejima wrote:

Thanks for the schematic.
I see that in principle, it is narrow bandwidth.
Re: HYBRID QUADRATURE JH-6-4 or equivalent

 

Hi Martin,

Thanks for the schematic.
I see that in principle, it is narrow bandwidth.
With the help of NanoVNA, I think I can adjust it.
I will give it a try.
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By the way, it seems that Mini-Circuits are readily available for commercial 90 degree hybrids.
I searched a few,?
SCPQ-10.5+ was the cheapest.
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and I was surprised to see the datasheet.
The electrical schematic at the bottom right of the DATASHEET is quite simple.
Is it actually one bifiler transformer and one resistor?
Or is it just an illustration?
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from View data
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AMP UNBAL (dB) <1?
9MHz 0.95 - 11.3MHz 0.95
appears to be the origin of the specs.
If do not want to be exact,?
7MHz to 14MHz looks like a practical range.
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In any case, it looks very simple and I will try later.
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tnx & 73, Hisami 7L4IOU
Re: HYBRID QUADRATURE JH-6-4 or equivalent

 

Hi Fred, Hi Martin,

Now I can understand the difference between "90 degree hybrid" and "0 / 180 combiner"
Thank you very highly for your help.
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73, Hisami 7L4IOU
Re: HYBRID QUADRATURE JH-6-4 or equivalent

 

Hi Matthias,

Thank you very much for your valuable information.
The schematics and pictures are helpful.?
Especially, I could understand the mechanical structure very well.
I will try to translate.

tnx & 73, Hisami 7L4IOU
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