N1JER Does it Again!

Jeremy, N1JER, hasn’t been a ham long, but he’s really gotten into it in a big way, building kits and homebrewing QRP stuff. His latest creation he calls the “Toilet Paper L-Network Tuner.” The name comes from the material he used for the coil form.

Here’s what he posted to the qrp-l.org mailing list:

I shot a video documenting this project, and have posted some photos.

Overview:

  • Uses the standard L-Network out of the 2008 ARRL handbook, pp. 19.44 and 19.45.
  • Borrows the switched inductance coil idea from KD1JV’s ALT, and KI6DS’s SLT.
  • Uses an air coil formed around a Toilet Paper roll with multiple tap points.

Details:

  • Uses a varicap out of a junk AM/FM radio I found on the street.
  • Uses 1 insulated binding post, and 1 binding post that connects to the chassis for ground.
  • Uses an array of inexpensive switches that are soldered together.
  • I used a formula to have each switch control a coil that is
    progressively smaller. In order from left to right ~7uh, ~4uh, 2uh,
    1uh, and 0.5uh. I didn’t measure the actual values, but did pay strict
    attention to how the coils went on the TP. Each coil can be turned on
    independently so I can have 2+1+0.5 = 3.5uh.
  • Total cost was about $11 USD. (including value of junkbox parts).

In use:

  • Using a 51ft wire with a peak at about 30ft and a 33 ft ground wire.
  • I get a solid dip at 40m. (Tested using KD1JV ‘Tenna Dipper the LED gets very dim, but I don’t know the actual SWR).
  • Using same setup 30m on 20m the LED can go completely out.
  • On 80m there is a very slight dip, but I wouldn’t think good enough to operate.
  • I made one contact with this using my 40m 3w Wilderness SST, ~750 miles.

Have a great day everyone,

Jeremy Chase, N1JER
http://jeremychase.net

Comments

  1. Dan,

    Thanks for putting this up!! Hopefully others will get the itch to build ‘stuff’. :)

    73
    N1JER
    Jeremy

  2. This is REALLY good stuff. This is the type thing that new hams/young people should be shown. The minute students learn about tank circuits, they want to build a transmitter. This type tuner would be excellent for them.

    Are you keeping track of all of these neat projects?

    73,

    Ronny, KC5EES
    Austin, Texas

  3. Way to go Jeremy….and great to hear that Call Sign again. (You’ve even got me wanting to solder a few wires). I worked you back on the 14th, from that mighty 2.5 watts in Brooklyn. Keep up the CW work….it seems everything is working just great!

    72′s

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