More mesh cross-posts

I am a visual person, so I built a quick diagram of how I visualize a mesh deployment. I have most of these parts already, with the notable exception of the two additional routers, three additional cameras, and additional ATAs.

 What does everyone think of this with specific regards to EmComm?

One of the goals of this layout is to allow Incident Commanders, etc, to be able to communicate with disparate agencies via multiple radio systems on multiple frequencies on multiple bands all from any corded or cordless phone.  Additionally the option exists to listen to the police/fire/etc scanner from anywhere as well.

Scalability is an core design goal with this architecture with the only limiting factor in theory being the ability of the mesh to scale to lots of node.  In theory it will scale to >2000 nodes, but in practice I would be happy to see 500 supported (not that there will ever be a full mesh that size).  In the current deployment another limiting factor is the Raspberry Pi that I am using for the voice server.  If this were to grow much beyond the size above a larger voice server would be needed.

73,

Richard, KK4JDO

OT: Christmas project with the kids

I managed to heat up the soldering iron and melt some solder during the weekend before Christmas, but it wasn't in pursuit of anything ham radio related.  I have a RockMite kit that I've been meaning to get to, but never seem to get around to it.  But no, this weekend's project was done with and for the kids.

While bumming around Radio Shack a few weeks ago I stumbled across the neatest little Velleman 3D Christmas tree kit!  It didn't look to complicated and was only $7 so I decided to give it a shot with the kids.  Now keep in mind, my kids (the two that were most interested in helping) are 7 and 10 so I couldn't do anything too complex, but this looked right up their alley!

Just like the last little project that I did with the kids, they are still too young to solder, but they can sort parts by type, sort resistors by color code and now they are old enough to actually put the components onto the board as well!  This kit comes with two boards that makes of the planform shape of a Christmas tree.  This worked out perfectly as each kiddo was able to get one board to work on.

The project did not require much in the way of tools.  A soldering iron, some solder, and some snips.




























Our process was this:

1. The kids sorted out the components into groups together (capacitors, resistors, transistors, etc).
1. My youngest daughter, the eldest of the group at the bench, took on the task of sorting the resistors by color code, learning a bit about said code in the process.
2. Each kid got a board, and with some help from Dad found the marked locations for each component (resistor X goes into the R1 location).
3. They then bent the legs of the components so that they would fit into the holes in the board.
4. As one kiddo got a part mounted, Daddy would solder it on and trim the excess off.  By then, the next kiddo would have a part mounted and the process would continue.
5. We continued on in this vain until all of the parts were on the board (first resistors, then capacitors, then transistors, and finally LEDs).
6. Once that was done, Daddy soldered on the battery leads and joined the two halves together with jumpers (the hardest part of the project).

All in all it was a fun little project that took about and hour and a half from start to finish, and we ended up with an ornament that we can use for many Christmases to come!  

Here is a shot of the eager little technicians that help during the build out, along with the fruit of their labors:

And a close up of the finished tree:

And a couple of shots with the lights off to show the blinking motion of the LEDs:

This was a fun little project and helped to keep the kiddos entertained while Mommy was a work!  I hope to get back to some radio related projects in the near future, like maybe that RockMite kit, or installing a 4BTV vertical, or building a 12el yagi for 2m, or a "turnstile" moxon for satellite work on field day, or you get the idea...  Maybe during some vacation time that I am planning on taking in January...  Time will tell.

Merry Christmas and Happy New Year!

73,

Richard, KK4JDO

Quarter Wave Ground-Plane Scanner Antenna (and 2m ham antenna)

One of the purchases that I got via eBay is a Radio Shack PRO-2050 police/fire/etc scanner.  I've never had a scanner before, and this was a cheap way to check it out.  I didn't get a pick of it before I ended up moving it from the shack to the truck, so I nabbed a picture of the internet.  Here is what my scanner looks like for those that haven't seen one:

Of course, since I had a scanner, I needed an antenna.  I'm just getting into the whole scanner thing, so I didn't want to spend too much on the antenna since I didn't pay much for the scanner (which is several years old).  One of the cheapest and easiest antennas to build is the quarter-wave ground plane.  I had some #8 ground wire laying around, as well as an SO-239 connector, so I was off to the races.

There are several good calculators out there to help get the proper dimensions, however, the math is fairly simple:

468 divided by Frequency in MHz gives you the half-wave element length in feet.
The quotient from above divided by 2 gives you the quarter-wave element length in feet.
Take the quotient from the last problem and multiply it by 12, the product is the length of element in inches.

