Some time ago I built an Internet gateway (iGate) for monitoring APRS packets and sending them to APRS-IS.  It never made it to the blog partly because it was built out of Direwolf, so it was mostly software configuration.

Since then, I've had trouble keeping soundcards running in the same configuration and the iGate was offline for some time.

Last summer (or the one before it, I don't remember), I bought the components to a packet station: an AEA PK-232 TNC, a Kenwood Mobile, and a broken power supply.  The broken power supply is still broken, but the rest is up and running.

The APRS Receiver Setup

The APRS Receiver Setup

The setup for the PK-232 is courtesy of LA6YIA on Google Groups:


The APRX setup is not groundbreaking, but it's below, too, since it may help someone...

Then, since the ultimate test is to make it work, I wrote a simple Arduino Sketch using the Argent Data APRS Arduino shield and my trusty IC-T90A...

Obviously, this only transmits once, and it is using manually-entered location, but it does the job.

Look! It's here!

Look! It's here!

And of course, I could find some repeats in the log:

I'm in the log!

I'm in the log!

So at this point there should be better coverage in the far east of Cincinnati.


Category: Equipment


Many months ago, my brother-in-law brought over a guitar with the thought of "you fix it, I'll cover the costs, and we'll split the profits". It wasn't a bad deal, so I started fixing it.  A month later, after I preceded to remove a large part of the partially-damaged finish, he called and told me that he got another guitar and he was no longer interested in pursuing it.

So it sat for many weeks.

And it sat for a few more weeks.

Finally, the same brother-in-law brought over a Marshall head that blew a fuse and a few diodes to repair.  I needed a guitar to test it with, so I finished stripping it and ended up with something that looked decent and actually played (which I ultimately used to test the amp).



Around the same time, Hack-A-Day posted about the 1Wamp, a small, battery powered amp. The schematic looked like an easy build, and I was fairly certain I had all the parts lying around.

Amp Build Part 1: The Preamp

The preamp is very simple: 3 resistors and a JFET.

Yeah, pretty simple.

Yeah, pretty simple.

Simple Schematic (well, this part is, anyway)

Simple Schematic (well, this part is, anyway)

I skipped the Zener diodes, which are there for static protection.  I'll probably add them in at some point in the near future.

It does work. I hooked it up to a 12V linear power supply and took a video of the input (from the guitar) trace and the output trace from the preamp.

The input is about 0.6 - 0.8 Vp-p. The output is about 1.6 - 2.0 Vp-p. That puts it somewhere in the range of 6-8 dBV.  That's a little over spec, but I'm also feeding it 13.8V instead of 9.0 - 9.5V.

Next up: the Tone Control. zOMG 6 components!


Category: Electronics
Tags: , , ,

I recently had the need to check a transceiver to ensure that it was on-frequency.  This is easiest done with a frequency counter, which is included in an MFJ Antenna Analyzer.  I use an inductive coupler made from some coil wire around a small (1/2 inch) piece of CPVC, with the coil connected to a BNC connector.

Inductive Coupler

Inductive Coupler

2015-11-15 12.28.59-2

Radio set frequency (28.5 MHz)

2015-11-15 12.28.52-2

Frequncy (28.499 MHz, or close enough considering the potential error in the antenna analyzer)


Category: Equipment

Hamvention is at a busy time for me, and I didn't know if I was going to attempt to go or not.  I think I'm going to go, though, because I need stuff.

  1. New NMO mobile antenna setup
    My current mobile antenna is a few years old and not only is it showing it's age - the coax is pulling out from the magnet and I can see braid - it probably took damage when I wrecked my truck last October.  The truck is repaired, but the antenna currently has a VSWR of 3:1.  Not good.  I'm going to completely replace the antenna setup with a better one.
  2. Parts
    I'm not looking for any real radio equipment other than parts.  I have some specific needs (linear-taper variable resistors, etc), but nothing out of the ordinary.
  3. Arduino/Raspberry Pi/Beaglebone Black stuff
    Because you can't have too much!
  4. Test Equipment
    Generally, another scope or a spectrum analyzer is out of my price range, but if I happen to find one...

So I'll probably be at any Reddit or WATwitter meetups, and I'd assume the same location as last year.

Category: General Stuff

WifE8P was complaining that her Shark Steam mop was not producing a lot of steam.  That's really the only way we clean the dining room, kitchen, and entry floors, so it's pretty important for it to work.

The steam would act like it was operating, but would put out little steam.


Category: General Stuff

I happened to stumble on an advertisement for a cool looking device that would work with a phone via Bluetooth.  It was ideally something that would be used for things like movie times, bus waiting times, or something else small and URL based... kinda like a QR code without the annoying camera part.

So I got a pair of RFduinos to play with it.  Programming it is quite simple, you just need Arduino 1.5 or later (which you would need for programming a Yun, Due, and possibly a few other Arduinos) and the RFduino libraries (see this).  The library comes with an example program accessible under File-Examples-RFduinoBLE-AdvertisementContinuous.

