Walter KA4KXX and Mike WN2A and I were recently talking about the degree to which we are 100% homebrew. Both these guys come a lot closer to this goal than I do. Here is my assessment of my gear:
I fall far from a state of 100% homebrew grace:
Serving the worldwide community of radio-electronic homebrewers. Providing blog support to the SolderSmoke podcast: http://soldersmoke.com
Walter KA4KXX and Mike WN2A and I were recently talking about the degree to which we are 100% homebrew. Both these guys come a lot closer to this goal than I do. Here is my assessment of my gear:
I fall far from a state of 100% homebrew grace:
This was a fairly typical session of the Old Military Radio Net. 3885 kHz AM 0500 local on Saturday mornings. (Distant listeners can tune in via WebSDR.) This clip shows W3EMD, N2CQR (me) and, N1SNG. Buzz W3EMD from the Hudson Valley of New York was on with his KWM-1. Normally he uses a BC-348 powered with a Dynamotor. Last week he told the group that someone had COMPLAINED about the noise that his mic was picking up from the Dynamotor. Geez! I told Buzz that we had been commiserating with him about this on the SolderSmoke podcast. Later in this morning's session I heard WU2D, WA1HLR, AJ1G, and others. I reported on an emergency De-Oxit spraying of my HQ-100's band switch, just minutes before net call up. I also noted that I had found a crystal for 3885 kHz; the radio gods have spoken (TRGHS).
-- April 27, 1973. Novice Ticket becomes effective. WN2QHL. Age 14.
-- July 19, 1973. First contact (with Elmer WN2NEC). Age 14.
-- February 1 and 2 1973. A grumpy old-timer calls -- during the Novice Roundup! -- to tell me that I'm putting harmonics onto the 20 meter band. I get scared and go off the air. Geez! I probably just needed to retune the tank circuit. Age 15.
-- February 23, 1974. I go back on the air with a DX-100. Age 15.
-- March 5, 1974. I take the General Class exam at the FCC office in New York City. I pass. Age 15.
-- April 11, 1974. I buy the Drake 2-B from WN2NEC. This revolutionizes my radio life. Fifteen meter contacts become possible. Age 15.
-- April 13, 1974. I work ZL2ACP on 15 meter CW. I wake up my parents to tell them. Age 15.
-- April 21, 1974. END OF NOVICE OPERATION. Apparently we were still working under a one year limitation on Novice operation. Could the expiration date have been marked on the license?
At this point the FCC screwed up and sent me a Technician License instead of a General Class License. My father got on the phone to Gettysburg and straightened this out. Thanks Dad. So I was only a Technician for a few weeks.
-- April 9, 1974. General Class License effective. I become WB2QHL, a man of substance. Age 15.
-- May-June 1974. I acquire a Heathkit HW-32A 20 meter SSB transceiver from the Crystal Radio Club. But I have to build the power supply from an old TV. Somehow, I survive. Age 15.
-- June 11, 1974. First contact with the HW-32A. Age 15.
-- November 9, 1974. Last contact with the HW-32A . Age 16.
-- March 15, 1975. First contact with my Hallicrafters HT-37. Age 16.
After working on it for a while I got so fond of my old Hammarlund HQ-100 that I moved it from the AM/Boatanchors operating position over to a more convenient spot right next to my computer. This left a big gap on the receive side of the AM station.
I briefly put my HRO-ish solid state receiver above the DX-100, but I'm afraid that receiver needs some work. More on that in due course.
I thought about putting my SOLID STATE Lafayette HA-600A atop the thermatronic DX-100, but this just didn't seem right. The Radio Gods would NOT approve.
So I turned my attention to the Mate for the Mighty Midget that I built in 1998 and have been poking at and "improving" ever since.
This receiver worked, but not quite right. It received SSB stations well enough, but when I turned off the BFO I could no longer hear the band noise. I wasn't sure how well the RF amp's grid and plate tuned circuits tracked. And I had serious doubts about the detector circuit that Lew McCoy put in there when he designed this thing back in 1966.
As I started this latest round of MMMRX poking, I realized that I now have test gear that I didn't have in 1998: I now have a decent oscilloscope. I have an HP-8640B signal generator (thanks Steve Silverman and Dave Bamford). I have an AADE LC meter. And I've learned a lot about building rigs.
FRONT END TRACKING
The MMRX has a tuned circuit in the grid of the RF amplifier, and another in the plate circuit of the RF amplifier. There is a ganged capacitor that tunes them both. They need to cover both 80/75 and 40 meters. And they need to "track" fairly well: over the fairly broad range of 3.5 to 7.3 MHz they both need to be resonant at the same frequency.
