[Milsurplus] Simple, Effective Loop Antenna for MF-LF

[B. Smith]

Dave
You can glue the rods end to end to make a nice 10 rod, 3 or those 10 
rods will make a nice core.
k4che

"Didn't have the big ferrite rod, but I do have a bunch of those 5/16ths 
diameter, 5 inch long rods used in early transistor radios. I bundled 
three of them with tap and wound 14 spaced turns evenly spaced, securing 
them with tape:"

On 8/17/2019 6:20 PM, David Stinson wrote:
>
> A Simple, Effective Loop Antenna for Your LF Receiver.
>
> On LF-MF, a well-designed ferrite loop receiving antenna will run 
> rings around random wires and "E-Field Probes," because they can be 
> easily rotated and tilted to "null-out" noise sources and interfering 
> signals.  There are a few commercial receiving loop antennas 
> available, but they are laughably expensive and no better than the 
> simple design presented here.
>
> The Loop Amplifier:
> I use the Palomar LA-1 Loop amplfier with all the plug-in coils.  This 
> is no longer being manufactured.  It was insane expensive when it was 
> and still is on the pre-owned market, going for $150 with only one 
> coil.    Inside is a tuning capacitor, a board about two inches 
> square,  a "stereo" quarter-inch jack for connecting the coil, 
> switches and  a nine-volt battery.  Here is the circuit diagram:
>
> https://photos.app.goo.gl/emcNuKcRe4XFZ5yu9
>
> The Coil:
> The original LA-1 coils used a 5/8 diameter, 7-inch ferrite cores with 
> u=125.  The coil is bifilar wound.  There is an excellent, short and 
> readable paper on this type of loop and specifically this type coil 
> published by NASA at:
>
> https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19800006804.pdf
>
> The discussion of loop design begins on page 2.   They used a 5/8th 
> diameter coil and that #22 speaker wire we all got from Radio Shack to 
> wind the coil, looping-back the end of wire "A" to the beginning of 
> wire "B" and grounding this point, makeina a dual winding with center 
> tap grounded.
>
> I did a little fiddling on this today.  Didn't have the big ferrite 
> rod, but I do have a bunch of those 5/16ths diameter, 5 inch long rods 
> used in early transistor radios.  I bundled three of them with tap and 
> wound 14 spaced turns evenly spaced, securing them with tape:
> https://photos.app.goo.gl/VFEBYyiw62JUxqN29
> The start of wire "A" is one side of the loop coil (left).  The end of 
> wire "A" is brought back and connected to the start of wire "B."  This 
> becomes the grounded center tap of the loop. The end of wire "B" 
> becomes the other side of the coil (right).
> https://photos.app.goo.gl/2aYiRse3Jg252KX18
>
> The loop center tap goes to the grounded "sleeve" of the stereo plug.  
> One side of the coil winding goes to the connector tip and one to the 
> connector ring.  With 14 evenly spaced turns, the loop tuned sensitive 
> and sharp from about 700 KC up to the 160 Meter Band.  Compressing the 
> turns together moved it down to cover about 500 KC to about 1600 KC.   
> Turning the loop displayed excellent nulls and peaks.  Once you find 
> the "azmuth" null, lift one end to deepen it with an "elevation 
> angle."  You can lean it against a block of wood with an angle cut or 
> just prop it on something.
>
>
> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient&utm_term=icon> 
> 	Virus-free. www.avast.com 
> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient&utm_term=link> 
>
>
> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
>
> ______________________________________________________________
> Milsurplus mailing list
> Home: http://mailman.qth.net/mailman/listinfo/milsurplus
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Milsurplus at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to smithab11 at comcast.net