For example, if you want an antenna for the middle of the 2m ham band: 

(468/146) / 2 x 12 = 19.23" which roughly equals 19 1/4" (since tape measures are in fractions of an inch).

It helps if you cut it a little long to allow you to tune to your specific location.  I actually cut mine for resonance on the public services band (~150MHz) since that is what is in use in my area, however, I get acceptable performance on the 2m band as well (about 1.7:1 VSWR).

Bending the ground plane elements down to 45 degrees brings the resistance of the antenna closer to 50 Ohms.  I'm not sure how this works exactly, maybe someone could drop a post and let me know why this works.

Here is a quick pic of the completed antenna.  The ground plane elements sag a bit with they are supporting the weight of the antenna.  They are straight when the antenna is suspended properly.

I also added vertical stubs for the 440MHz band as well as the 800MHz bands.  I didn't add ground plane elements for them as I'm not sure that I would see any benefit from doing so since I have the 2m elements.  Here is a close up of the verticals.

The last thing that I did was to seal the top of the connector with some silicone caulking.  This will help to keep water out of the coax, which would degrade the metal over time.  I would have used coax-seal, but I ran out and didn't feel like spending the money on this antenna.

And the final thing that I need to do, as you can tell from the background of the picture above, is clean my work bench!  It is getting crazy in there, so hopefully I can get that squared away soon.

My Parts List:

• 1 x SO-239 connector
• 8' of #8 grounding wire
• 4 x little screws
• Caulking

Time to Completion:

• About one hour for this one, mainly getting the jig built to solder the pieces together.

Next time I'll work on getting better pictures.  I tend to feel my way through some of these projects and don't think to document as I fumble along.

73,

Richard, KK4JDO

Installing an IC-10 kit into a Kenwood TS-440S/AT HF Radio

I use Ham Radio Deluxe, or more specifically, Digital Master 780, for most of the digital mode communications that I do (usually just PSK31).  This software is great and does a lot of awesome stuff.  One of those cool things that you can do with HRD is rig control.  This makes it easy to jump from frequency to frequency (QSY in ham-speak) from within the software, instead of having to tune the radio and adjust the software accordingly.  It also keep your PC up-to-date on what frequency your radio is on for automated logging (really help for lazy guys like me).

Anyway, since I have an older radio, I had to modify it with an add-on kit, originally called the Kenwood IC-10 kit.  Kenwood no longer sell this kit since they made the TS-440 over 20 years ago.  However, since this kit is just basically two ICs (an 8251A and a TC4040BP), they can still be obtained.  I got mine off of eBay for $20.  This will allow 4800 baud serial communications via the ACC-1 interface on the back of the radio.

You can then use a round 6-pin DIN connector and a DB9 connector to make a serial interface cable.  Be careful as the TS-440 ACC-1 interface uses TTL voltages (5V) and serial wants to use 12V, you will either need to use Kenwood's IF-232 kit to match the voltages, or use a USB-to-serial converter with normally operates at TTL voltage levels (beware Prolific chipsets).

The install process is fairly simple, it took me around 20 minutes to complete the installation, including the time it took to take the pictures.


This is a picture of the kit itself, basically a serial UART and a CMOS timer chip.  Be sure to take static precautions, it would be a shame to do this install and have it not work due to fried ICs.  Basically, just stay at the same electrical potential as the radio and you'll be fine.  Never touch the chip without touching the radio first.  You could also use a static strap, although I generally find this to be overly cautious unless you are working with extremely sensitive parts (or extremely expensive ones).

Below is a picture of the radio that we are about to perform surgery one, to wit, a Kenwood TS-440S/AT:

Step one is to remove the top cover, which consists of eight screws (four on top, two on each side):

Be sure when you remove the top that you keep track of where the speaker cable goes so that you can put it back together when you are finished.  It is the yellow cable in this picture:

Next, flip it over and repeat the process with the bottom cover (nine screws this time, five on bottom, two on each side):

After that, remove the three screws on the bottom of the heat shield (silver part to the right with the three holes).  Also remove the four screws (two on each side) that hold the front panel in place:

Then remove the two screws that hold the top of the heat shield on:

Finally, you will be able to see the two sockets for the two ICs.  The part of the IC with the half-circle indicates the location of pin one.  This view is from the top of the radio, and pin one goes to the left:

I forgot to take a picture before I put the heat shield back on, but this is what it looks like with the IC installed.  I had to compress the pins on the ICs a bit to get them installed, which is common.  Just be careful not to bend them too much, else they may break.