McCoy's article just called for "ten turns on a pill bottle" for the coils in these parallel LC circuits. The link coils were 5 turns. No data on inductance was given. Armed now with an LC meter, I pulled these coils off the chassis and measured the inductances of the coils. I just needed to make sure they were close in value. They were:
L1 was .858uH L2 was 2.709 L3 was .930uH L4 was 2.672
Next I checked the ganged variable capacitors. At first I found that one cap had a lot more capacitance than they other. How could that be? Then I remembered that I had installed trimmer caps across each of the ganged capacitors. Adjusting these trimmers (and leaving the caps connected to the grid of V1a and V2A, I adjusted the trimmers to get the caps close in value. I think I ended up with them fairly close:
C1: 63.77-532 pF C2 64.81 -- 525.1 pF
I put the coils back in and checked the tracking on 40 and on 80/75. While not perfect, it was close enough to stop messing with it.
DETECTOR CIRCUIT
I've had my doubts about the detector circuit that Lew McCoy had in the MMMRX. In his 1966 QST article he claimed that the circuit he used was a voltage doubler, and that this would boost signal strength. But I built the thing in LT Spice and didn't notice any doubling. And consider the capacitors he had at the input and output of the detector: 100 pF. At 455 kHz 100 pF is about 3500 ohms. At audio (1 kHz) it is 1.5 MILLION ohms. Ouch. No wonder years ago I put a .1 uF cap across that output cap just to get the receiver working.
Scott WA9WFA told me that by the time the MMMRX appeared in the 1969 ARRL handbook, the second "voltage doubling" diode was gone, as were the 100 pF caps. Now it was just a diode, a .01 uF cap and a 470,000 ohm resistor. I switched to the 1969 Handbook circuit (but I have not yet changed the 1 meg grid resister to 470k -- I don't think this will make much difference). Foiled again by a faulty QST article, again by one of the League's luminaries.
6U8s out, 6EA8s in
We learned that the 6U8 tubes originally called for by Lew McCoy are getting old and not aging well. So I switched all three to more youthful 6EA8s. This seemed to perk the receiver up a bit.
MUTING from the DX-100
My K2ZA DX-100 has a T/R relay mounted in a box on the back of the transmitter. When the Plate switch goes up, it switches the antenna from receiver to transmitter. The box also has a one pole double throw switch available for receiver muting. I put the common connection to ground, the normally connected (receive position) connect the ground terminal of the AF output transformer to ground -- it is disconnected from ground on transmit. The other connection (normally open) is connected to the antenna jack -- on transmit this connection ground the receiver RF input connection. These two steps mutes the receiver very nicely.
Replacing Reduction Drive
Over the years I have had several different reduction drives on the main tuning cap. I had a kind of wonky Jackson brothers drive on there that needed to be replaced. I put in a new one -- this smoothed out he tuning considerably.
Ceramic Resonator
I never could get McCoy's 455 kc two crystal filter to work right. So at first I made due with the two 455 kc IF cans. This made for a very broad passband. Then I put a CM filter in there. This was more narrow, but with a lot of loss. There may have been others. But the filter spot is currently held by a 6 kHz wide ceramic filter. This one is my favorite so far.
Digital Readout
When I was running the DX-100 with the Hammarlund HQ-100 I built a little frequency readout box. The box was from a Heath QF-1 Q multiplier (I am sorry about this). The readouts are in Juliano Blue and come via e-bay from San Jian. I now have it hooked up to the DX-100's oscillator. I haven't tapped into the MMMRX's oscillator yet.
In Part II I'll show you how this thing sounds and what it is like to use it for SWL, CW, SSB and AM.
Bill,
Why do you guys make your Soldersmoke podcasts so darn intriguing such that I can’t listen to them in the background while I’m doing something else? Good grief! I start listening and before long you make me stop and chase down a rabbit hole to find something new that you mentioned that I had no clue was out there. Before long I’m doodling out a new sketch or playing with at a new design for something I really need to experiment with or build “next” or something I need to try. It is taking too much of my time!! J
I’ve been listening to your podcasts for years. Way back, before I knew you and before I knew you were doing these Soldersmoke blogs with Mike, KL7R, and just before he was so tragically killed, I was collaborating with him on a simple frequency counter project using a PIC microcontroller. We were making good progress on a neat design. I later completed the project but always kept his contributions noted as part of the source code.
