Quick and dirty L match tuner

After having good success with the little wspr thing I put together, I decided to put up my old end-fed half-wavelength qrp antenna outside.  I still have a under-window coax connector, so strung it up between my workshop window and the garage across the driveway.  Got much nicer results.

I did notice though that it was resonating low - it was more like 13.5 rather than 14MHz.  I need to adjust it, but it was already dark.  So I decided to have a play with throwing together an antenna tuner real quick.

I took the 3D printed variable capacitor I made a while back, wrapped some wire around an inductor (making taps every once in a while, and threw it together on a little board I made the other day to hold my low-pass-filter.  I'm using an alligator clip to adjust the inductance (choosing different taps on the inductor).

I managed to tune it for 7MHz ok. 

Was having trouble dialing in 14MHz - I think I needed more inductor value choices, and maybe the ability to go lower on the capacitance.  I could have a play with some switches to switch caps in, but this was more just an excuse to put one together, as I've not built one before.  Probably won't use it, but was fun.

Long time, no ham

 I haven't done anything radio related in quite a while.  The past few weeks though I have started poking at stuff again.

I started off building a QRP Labs QDX.  Build went ok, but I keep having an issue where it restarts when I transmit.  I need to debug it more.  But I didn't feel like debugging it, so instead I thought it would be fun to just build the transmit chain.  

Not working great, either.  Probably the stray wires are a bad idea.  Should have built it ugly/Manhattan.

But I got enamored with the drive chip.  I had some 74AC240's sitting around, so built one like was done here.  

I figured while I was at it I should try it out by itself, so put together a 20M lpf, and built up a little board with an SI5351, and made a little wspr transmitter using the gist here.  Pretty sure I used the same one years ago.  

Didn't expect much since I just threw an old efhw antenna around my office.  Checked with my vna and saw it was resonating low (more like 13.5MHz), and was like 2.5:1 at the wspr frequency, but tried anyway.

When I going into a dummy load, it was doing around 1.4V rms, so I think it was only doing 40mw, and with the mismatch less than that.  Still, got picked up.  WSPR is pretty much magic.

I might try to put a transformer after the `240 to lower the impedance it is seeing to get more power out, but ran out of time.  

Also somewhere in the past few weeks, I got a neat BM83 dev board.  I wanted to see if I could use iFTx working via a bluetooth connection.  Unfortunately, I didn't really fully understand the various BT profiles.  The only bidirectional one (before the latest BLE "gamer" profile) is the headset profile (HSP), which is pretty low quality.  I think it would have been enough, but the iPhone won't use that except when answering a call.  (You could access it via your own program, but that isn't what I wanted.)  I found a program that lets you route audio to it, but it doesn't use the microphone.  The only other option would be to use two bluetooth devices in A2DP mode (one source and one sink), but the iPhone apparently won't act as a A2DP sink for some reason.  ::sigh::  Wish I would have understood all of this before buying the dev board, but going through the exercises of trying to get this to work made me understand all of this a lot more than reading would have I think.

JS8Call and 15m Activity

 Used JS8Call I think for the first time today (though I already had it installed, so maybe I had tried it before).  Had to do some adjustments - it thought I had rig control on, and had to increase vox gain on the g90.  But responded to someone in California calling CQ and had a quick QSO.

Was trying 15m today on the small EFHW out the second floor window.  Did ok on WSPR.

New Paddle

 Can't find my paddle.  But then kb9rlw posted a new design that was quick to make.

RF Choke

 

From this thingiverse page.

Magnetic Loop Antenna

 

After I had a variable capacitor, I thought I'd go ahead and try my hand at a magnetic loop antenna.  This used 15 feet of RG58u I had sitting around that I wasn't going to use (as it was kind of chewed up from having been caught in a door a few times - used the good parts that were left).  Used a 3 foot length for the coupling loop.  Have the cap hanging from a hook at the top, have the coax zip-tied to it.  Using some PVC pipe I had laying around for the mast/shape, and have that one a little base I had printed for a e-drum I made at some point.

I made this for 20m, but couldn't get that to tune.  The lowest capacitance I have seems to be too much.  I might try putting in a cap in series to tune down (if I have any 500v ones sitting around).  But for now I tried 30/40m.  I was using 1W (as I wasn't sure about the voltage the cap could handle, plus I was using this in my garage...), and didn't really get anywhere on wspr on 40m (got picked up in the immediate area, but no farther).  But on 30m, did ok

Tuning it is *hard*.  Just barely turning the knob moves the SWR dip a *lot*.

This was a fun experiment.  I don't really see using it much, but might play with it some more at some point.  Definitely felt like I learned a bit along the way.

Mostly 3d printed variable capacitor

 

Made a variable capacitor.  Measured it as 34-164pF.  Have notes about it on the thingiverse page.

As an aside, I went to measure it with the LC100A LC Meter, and the stupid usb port snapped off.  Wasn't feeling like fixing it right now, so tried using the nanoVNA.  But wasn't getting numbers that made sense - probably didn't calibrate it well (my dummy load may be more inductive than I thought).  So was getting some other resistors together to calibrate with, and in doing so I got out my regular multimeter (as my eyes are tired).  And turns out, *it* can measure capacitance.  I never noticed that before.  It was one I got at Radio Shack for cheap when they were going out of business, and I don't think it had the manual.  Anyway, that was a win.