Category Archives: Amateur Radio

Surplus Summit 2012 Part One: Los Angeles

Testing 47GHz radios

(Photo: Tony KC6QHP testing out his 47GHz amateur radio. Remember this post? All that work paid off, the radio works!)

Last month I cashed in some airline miles and finally got to visit some old friends and spend some time in beautiful Southern California. Some long-time readers of the blog may remember the last time I did something like this in 2009.

While I was there I visited my good friend Tony in Los Angeles, and we went on a tour of surplus electronics and swap meets that we called Surplus Summit 2012.

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New call sign, RIP KF6PBP

I got my amateur radio license on December 31st, 1997.

I was an undergraduate at the time. My friend and classmate Tony (KC6QHP) had been trying to convince me to get my ham license for months.

I finally decided to go for it over winter break. I picked up a copy of Now You’re Talking! from a local bookstore (remember those?) and crammed for a week. I took the test the following weekend and passed with a perfect score, 35/35. (The morse code requirement for the Technician license was eliminated in 1991.)

That Christmas I got a Kenwood TH-79A/D, a very modern-looking radio at the time. (I still think it looks great, but it has aged poorly, the controls are scratchy and the battery becomes disconnected easily.) I nervously waited for my new call sign to show up in the FCC database. (This was before the ULS existed, but there was a website where you could see the call signs that were issued each day.)

Imagine my horror when on December 31st my name came up listed next to the call




What’s wrong with that, you say? Sound it out. K F 6 P B P. Imagine trying to make a contact on the air with that call. PBB? BPP? PPP? I have even had operators struggle with the phonetic version (Papa Papa Bravo? No, Papa Bravo Papa. Easy, right? Wrong.) I remember some old-timers trying to console me when I first got my license by coming up with clever mnemonics such as “Peanut Butter Pretzels”, which I still chuckle at.

Admittedly, my frustration level has always been kept in check by the fact that I have never been very active on the air, and most of the contacts I have made have been with friends who had memorized my callsign anyway.

This year, after having the callsign KF6PBP for over 13 years, I finally decided to do something about it. I applied for a vanity call sign.

But which call to apply for? I’m an Amateur Extra now (I tested for General and AE in 2009 and 2010, respectively), so I could have tried to get one of the much-fought over 1×2 or 2×1 callsigns (like K6RF, W6TC, etc). I didn’t see any that were worth fighting (and waiting) for. So, I decided to take a different approach and searched for an easy-to-get 1×3 callsign that reflected my personality or interests. I found a few that I liked and narrowed them down to 2 candidates (one favorite and a backup in case someone else applied for the same call and I didn’t get it).

As luck would have it, I got my first choice. Last night, I was granted the new call sign


It feels a little bit weird to be saying goodbye to the call sign I’ve held for so long, but I’m looking forward to operating with my new call with fewer corrections. (The phonetic version has a nice ring to it – Whiskey 6 Oscar Hotel Mike.)

I’m getting back into amateur radio these days, so expect to see more posts on the subject. Maybe I’ll even get to chat with some readers of the blog on the air?

(Are you a ham?  Leave a comment!)


Surplus Electronics Wiki Growing Fast

The past few weeks have seen a lot of activity on the MightyOhm Wiki!

Since it was mentioned on the Make: blog last week, helpful readers have been making significant contributions every day.

One highlight of the wiki is the Surplus Electronics Resources page, which I first posted about in February.  It has more than quadrupled in size since then and now includes surplus shops in the United Kingdom and Canada in addition to dozens in the United States.  If you haven’t seen this page yet, you should definitely check it out.

If you don’t see your favorite electronics surplus store on the list, please add it!  Several of these “junk shops” close every year due to rising rents and competition online.   Anything we can do to keep them in business will benefit the maker community.  One way to do this is by making sure that folks know that these resources exist, and this is where I hope the wiki will help.

