VE3DO Receive Antenna Build Problem

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by N7BB, Jun 13, 2021.

ad: L-HROutlet
ad: l-rl
ad: Left-2
ad: abrind-2
ad: L-Geochron
ad: L-MFJ
ad: MessiPaoloni-1
ad: HRDLLC-2
ad: Left-3
  1. N7BB

    N7BB XML Subscriber QRZ Page

    Hello. Time to reach out to the collective knowledge base!

    I've built many, many antennas. This is the first time I've tried to roll my own transformer, however.

    This antenna looks interesting, and I happen to have all the materials, except my resistor is only 1/4 watt.

    I think the problem lies with the transformer, because I'm getting NOTHING off this antenna. It needs amplification, but I'm getting absolutely nothing.

    (OK I can receive my local 50,000 watt flamethrower AM station, but I'm pretty sure I'm getting it off of the feed line only)

    I used a #43 ferrite ring I had laying around, and tried to follow the diagrams, which I've attached for your reference.

    To me, it looks like 9 turns and 3 turns. The 9 turns I've connected to the top studs of my transformer enclosure: Stud Connection, 9 turns around the ring, then connection to the opposite stud.

    The bottom of the ferrite ring is connection to the center pin of the SO-239, 3 turns, and connection to center pin.

    This diagram looks like the shield is tied in to the center pin as well. I've jumpered ground to center pin on the SO-239. (this may be my issue, & I can easily cut this).

    I got NO continuity between center pin and either top stud, nor coax ground and top studs. Continuity between center pin and ground shows as expected even though I though it was weird.

    This struck me as odd, but maybe the signal is coupled through inductance? (I still think it's a connection error on my part). As I type this, my next trouble-shoot is to clip a test lead from the center pin of my coax connection to the center pin only, to see if I get any signal.

    The antenna ground rod is attached to the stud opposite the stud with the terminating resistor. I also made a short jumper between the studs to tie-in the ground. The antenna is dead both with, and without, this short jumper.

    I have some pretty thick insulation on the 16 gauge solid wire I'm using. Could this be the problem?

    I've gone back and re-read the articles. Neither article has a photograph of a finished transformer for this antenna. I'm thinking, even though I have the turns ratio correct, I've got the connections wrong.

    Any assistance would be appreciated!!
     

    Attached Files:

  2. N7EKU

    N7EKU Ham Member QRZ Page

    Hi,

    If you connect the center conductor of you coax to the shield of the coax, you have just shorted out your antenna connection! Please clip the jumper. Enlarge the picture and you can see the little black dot just goes to the shield and not the center.

    There should be no conductivity between the top stud and any of the coax; it is as you said, coupled inductively.

    The insulation thickness makes no difference for the inductive windings.

    Cheers and it should work once you remove the short.
     
  3. N7BB

    N7BB XML Subscriber QRZ Page

    I've uploaded a couple of pics of my transformer build. Please excuse the residue inside the transformer box: this is leftover spray foam. (I had re-purposed an old Palomar 9:1 balun; they're apparently very generous with the spray foam. It is just what I needed for hardware: enclosure, top studs, etc.)
     

    Attached Files:

  4. N7BB

    N7BB XML Subscriber QRZ Page

    Interesting!!! I just tried a banana plug to the center of the SO-230 and clipped to center of coax: nothing. Wouldn't this be the same as clipping the ground? In any case...even though it's raining...I'm going out to clip that sucker and will report back!
     
  5. N7BB

    N7BB XML Subscriber QRZ Page

    What about the jumper between the studs to tie in the ground? Seems unecessary.
     
  6. N7BB

    N7BB XML Subscriber QRZ Page

    Well...crud. I clipped the center pin to coax ground jumper. Same result. I replaced the top studs jumper. No improvement. I'm completely dumbfounded as to why this isn't working.
    I am stuck on this detail, and a bit confused. It says, "Tie transformer ground and resistor ground together". My termination resistor is external. I can easily move it inside the box, but the proper application isn't clear. I have resistor terminated to a stud, the two studs tied together, and the ground lug on the other stud. I can move this configuration inside the box, but I'm wondering if the wire ends from the windings should be tied together, with the resistor, to one stud, and the ground to the other?
     
  7. N7BB

    N7BB XML Subscriber QRZ Page

    I meant to upload this on my previous post
     

    Attached Files:

  8. N7BB

    N7BB XML Subscriber QRZ Page

    I figured it out!!! Right now it's just test leads, but the secondary winding goes center pin, 3 turns around the ferrite, then terminates at coax shield. It's working FB right now.
     
  9. N7EKU

    N7EKU Ham Member QRZ Page

    Just like in the schematic LOL!

    Sometimes it takes a little time to get used to reading those.

    Good listening!
     
  10. W5VQ

    W5VQ Premium Subscriber QRZ Page

    Reading this reminded me of the W7IUV flag antenna for 160m. I built and used one years ago with very good results. There is still a lot of info on the internet on this antenna. Also in ON4UN's Low Band Dxing book. Larry also designed a very nice preamp too. Just thought I would throw this out there.
     
    N7EKU likes this.

Share This Page