CDV-720 3A High Range Radiation Meter

This post is cross-posted to my ham-radio specific blog,

I went to the WCRA Hamfest in St. Charles this weekend in search of test gear (I had been fortunate to find a working Heathkit IM-2420 Frequency Counter there a couple years ago). I didn’t come away with anything of that sort, but I did scoop up this yellow beauty:

This beaut is a CDV-720 3A High Range Radiation Meter. It’s a remnant of the early cold war, the beginning of the atomic age – thousands were produced in the late fifties and early sixties by the Victoreen Company out of Cleveland Ohio. It’s got a cast aluminum case that feels like it’s made to survive a bomb, and maybe it was. The manual notes that:

It is designed to be used by radiological Civil Defense personnel in determining radioactive contamination levels that may result form an enemy attack or other nuclear disaster.

The really staggering thing about this meter is the range it covers: up to 500 Roentgens/hr. At that rate, your goose is cooked in a matter of minutes (first metaphorically, then literally).

Here’s a brief video overview of the meter, its circuitry, and the scary-high levels of radiation that it’s meant to measure:

Stay safe and non-irradiated out there!

Homemade Cheddar Cheese

Over the past 12 months or so, I’ve dipped my toes into some basic cheesemaking, including cream cheese, farmer’s cheese, and ricotta. But for me, there’s no better cheese than a sharp white cheddar, and with an eye toward making cheddar and some other hard cheeses, I’ve built my own cheese press and my own first hard cheese.

The process I used to construct the press is very similar to this instructable. I used a 1x6x48″ Maple board from Menards as the base, and two pieces of 1×2 Poplar from an earlier project. The threaded rod, nuts, wingnuts, and washers are all 3/8″ hardware. I added four threaded furniture feet to raise the press off the countertop and allow for tilting the press slightly to allow the whey to run off. I used some butcher-block conditioner to help seal the wood before use. (Having access to a theatrical scene shop helps.)

My first pressed cheese is a “farmhouse cheddar”, made according to this recipe from Gavin Weber. Specifically, the ingredients I used were:

  • 2 Gallons (4 half-gallon containers) of Kalona Whole Milk from our Fresh Thyme Market. While unpasteurized milk seems to be recommended for a lot of artisinal cheese making, that’s hard to come by in urban Chicago, so this non-homogenized milk is the way I’ve gone.
  • 1 Sachet of Mesophillic Culture, purchased from Pursuit Supply Co, a small business here in Chicago that focuses on homebrewing and distilling, cheesemaking, and film development.
  • 1/2 tsp of Liquid Vegetable Rennet, also from Pursuit Supply
    • This was diluted in 1/4 cup of bottled (unchlorinated) water before adding, since apparently chlorine kills the coagulating action of the rennet
  • 1/2 tsp of Calcium Chloride (from, where else, Pursuit), also mixed with 1/4 cup bottled water. I understand this introduces more soluble calcium to the mixture and helps the curds to form.
  • 2 generous tbsp of non-iodized sea salt.

The process, as outlined by Gavin (of Little Green Workshops) is straightforward. Here is is summarized by me, with comments as to how my own process went:

