Re: Ocon Oscillator Hunt


Jim Sheldon
 

Thanks for this one Jim.  I really didn't like the heavy cardboard frame and I just happened to have a small sheet of 1/16" plexiglass that was big enough to use for the frame.  I found a roll of #22 ga enameled wire (dang stuff was not heat strippable though) and used that for both loops.  The junkbox gave up a 7-50 pf air variable that also got used.  Took a bit longer than 10 minutes on the kitchen table to make it, but it is reasonably sturdy.  The extra handle is some nylon rod I had laying around and after slotting it with the bandsaw, I used some 1/8" brass tubing to pin it in place.

The RF connector is a 4 hole panel mount SMA female that came out of some surplus military gear that got scrapped for parts.

5 turns in a 6.5" diameter loop for the big one and 1 turn in 4.5" for the little one.  

It will just resonate at 7.040 MHz with the 50 pf variable almost completely meshed and it is directional on 40 meters.  I plugged my 7.040 Bayou Jumper crystal into the crystal tester I have and turned it on.  I hooked the loop to my KD1JV ATS-2 which on 40 meters, powers up on 7.040.  I could hear the crystal tester's oscillator on 7.040 anywhere in the house and in most of the yard (the ATS-2 is quite sensitive) and even within 2 feet of the tester, I could get an audible null with the loop even unshielded (I don't see a way to make a shielded loop out of this one).  The actual null is not quite at a right angle to the loop, but about 20 degrees off but that's probably due to the fact that it was hastily made and there is nothing really precision about the circumference of the loop.  It is, however very usable and should do nicely for it's temporarily intended purpose - LOL.

Jim - W0EB




------ Original Message ------
From: "n5ib@... [4sqrp]" <4sqrp@...>
Sent: 2/9/2017 12:07:27 PM
Subject: Re: [4sqrp] Fwd: Ocon Oscillator Hunt

Just to prime the pump a bit on the huffduff (HF DF) activity at OzarkCon, I've posted in the Files area of this Group a one-page PDF document showing how I cobbled together a small loop on the kitchen counter in about 10 minutes. Note that this is not (yet) a shielded loop.

It has a very sharp resonance that can be found by peaking the noise It does show directivity, but not much on 40 m right now to test with. On 30 m it was clear there was directivity. Being a very small loop it's not very efficient so signals (and external noise) are way down. It was also apparent that the noise at this QTH was directional

Jim, N5IB

 

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