The only somewhat difficult part is dealing with the URIBeacon, and Adafruit publishes a tool to help with that, and Google has a more detailed explanation.

The top is the RFduino, the bottom is the USB shield, which is the easiest way to load it.

The top is the RFduino, the bottom is the USB shield, which is the easiest way to load it.

Of course it does nothing unless you have a device setup to receive it.  In the Play Store, there is a Physical Web app that can be used to receive the messages (until these become part of Android... and hopefully iOS, too).

The app is fairly simple, but it works!

The app is fairly simple, but it works!

Where This Is Going

Rather than beacon a web URL, I imagine with the proper programming (on both the RFduino side and the Android app side), it could be used to pass a variety of messages.  In fact, since the app looks up the description information, that could probably be used for simple messages (e.g. "the plant needs water").

This has some pretty cool IoT and alerting uses.  Stay tuned!


Category: Arduino

This is two out of four for me.  I'm too busy.

So last year I had a number of things I wanted to do.  Then my radio went kaput and I still haven't fixed it.  Other things happened, too.

This year I am definitely going to fix... or pay someone to fix my IC-706.  I will probably get into FreeDV and maybe another digital voice mode.  I want to build a receiver, too, and not from a kit.

I know there will be a lot more Arduino stuff going here, and there will be some FPGA stuff, too.  I also have some electronics-but-not-ham stuff coming (some of which has no other blog of mine to go to, and some will be cross-posted from another one of my blogs).

I've been somewhat silent out here, but that shall change soon.


Category: General Stuff

This is one of those "I keep needing this, so I bet it will help someone else" things.

A few months ago I purchased a "Basic Electronics Parts Kit" from Radio Shack (I'd have linked to it right there if I could find it, but sadly I cannot... it's part number 09A12, which no longer shows up on Radio Shack's website).  In said part assortment is a handful of ICs, but it appears that they are only for those that have the important parts of the 4000 and 74LS series of ICs memorized.  Since I am not one of those people, I looked up each one.  Here's the list and what they are:

LM386: Op Amp
NE555N: single timer
UA741CN: Op Amp
CD4013BD: Dual D-Type Flip-Flop (similar to 74LS74)
CD4017BD: Decade counter
UTC7805: 5V Linear Regulator
LM7812: 12V Linear Regulator
HD74LS00P: Quad 2-input NAND Gates
HD74LS02P: Quad 2-input NOR Gates
HD74LS08P: Quad 2-input AND Gates
HD74LS10P: Triple 3-input NAND Gates
HD74LS74AP: Dual Flip-Flop, D Type w/Set Reset
HD74LS86P: Quad 2-input XOR Gates



Category: General Stuff

On the way back from a meeting, I dropped by the Columbus Micro Center Mall.  I really didn't know what I was looking for, but I figured I'd want to look at something for a project in the works (that involves an accelerometer or two), my Hack A Day Trinket Project, and anything else that looked good.

It was a good trip.

I grabbed a few (relatively expensive) breakouts for SOIC and SSOP chips, which I'll ultimately use one for an SA602 mixer. I also grabbed a small pack of resistors, which will be in use for my HAD Trinket project.  I found two accelerometers for $5 each (!!!).  I grabbed a few PC boards.  And the best part - a Yun for $55 (off their normal $75)!

I uploaded a microcontroller Hello World (a blinking LED) to the Yun via Wifi.  It was awesome and convenient.  The code is below, and it'll work for any Arduino or clone (I initially wrote it for a Trinket).

In action on a Trinket:

And on a Yun (I used the onboard LED):

Next week, back to the normally scheduled DDS mischief.


Category: Arduino

A while back, I bought a few DDS modules through eBay.  I used code from NR8O to program one of them and started pulling parts from the bin and pushing the output signal through the parts and into a load resistor.

2014-11-28 23.23.26

Experiment 1: Just a diode

2014-11-28 23.23.36

Result 1: the large waveform is the input signal (A), and the small bumps are the scope channel 2 (B). The diode rectifies the signal, which is why the bumps are only going up (and not down). The forward voltage drop on the diode is why the bumps are so small.

2014-11-28 23.30.07

Experiment 2: a diode bridge

2014-11-28 23.30.13

Result 2: This is similar to the circuit above, just more voltage drop because more diodes are involved.

2014-11-28 23.38.55

Experiment 3: Through a capacitor

2014-11-28 23.39.01

Result 3: the capacitor blocks DC, but allows AC through, with some voltage drop.

2014-11-28 23.39.50

Experiment 4: Capacitor parallel with load.

2014-11-28 23.39.56

Result 4. No change because there is nothing between the test points.

2014-11-28 23.41.35

Experiment 5: through an inductor

2014-11-28 23.41.39

Result 5: there was no change.

2014-11-30 14.23.58

Experiment 6: inductive load

The video below shows what happened.  I'm sure there's an explanation of the instability, but I don't know the explanation.

Stay tuned for experiments 2!

73 de KE8P

Category: Arduino

Subscribe to Blog via Email

Enter your email address to subscribe to this blog and receive notifications of new posts by email.

This is the new server