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73′s Expanded L Meter

IMG_0109.jpg July 2013

I’ve actually been building this meter for a while because I had a hard time sourcing the chokes for it. Choke coils come in a variety of diameters and lengths for any given value and most of the ones commonly found are huge. The design originally called for Radio Shack chokes, which are the right dimensions but they only make one value these days.

As you can see here, the device converts Henry measurements into milivolts and you just read it from a connected DVM multimeter. The coil under test here is rated 100 uH, so why is it reading 98? This is not unexpected for several reasons, first that most manufactured inductors are rated +/- 20% though the type under test is supposed to be a precision inductor and more likely to be within 5%. Secondly, inductance is a measure of stored electricity and while coils are an effective way to trap electricity temporarily the value can read differently for the same coil tested at different times, in different positions or conditions. Lastly, my test leads were common alligator clips about ten inches long and even wire stores a little current – a shorter test lead would read higher values. Now you see why no one really sweats the values on inductors. With inductors close enough is close enough.


13-1.jpg June 2013

I purchased the Soft66Lite kit on eBay and put it together over the weekend. After assembly I placed it in a case I had lying around and I must say it came out very well. This kit is fairly easy to build, though the web site for this radio is in Japan and the English instructions are minimal. If you can follow the schematics the radio is a no brainer, though.

I added a bright blue indicator light that was not in the design, just because. I conveniently found a connection on the board that was exactly the right voltage and tapped into it for the indicator.
13-2.jpg The 10K Pot on the back is used to tune the sensitivity of the amplifier and is optional in the design.
13-3.jpg In the past I have fought with aligning the mounts for the board – this time I put the mounts on the board and superglued them to the case. What the heck, it worked.

Funmitter QRP

IMG_0116.jpg 2013

The Funmitter QRP design is an oldie, but a goodie. This radio uses old school parts including 1 watt resistors and disc capacitors you could use as bread plates. It wasn’t hard to put together, and I purchased the circuit boards for its companion transmitter and amplifier that are in the drawer waiting patiently in line to be assembled. I went as far as texturing the case, an old printer switch box, like an 80′s radio and hand stenciled the name on it. I especially like that it uses the old military crystals plugged into the front for its IF frequency.

2020 Update
I now have the Fun Receiver and Fun Amp boards to go with the Funmitter and will be building those soon too.

ZM-2 ATU Z-Match Tuner

IMG_01141.jpg 2012

One of the problems with operating low power QRP radios is finding a way to tune the antenna. This Z match tuner will tune pretty much anything you want to hook up to it. I generally use a roll up Norcal Doublet antenna made out of computer ribbon cable that fits in my pocket, though I’ve tuned up pieces of scrap wire and an aluminum rain gutter (among other random pieces of metal).  This project uses a monster toroid wired to one of the potentiometers to vary capacitance and of course the other varies the reactance. You twist the knobs to try to get the lit up indicator as dim as possible and you’re tuned up. This isn’t the smallest tuner I have put together, but so far it’s the best one.

The greatest part is that I bought the kit at a hamfest for five bucks. I couldn’t wait to get home and whip it together and by later that evening I had tuned my first piece of scrap wire with it.

Goodwill Robot

IMG_0118.jpg I call this my Goodwill robot because I found the kit in the toy section of Goodwill for under five bucks. The kit originally retailed for over one hundred dollars and I see it in some of the discount catalogs for around ninety dollars these days. Every time I go to Harbor Freight I stop in at the Goodwill next door. I find reasons to visit the other Goodwills in town too. Many of my cases, motors, power supplies and such come from there. Seriously! Start dropping by the Goodwill every now and then for really cheap parts.

My Soap Box

IMG_0117.jpg No, really, it’s a soap box.This box was the best size for the little power regulator, so why not? I put a lot of my projects in Altoids cans too. Sam’s Club used to carry Altoids size tins with clear plastic windows in the top that I always wanted to grab but never did. Now I wish I had scarfed up a bunch of them.

UPDATE: I talked to the manager at Sam’s Club and she said that they only stock the windowed boxes around Christmas time. Now you know where I’m starting my holiday shopping.

UPDATE to the UPDATE: It turns out that the container store carries these little boxes all of the time, but they are pretty pricey.

NorCal Doublet

Norcal-Doublet.jpg The NorCal Doublet has to be the smallest antenna for it’s length one can make. It’s made out of computer ribbon cable cut fifty foot long and then split a little more than halfway down into the two arms of the doublet. You can literally hold it in your hand. Add a Z-match tuner and portable radio and you are up and running pretty much anywhere. Of course you don’t want to put more than about thirty watts through it, but otherwise its a good use of wire.

The last one of these I made was out of a 24 wire ribbon, and each antenna takes four wires so I ended up with six antennas. So far I have sold three on eBay, which more than pays for my supplies and maybe another toy or two.

Not pictured here (yet)

Altoids longwire tuner

Altoids five watt dummy load

Various dipole antennas

Other projects on the bench

  • M0NRZ LED S-Meter 2020. I met John, M0NRZ in a Facebook group and agreed top try building his protoype S-Meter. I am waiting for some parts to come in to finish it. This has been a lot of fun so far.

  • KD1JV MMR-40 "dead bug" 40 meter rig with SSB (voice) and CW (Morse code) operating modes. This one is also waiting for the UPS man to bring me parts.

  • KISS-RX AA2TX Space Radio. This radio is a small software defined receiver for listening to various signals from space like the ISS and a few satellites. It’s a general band receiver for a range of lower a.m. frequencies, basically. I have pretty much completed it, I just need to order one transistor I forgot to get for it and need to dig up a case.
  • Avala YULM1 SDR (Need to wind the toroids and smoke test)
  • BITX Version 3 (just waiting to be cased)
  • BITX 6 (Waiting on me to finish the BPF)
  • Softrock 40 SDR (was working, but I broke the USB cable and am re-engineering that so it won’t happen again)
  • Lightning Detector for the Shack.

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