Put the radio back together in the reverse order of above, and you will be off to the races!

 This is the rig control interface for HRD, you can see where I have set the frequency to the 20m PSK calling frequency:

And this is the radio after reassembly and being controlled by the PC.  The downside to this is that you cannot control the volume, nor can you get current S-level readings from the radio back into the software like you can with newer rigs.  But being able to control a 20 year old radio via the PC at all is awesome!!

Put this project together with the soundcard interface that I build in an earlier post, and you have a fully functional rig for digital modes on the ham bands!  This was a really easy and fun project and I gained a lot of useful functionality from my rig!

73,

Richard, KK4JDO

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 bin...lol.

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.

73,

Richard, KK4JDO

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 me..lol

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, soundcardpacket.org 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.

73,

Richard, KK4JDO

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!

73,

Richard, KK4JDO

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: http://www.soundcardpacket.org/.  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. 

73,

Richard, KK4JDO

Update to the PTT Mic via USB Project

So since I've gotten into trying to learn Morse code, I needed some type of oscillator, so that I can hear my key as I practice.  You can purchase an oscillator from companies like MFJ, or you can make the on the cheap with a piezoelectric buzzer and a 9v battery.  I chose a slightly different route.

My option was to add a 1/4" jack to my PTT desk mic via USB project box.  I did keep the piezo buzzer in case I wanted to practice without interacting with the PC, but I am currently using a program called MorseRabbit, which can accept input from the keyboard spacebar.  Only, in this instance, the input is coming from my straight key, which in turn is connected to the Teensy USB microcontroller, which is emulating a keyboard.

My Parts List:

• 1/4" mono audio jack (panel mount)
• 5v piezo buzzer
• bit of wire and solder

Time to Completion:

• 30 minutes, including adding the necessary code to the "sketch"

Here is a pic:

Here is a copy of the code "sketch" that I am using:

#include <Bounce.h>

Bounce button0 = Bounce(0, 10);

Bounce button1 = Bounce(1, 10);

void setup() {

  pinMode(0, INPUT_PULLUP);

  pinMode(1, INPUT_PULLUP);

  pinMode(12, OUTPUT);

  pinMode(14, OUTPUT);

}

void loop() {

  // Update all the buttons.  There should not be any long

  // delays in loop(), so this runs repetitively at a rate

  // faster than the buttons could be pressed and released.

  button0.update();

  button1.update();

if (button0.fallingEdge()) {

   // press and release CTRL

   Keyboard.set_key1(KEYPAD_PLUS);

   Keyboard.send_now();

   Keyboard.set_key1(0);

   Keyboard.send_now();

   analogWrite(12, 200);

  }

 if (button0.risingEdge()) {

   // press and release CTRL

   Keyboard.set_key1(KEYPAD_PLUS);

   Keyboard.send_now();

   Keyboard.set_key1(0);

   Keyboard.send_now();

   analogWrite(12, 0);

  }

  

if (button1.fallingEdge()) {

   // press and hold space

   Keyboard.set_key1(KEY_SPACE);

   Keyboard.send_now();

   analogWrite(12, 200);

   //analogWrite(14, 255);

  }

 if (button1.risingEdge()) {

   // release space

   Keyboard.set_key1(KEY_SPACE);

   Keyboard.set_key1(0);

   Keyboard.send_now();

   analogWrite(12, 0);

   //analogWrite(14, 0);

  }  

}

You have to forgive the sloppy wiring, it was too much hassle for this project to etch a pc board.  Now I have the ability to practice CW on my PC, both sending and copying!

73,

Richard, KK4JDO

Mic Adapter

I was recently in a position where I had a 2m radio that needed a new mic.  Specifically, I have a Yaesu FT-2200 that I picked up from eBay on the cheap.  This supposedly perfectly working radio had a myriad of issues, one of which being a mic with two bad capacitors.  One solution was to go purchase a new mic.  Well, this is an older radio, so they don't make mics specifically for this rig any longer.  However, I was able to find a suitable replacement, the only down side being that said replacement cost almost as much as I paid for the radio!  That wasn't gonna happen.  Another option was to rewire a mic that I already own to use with this radio.  The downside was that I actively use both mics, one for my Kenwood TS-440S, and the other (wired for the Kenwood), I use via my USB PTT box with EchoLink.  So I didn't really want to rewire either of those.