  1. Sterilize all materials that will come into contact with the milk or cheese.
    • I used a preparation of Star-San mixed with water in the recommended ratio of 1:640 (1 Oz per 5 gallons). I soaked the large stirring spoon I planned to use, as well as all the measuring cups in this for a few minutes. Meanwhile, I boiled a couple quarts of water in my large stockpot to sterilize the pot itself, then wiped the lid down with the Star-San mixture.
  2. To a large stockpot set up as a double-boiler, add the 2 gallons (8 liters) of milk.
    • I used one of my large general-purpose pots underneath my stockpot as a double boiler, and it was remarkably stable.
  3. Heat the milk to 33C (92F)
    • This took about 20 minutes with my double boiler setup.
  4. Stir in the diluted calcium chloride
  5. Sprinkle the starter culture over the top, then stir for 1-2 minutes to incorporate
    • Gavin’s recipe calls for 1/8 tsp of culture, I simply used one small sachet.
  6. Cover, and allow the milk to ripen for 45 minutes
    • This allows the culture to start to grow a little and the milk to begin to acidify
    • I turned off the heat at this stage to allow things to maintain their temperature, but when I returned after 45 minutes, the temperature had shot up over 40C! Oops!
  7. Stir in the diluted rennet while stirring. Stir for no more than a minute as the milk with start to set.
    • I treated myself to a very large metal spoon for this project
  8. Check for a clean break with a clean finger
    • Basically, stick a finger in through the top layer of curd – if it feels firm-ish, it’s good to go. If it’s a little soft and yogurt-y, you can cover and wait another 10 minutes or so.
  9. Cut the Curd
    • There are some fancy curd cutters out there that look like a wire mandolin or harp, but I just used a long clean knife, run through up-down, left-right, and twice angled.
  10. Slowly heat the milk and curds to 38C (100F) over about half an hour
    • Even with a double boiler setup, my setup took a little modulation (higher heat, lower heat, higher heat) to not spike in temperature too fast. I took about 25 minutes to raise the temp up to 38C, sitrring continuously
  11. Let the curds rest for 10 minutes at 38C
    • At this point, I should have taken the pot off the double boiler, but I figured it would help keep the milk warm. It sure did – by the time I returned 20 minutes later, the temp was up to 44C! It remains to be seen whether this will have a negative effect on the cheese.
  12. Drain the pot into a clean cheesecloth-lined colander
    • I collected the Whey at this point and made a Whey Ricotta out of it. Yum!
  13. Tie up the edges of the cheesecloth and hang for an hour to drain some of the whey out
    •  I had a spare bit of PVC pipe leftover from my multiband antenna project, so I set that between the backs of two chairs and set the pot underneath to catch the drippings.
  14. After an hour’s dripping, transfer the curds back into a pot. Break the cheese mass into walnut-sized pieces. Toss 2+ TBSP of non-iodized salt throughout.
    • I used non-iodized sea-salt, instead of some of the products which are marketed as “cheese salt.” Not sure what the difference is
  15. Line a sanitized cheese mold with a sanitized cheese cloth. Transfer the curds to the press. Flip a corner of cheese cloth over the top of the curds, and place the follower on top.
    • I originally tried 3D printing a mold, but I got cold feet about subjecting a 3D print to 50+ lbs of pressure overnight, fearing it would crack. I also thought it would be good to seal the PLA with polyurathane or similar before trusting it to be food-safe. So I made a simple press out of a plastic jug from Walmart with the bottom and handle cut off, and holes punched through the sides.
  16. Press for 10 minutes at ~10 lbs.
    • I set up my press in a low-sides baking sheet to catch the whey as it ran off, and used the threaded-feet to set the press slightly off plumb so the whey all ran off one side.
  17. Remove the curds from the press and cloth, turn over, and press 10 minutes at ~25 lbs.
    • Quite a lot of whey running off at this point. Fairly cloudy, which I read is not good, but I’m not sure why…
  18. Remove the curds from the press and cloth, turn over, and press for 12 hours at ~50 lbs
    • I left the cheese to press overnight, checking it once a couple hours and tightening the springs a bit.
  19. Remove the wheel of cheese from the press and cloth. Trim any bits of cheese that have popped up around the follower.
    • Leave these in the fridge for a couple days and they’re basically cheese curds! So tasty!
  20. Place the cheese on the counter under a bit of cheesecloth or similar to air-dry. Turn twice daily until it has a nice rind and is quite dry to the touch.
    • I left my cheese on the counter for a little under 3 days before waxing. Possibly I should have left it longer to develop a drier rind, but we shall see when we break the thing open.
  21. Wax or vacuum seal the cheese
    • After drying for a couple days, the options are to either cloth-band, wax, or vacuum seal the cheese to prevent any nasty bugs getting into the cheese.
    • One of Gavin’s most popular videos describes Cloth-Banding the cheese, but in his final tasting of that cheese, he describes the process as too fiddly (and he did get some mold in a bit of that cheese early on). So I decided to wax the cheese instead. Pursuit was sadly out of cheese wax (soft parafin-based wax) when I stopped by, so I ordered some Beeswax from the internet to arrive the next day.
  22. Age the cheese for 1 month to… forever?
    • Currently, the cheddar is aging in a small mini-fridge in the basement, though with it being the early  months of winter, the fridge is turned off and is just functioning as an airtight box. I added a small dish of water and a small dish of saturated salt to raise the relative humidity to around 80-85%.

