Saturday, July 28, 2012

Off-Topic: Mount Flip Camera to Bicycle Handlebars

Well, this isn't really ham radio related, but it was a fun project that I did a while back.  My wife and I wanted a way to film some of our cycling "adventures", but we didn't want to spend the money on a GoPro camera.  So instead of spending $200+ on a camera meant to do this, I went to Home Depot and spent $5 in parts.   Basically, I took a mending plate, bent it into a top-hat shape using a bench vise and a hammer, added a couple of hose clamps and a machine screw, and voila, a Flip Cam mount!  I inserted a bit of rubber between the mount/clamps and the handlebar to somewhat isolate vibration.  I also trimmed the corners off of the hose clamps to limited getting scratched if I accidentally ran my hand into it!

My Parts List:

  • Mending plates
  • Hose Clamps
  • Machine screw
  • Washers
  • Small piece of rubber
Time to Completion:
  • About 30 minutes for this one.  The longest time was finding where I put my vise after we moved here.
Here are some pics:

While this wasn't really a ham radio project, it could still come in handy for mounting an HT radio or GPS if you are into APRS.  I'm considering mounting a 2m/70cm HT to my bike to talk and ride, but I want to add a decent antenna instead of the rubber duck.  I've also considered figuring out a bracket for a directional antenna so that I can work satellite contacts from some more remote locations in Florida.  There are some nice "rails2trails" here.  More info will be forthcoming on this as it evolves.


Richard, KK4JDO

Sunday, July 22, 2012

A Plethora of Project Boxes

As I was cleaning up after our little project this afternoon, it occurred to me that I am slowly accumulating a plethora of small project boxes.  I find myself picking up another one every time I go to Radio Shack.  In addition to the ones in the picture, I have two more in the parts

Anyhow, just thought that I'd share a picture of them.  I've had a lot of fun so far with these projects, and I'm looking forward to many more!  All that being said, here is a quick pic of my little project boxes:

Starting clockwise from the left, these boxes contain:

  • Soundcard interface for APRS/Packet/and other digital modes
  • PC interface for PTT desk mic and morse code straight key
  • Control box for cycling through (manually, or enabling automatic shifting of) colors on my LED lit glass blocks.
  • Simple Coax Tester

It pains me that I paid around $100 for the SignaLink and associated cables when I could have built an interface for around $20.  Not knocking the SignaLink USB, it is a great device, but I like building things myself when possible.


Richard, KK4JDO

Rainy afternoon project with the kids: Coax Tester!

After finishing up the souncard interface yesterday, I thought that I would be done for a few days, but a house full of boisterous kids on a rainy day dictated otherwise.  As they say, necessity is the mother of invention, or in this case, maintaining my sanity was...  ;-)

I recalled watching a YouTube video by W5CYF (Tinker John) on how to make a simple go/go-go coax tester.  It seemed like a good project for the kids and I to do.  Like John, I used a green LED to mean the coax is bad, but hey, it's what I had on hand.

This is a simple, quick and dirty schematic of what we built:

In a project list this, there are a few things that kids can do, and a few that an adult needs to do.  While watching the kids play with the drill or soldering iron would be entertaining in a scary sort of way, the trip to the hospital afterwards would have been annoying.  However, seven year olds are good at sorting resistors by color, and 9 year olds are good at tightening screws.  They are also both helpful when small parts are dropped by fumble fingered parents.  Just remember that kids are kids, and tend to be distracted and not remember the goal.  They also like to fidget A LOT.  My son got to spend a few minutes in his room due to this, but he settled down and was back for the finish and testing.

My Parts List:

  • 1 x SO-239 connector
  • 1 x 9V battery connector
  • 1 x 350 Ohm resistor
  • 1 x Green LED
  • 1 x Small project box
  • 1 x 7 year old boy
  • 1 x 9 year old girl

Time to Completion:
  • About two hours, after all, the kids were helping me!  ;-)

Here are a few pics:

Here are the two proud builders!