The final solution was a mic adapter!  It was a little aggravating to build as I had to cross between two vendors that do things slightly different (Kenwood uses two grounds, one for the mic, one for the PTT, while Yaesu uses a single common ground).  But it wasn't really all that bad, and seems to work.  Now I just need to get my Moxon mounted where I can use it, and I can talk on my preferred repeater without being all scratchy!

My Parts List:

• 1 x 8-pin female mic connector
• 1 x 8-pin male mic connector
• 1 x 1' length of mic cable (initially I used Cat-5e, which worked good also)
• 1 x 3" length of 1/2" PVC
• 1 x 1/2" PVC cap

Time to Completion:

• It took around 30 minutes to make, including scrounging the PVC to hold the male side of the connection since I didn't have a non-chassis mount connector handy.

Here is a pic:

This was an easy project that was a quick fix for a problem, and certainly cheaper than buying a new mic!

73,

Richard, KK4JDO

Intermod and Spurious Emissions!

So, as I was scanning the 10m band, I noticed that I was receiving occasional bursts of static on my 2m radio.  These were occurring as I crossed fairly strong carriers, which means that these carriers were interacting with my rig in receive mode, and causing what is called intermodulation, which was resulting in a spurious emission.

Here are some links for more reading on these phenomena: 

http://en.wikipedia.org/wiki/Intermodulation

http://en.wikipedia.org/wiki/Spurious_emission

I recorded a quick video of it to show folks that just because you are using a receiver, it does NOT mean that you are not also broadcasting a signal!  Something to be mindful of, especially if you are in an area that is sensitive to RF fields (thinking of mining sites that use an RF signal to detonate explosives, among other scenarios).

I should probably point out that the volume on the radio that I am adjusting is completely down, the only radio that has its volume turned up is my Yaesu FT-2200 2m radio.  The sounds that you are hearing are the spurious emissions generated by my TS-440S tuned to ~28.5MHz being received by my FT-2200 on 147.120MHz.  I should also point out that these are extremely localized and can not be picked up beyond my shack.  I tried with an HT in the yard under the dipole and got nothing.  Also, I apologize for the poor quality of the video, I shot it with my iPhone 3GS, which has a pretty lousy camera.

73,

Richard, KK4JDO

Using a PTT desk mic on a PC

So in this post, I'm going to talk about a cool project that I finished a few weeks ago.  I like to use EchoLink (http://www.echolink.org/) to chat with people all over the world.  One of the uses for EchoLink, and the only thing that I use it for, is to connect to a repeater that you are too far away to hit using RF alone.  This software connects you to that repeater, and broadcasts what you say into your PC mic as if you were using a radio.  That being said, I like to feel like I am talking into a real rig, instead of talking on Skype or some other VoIP application when I am using EchoLink, especially since it is only accessible by other licensed Hams.  To that end, I had an old mic laying around, so I decided to connect it to the computer.  There were several obstacles that needed to be surmounted, the first being that the mic used an 8-pin connector for Kenwood HF radios, and the second being that you needed the press the PTT (Push-To-Talk) button in order for your audio to be sent out of the mic's audio pins.  The final issue was that the EchoLink software needs to be "keyed" as well by pushing down the space bar on your PC.  Here is how I solved these issues:

To convert from 8-pin to something that the PC could accept, I wired up the audio pins from an 8-pin male connector (the mic has a female, although it seems as though the names should be reversed) to an 1/8" female audio jack.  I mounted both in a small project box to make the assemblage a little easier to use.  This took care of getting the audio into the PC, but I still had to hit the space bar to "key" EchoLink, and at the same time hit the PTT button on the mic to connect the mic element to the audio pins inside the mic.  This was annoying to say the least.  Enter the Teensy USB Development Board:

This board connects to the PC and is recognized as one of several devices, a keyboard, a flash device, a MIDI device, etc.  The main one that I am concerned with was the ability to emulate a USB keyboard.  I soldered a connection from the PTT pins in the mic jack to one of the digital pins on the Teensy board, and another one to the ground pin.  This allows me to detect when the PTT button is depressed on the mic.  I then took this detection, and triggered a key press event to key EchoLink!  Now I can use EchoLink just like a normal radio, via the desk mic, without keyboard input.  Just for fun, I added a red LED to know when the mic PTT key is depressed (to hopefully avoid "hot-mic" issues).

