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Forums | Crystal Radio Think Tank ** Advanced Forum | Loop antenna with regeneration Post Reply Send Topic To a Friend
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John Bruce McCreathPosted - 3 December 2012 12:12  Show Profile  Email Poster  Edit Message  
Over the weekend I built the circuit shown on the linked site below and was quite impressed with how it
performed on the AM broadcast band with just a 14 inch diameter, 8 turn loop tuned by a 395pF varicap.
Scroll down the page to the
schematic titled:

DL7MWN Q-Multiplier circuit.

http://theradioboard.com/rb/viewtopic.php?p=38740

R6 is removed from the tank circuit, leaving just the C and L. If you bother to read the entire post, the
resistor is explained as representing the R losses in the tank circuit. I intend to try it with a ferrite rod
loopstick to see how that compares to the 14 inch frame loop.

73, J.B., VE3EAR

John Bruce McCreathPosted - 5 January 2013 11:54  Show Profile  Email Poster  Edit Message  
I finally got around to trying my "regen device" on a 7 inch ferrite loop-stick in place of the 14 inch round frame loop. It was awkward to do a quick A-B comparison, but I'd give the ferrite a slight edge.

73, J.B., VE3EAR

Dan McGillisPosted - 8 January 2013 18:53  Show Profile  Email Poster  Edit Message
JB -- couple of questions:
What was the diameter of the ferrite rod?
What type material (61, etc)?
And, how many turns of wire on it?

These loops are addictive. :-)

73, Dan

John Bruce McCreathPosted - 10 January 2013 7:58  Show Profile  Email Poster  Edit Message  
Hi Dan,

I've had the ferrite antenna for decades, so I don't know where it came from or its original usage, but here are some details:

1) It's sealed inside a plastic tube that is 0.75" dia. and 7.5" long
2) Four leads come out one end of the tube.
3) There is adjustable ferrite "slug" at the opposite end.
4) Total inductance is 195 uH.
5) There are two taps near the "cold" end of the windings.

That's about it, 73, J.B., VE3EAR

Dan McGillisPosted - 10 January 2013 9:39  Show Profile  Email Poster  Edit Message
Thanks JB.

I had wondered about the performance benefits of a longer ferrite rod.

Comparing a 14" air loop to a 0.5" x 4" type 61 loopstick (60t cw 165/46), I found the 14" loop to be louder.

73, Dan

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