Picture of the tester.

In this picture, I used a small bit of solder to simulate a piece of bad shorted coax.  Notice the green LED is on.  Green usually means good, but in this case, green is NO-GO!

Again, this was a fun little project that will give you an absolute basic go/no-go test of a piece of unknown coax.  It won't tell you impedance or length, if you need those tests go get an MFJ-259B or something similar.  If you want to make sure that you don't have a dead short and won't blow up your finals, this is the tool for you.  ;-)


Richard, KK4JDO

Saturday, July 21, 2012

Soundcard Interface for APRS/Packet - Part 2

Well, I finally got the PTT part of the soundcard interface working.  This was fun, and sometimes frustrating, but very educational.  I am lacking in my understanding of component level electronics engineering.  As a network engineer, I would be comfortable designing and implementing an enterprise network for a new hospital (that's a different story), but understanding why a transistor works the way it does is beyond me at this point.  So I kind of fumbled my way through this.  One thing that is very important in network engineering is attention to detail, and solid planning.  For some reason I didn't carry this over to this project, and it bit

Let me state, for the record, plan your work, and work your plan.  Don't just wing it.

Okay, on that note, on to the project.  Once again, was a great source of information on getting this part working.  I used this schematic from their site (click on the image to see more details):

R1 = Resistor, e.g. 1K2, to reduce voltage on the IC pin 1
IC =  Integrated Circuit; this sketch shows an IC, such as a 4N33
        or PS2603 Optocoupler, which uses a Darlington pair transistor.
        (Note: to identify pin #1, look for a small embossed circle on
         the top of the IC above pin 1; or looking into the notch in one
         side of the IC with the pins down, pin #1 is to the right of the notch.)
D1 = Diode, e.g. IN4001, would shunt any potential reverse voltage
        that might damage the sensitive diode/emitter in the IC.
        (Note: the band printed on the diode marks the cathode end,
        which attaches to the Serial Port/IC Pin 1 line in the sketch above.
        The opposite/anode end attaches to Ground.)

In the last post about this project, I built the receive and transmit cables that connect the output of the radio to the input on the soundcard, and the output on the soundcard to the input on the radio.  This worked well for listening to APRS and packet conversations, but I couldn't join in without manually keying the mic, which works okay if you're doing PSK31 or other HF digital modes, but isn't as easy with packet or APRS.  With this addition, a signal is sent via the PC's comm port to key the PTT circuit on the radio.  This allows the radio to be keyed via software instead of manually.  This allows things like APRS beacons to work normally.

This particular design uses an optocoupler to isolate the radio and the PC, while still allowing communications to flow.  This, along with the audio transformers used in the last post, helps to eliminate ground loops and voltage differentials, which are a source of hum in your transmission audio.

While building my version, I found that I didn't have the required 1.2K Ohm resistor, so I substituted a 1K and a 220 Ohm resistor in series.  This took a little additional space, which was at a premium in the tiny project box that I used, but ended up working well.  As you'll recall, in the last post, I decided to build this in a project box, instead of as a set of cables.  I think that in the long run my way will be more durable since there will be less movement of the internal solder joints due to cables wiggling around.  Time will tell.

A couple of issues that I ran into:

  1. On Windows XP (need to upgrade my shack PC), the serial mouse driver keeps the RTS pin HIGH, which causes the mic to key if nothing has taken ownership of the comm port that you are using (AGWPE, Digipan, etc) to bring it LOW.
  2. The pinout of the IC that I used was different than the one pictured in the schematic, don't blindly trust any schematic, do your homework first.  It saves solder (and frustration)
  3. Don't use too small of a project box, it is easier to do things if you have the room to do them in.

