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air core loop antenna balun
Hi, looking for the winding details of a 2.5:1 air core balun for a single band loop antenna, I have read lots of arguments against these but still wish to try one against my 4:1 toroid balun out of interest, there is a guy in the USA selling them with good reviews but for the sake of a plastic tube former and some wire it would not be cost effective to have one shipped to over here in the UK, does anybody on this forum have the winding details or a link to constructing one as I cannot find it anywhere?
cheers Phil M6MRP? |
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Re: Alpha Loop
If some owns a Alpha Loop antenna can they post some clear pictures of the coupling box and antenna in general. I think these are great antennas for portable use, from descriptions I have heard they are well built but even the manufacture does not have clear pictures of the antenna on their web page. There are hundreds of pictures of the Alex Loop antenna and with this being a the same type of antenna, it would be great to compare the way they are made. I am currently working on a Aluminum loop antenna made from 5/8 inch wide strips of flat bar about 1/8 inch thick. They bolt together and have a permanent bend to them so when assembled form a near perfect 4 foot diameter loop. I am using 1/4 inch Teflon insert lock nuts, washers and bolt to assemble the antenna. Takes a little more time to assemble than the Alex loop but over all I like the way I have it. From the pictures of the Alpha loop, they seem very similar. Don't have any idea what type of capacitor is used in the Alpha loop but at this point it really does not matter. This loop design is always up for improvements. But if anyone has one of the Alpha loop, some clear pictures and descriptions would be great!
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Re: N3FJP's Nested Loop article 2014 March QST
N6RK-Rick, Hello-sure didn't mean to get you upset...sorry if so. Just with good intentions I wanted to share, some may have been more receptive to it. Having said that-do know I for one personally value your vast-proven knowledge-especially regarding loops-radials etc, You and I had been exchanging messages regarding your "remote tuned" loop design. Last communication was this past November.?I had expressed great interest in a design favoring 80-40-30 meters, you had referenced a 10' and 20' design, with a few tweaks-eliminations of a few diodes. conversation?ended with you stating you were field testing this modified design and was going to check performance of the modified circuit with the 10' loop and also a 20' which would also include 160m! I had continually expressed my interested, but requested?for you?work on it only as you could. Very last message you said possibly over that weekend you may give it a field test...My concerns all along were I wanted you to accommodate my request truly at your convenience as I know you remain busy, I was sincere in my interest request, but after November I received no further communication? I didn't want to harass you or bother you, so I have sat back, checking often for?any follow-up?reply with your findings. When I seen your reply to my QST nested loop post, I thought it may be an opportunity to touch base once more in the interest and hopes of some positive findings, allowing to move ahead. Please follow-up if you wish-off list possibly would be best, I am good on QRZ, or at jrl@... It was good to see you in there-although sure didn't mean?to create a problem with my post. Was just trying to pass on the article to others to view and digest. Thank you Rick, for working with me on my previous interest in your remotely tuned receiving loop and my inquire we previously had been exchanging communication up till November 2013....Thinking something may had come up, so was relieved to see your recent active post- as now I know all is ok on your end friend. Kind Regards Rick. Ross? -KB8NTY- |
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Re: N3FJP's Nested Loop article 2014 March QST
Yet another worthless QST antenna article.
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This is nothing new, it is just the driven element from a quad antenna. Lightning Bolt sold a 5 band quad 30 years ago. Only they wisely used fiberglass spreaders, instead of PVC. PVC is a terrible structural material. They also wisely used a broadband transformer instead of bandwidth limiting 75 ohm sections. The article claims there is no interaction between elements. I don't know how the author arrived at this, but I modeled this configuration a few years ago and found that there is substantial interaction especially on 10 meters. And I modeled it with relays at the feed points to open up the unused loops. As described in QST, it would have even more interaction. Rick N6RK On 2/14/2014 9:17 PM, kb8nty@... wrote:
Check out N3FJP's Loop antenna article in the new 2014 March QST issue. |
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Nested Loop Antenna March QST (duplicate post)
Just wanted to report, my duplicate (not exact) nested loop post was due to a long delay. Well what seemed long as I posted my first, then the next day I didn't see it up yet, so I created another. Other yahoo groups my posts usually post within minutes to less than 1/2 hour so I thought maybe I had made an error in the original post. To my surprise now both appear?...Go figure?...No big deal, just wanted to explain! So anyway regardless checkout the article, I just wanted to share with the group. -73- Ross? -KB8NTY- |
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Re: Nested Loop Antenna March QST
¿ªÔÆÌåÓýOne of club member built a similar multi-band loop out of fiberglass poles and tie wraps.? It performed very well and did many QSLs on field day. 73, Alan - W6ARH ? ? From: loopantennas@... [mailto:loopantennas@...] On Behalf Of kb8nty@...
Sent: Sunday, February 16, 2014 8:28 AM To: loopantennas@... Subject: [loopantennas] Nested Loop Antenna March QST ? ? N3FJP & son?had built a multiband nested loop...looks interesting...and a good read! ? ? It is featured in the March 2014 QST, and is available also on-line. ? -73- Ross? -KB8NTY- ? ? ? ? |
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Re: Loop Antenna Balun
It may be true that HOAs can seem to be overbearing.? But everywhere I know of the homeowner is informed of the HOA before buying the home.?
That said, one of the great things about a loop antenna is that it can have nearly any shape and can be easily disguised within the normal architectural features of nearly any home.? After all, it is just a piece of wire.? :) |
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Re: Loop Antenna Balun
HOA = Home Owners Association, also may be known as the Nazi Architectural Control Committee, etc. that often abitrarily and strictly enforces silly regulations and rules created usually by a small group who want to control how others live, and charge you for the privilege...fortunately not all neighborhoods have one.
