Bench Report – HamRadio360 Podcast, Beach-40, SigGen, Power Meter Projects

A few weeks, back, I spent about half an hour chatting with Jeremy, KF7IJZ, for a listener-projects segment on the HamRadio360 Workbench podcast. That episode just went live this morning, if you want to take a listen online. Jeremy and I had a swell time chatting about the QST 40-9er Transceiver project I built awhile back, and ended up packaging with a laser-cut faceplate.

Seeing the podcast pop up got me thinking – from the last few months of posts, you’d think that I’d been spending all my time operating and that my bench was empty. Not so! There are three major projects milling about the bench these days. None are complete enough to merit a full post, but consolidating them all in to one post feels right.


First on the bench is the continuation of my Beach 40 Transceiver project, that I’ve been working on since the Fall. I’ve been making steady progress recently on the penultimate stage, the RF amplifier, which will take the ~10dBm modulated voice signal from the balanced modulator and turn it into ~33dBm (2W) of RF output power to send to the LPF and out into the world. The amplifier is a three-stage design, with a 2n3904 buffer feeding a BD139 driver and another BD139 final.

IMG_2291.JPG
Beach40 PA Schematic and Layout, in Graphite-O-Vision.

The module is assembled manhattan-style on single-sided copper glad, just like the rest of the project. The layout surrounds the +12V-on-transmit bus down the center of the PCB… more on that error later.

IMG_2155.JPG
The Beach40 PA mid-assembly – you can see the +12VT buss running down the middle, and the buffer and driver stages starting to take shape.

The module assembly and testing went fairly smoothly – using a variable-voltage power supply, it’s easy to vary the output power of the amplifier, and to observe the changes in PA heating that this causes. You can see the two large screw-on heat sinks on the BD139’s in the following pictures, as well as the the large ferrite bead which feeds the Final. There’s also a chunky 100uF cap at the DC input to the board for additional decoupling.

IMG_2288.JPG
The assembled Beach40 PA.

 

The problem I’m having now is the same one that plagued me way back in my assembly of the Virgin Receiver, my first first homebrew receiver: this amplifier would really love to be an oscillator. With the PA voltage set at 12V, any time the signal imput is sufficiently strong, the PA will fall hard into oscillation, and won’t stop until the PA voltage is brought way down or cut. I’ve been experimenting with emitter degeneration for the final BD139 (the original schematic has the emitter directly grounded). That’s helped, but not much. I’ve also changed the RF-carrying wires from hookup wire to coax, to mitigate feedback through other modules. Another help, but so far, the oscillation problem is still there. The next step will be to move the modules themselves around, to limit the amount that the high-power RF coming from the PA has to pass by earlier stages of the transmit chain (VFO, mic amp, balanced modulator) to try to eliminate feedback that way. Fingers crossed!


Next on the bench is a repackaging of an old project – my SI5351-based “VFO,” which for the better part of a year has been serving as my primary signal generator for experimental projects, spread out in all its Al-Fresco glory on a breadboard. With the amount of troubleshooting I’ve been going through on the Beach 40 project, I’ve decided to finally box up the SI5351, Arduino, and display into a proper project box, and make the thing a real SI5351-based Signal Generator. The schematic is essentially unchanged (minus the PA) since I used the project in my SI5351-based transmitter project, which is reproduced below:

CW Transmitter sCHEMATIC

To that end, I purchased an inexpensive nibbling tool and an expensive project box from the local Fry’s electronics, and have been working in the past couple weeks to marry the spread-out guts of the previous project with the clean lines of the enclosure. Biting out the large hole for the display 1/8″ at a time was time-consuming and strangely soothing.

At this point, the display and Arduino are connected, but I have yet to wire the two control buttons, rotary encoder, and Si5351 breakout board back into the Arduino. I also need a provision for getting the signal out the front of the darn thing, so I’m waiting on a shipment of SMA connectors and a jumper to go from the SI5351 breakout board to the front panel. So far, so good.

The code for this project is still on Github.