A couple of lessons that I learned:
  1. When if doubt, check solder joints.
  2. Follow the voltage, step through the circuit with a multimeter and make sure that you are seeing what you expect to see.
  3. Amperage kills...  This applies to ICs and other components as well as people.
  4. Be sure that the part is installed correctly BEFORE soldering...  

My Parts List:
  • 1 x 4N33 Optoisolator
  • 1 x 1K Ohm resistor
  • 1 x 220 Ohm resistor
  • 1 x IN4001 diode
  • 2 x 1/8" mono audio jacks
  • 1 x 6-pin mic connector to interface with my TR-7730
Time to Completion:
  • This part took me about eight hours due to lack of understanding and being too trigger happy with the soldering gun.  Next time should go smoother as hopefully I have learned my lesson on this.
Here are a couple of pics:

The IC and diode on the bottom right, and the two resistors on the bottom are all that make up this part of this circuit.  The other two resistors and the two transformers are for the rx and tx circuits.  You can also see the two audio jacks that I used to connect the PC and Radio.

This shows the completed and closed project box.  Again, while I at first thought that smaller would be better, after building it, I should have used a slightly larger box.  The next one that I build will be a bit bigger.

These are the cables that I built to connect the computer to the project box, and then on to the radio.  The gray DB9 connector attaches to the comm port for RTS based PTT.  The other end of that cable is an 1/8" mono connector that attaches to the project box.  The 6-pin cable actually has two pig-tales, one 1/8" mono for audio, and another 1/8" mono for the PTT signal.

And here is a shot of the APRS terminal showing me sending and receiving traffic.  I need a better antenna to hit more than one or two stations directly, but thankfully, one of the stations that I can hit is a digipeater/IGate.

All in all this project was a lot of fun and extremely educational.  It is also a LOT cheaper than buying another SignaLink.  I think that I have around $20 invested in this, plus my time.


Richard, KK4JDO

Thursday, July 12, 2012

SS-64 Encoder installation into Kenwood TR-9000

Recently I had the opportunity to purchase a pristine Kenwood TR-9000 radio.  It was manufactured in the 1980s, but looks like it just came off the showroom floor.  I love these older Kenwood radios!  So far I have a:
  • TS-440S/AT for working HF
  • TR-7730 that I use for VHF packet and APRS
  • TR-9000 all mode 2m radio that I use for weak-signal work and now local ragchews
The only drawback to the older VHF radios is a lack of ability to encode CTCSS (PL) tones.  For APRS or packet use, this isn't an issue, so my 7730 is great at what it does.  However, I really want to use my new TR-9000 to participate in local nets, in addition to (trying) to work SSB.  Since this radio doesn't have a tone encoder, I have been unable to use it on local repeaters that require a subaudible PL tones to key up.  Enter the Com-Spec SS-64 encoder board.  For a whopping $30 I was able to purchase one of these babies to add this functionality to my Kenwood!

The installation process was much simpler that I had anticipated. All that was involved was taking the case off of the radio, removing one of the sub boards, and soldering three wires.  Boom, done!  To aid anyone that may be trying to do that, I have taken some pictures of what you need to look for.

There are three leads that are of primary concern with this board, red and black for power and ground, respectively,  and yellow for modulation.  The red and black are easy enough to figure out.  I connected them to the incoming 12V lead on the back of the radio, and to the chassis ground lead in the same location.

The yellow wire is a little more complicated.  It needs to be connected at the junction of the VR-2 variable resistor, and the C-16 capacitor.  Finding these required digging through the schematics and snooping around the boards themselves.  Here is a picture of the board that you will find them on:

This board is located in the back of the radio, under the top cover.  The specific two components that you are looking for are located in the bottom left of this picture.  Here is a close up (hint: look at the brown round thing standing up, and the green thing that looks like a tic-tac right next to it):

The tricky part is that you cannot solder to this side of the board, you will need to flip it over, then locate the proper pins to connect to.  Here is a picture to help you identify the proper pins:

I forgot to take any pictures of after I had solder the connections, I was too eager to talk on my local 147.120MHz repeater!  