So… now we wait! I’m thinking, with this being a first cheese, we’ll crack it open around valentine’s day (~3 months) to see how I did, then possibly re-seal it and age longer if it seems like everything’s going well.

One next step will be to measure the pressure that my chosen springs will create when the press is tightened down entirely. I discovered that my bathroom scale doesn’t fit within the scale, so much like the instruct able suggests, I’m putting together a test jig with a wider base to allow me fit the springs around the scale and make a weight gauge. I’ll also need to replace the felt-bottomed feet with something that doesn’t absorb whey (I threw the feet out after this batch).

Here’s hoping it all turns out well!

150 Switches

I got lots of wonderful little gifties for my recent birthday, but one of the most out-there was a bag of 150 Assorted Rocker Slide and Toggle switches from Jameco. It’s literally a 2 pound scoop of switches in a plastic bag, sealed and mailed. Thanks Mom and Dad!

I spent a good 10 minutes sorting it out – here’s all that squinched into 45 seconds:

So, what do you get in a two pound sack of switches? Well, after another hour or so of cataloging, here’s the results:

(It’s exactly 150 switches! Well I’ll be…)

Quantity Genus Action Poles Description
11 Rocker ON-OFF-ON 1 Large Black
15 Rocker ON-OFF 1 Large Black
3 Rocker ON-OFF 2 Large Tan Power
9 Rocker ON-OFF 1 Medium Black
3 Rocker ON-OFF 1 Round Black
2 Rocker ON-OFF 2 Round Black
11 Rocker (ON)-OFF-(ON) 1 Medium Red
4 Rocker ON-OFF 2 Large Black Illuminated
4 Rocker ON-ON 3 Medium Red
11 Rocker ON-ON 1 Panel-mount Red
2 Rocker ON-ON 1 Right-angle mount
2 Rocker ON-ON 2 Right Angle mount red
1 Rocker ON-OFF-ON 1 Medium Blue
1 Rocker ON-OFF 1 Small Black
2 Rocker ON-OFF-ON 1 Large Red/Green Illuminated
8 Pushbutton ON-(ON) 1 Right angle plunger
11 Pushbutton ON-(ON) 2 Spring-loaded plunger
5 Pushbutton ON-(ON) 2 Small red/white plunger
2 Pushbutton ON-(ON) 2 Small black plunger
2 Pushbutton ON-(ON) 2 Small blue plunger
2 Pushbutton ON-(ON) 2 Tiny pushbutton
2 Pushbutton ON-(ON) 1 Panel mount square illuminated
2 Pushbutton OFF-(ON) 1 Grey rectangle illuminated
3 Slide ON-ON 2 115-230V Selector Switch
5 Slide ON-ON 2 250V-rated slide switch
2 Slide ON-ON-ON 2 Small silver 3 position
4 Slide ON-ON 1 Tiny slide switch
1 Slide ON-ON 2 Square blue slide switch
4 Dipswitch OFF-ON 2-Lever Red Dipswitch
1 Dipswitch OFF-ON 4-Lever Dipswitch
1 Dipswitch OFF-ON 5 Lever Dipswitch
1 Microswitch OFF-(ON) 1 Microswitch w/ 4″ tails
2 Microswitch ON-(ON) 1 Black microswitch with trigger
4 Pushbutton OFF-(ON) 1 Blue breakboard pushbutton
4 Pushbutton OFF-(ON) 1 Illuminated breadboard pushbutton
2 Pushbutton OFF-(ON) 1 Misc tiny pushbutton
1 Keyboard Switch OFF-(ON) 1 Large grey keyboard switch
(5) Cap Round black button cap

50W QRP Amplifier – 3D Printed Case Design and Livestream

  1.  With the 50W QRP amplifier project coming along nicely, I felt it was time to start thinking about a reproducible case for the project. And for custom, reproducible cases, 3D printing is my current tool of choice.

I ended up designing the case on a YouTube Livestream on Saturday night, to which a few great colleagues stopped by to ask questions and offer advice. The full video is below.

