Re: Experimenting with Loop Antennas
Roland: You've opened up a very large can of enigma. We made many tests with multiple loops some years ago. Not long into the experiments we realized how complex the study would be. Considering all the factors of wavelength spacing, phase mixing, natural and harmonic resonances, azimuth lobes and nulls, self-resonances, etc. If I can find the file, I'll post some scans on the group's files section. A good place to start was some of the formulas and Theory of Ops found in the ARRL Antenna book. It's a great reference, especially in not repeating some of the mistakes of others. We standardized on the Pixel Pro for the twin loops (Receiving only). Our first tests were using AM B'cast stations with known signal strength (from an omni vertical pole 62 ft tall and bottom fed). That remained our baseline standard for stations all around us. I can't give you any real tech help since so much results from all the iterations. I'd suggest you make the boom adjustable for loop spacing, a phase reversal switch and an adjustable combiner to mix and match the signal levels between A and B.
The humor of all this cut-and-try activity was the customer ended up deciding on a loop of our design (30kHz-7MHz) which was just a single turn, 1 meter dia, feeding a ferrite balun (49:1) to match the loops reactance as it varies with frequency. We finally decided to not use a differential preamp, but went into the balun balanced and grounded one leg of the high side (output) and fed the preamp as single-ended. The preamp's output was an emitter follower for 52 Ohms.
So, that's a lot of words with no specific help, but I hope it helps you sort out all the possibilities. Stay encouraged to experiment.
Bob, N1KPR AmComm/Dynametrics
-
- Youtube: N1KPR
- Youtube: Ham Radio Doctor
Engineering, where enigma meets paradox
On Monday, January 20, 2025 at 09:42:54 AM EST, Roland via groups.io <roland@...> wrote:
Hi, I am a new member of this group. Callsign HB9VQQ.
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I have been experimenting with Loop antennas for some time. I have been using a Wlelgood 3.1 loop with a diameter of 1m (single loop) for many years. When I came across the Mag-Loop calculator, I was curious to see if I could improve my RX with a new design. So I came up with a new design with the main focus of reducing inductance and increasing conductor area.
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I finished building the dual parallel loop yesterday and put it in operation. I am using a Wellgood 4.1 Amp. Wired like this. Should I cross the connections?
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So which of the two is better? I use WSPR to compare the decoding performance with my “old” Wellgood loop with 2 RX-888 Mk2 and wsprdaemon. This allows simultaneous WSPR decoding on multiple bands. In my case from 2200 - 40m band (bands of interest).
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This is my test setup to compare the performance
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The results can be seen here (still running at the time of this writing). I am not overly happy with the results, especially with the DX Spots (Distance > 3000km) on 40m.
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I am not sure if my 2 parallel loop design is a good one, maybe 2 crossed parallel loops in the same plane (LZ1AQ) would be better. Also, I am not sure if the Wellgood Amp is well suited for this setup.
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73
Roland
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Experimenting with Loop Antennas
Hi, I am a new member of this group. Callsign HB9VQQ.
?
I have been experimenting with Loop antennas for some time. I have been using a Wlelgood 3.1 loop with a diameter of 1m (single loop) for many years. When I came across the Mag-Loop calculator, I was curious to see if I could improve my RX with a new design. So I came up with a new design with the main focus of reducing inductance and increasing conductor area.
?
?
I finished building the dual parallel loop yesterday and put it in operation. I am using a Wellgood 4.1 Amp. Wired like this. Should I cross the connections?
?
?
?
?
So which of the two is better? I use WSPR to compare the decoding performance with my “old” Wellgood loop with 2 RX-888 Mk2 and wsprdaemon. This allows simultaneous WSPR decoding on multiple bands. In my case from 2200 - 40m band (bands of interest).
?
This is my test setup to compare the performance
?
?
?
The results can be seen here (still running at the time of this writing). I am not overly happy with the results, especially with the DX Spots (Distance > 3000km) on 40m.
?
I am not sure if my 2 parallel loop design is a good one, maybe 2 crossed parallel loops in the same plane (LZ1AQ) would be better. Also, I am not sure if the Wellgood Amp is well suited for this setup.
