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Re: HYBRID QUADRATURE JH-6-4 or equivalent
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Jim
thanks for the inspiration, however, things are not that simple. A hybrid analog coupler can be placed directly at two orthogonal antennas (e.g. small loops). Behind the coupler is a chain: amplifier, cable, receiver (two-channel, to its second receiver is fed the signal from the vertical antenna and its amplifier).
Now let's follow your line of thinking: Feed the signal from two orthogonal small loops to two mixers. But how to ensure that these loops are broadband matched (across the HF range, and perhaps even lower to LF) to the impedance of the cable. ?This task is usually fulfilled by amplifiers such as the LZ1AQ, Wellbrook, etc. However, introducing amplifiers also means introducing a gain difference between them, and this already affects the accuracy of angle-of-arrival measurements. A simple analog solution allows accuracy of better than 5 degrees over a wide frequency range. I don't know if the inclusion of two amplifiers in the circuit won't cause more deviation. I once wrote to Andrew Ikin asking if he could produce two reasonably identical ALA100LN amplifiers. His answer was short: "forget it". These are my thoughts on a Sunday afternoon. ? |
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Re: HYBRID QUADRATURE JH-6-4 or equivalent
or more precisely: /g/loopantennas/files/NX0E_hybrid_coupler/loss_precise.jpg? |
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Re: Coupling loop advice
The unshielded coupling loop is likely to produce the lowest losses.
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When using a toroid, especially on the lower frequency bands, a high permeability core material is required. These tend to be lossy, in addition, core saturation can also occur. This is because a small diameter core is required to achieve adequate coupling to the loop structure, and this in turn means that a very small core cross-section is carrying the majority of the flux.
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Regards,
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Martin
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On Sun, Apr 27, 2025 at 09:05 AM, V¨ªctor J. S¨¢nchez wrote:
At first I'll made an unshielded coupling loop so it's the easiest method althougt the toroid is an excellent alternative too. |
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Re: HYBRID QUADRATURE JH-6-4 or equivalent
Hi Hisami,
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I've attached a new file: /g/loopantennas/files/NX0E_hybrid_coupler/loss_plot.jpg . V(n005) is the voltage at the source.
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The losses are not 9 dB but about 3 dB.?
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Kind regards
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Piotr
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Re: Coupling loop advice
Yes, this would work quite well.? In technical terms, its called a Rogowski Coil.? Uncle and amateurs have fed the base of a water fountain using a Rogowski coil as well as feeding trees.? I'[ve never tried it, but the theory is sound! Dave - W?LEV On Sat, Apr 26, 2025 at 7:28?PM Dan Clementi via <dan=[email protected]> wrote:
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Dave - W?LEV |
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Re: Coupling loop advice
On Fri, Apr 25, 2025 at 07:25 PM, V¨ªctor J. S¨¢nchez wrote:
Hi, Victor.
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Not to derail the discussion too much, but the toroid coupling method shown in figure 32 of that link works very well indeed.
Not only is it mechanically very simple and robust, but you can also infer something about the parasitic resistance of your main loop and interconnect to the capacitor.? I.E. once you have the turns ratio for best SWR at resonance, you can calculate the total resistance loading the secondary side of the transformer and then subtract out the radiation resistance.
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Dan - K3GMQ |
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Re: Coupling loop advice
Hi Dave
Snake oil..lol Just dont make any improvement..good selling point though! Simon g0zen, ex maker of 160/80m mag loops that can get into USA, Caribbean etc from UK ssb.. ( now live on Dartmoor.. as you know,( rsgb tech marconi T) no longer need a tx mag loop. Though I do still have it incase I end up end of life in a HOA.( put a bird box in it..its a modern art tree..!) Regards.Simon |
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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:
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Dave - W?LEV |
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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. |
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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.
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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. ?
Kind regards
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Piotr, SP2BPD
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Coupling loop advice
Hi all and thanks for accept me in the group.
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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.
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I'm in doubt with this. Any advice or experience?
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Thanks in advance. Regards. |
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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. |
James Redding WA9VEZ
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