I’ve been making PIC-based VFOs for years – dating back to about 2000 – aiming them at builders who were looking for something to go along with Rick Campbell’s (KK7B) receivers. Rick is a good friend now, after we met in the Kanga booth at Dayton where we both were demonstrating our stuff. (Bill Kelsey (N8ET) of Kanga, was the “marketer” for my kits as well as Rick’s for many years.) My original VFO kits used a DDS (high-end AD9854) that simultaneously produced I and Q signals which made it perfect for Rick’s phasing gear. Rick is a big supporter of my work but he still kids me about polluting his beautiful analog world with my “digital crap” (copyright KK7B term). When I came out with a newer version VFO using a Silicon Labs Si570 PPLL (I can hear already Pete Juliano groaning) it was a big improvement over the AD9854 in noise/spur reduction. I documented this all in a QEX article in about 2011 and Rick (and Wes Hayward) were very supportive/appreciative of my work.
I have used the Si5351 also and I understand Pete’s point of view. It’s “plenty good” for most amateur projects. However, it remains a fact that the Si570 is a better part and produces a cleaner signal. That’s the reason why the Elecraft KX3 uses a Si570. Granted, the newer Elecraft KX2 uses a Si5351 but it’s most likely because they wanted to preserve battery life (the Si570 uses more power but not nearly as much as the AD9854) and also to reduce the cost. I do understand! I also fully understand the ability of the Si5351 to produce I and Q signals via different channels. I’ve had extensive conversations about this with Hans Summers, at Dayton and online. I use a pair of Flip-Flops on the output of the Si570 instead. My PIC code driving the Si570 is ALL written in ASSEMBLER code. Yep! I’m an EE but have had a career mainly in software development and much of it was writing assembler code. I dare say there aren’t too many gluttons for punishment that do it this way. I do it because I want to understand every line of code don’t want to be dependent on anyone else’s libraries. Every line of code in my VFO’s and Signal Generators is MINE so I know I can debug it and it can’t get changed out from under me. (This problem bit Ashar Farhan hard on the Raduino of his BitX. Tuning clicks appeared because the Si5351 libraries he used changed between the time he tested it and released it. I was really appalled when I dug into this and resolved to NEVER use libraries that I didn’t write myself. Similarly, this also makes me have some distaste for Arduino sketches. I would rather see ALL of the code including the initialization code, the serial routines, etc, rather than having them hidden and get pulled in from Arduino libraries. That’s similar to the reason why Hans Summers didn’t use an Arduino in his QCX. He used the same Atmel microprocessor but developed/debugged it as “C” code with the full Atmel IDE/debugger.
By the way, Pete mentioned the Phaser FT8 transceiver by Dave, K1SWL, in a recent podcast. Dave is a very close friend, even though I haven’t met him in person since about 2000. We Email at least daily and some of it is even about radio. J I did the PIC code for the tiny PIC that controls the Si5351 in the Phaser. Yes, it’s written entirely in Assembler again! I do know how to do it for a Si5351. That Si5351 code is not nearly as much “fun”, though. I know, this will make very little difference to guys who write Arduino “C” code to control it but under the covers it’s a world of difference. It takes me about 15 serial, sequential, math operations to generate the parameters for the Si5351. None of them can be table driven and they all have to be performed sequentially. (This is all hidden in about 5 lines of complex, Arduino “C” code but the operations are all there in the compiled assembler code.) In contrast, my Si570 code is almost all table driven. I just have to do one large (48-bit) division operation at the end to generate the parameters. Yes, that’s a bit of trickery to do in ASM. There are no libraries do this.
I will point out one more advantage of the Si570 in comparison to the Si5351. It has the ability to self-calibrate via software instead of relying on an external frequency standard. In my Si570 app I can read up the exact parameters for the crystal embedded inside the Si570, run my frequency-generating algorithm “backwards” and determine the exact crystal frequency (within tolerances, of course) for that particular Si570. Then I update all the internal tables using that crystal frequency and from then on all generated frequencies are “exact”. I love this! Frequency often moves by about 6 kHz on 40M.
Oh yes, I must mention the difference of home solderability of the si570 vs the Si5351. Those little Si5351 buggers are terribly difficult to solder at home while the Si570 is a breeze. I know, many folks will just buy the AdaFruit Si5351 board and it’s already soldered on but, again, I like to do it all myself. No “magic Fruit” for me.