?
73
Roland
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In case anyone is interested, I bought an LZ1AQ type amp from Everett before Christmas and finally got it up today.? I'm using a 4 foot loop made from 1/2 hardline, fed with about 50 feet of RG6, and 8 feet AGL.? I was fat, dumb, and happy with my homebrew? amp based on the G8CQX design with a pair of 2N5109 transistors and a 3 foot loop of the same material but as a mobius.? The difference is amazing.? Just as a point of reference for myself , I am now receiving solid copy NAVTEX on 518Khz from Labrador and seeing signals from Greenland. ?Those stations where not even a squeak previously. Florida and PR boom in like they are local. I am in coastal NJ.? ? NDB stations are all over the place.? 160 and 80 are a pleasure with an S1 noise floor and very little reduction in signals from my transmitting antennas.? Good stuff!
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Re: loop material question
For inductive reactance reduction of a rectangular cross section conductor compared to a circular one, the width to thickness ratio of about 16:1 is about the point of diminishing returns. This does not apply to applications where extreme currents are involved as in station grounding and lightning abatement.
Bob, N1KPR AmComm/Dynametrics
-
- Youtube: N1KPR
- Youtube: Ham Radio Doctor
Engineering, where enigma meets paradox
On Friday, January 17, 2025 at 09:54:30 AM EST, Phil via groups.io <k0twa@...> wrote:
The intent of my comment was not to change the topic; rather to ask the question; "If a flat [sheet metal, such as copper] conductor is a lower inductance than a round [copper/aluminum] conductor, shouldn't it be well suitable for a receive-only loop?"
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I believe it would work just fine.
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ON THE OTHER HAND... there is a lot more wind resistance with a flat conductor.? Even a small flat-conductor loop would require a very stout mounting and construction to withstand anything more than a light breeze.
--
Phil, K0TWA
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Re: loop material question
The intent of my comment was not to change the topic; rather to ask the question; "If a flat [sheet metal, such as copper] conductor is a lower inductance than a round [copper/aluminum] conductor, shouldn't it be well suitable for a receive-only loop?"
?
I believe it would work just fine.
?
ON THE OTHER HAND... there is a lot more wind resistance with a flat conductor.? Even a small flat-conductor loop would require a very stout mounting and construction to withstand anything more than a light breeze.
--
Phil, K0TWA
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Re: loop material question
Lots of "hand waving" data here. Suggest you take a look at:
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There is also an extensive study buried in the "Journal of the Franklin Institute". I remember reading 20,000 ampere per microsecond average rise times. I think I recall calculating the volts per meter on a #6 ga. copper ground (vertical) at 10kV per meter resistive and 100kv/m inductive and a final temp of 180 F afterwards.
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I still wonder the grad student who was watching a Tektronics oscilloscope connected to the .001 ohm current sense resistor at the base of the lightning tower. There is mention in the paper that one giant bolt exploded the special resistor.?
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There are also "super bolts" that you just can't protect from, but fortunately they are very rare and mostly sky to sky.
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My personal antenna lightning solution is to always disconnect all feed lines and drag the ends 20 feet from the house. I live at the top of a 900 foot hill and used to get struck about two or three times a year. Many, many telephone lines replaced. As my grandparents said, "If the telephone rings during a thunderstorm, do not answer it!". For years, until I rebuilt the kitchen, there was a 1/4" melted burn at the edge of the kitchen sink caused by a lightning exploded telephone. The family dog was never the same after that.
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Jim/VEZ
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Re: loop material question
The higher in frequency you go, the more you need ribbon conductors to deal with monsterous currents line lightning strikes.? The reactance does not change.? Its reactance can easily be calculated using:
????????? X(L) = 2 x pi x f x L
pi = 3.14159 f = frequency in Hz L = Inductance in H
Both the ribbon and cylindrical conductors exhibit inductive reactance.? For a unit length of each the wide ribbon conductor exhibits less inductance than the cylindrical conductor.? As the reactance increases (wire is worse than ribbon conductors) AND the frequency increases,? the copper ribbon and the cylindrical conductor become less and less capable of handling very large currents.