The last project on the bench is an RF power meter circuit, based on a circuit by W7ZOI from 2001. While the old scope-probe-across-a-50-ohm-load technique has proven very useful, I’ve found myself wanting a way to more reliably measure RF power at low levels, and to do it in a way that could be interfaced to a microcontroller or computer. To that end, I plan on using the W7ZOI circuit connected to an Arduino, much like Vu2ESE’s Sweeperino, to make digital power measurements.

IMG_2292.JPG

I rolled a little PCB for this project from OSHPark, and since that service provides PCBs in multiples of 3, I figure I’ll connect one board to an analog meter (for that old-school feel), one to an independent Arduino (for digital measurements), and embed one inside the SigGen project, for marrying signal generator and power measurement at specific frequencies. This last project, I figure, will be especially useful for examining filter behavior at HF and piping the information to a PC for display an analysis.


So that’s what’s on the bench at the end of March 2017. All of these will hopefully merit full posts in future as the projects come to fruition, but for now, the is the smorgasbord that is my bench.

Hear you on the air!

73

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From DX with Love – RDXC 2017

In a further example of the benefits of DX contests for those looking to rack up new countries, this weekend’s Russia DX Contest served up another bounty of new DXCC entities on CW.

All in all, I landed 11 new DXCC entities. Since part of the fun of contesting is imagining the operator at the other end of the ionosphere – doing the same thing you’re doing, furiously decoding CW in front of a radio, thousands of miles away – I’ve included the names of the ops below where I could find them:

  • Switzerland (HB9ON – Radiogroup in Piancamara 7, a profilic DXpedition team)
  • England (M2G – not a special event station, just a contest call of John in the UK)
  • Croatia (9A7V – Eugen)
  • Poland (SN8B – Bobowsi)
  • Germany (DA0AA – A radio club in Germany. “Emergency Radio Station Frank Cut Switzerland”, says Google Translate…. so that’s something)
  • European Russia (RU1A, a contest station out of St. Petersburg)
  • Northern Ireland (MI5I – Colin)
  • Serbia (YT3X – Miki)
  • Sweden (SH1DX – could not find)
  • Argentina (L6HKA – could not find)
  • Slovenia (S51J – Janez)
VmB+vAB5.png
A bevy of new European countries worked during RDXC 2017. Argentina can come too.

I also connected with a second Alaska station, my first AK contact on 20m, which should help to cement that state for my WAS goal this year. (To be sure, KL7/VE7ACN has been tearing up the bands this week, since I heard him a week ago. But more contacts in the log never hurt.) As icing on the cake, I heard, but couldn’t contact, Arthur 4X2M in Israel . Still searching for that first elusive contact in Asia.

Unlike the ARRL DX contest, where contacts within the same country don’t count for anything, the Russia DX contest does award a (small) number of points for contacts in the same country. So I picked up a few stateside contacts on 40m later in the evening, just to add to the contact count and continue drilling my CW.

There’s a joke in radio circles about “contest propagation”, which is the notion that even when “the bands are dead,” they somehow “magically open up” when there’s a contest going on. Certainly, during major contests, when everyone who has one brings out their big amplifiers and aims their beams most precisely, contacts are more frequent.

But this weekend, I suspect that the ol’ ionosphere was actually on our side for a change – in the late afternoon, after I’d worked what there was to work on 20m CW and before 40m opened up, I dipped over onto 20M JT65. . After noodling around for about 20 minutes, I had landed both PD7RF (Frits in the Netherlands) and MC0CSO in Wales.

Two more DXCC in the log. That brings me up to 49 DXCC entities reached, with 30 confirmed.

And as a final sign of Sol’s grace upon the upper atmosphere, the following afternoon I heard (but could not reach) both Asiatic Russia (RA0CGY) and Japan (JM7OLW, JH1HRJ, JA1PSS, and 7K4GUR) on JT65.All are over 6000 miles away. They were way below the noise floor at -20 to -24 dB, about the limits of what JTDX will decode. But things look promising as the summer months move closer.

stationsheard_20m_JT65_2
Stations heard on 20m JT65, afternoon of 3/19/17. What a spread!
Image by PSKreporter.com

Hear you on the air, all over the world!

