I decided to build a Colpitts oscillator after watching one of W2AEW's videos.

Circuit Board

Circuit Board

Frequency Counter

Frequency Counter

Waveform on the scope

Waveform on the scope

The only issue I ran into was that I had the power supply hooked up backwards, so when I initially connected it to the scope, the +12V shorted to ground (and it burned a small hookup wire in the process).  I should have paid more attention to the testing that W2AEW describes in his video - on a second try, I was seeing -7V where I should have been seeing +5V.  And I shouldn't have trusted the two hookup wires I was using to get from a computer power supply output to a circuit.

I also didn't have 2N2222 or 2N5904 transistors, I used 2N3904s, which seem to work fine.

-73-


Category: Electronics

This is the second part of something that has been sitting on my workbench. Part I.

The schematic...

The schematic...

The video below shows the two traces of the input and the output of the second JFET.

The board is coming together as much as it could be for not being printed or having an enclosure.

Through the tone control

Through the tone control

The third part will be waiting for me to order a few pots, which I forgot to put on my last parts order.

-73-


Category: Electronics
Tags: , ,

With all the issues surrounding FTDI chips and drivers, I decided I'd look at a competing chip - the Microchip MCP2221.  Unlike the "standard" FTDI FT232 (which is most similar to the MCP2200), the MCP2221 includes both a UART and an I2C interface.

Hookup and Configuration

Hookup

Hookup

Hooking up this is pretty easy.  I sacrificed a USB cable and pulled the red to Vcc on pin 1, black to ground on pin 14, white to Data- on pin 12, and green to Data+ on pin 13.

After that, I checked things using the Microchip MCP2221 Utility from Microchip.  One of the more interesting things in the utility was being able to configure four pins:

GP0 (pin 2), default is UART RX LED, but can also be SSPND (suspend?) or GPIO

GP1 (pin 3), default is UART TX LED, but can also be CLK_OUT (clock out?), ADC1, IOC, or GPIO

GP2 (pin7), default is USBCFG, but can also be ADC2, DAC1, or GPIO

GP3 (pin 8), default is I2C LED, but can also be ADC3, DAC2, or GPIO

Screenshot 2016-03-05 20.56.04

I2C Connection

The real reason I got this was to be able to interface to both I2C devices and UART (serial) devices, so I hooked a TC74 temperature sensor to it.

TC74 hooked up to the MCP2221

TC74 hooked up to the MCP2221

The hookup is straightforward, the TC74 uses four of it's five pins, Vcc, ground, SCL, and SDA.  Vcc and ground are pretty self explanatory, SCL and SDA go to pins 10 and 9 on the MCP2221 (respectively).  The SCL and SDA lines need pull-ups, I used 1.5k resistors.

To check things, Microchip provides an I2C/SMBus Terminal program.

Under "Advanced settings" you can scan the bus by giving it a range to scan...

Scan the entire bus

Scan the entire bus

Scan results. Found the TC74 right where I expected it.

Scan results. Found the TC74 right where I expected it.

Once I verified that the sensor was where I thought it was, I used the terminal tool to read it...

0x17... 23C... 74F...

0x17... 23C... 74F...

So the next steps are to figure out what I want to do with all this... I'm partly thinking a multi-function breakout board - UART, ADC and DAC

-73-


Category: Electronics

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:

XFLOW OFF
AWLEN 8
PARITY 0
RESTART
CONMODE TRANS
TRACE OFF
HID OFF
BEACON EVERY 0
PACKET
RAWHDLC ON
HPOLL OFF
PPERSIST ON
KISS ON
HOST ON

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.

73!


Category: Equipment

Backstory

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).

Guitar

Guitar

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!

73!


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)

-73-


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.

-73-


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!

-73-


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.

-73-


Category: General Stuff
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