I want to express my sincere gratitude to everyone who has been contributing to the wiki.  In particular, thanks for making it one of the best directories of electronics surplus stores on the web!

Tony’s Diamond Chop Saw (Part 4)

Finally, I bring you the conclusion of my Diamond Chop Saw series!

In this part I’ll cover a few remaining issues, but mostly I’ll report on my use of the machine in the construction of my 47 GHz radio, for which this project was intended.  If you’re not already familiar with this project, you might want to go back and start by reading Part 1.

Attaching/Aligning the Blade

Attachment of the blade to the hard disk platters (see part 2) sets the basic accuracy of the tool.  If the blade is out of plane the cut will be wider than the blade.  If the blade is off center, portions of the blade will wear faster.  Achieving perfection is virtually impossible, but I managed to get a ‘good enough’ result.

My method was to lay the ring blade down onto the larger platter and use tape to temporarily hold the blade in place while I manually spun it around to check for centering.

Method for centering the blade
Method for centering the blade

A little fiddling and re-alignment will get things pretty close.  After the centering is good, the next step is to glue the blade into place.  I used tiny drops of Zap-a-Gap around the inner edge of the ring and held the two together firmly as the glue set.

After gluding the blade, spots of glue are visible on the top surface
After gluding the blade, spots of glue are visible on the top surface

The result is not perfect, but cuts I have done seem to be sufficiently narrow.

The Cutting Setup

The picture below shows the setup for making cuts.  The large silver box in the background is the vacuum pump, the green vise in front is holding a digital indicator (for making precisely measured cuts) and the blue airbrush is ready for spraying water onto the cutting surface.

Dicing saw setup
Dicing saw setup

The parts to be cut are mounted on glass slides using Crystalbond adhesive, a thermoplastic mounting polymer.

Test substarets about to be cut
Test substrates about to be cut

Using the Chop Saw

Below are some pictures of cuts made with the saw.

A partial cut through one of the substrates
A partial cut through one of the substrates
Several diced pieces.
Several diced pieces.
Microscope view of a part diced into three pieces
Microscope view of a part diced into three pieces

From the photos above it is clear that the saw is working reasonably well.  The cuts are straight, the pieces have no obvious large chunks missing, and the gold metallization shows minimal signs of peeling.  I have made many cuts using this saw including angled cuts.  I have also used the saw to carefully strip off the backside metallization.  This will come in handy when I am making diveboard-style waveguide transitions.  I have also used the X/Y table to feed the piece along the blade, allowing me to make much longer cuts than in “chop” mode.  These came out very nicely as well.

The accuracy of the saw is reasonably good.  Using a dial or digital indicator, cuts can easily be made with 0.001 inch accuracy, which is sufficient for circuits working through 50 GHz at least.

One issue that was of concern initially was whether a hard drive motor actually had enough power to do the job.  It turns out the motor works fine as long as the cuts are made slowly.  Fast cuts are not advisable anyway, as the part is more likely to fly off into oblivion.  Some of the substrates I cut had fairly thick metal backing and required slower cuts.

Future Improvements

Every project ends up with room for improvement.  With this project a few things come to mind including a precision machined spindle with a better mounting mechanism.  This would require a much larger lathe than what I own, and some careful though into balancing.  Another improvement would be a self-contained coolant sprayer and vacuum pump for the chuck.  Setting up the dicing saw currently requires a vacuum pump, an air compressor, and so on.  Another nice feature would be a microscopic camera to observe the cutting in action.  And finally a CNC retrofit would be nice.  All of these upgrades would be handy, but as it is, the saw is immensely flexible and precise.  I’m still on the first blade which is showing no signs of wear.


It has been a lot of fun putting together this series of articles and even more fun putting together and using this saw.  So if you are planning on putting together a saw like this, happy cutting!  If you are just planning on building something with a hard drive motor, they are really handy for certain applications where high precision, high RPMs, and cheapness are required.