73

Alaska

Just put Alaska in the log – KL7/VE7ACN was coming in about S7 to Chicago this evening, and I bagged him after about 10 minutes of chasing. To make it extra special, I he was working split on 7.001.5 UP, which makes this both (a) my first use of the Split feature of the FT-767 to work a station and (b) my first use of my Extra class privileges!

Per my New Year’s resolution, I only have 5 states left to work: Indiana, North Dakota, Nebraska, Nevada, and Utah. With 9 month’s left this year, I’m feeling confident about hitting all five before 2017’s end.

Hear you on the air!

73

KK9JEF/AE – Sterling IL Hamfest

Yesterday, I went out to the Sterling IL Hamfest. It was quite a hike from my QTH in Chicago, but it turned out to be totally worth it: I finally upgraded to an Extra class license!

I’ve been casually studying for the Element 4 exam (extra class) for be past few months, with an eye toward upgrading at some point. But what really pushed me into action this weekend was a single Croatian station working the ARRL DX SSB contest, down in the part of 20m that I, as a general, wasn’t allowed to transmit on. He was at least 10-over-S9, just begging to be worked, but I couldn’t… so, a few more practice tests and a two hour drive later first thing Sunday morning, I had the Element 4 exam in hand. An hour after that, I had my Extra.

There were a few more finds at the fest – the club table had a big ole junk in of parts. Mostly miscellaneous circuit breakers and switches, but way down at he bottom were seven or eight multi-turn pots for $0.75 each. What a steal! I bought as many as I could pull out of the bin. I also pulled a few NP0 caps an a bag of 12V DPDT relays.


What a rush of a day it was. Looking forward to excercising my new frequency privileges this week.

Hear you on the air, wherever in the band you are!

73

Heading in the Right Direction

I put a new DXCC entity in the log last week: Hungary

I ran across HG5F calling CQ TEST on morse code on 14.086 MHz on February 25th. This was smack in the middle of the UBA DX CW contest, which is actually a Belgian contest, but thankfully that awards points to non-Belgian countries making contacts with other non-Belgian countries. Admittedly, I wasn’t worth many points.

So, why did a Hungarian station come in at a solid 579 during the local afternoon on 20m, when he wanted to be talking to Belgium? There are two parts to unfolding that mystery. The first is John, HG5F’s, antenna; his QRZ page shows a large beam antenna (tribander?) in the foreground, on top of maybe a 30′-40′ tower. That would certainly have helped. (There’s also a small beam in the background of the picture, perhaps for 40m.)

hg5f_tower
HG5F’s antennas, from QRZ.com

The second and more interesting reason that HG5F was so audible has to do with geography. HG5F’s QRZ page lists his QTH (home station) as Jakabszállás, Hungary, a little Southwest of Budapest. If John was pointing his beam toward Belgium, (say toward Brussels in the center of the country,) his beam would have been pointed at roughly 300° ENE. If instead John had wanted to point his beam directly at me, he would have been aiming at ~310°. Put another way – by aiming his beam toward Belgium, John was also aiming toward the midwest United States.

These coincident transmission angles become clear when one looks at them with the proper map projection. Something like an azimuthal-equidistant map, which displays all points as proportionally equidistant from a center point, is perfect for this task. Check out the following AE map centered on Budapest:

hungary_ae_map

Notice that, from John’s perspective in Hungary, Belgium and the US Midwest line on almost the same Northeasterly line. Here’s the same illustration in a more familiar equirectangular map projection:

hungary_rect_map.PNG

So, I was quite a bit of an overshot for John, but I’m always happy to make a transatlantic contact – and on CW no less! That makes 35 countries in the log so far, and with the ARRL SSB DX contest this weekend, I’m hoping to hear and work several more.

Hear you on the air!

73