The case is in two parts – a box with standoffs for the PCB and holes for connectors, and a lid with labels. The standoffs and the attachment holes for the lid are meant to connect with M3 threaded-inserts and be held down with M3 machine screws.

This was my first time using Fusion 360’s Eagle Sync function – since Eagle PCB design software was acquired by AutoDesk in 2016, it makes sense that they’ve been working to integrate PCB design workflows into their other products. The sync was fair straightforward – open Fusion360, select Eagle Sync, select your board file in Eagle, and after a minute or two of importing, up pops your PCB in Fusion360. Neat! I’m still struggling with how to handle board cutouts in eagle, and I’m not sure how well they’ll be supported in Fusion, but that’s a project for another day.

Here’s the final design as it turned out in Fusion360:



The PowerPole model was provided by Chris Wych, a theatrical propmaster who’s done some really interesting work with Fusion360, including using it to model some 2d-printable geodesic designs which then folded up into geometric shapes. Very cool!

First print of this design coming soon!


This post is cross-posted to my ham-radio specific blog,

50W QRP Amplifier – Schematic, PCB Ver 1

The 5W-to-50W QRP HF Amplifier project is rolling along nicely  – I received the first PCB draft in the male this week and am 90% of the way through assembling it, with only heatsink-placement left to sort out.

I’ve made a couple of additions to the schematic since the original layout, including a relay-activated indicator (R27 and its LED) and an RF-output sensing LED (from C14 to its associated LED to ground) along the the lines of VK3YE’s recent project. There’s also a space on the PCB now for a low pass filter with the same footprint as Hans Summers’ LPFs over at QRP-Labs. Not that you’d necessarily want to reuse a QRP LPF for a 50W amp, you’d be in danger of putting too much voltage on the caps, but that would be a simple change.

Here’s the schematic as it exists now:


And here’s the current boards (layout, unpopulated, populated):


FullSizeRender (1)


I’ve already got a little laundry list of things to modify for a second rev of this board, including, in no particular order:

  • Swap the Diode placements the vertical to preserve board space
  • Add footprints for alternate relay packages
  • Add footprints for alternate trim-pot packages
  • Re-think component designators for clarity
  • Add bypass jumpers for the 3dB input pad and the LPF.
  • For some reason, the none of the component values printed on the silkscreen, will need to sort that out
  • I’m not sure if I screwed up how to designate a cutout or if JLCPCB doesn’t do them for its bare-bones PCB service, but I’d like not to do the next set with a drill press and a nibbler.

Hoping to put this on the air soon for some signal tests. Hear you there!


This post is cross-posted to my ham-radio specific blog,

50W QRP Amplifier – PCB Layout Video

This past weekend, I started on the process of laying out the 50W QRP Amplifier project as a PCB. Small PCBs can be remarkably inexpensive these days – $10-$15 for 5 pieces of say 4″x4″, shipped in 2-3 weeks. I’m treating this amplifier project as a chance to experiment with different, similar FETs to learn about critical power MOSFET properties, and also as an opportunity to brush up my layout skills that I haven’t used in awhile.

As the first step of PCB design, I captured the schematic of the amplifier as built in AutoDesk Eagle. I did this on a livestream on YouTube, the first time I’ve tried such a thing. It was great fun! Kenneth W6KWF stopped by to lend advice – he deals with prototype PCBs as part of his day job, though he has team members to do most of the actual layouts when needed. We’ve had a great deal of fun over the years, including building a cloud chamber for seeing charged ions in high school.

Here’s the full (2h45m!) livestream in all its glory! There’s a recap and full-circuit overview at 2h41m for those who want to see the final circuit.

Hear you on the air!

This post is cross-posted to my ham-radio specific blog,

50W QRP Amplifier – First Demonstration

This post is cross-posted to my ham-radio specific blog,

As I alluded to last week, I’ve been working on a simple “QRP Amplifier” to kick my power up from 5W to something a little more punchy. Specifically, an amp I can still use when portable. There’s something wonderful about achieving a contact with only 5W, but there’s also the frustration of getting into the field and having band conditions just wreck your day. It’d be nice to have the power to crank up the juice for special occasions.