Dave - W?LEV
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Back when I was working with several radio sites, we were using 2" wide flat copper ground strap; because it was supposedly lower impedance than wire ground conductors. [Lightening as you know is NOT a DC impulse.] Mmmm. At what frequencies do flat strap conductors stop being lower impedance than round conductors or vice-versa?
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On the other hand, flat strap in the open air outdoors would tend to flap and twist in the wind, making it unsuitable for an outdoors antenna.
--
Phil, K0TWA
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VE6WZ cat6 feed cable low noise rx antenna
A interesting summary on using cat6 for low noise rx antenna feedlines.
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?https://www.youtube.com/watch?v=i44PU8NJf1M
I have used a single VE6WZ transimpedance amplifier vertical and? I happy with the results especially on the lower frequencies. I dont have? RFI noise issues? and this antenna performs better as general purpose antenna than the loop especially on NDB targets.
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It would be practical for small loop antennas especially when you want to protect, power? them or bypass the preamp all together.
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The costs of coax cables seems to be sky rocketing while more commonly used cables like cat6 seems to be falling.
Long term it might be in everyone's interesting to design loop amplifiers for feedlines like cat6.
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I understand that LZ1AQ was the first to use catX cables for a feedline, although twisted pair balanced lines have been around for a while and used on low noise rx antennas in the past.
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Henry
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Re: Wellbrook traced-out loop amp schematics uploaded to Photos
Hi Bernard,
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If you still need spice model,
you will find "2SK932-23 Model_Rev0" at?
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https://www.onsemi.jp/products/discrete-power-modules/jfets/2sk932#technical-documentation
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Re: loop material question
Back when I was working with several radio sites, we were using 2" wide flat copper ground strap; because it was supposedly lower impedance than wire ground conductors. [Lightening as you know is NOT a DC impulse.] Mmmm. At what frequencies do flat strap conductors stop being lower impedance than round conductors or vice-versa?
?
On the other hand, flat strap in the open air outdoors would tend to flap and twist in the wind, making it unsuitable for an outdoors antenna.
--
Phil, K0TWA
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Re: Common_Mode_Chokes Video
The ferrite used all came from digikey and is a product of fairite corporation. The coil I used has 3 rod assemblies inside.
? 1 assembly is made of 1.02 inch diameter beads 1.125 inches long. The other 2 rods are a stack of .736 diameter 1.125 inches long.
40 beads in each rod for a 45 inch long rod bundle. Mix is 75. Total weight is 10.14788 lbs.
? I use polyester printer media cut in strips to string the rods on...then one layer of a clear plastic tape over the beads. The whole stack pretty much fills the pipe and dense urethane foam is in each end cap of the PVC pipe which puts the stack under compression.
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?2.39 Lbs of # 20 wire on the 2.375 inch outer diameter PVC.
?5.04mh in the audio range with no core.
?331mh with the core installed.
?Q is 362 @ 2.5 kc.
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?It is a heavy antenna that works well. The winding is secured and ruggedized by using 3 inch diameter marine shrink wrap with a hot glue lining installed with a heat gun.
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Re: loop material question
john
Go look at Lz1aq website.. much info on there re loop antenna fabrication..plus much much more.
Chavdar is a well know and respected wealth of knowledge.. ie on here one can buy from USA his modded preamps etc. see Everett..
Regards Simon g0zen
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Re: Common_Mode_Chokes Video
Hi
Just DONT buy on ebay/ preferred vendor from China! ( even if cheap!) Always more expensive but as above..mouser etc.
Simon g0zen
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Re: loop material question
thanks for all the replies everyone. Much appreciated. I’ve been ruminating on the connection point. Supporting and fabricating the loop is the easy part. I don’t think having a squared off end of loop will be good. Possible I will taper the sheet to a smaller size at the connection. Possibly have multiple bolts or even a bar type connection at the amp housing. So many possibilities. I will just start experimenting and post my results. Thanks everyone.?
john.?
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Re: Common_Mode_Chokes Video
I stocked up from
Fair-Rite at Mouser about a year ago. Digikey also had them as
well as several other companies.