I routed the rest of the cables from the under side of the radio since there is more room to install the encoder board there.  I used the double sticky tape enclosed with the board to mount it next to the speaker.  According to the instructions, you may need to make some fine-tuning adjustments to the frequency by adjusting a pot on the encoder board itself, but I did not find this to be necessary.

I hope that this has helped anyone that is trying to do this installation to this radio.  It may seem complicated, but it is fairly straight-forward if you approach it methodically.  Take plenty of pictures to remind yourself what cables went where, or take good notes.  But that holds true for any project.

My Parts List:
  • 1 x Com-Spec SS-64 encoder
  • 1 x Kenwood TR-9000 2m radio

Time to Completion:
  • Approximately one hour

This was a fun little project that added a tremendous amount of functionality to my radio!  There are several more mods in this radio's future.  An extremely knowledgeable ham that I talked to on the repeater (N4LGH) has mentioned a few, and I've been reading about a few, so stay tuned!


Richard, KK4JDO

Monday, July 9, 2012

Fun with LEDs

After building a quick shelf in my ham shack out of a laminated board and some glass blocks, I decided to pretty it up with some LEDs in the blocks.  Here is a quick video:

I will do a better post of this as soon as I have time with schematics and some pictures of the LED boards themselves, but I wanted to post this today to show off... ;-)  I have two more to build, so I'll include some build pics as well.


Richard, KK4JDO

Wednesday, July 4, 2012

Soundcard Interface for APRS/Packet

Happy 4th of July to all of my American visitors (and also to everyone else, although I don't imagine that it is quite the same).  Not that I have that many visitors from anywhere, but it's the thought that counts.  It's been a few days since I posted anything, so I wanted to get this up on the site.  I've been enjoying my SignaLink USB soundcard interface for digital modes on HF, but I would like to run APRS on the same PC, and running two SignaLinks with APRS can be problematic.  Besides that, I didn't want to spend another $70 to $100.  So I decided to build my own interface.  There is a great resource for this at:  They walk you through the build options and troubleshooting if needed.  That being said, I've borrowed their schematics to post here (full credit for the schematics goes to them).

For this interface, you will need three connections, one for receive, one for transmit and one to activate the PTT switch on your radio to allow the transmission.  I am 2/3 of the way there.  I have the send/receive portions complete, and am waiting on the parts for the PTT circuit (it requires an opto-isolator, which I couldn't get from Radio Shack).

I tested the receive and transmit using DM780, which is part of the Ham Radio Deluxe suite, and was able have a QSO via PSK31 on 14.070MHz (manually keying the mic, which is annoying).  That being said, it seems to work well, and hopefully the parts will be in soon for the PTT portion.

Here is the schematic for the receive cable.  The radio that I am using (old Kenwood TR-7730) does not support audio out via the MIC at line-level, so I opted for the 1000:8 transformer to allow me to use the speaker out jack on the back of the radio:

And here is the schematic for the transmit cable:

These are fairly basic circuits and do not require a lot of time or effort to build out.

My Parts List:

  • 1 x 1:1 audio transformer (transmit cable - RS Part #274-1374 - these are getting scarce)
  • 1 x 1000:8 audio transformer (receive cable - RS Part #274-1380)
  • 1 x 100K Resistor
  • 1 x 1K Resistor
  • 2 x mono audio jack
  • 2 x stereo audio jack
Time to Completion:
  • This one took a few hours to put together, but quite a bit of time finding the right transformer.
Here are some pics:
(I nabbed the TR-7730 pic off of the net, but it looks identical to mine)

I decided to build this out as a stand-alone box with audio jacks instead of as a set of cables for neatness.  I'm an engineer by trade, and am rather stuffy about how wiring looks.  Stay tuned for the next installment in this post when I get the parts in the complete the PTT circuitry. 


Richard, KK4JDO