While I have awhile to go before this project is wrapped up with a bow and ready for field use, here’s a brief video about my first successful test. 5W in, 50-60W out when run off two 13.8V sources in series:

More technical details to come, but for now, I consider this a really successful validation of the idea! Like I say, a few more critical steps to come, including an input 50-ohm pad, a low pass filter, and a case, but this is enough of a proof of concept to move forward.

Hear you on the air!


A Portable 20/30/40m Vertical Antenna

This post is cross-posted to my ham-radio specific blog,

Following the Forth of July, I took a few days off of work to recuperate from a grueling work project that we pushed over the finish line on the third. And what better way to relax in the wake of a heatwave than getting out in the beautiful, low-70’s weather and working on a new portable HF antenna.


From eBay listing

The heart of the antenna is an inexpensive ‘7.2m’ telescoping fishing pole, which can be had for less than $30 with Prime shipping or for less than $10 if you don’t mind waiting. The pole weighs about 10 ounces, comes with a small fabric sheath, and collapses down to about 24″. I’ve been wanting to try out something like this since I stumbled across VK3YE and his squid-pole setups awhile back – Peter’s also featured these particular poles in another video. Be aware, a pole called “7.2m” may not actually be 7.2 meters from end to end: check the listings carefully:


Note the difference between the “stretch” column and the “specification” column.

The length of the pole is enough for a quarter-wave vertical for 20m with some room to spare on either end. To allow for multi-band operation, I added a QRPGuys Tri-Band Vertical accessory to the bottom of the antenna. The piece is essentially just two loading-coils (in this case, iron-powder toroids) with slide-switches to short them out. The 20m configuration is a true quarter-wave vertical; one of the toroids is switched in series for 30m, and both are placed in series for 40m. Ultimately, not a complicated setup. While it would be easy enough to homebrew, the ergonomics of the switches, the hardware to attach the antenna wire and radials, and the clever PCB setup are enough to make it worth the $15 to just buy the darn thing. It even has little notches on the edges of the PCB for straps/ties/rubberbands to attach it to the vertical.



Tuning the antenna is straightforward: you cut a piece of wire (a bit long) for a 20m quarter-wave, and lay out four 10′ radials. Then, you bit-by-bit trim down the vertical element to resonate at the desired point in the 20m band. Then you switch in the 30m coil and compress/expand its turns without changing the antenna length to resonate on 30m. Finally, switch in both coils and adjust the second coil to resonate on 40m without changing either the antenna length or the first coil. Voila, a tri-band, base-loaded antenna.

Unfortunately, my antenna analyzer is old school, and doesn’t have a frequency readout. It’s an old MFJ-207 that I scooped up at the SMCC Hamfest in 2016, and while it does have a port to attach a portable frequency counter, I couldn’t find my cheapie one on the day. But I do have a nice Heathkit IM-2420 Frequency Counter with an internal OXCO that I scored an amazing deal on at a hamfest last year (it had an intermittent power switch). So, I attached the MFJ to the antenna, tuned its analog VFO for lowest SWR, walked inside without touching the dail and hooked it up to the frequency counter to see where the center frequency was. Repeat for say the upper and lower 2:1 SWR ranges. Trim the antenna a little, and repeat measurements. Once 20m is tuned, repeat with adjusting the coils for 30m and 40m. A fairly cumbersome process, but for three frequency ranges on one antenna, it was a half-hour project at most.


In the end, the antenna is less than 2:1 SWR across all of the 20m band, all of the 30m band, and all but the top 50 Khz of the 40m band.

I’ve glossed over the mechanical details of the antenna to this point – the base of the telescoping pole fits snugly-yet-easily into the a piece of 1″ schedule-40 PVC pipe. I bought a 5′ section from the local big-box store and cut off a ~10″ section to hold the antenna. I strapped two ground-stakes that I got at Hamvention this year to the bottom with a couple zip-ties and a couple rubber-bands. Finally,  I threaded a long 3/8″ eye-bolt though a matching hole about 2″ from the bottom of the pipe and secured it with a nut on either side – this acts as both a stop for the pole so it doesn’t fall out the bottom, and provides an easy hand- or foot-hold for pressing the stakes into the ground.


The finished antenna mount. It may be getting a coat of high-vis paint in the near future.