Now that I retired a couple of years ago and am getting out of the VFO kitting business I can finally build complete rigs instead of just making the next-generation VFO’s for everyone else to use. I recently build a tiny, Direct Conversion rig with a Si570 signal generator (of course) and a diode ring mixer (ADE-1). Look at my web page, www.aa0zz.com to see it, along with my VFO projects that I’ve been building in the past. As you well know, Direct Conversion is fun to build and the sound is astounding; however, they are rather a pain to use! Yes, I did make it qualify as a real rig by making several contacts all over the country. (Wes Hayward gave me the criteria: he told me that I must put any new rig on the air and make at least one contact before it qualifies as a real rig.)
The new rig that’s on my workbench is my own version of a phasing rig, experimenting with a Quadrature Sampling Detector (QSD, sometimes called a “Tayloe” mixer), using some ideas from Rick’s R2 and R2Pro receivers and many innovations of my own. At present my new higher-end Signal Generator works great, the QSD receiver works great (extremely quiet and MDS of -130 dB on 40 meters) and the transmitter is putting out about 16 watts with two RD16HHF1’s in push-pull. You can take away my “QRP-Only-Forever” badge too, not that I’ve ever subscribed to that concept! Still more tweaking to do with the TX but now I’m also working on the “glue” circuitry and the T/R switch. The SigGen, RX and TX are all on separate boards that plug into a base board which has the interconnections between boards and the jacks on the back. I’ve built DOZENS of variations of each of these boards. Fortunately they all fall within the size limit criteria to get them from China at the incredible price of $5 for 10 boards (plus $18 shipping) with about 1 week turnaround. Cost isn’t really an object at this point but it’s more of getting a hardware education that I sadly missed while I concentrated on software for so many years. it’s certainly nice to have willing mentors such as Rick, Wes, Dave (K1SWL), Don (W6JL) and many others to bounce my crazy ideas off. Yes, I’m having a ball!
I was licensed in 1964 but out of radio completely from 1975 to 1995. Do you like the picture of my DX-100 on my web page? My buddy in the 60’s had a Drake 2B and I drooled over it but couldn’t afford one.
Now I must finish this rig before you guys send me down another rabbit hole. Too many fascinating things to think about! I literally have a “priority list” on the my computer’s desktop screen. Every time I come up with a new project idea – something I really want to play with such as a Raspberry Pi, SDR, etc, I pull out the priority list and decide where it fits and what I want to slide down to accommodate it. That’s my reality check!
Take care, Bill. Thanks for taking the time to give us many inspiring thoughts and ideas.
73,
-Craig, AA0ZZ
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Hi, Bill!
While listening to SS137, you brought back some warm memories.
Bert Sessler, WA3WAW and I both grew up in Uniontown and met via CB – which was a gateway drug to Ham Radio for many of us. Within a fairly short time, we became good friends. Although I moved away some 30 years ago, I always try to get together with him when I’m back in town.
The HW-7 references also reminded me of trips into the nearby hills (being a few years older, I had my driver’s license and car before him) with his HW-7 and some lantern batteries. We’d park my ’69 Chevy Nova and then hike the trails to find some suitable trees for antenna supports. Bert’s code speed was impressive right from the start and he’d work more stations than me, in rapid succession. (How many 25+ WPM Novices do you know?)
Later, I’d get a HW-7 (and TenTec Power Mite 2) for those hikes alone, but it wasn’t quite the same as doing it with a friend. These days, I go to parks in the relatively flat South Jersey or Delaware with a FT-817ND, MFJ-9030 or 20M VXO’d RockMite and TX Topper Amp. Recently, pangs of nostalgia for my HW-7 (and ARC-5 station, for that matter) have arisen. I know the receiver doesn’t stack up against the new stuff I have, but it was certainly good enough for many enjoyable contacts.
Also, John Zaruba, K2ZA, is a good friend of mine here in Gloucester County. I’ve laid hands on the DX-100 you now have. You should have seen the Collins A line John’s dad had in the racks. Everything looked almost factory new.
At our GCARC Hamfest over the weekend, John helped feed my tube addiction with 4 boxes of NOS tubes, shields, etc. I also bought his dad’s Meissner Signal Shifter. After giving it a respectful time to warm up and colorfully glow again (orange, purple and green from the “magic eye”), I attached it to a tungsten lamp – the “manly” way to tune a tube transmitter – and got RF! As it has a balanced 300 ohm output, I have to build a 6:1 balun and hope to have it on the air next week with its characteristic chirp. Hmm, just like the HW-7 and my ARC-5’s of years gone by…
I hope you and your family are enjoying life back in DC. It’s not the milieu of Italy, but at least you’re much closer to a Ham Radio Outlet!
All the best,
Cory – WA3UVV
PS - If you have a desire to home brew a 6L6 transmitter and need a tube, let me know. My mom taught me to share...
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