Gedas, W8BYA EN70JT
Light travels faster than sound.....
This is why some people appear bright until you hear them speak.
On 1/15/2025 3:46 PM, Fred Moore via
groups.io wrote:
toggle quoted message
Show quoted text
Quick Question.? Who do you purchase your 77 and 75
mix from?
Fred
N4CLA
On Mon, Jan 13, 2025 at
11:32?PM VLF Dilletante via <brownpiggin= [email protected]>
wrote:
I use 77mix for my AM BCB filters. I have to get some
75mix for the usb cables to my Airspy for VLF.
?
?I used my giant ferrite VLF loopstick in the aftermath
of Helene here in Asheville for some natural radio listening
in the middle of the blackout. It was beautiful listening. I
used the 1246 turns of #20 over over 10lbs+ of ferrite 45
inches long into a 33k to 600 ohm transformer into a MM-1
Sound Devices preamp using Sennheiser HD620S headphones. It
was incredible listening...the best of my life.
? I ran the gain @60db and had to be careful to avoid
feedback!
?A real bright spot in the disaster! I could also listen
and tell how fast they restored the grid. It was epic. I had
no power for a week and no water for 2 weeks. No potable
water for over a month.
?
?But no AC grid for miles and miles working? Fantastic
for natural radio!!!
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Re: Common_Mode_Chokes Video
Quick Question.? Who do you purchase your 77 and 75 mix from?
Fred N4CLA
On Mon, Jan 13, 2025 at 11:32?PM VLF Dilletante via <brownpiggin= [email protected]> wrote: I use 77mix for my AM BCB filters. I have to get some 75mix for the usb cables to my Airspy for VLF.
?
?I used my giant ferrite VLF loopstick in the aftermath of Helene here in Asheville for some natural radio listening in the middle of the blackout. It was beautiful listening. I used the 1246 turns of #20 over over 10lbs+ of ferrite 45 inches long into a 33k to 600 ohm transformer into a MM-1 Sound Devices preamp using Sennheiser HD620S headphones. It was incredible listening...the best of my life.
? I ran the gain @60db and had to be careful to avoid feedback!
?A real bright spot in the disaster! I could also listen and tell how fast they restored the grid. It was epic. I had no power for a week and no water for 2 weeks. No potable water for over a month.
?
?But no AC grid for miles and miles working? Fantastic for natural radio!!!
|
Re: Common_Mode_Chokes Video
On Tue, Jan 14, 2025 at 06:31 AM, VLF Dilletante wrote:
I used the 1246 turns of #20 over over 10lbs+ of ferrite 45 inches long
Wow. From where did you got that ferrite?
?
73, Jukka
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Re: Common_Mode_Chokes Video
I use 77mix for my AM BCB filters. I have to get some 75mix for the usb cables to my Airspy for VLF.
?
?I used my giant ferrite VLF loopstick in the aftermath of Helene here in Asheville for some natural radio listening in the middle of the blackout. It was beautiful listening. I used the 1246 turns of #20 over over 10lbs+ of ferrite 45 inches long into a 33k to 600 ohm transformer into a MM-1 Sound Devices preamp using Sennheiser HD620S headphones. It was incredible listening...the best of my life.
? I ran the gain @60db and had to be careful to avoid feedback!
?A real bright spot in the disaster! I could also listen and tell how fast they restored the grid. It was epic. I had no power for a week and no water for 2 weeks. No potable water for over a month.
?
?But no AC grid for miles and miles working? Fantastic for natural radio!!!
|
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Re: loop material question
If you remember when MFJ first was selling its transmit loops, the short period when these were contemporaneous with the AEA Isoloop, MFJ touted that their loop
was not a flat element, was instead round tubing. Supposedly, the not crowding of the RF currents in the middle of the flat strip, away from the thin edge dimension, was an advantage
of the MFJ antenna. But i don’t believe their ad; this “loss” would be, i think, minor compared to other small transmit loop losses.
-Hue Miller
Newport, Oregon, USA
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Bob, N1KPR
James Redding WA9VEZ
Superlite