My Parts List:

• 1 x Teensy USB Board ( http://www.pjrc.com/teensy/)
• 1 x Project Box
• 1 x 8-pin male mic connector
• 1 x 1/8" (3.5mm) audio connector
• 1 x Red LED
• 1 x 220-Ohm resistor

Time to Completion:

• About four hours including figuring out the code for the "sketch" on the Teensy board.

Here is the simple schematic:

Here are a few pics:

Here is the code that I used on the Teensy board (which uses the Arduino IDE environment):


#include <Bounce.h>


Bounce button0 = Bounce(0, 10);


void setup() {
  pinMode(0, INPUT_PULLUP);
   pinMode(12, OUTPUT);
}


void loop() {
  // Update all the buttons.  There should not be any long
  // delays in loop(), so this runs repetitively at a rate
  // faster than the buttons could be pressed and released.
  button0.update();


if (button0.fallingEdge()) {
   // press and release CTRL
   Keyboard.set_key1(KEYPAD_PLUS);
   Keyboard.send_now();
   Keyboard.set_key1(0);
   Keyboard.send_now();
   analogWrite(12, 200);
  }


 if (button0.risingEdge()) {
   // press and release CTRL
   Keyboard.set_key1(KEYPAD_PLUS);
   Keyboard.send_now();
   Keyboard.set_key1(0);
   Keyboard.send_now();
   analogWrite(12, 0);
  }
}

Well, that's all for this post, I hope that you have enjoyed it, I certainly enjoyed making it!

73,

Richard, KK4JDO

The Obligatory Shack Pic

So now I can show you what all of those antenna are used with!  This is a quick overall shot of my "shack" as it stands right now.  I am considering some upgrade options in the near future, so stay tuned to see what kind of rig takes center stage (thinking TS-2000 for the shack and IC-7000 or FT-857D for the truck).

Included in this pic are:

Kenwood TS-440S, 20 years old and still talking around the world!  (just talked to Russia and Ukraine!)
Yaesu FT-2200 (look for an upcoming post on lessons learned about eBay)
MFJ-941D Antenna Tuner
Heath 3A power supply for testing purposes
Kenwood PS-30 for powering the TS-440S
SignaLink USB for APRS and other digital modes (trying to talk to the ISS, but need higher gain antenna)
Wouxun UV3D HT
Kenwood TS-120S (not feeling so well these days)
Homebrew PTT Mic to USB adapter to allow me to use my desk-mic with EchoLink (look for a future post)
Shure 256T desk mic
Kenwood MC-50 desk mic
El-cheapo CW straight-key (again, look for an upcoming post)
Radio Shack SWR/Power meter


Here are some more pics:

So that sums up my current shack.  More details as things change!

73,

Richard, KK4JDO

Last antenna post for now... ;-)

Okay, last one for now.  So the j-pole works pretty well, but I was still staticy when transmitting.  What I needed was a directional antenna for maximum gain.  Again, purchasing one at the Candy Store would have been $50 or more.  But for less than $8 at Home Depot, I was off and running.  When I use this antenna, I am full-quieting on the repeater.  The downside for me right now is that I cannot permanently mount this one outside, as I need to be in the front of the house to point at the repeater that I like to use (147.120MHz,+600,PL-103.5).

My Parts List:

• 10' of 8AWG copper wire (enough for about three antenna like this, I want to make one for 70cm also)
• 10' of 3/4 PVC pipe (again, enough for multiple antenna)
• 50' of RG-58 coax

Time to Completion:

• About four hours

Here is a pic:

More information on this type of antenna can be found at:

http://www.moxonantennaproject.com/

I have to say that I am impressed with how well this antenna functions!  The one thing that I do need to add is a balun at the feed-point, that is on the project list!  ;-)

73,

Richard, KK4JDO

And another antenna!

Alright, this is almost the last one for now, I promise.  I needed something to get better reception on my little handheld Wouxun HT, but didn't feel like spending $25 or so for one from the local ham store (referred to by other hams as the Candy Store).  My solution was to build a roll-up j-pole antenna out of left-over twinlead from my dipole.  Again, before I was not able to use my HT from home as the repeater is clear across town from where I live, and 5W wasn't going to cut it with the little rubber-duck that came with the HT.

My Parts List:

• 6' of 300-Ohm twinlead
• 10' of RG-58 coax with a PL-259
• 1 PL-259 to Reverse-SMA adapter (had to buy this one, too much of a pain to make it)

Time to Completion:

• 30 minutes or so

Here is a pic:

So admittedly I need a better pic of this one.  I'll work on that...

73,

Richard, KK4JDO