The setup for the radials was something I stumbled across by chance while buying the PVC pipe. Our local big-box hardware store was having a sale on these RECOIL Brand cable winders that are meant for headphones or charging cables or similar. I’ve found that they can almost hold four 10′, 24-guage speaker wire radials. This is solving the problem of wires-getting-tangled-in-a-bag that I’ve had with all my antennas to date. Thank goodness!


A few loose ends are worth it for the assurance that the wires won’t get tangled in transit.

It takes about 6 minutes to setup or tear down the antenna:

  • The stakes are driven into the ground with a firm foot.
  • The telescoping pole is unwrapped and placed in the base
  • The antenna wire is unwound from the QRPGuys winder and tied to the tip of the telescoping pole with a small bit of cotton-wrapped nylon line (what we’d call tie line). The top section the pole is very flimsy, so I add a second tie to the next-largest section.
  • The pole is pushed up to full height, taking the antenna wire with it, which leaves the QRPGuys rig hanging about 2′ off the ground.
  • The QRPGuys rig is tied to the pole with another bit of tieline.
  • The radials are unstrung from their winder, pinched to the ground terminal on the QRPGuys rig, and spread out.
  • Run coax to a nearby table/seat/rock.
  • Set up radio, battery, key, antenna, and logbook.


The antenna fully set up and freestanding.

Of course, my very first time away from home with the antenna… I forgot the radial wires. D’oh! I was way out in the suburbs, too. I wasn’t about to drive an hour home and an hour back for 4 bits of wire, so I first tried out the antenna with no radials (just the coax as a counterpoise). This worked alright – I picked up K2D in CT in the 13 Colonies event on the second call (this at 5W QRP with the ATS-4), but was having trouble with other contacts.

Since I planned to swing by the local Fry’s Electronics on this adventure, I decided to pause operating for a while and make that run. Mostly I was picking up parts for an amplifier project (more on that to come), but while I was there, I looked for solutions to my radial problem. I found a 10′ section of RJ11 phone cord with 4 wires for $1.69 – perfect! Back out in a new park, I stripped the wires out of their jacket, spread them on the ground, and tied them to the antenna’s ground terminal. Instant radials!


And such colorful radials too!

With the antenna back to spec, things really picked up – surely, being on 20m at sundown didn’t hurt either. I scooped K2A (NY), K2B (VA), K2H (MA), K2L (SC), and K2M (PA), as well as the 13-cols bonus station WM3PEN in Philly. Many of these I got on the first or second call, though K2L was a real struggle. There was a very patient operator on the other end though.


The 13 Colonies special operating event runs each year for a week around the 4th of July in the US.

I picked up a couple of other interesting stations along the way: PJ2/KB7Q out of Curacao (though the license gives away that he’s either an ex-pat or visiting), and CQ918FWC from Madeira Island (!) off the coast of Portugal. There were a number of these World Cup special stations on the bands this week as we close in on the finals. At 3800+ miles away, this was my best DX of the day, and a great proof of concept for the new antenna.

ord fnc

At QRP wattage ,this 3800 mile contact was made at 760 miles/watt.

Hear you on the air!


Geared 7-Segment Display, Part 4 – Pinion Gears and First Rotation

This weekend I’ve added the pinion gears to the seven-segment display, and performed the first test rotation of the mechanism.

As previous noted, the arm gears are 6-tooth gears of module 4 (metric) – in clockmaking terms, these would be pinions. In the clockmaking world, where I’ve been doing quite a bit of research during this project, there doesn’t seem to be a hard dividing line between what’s considered a “gear” and what’s considered a “pinion,” except that gears are big and pinions are small. Fair enough. From this point forward I’ll be referring to the arm gears as arm pinions.

I printed 6 of the pinions in just over an hour, and fitted them to their axles, which are just hacked-off pieces of 1/8″ rod stock from the hardware store. With the tolerancing on the prints as it is, the pinions are a snug fit on the axles, so I’m not too concerned about slippage once I can get the whole thing turning smoothly.

Speaking of turning, here are the first (partial) rotations of the mechanism.

Right now, the biggest impediment seems to be that the frame lacks rigidity, and easy warps and slews far enough to drive the arm pinions out of mesh with the drive gears. I’m currently working on a two-part version of the frame with interlocking members that firmly affixes both halves on the frame so that they remain rigid and parallel.