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Nested Loop Antenna March QST
N3FJP & son?had built a multiband nested loop...looks interesting...and a good read! ? It is featured in the March 2014 QST, and is available also on-line. -73- Ross? -KB8NTY- |
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N3FJP's Nested Loop article 2014 March QST
Check out N3FJP's Loop antenna article in the new 2014 March QST issue. ?Don't have it yet, it's also now on ARRL website. Interesting read... -73- Ross? -KB8NTY- |
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Re: Loop Antenna Balun
Harry, I have used an untuned loop about 90 feet circumference ( a two turn loop sides 6 metres x 2 metres, hung under the eaves at this QTH.) The plane of the loop North/South used it to listen to the Sydney Hobart Yacht race. Armchair copy, you could almost swell the salt air! Positioning it on the roof may make it susceptable to mains bourne QRN. Could you position it under the eaves of the building Am not sure what a HOA is. Give it a go, temporarily? at first, if it's OK make it permanent. Tuned loops need to be say 1/3 to1/4 wavelength and brought to resonance capacitivly. An untuned loop will have a basic resonance derived from its native inductance and capacitance. Again give it a go. Regards Max VK2TTI
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Re: Loop Antenna Naivete
It is fascinating that I would compare any antenna, except in an antenna shoutout, to a loop. I find that fascinating because no where in the design of a small Magnetic Loop Antenna will you find the formula used on the other antenna systems used (i.e. 468/frequency mhz). When an MLA is tuned, for the RECEIVE side there is indeed an increase in the noise floor, a VERY big increase. To say that the receiver does not benefit from a lower SWR is wrong. Also wrong is that the loop is anything but inefficient, rather the efficiency of a loop is higher than other wide band antennas like a dipole. Isn't it true that the effective radiated power is greater from a loop than a traditional dipole?
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Re: Loop Antenna Balun
? Harry, ? Might you not be better off with an easily homemade multiband dipole, cut and orientated to the frequencies/regions of your preference? Such an antenna is easily hidden, too and its installation may not even contravene your local legislation. ? J. |
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Re: Loop Antenna Balun
A 100 foot long receive loop makes no sense. Receive loops
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need to be less than 1/3 wavelength at the highest frequency, which would limit you to 3 MHz. You should probably be looking at a Pixel or Wellbrook loop, 3 foot diameter. You should be able to deploy that even in an HOA. Rick N6RK On 2/14/2014 10:12 AM, hmholden69@... wrote:
I live in an area that has HOA rules against outdoor sw antennas. I |
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Loop Antenna Balun
I live in an area that has HOA rules against outdoor sw antennas. I think my best bet is a stealth loop antenna laid directly on the roof. It would be trapezoidal in shape and about 100 feet long. I want to feed the receiver with small coax {RG 174}. I want to make a balun on a ferrite rod or air core type. I have some torrid cores but go crazy trying to wind them. Any ideas on the ratio I need {4:!, 9:1, etc} and a place to get plans for winding.This will be a? receive only antenna.
Harry |
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Re: Measuring very small AC resistances
On 2/12/2014 7:34 PM, John Maxwell wrote:
And it occurred to me: I have no idea how to measure _any_ ACForget about this handbook. What you want to do to measure a low impedance is to use a TWO port network analyzer (not a one port NA or an impedance analyzer) and connect the ports to an SMA tee. Connect your DUT at the third port of the SMA tee. By measuring S21, it is possible to work backwards and calculate the impedance on the 3rd port. This technique works down to extremely low impedances. In some cases, you may want to replace the SMA tee with a more precision fixture that puts the DUT in shunt with a through line. Full disclosure: I work for Agilent doing advanced network analyzer R&D... until March 14, when I will be retiring. Rick Karlquist N6RK |
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Measuring very small AC resistances
I was perusing Chris Trask / N7ZWYChris Trask's paper "A Simple
Varactor-Tuned Loop Antenna Matching Network", wherein he makes the sensible statement "...and the designer should always rely to measured data, especially when designing matching networks." And it occurred to me: I have no idea how to measure _any_ AC resistance (as distinct from impedance), let alone the sub-ohm values he's talking about in that context. A few minutes work with Google turned up this: which looks to be a decent introduction to the subject; I'm digesting it now, but I thought I'd ask if anyone has any advice/pointers/lore on the subject. So? -John -- John Maxwell KB3VLL jmax@... Sufficiently advanced incompetence is indistinguishable from malice. |
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Re: Alpha Loop
I bought a Pixel RF-PRO-1B a couple of months ago and put it up on my roof.? I use it with a QS1R software defined radio.? I am very happy with it.? For me, it works as well as a resonant dipole at any particular frequency, but it does this from below 500 KHz to over 30 MHz.? Also, it can be rotated if needed to null out a noise source.? If you are only going to have one antenna to monitor the whole HF/MF band, get this.
Greg Ella Ft. Collins, CO? |
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Re: Alpha Loop
Is the reason that coax is worse than soft aluminum (not rigid aluminum) to build a magnetic loop antenna from because there are thousands of lossy connection points as the braid of the coax weaves itself inside the sheath of the coax? If so, I can understand why a loop with just a few connection points around it would have less resistance than a braid with thousands of connection points. That's the only explanation I can come up with that explains why resistance is less and the skin effect is more on soft aluminum vs braded coax.?
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