I’d assumed when I started this project that the axles (arbors) would need to be made of metal rod or dowel stock, so that they were firm, perfectly round, and rigid. But this being a 3d printing project, I’m now experimenting with a fully3D printed arbor-and-arm-pinion assemblies. These have the advantage that there’s no need to manually locate the pinion on the arbor by sliding the arm pinons up and down the arbors – they’re all one piece. As a sample, I printed a C-Arm assembly in two different orientations, both vertically and horizontally:

The vertically-printed arbor and pinion came out much better – the axle on the horizontally-printed unit is limited in smoothness by the layer height of the print, while on the vertical print it’s limited by the X and Y resolution of the printer. Additionally, while there is significantly more support plastic on the vertically printed unit, it’s not touching any of the working surfaces of the pinion itself, making the post-processing and filing significantly simpler. Both seemed to rotate well in the axle holes, however; well enough that I plan to work up a full set of these and test them in the next version of the frame. That means the only non-3D printed part in the project would be the main axle, and possibly the G-Arm tubing.

Next steps are printing the stiffer frame and the pinion/arbor assemblies.

Dayton Hamvention 2018

This post is cross-posted to my ham radio-specific blog,

While I’m still exhausted from the travel and the good times, I wanted to put up a little note from this year’s Hamvention, the largest annual gathering of ham radio operators in North America. I only decided a week ago that I was going – I left Friday after work, drove 5 hours to Dayton OH (well, Xenia), and crashed at a hotel. Up bright and early, spent the day at the convention and checked out some local beer and grub in Dayton. Sunday, caught an early breakfest with some friends new and old, then got on the road back to Chicago. What a ride!

Others are doing fuller summaries of the convention – SWL-ing post always does a photo wrap-up of both the indoor and outdoor experience, and the Ham Radio Workbench podcast from the event is now up.

Hamvention is a great place for meeting the hams you’ve yet to meet, and seeing again those you already know. I spent most of Saturday hanging out with the Workbench crew, but I also ran into hams that I knew from elsewhere. Plus this guy, who falls into both categories:

It’s wild that 15 years after I accidentally introduced the future W6KWF to ham radio we hung out together at giant swapmeet in the middle of Ohio. Totally wild.

The flea market was certainly the biggest radio swapmeet I’ve ever been to – it’s probably bigger than that De Anza flea market by a good 300% – but it wasn’t all that special. I would say there was the usual assortment of used radios, test year, bits and parts, old tools… nothing super intriguing. Of course, I did get there on Saturday, so perhaps all the interesting things were just scooped on Friday.

It was neat to see a lot of the vendor products in person that I’d only heard about, but since I wasn’t in the market for anything in particular, I didn’t linger too long at any of the booths. Except Elecraft – those are some very, very attractive radios. I chatted with Wayne N6KR (one of Elecraft’s founders) for about 15 minutes about the KX2 and its SDR structure, which, not to be a fanboy, was pretty exciting.

In the end, I don’t know if I would go back the very next year – it was a really neat experience, and I’d go to see the people, but in this age of eBay, Amazon, and vendor websites, seeing everything in person and picking through the fleamarket feel just a little bit like a relic of the days when everything had to be done in person.

That said, I did find a few treasures… here’s this year’s haul:

Roughly from left to right:

  • Some panel-mount SMA connectors
  • An old automatic shutter trigger/timer
  • A tube of TFM-2LH Level 10 2Mhz-1000Mhz mixers from Minicircuits ($15 for 20, a steal!)
  • Six interesting potentiometers (dual with concentric controls or dual with concentric switch)
  • A bag of assorted HF/VHF H49 Crystals
  • An old Collins 250Khz crystal filter
  • A ZUMspot DMR hotspot/raspberry pi kit
  • A pair of QRP-Labs filters, both a low-pass and a bandpass filter for 40 meters.

Sometimes, you get back from a big trip or conference or meetup thinking Boy, am I worn out, I don’t need to do any more of that thing for awhile. This time, I came how itching to get back to work, revive some projects that had been dormant for awhile, and make things. So for that, at least, Hamvention 2018 was worth it.