Video -- Mythbuster II Rig Gets a Front Panel -- Circuit Build Almost Done

Yesterday I built a front panel for my Mythbuster II 20 meter SSB transceiver. 

I used 1/8 inch plywood available from Amazon. 

I cut holes for the main tuning knob and dial, for the AF gain control, for the mic plug and for a 6 figure PLJ PIC frequency counter.   This gives me 100 Hz read capability, but I can hit the lower button on the counter to get 10 Hz reolution.  This may help when the other guy complains bitterly that I am 40 Hz off frequency.  The counter added noise to the receiver, but I was able to knock this down completely with a resistor and a cap on the power line to the counter. 

I put copper tape on the inside of the panel. 

I added a reverse polarity protection circuit.  I now sleep more soundly. 

I increased the size of the heat sink on my RD06 final.  This decrease the danger of blowing up this device. 

I added a jack for the connector that will switch the outboard .1 kW linear from R to T.  

Video above. Comments welcome.  

 

Part III: Curious Marc Repairs an All-Discrete Freq Counter: DO NOT ATTEMPT REPAIR OF CAVITY RESONATOR

I love all the "DO NOT ATTEMPT" warnings.  Wow, even HP got so skittish about this stuff.  Marc has a great sense of humor and notes that, "no cavity resonators were harmed in the production of this video."   I like the description of the mixers and the photo of the mixer antennas. 

Part 2: CuriousMarc Fixes an All-Discrete Counter -- "Like an IC, but in discrete form."

Marc nicely sums up this project with this line:  "It's an IC but in discrete form!"  On the same theme, he later says, "Who needs a logic analyzer when you can do a visual debug with neon bulbs?" 

Very cool.  Lots of troubleshooting and repair lessons in this video: 

-- Again we see the benefits of paper manuals.  (Todd K7TFC commented astutely on this under yesterday's post.)

-- 2N2222s to the rescue.  

-- A surprisingly large number of bad transistors (6?) found.  Why did they go bad? 

-- Marc repeatedly says, "Let me poke around."  Poking around is often important.  Mark fixes the reset line after poking around.  He is not sure HOW he has fixed it, but he has... by poking around.  Sometimes this happens.  Thank God for small favors. 

-- Marc has some fancy HP board extenders.  I am jealous.  

-- He also has a cool de-soldering tool.  More jealousy.  Want one. 

-- Marc's understanding of how the HP engineers had to put one of the flip-flops "on the edge of stability," and how his 'scope probe was capable of disturbing this stability. 

-- Remember that those Nixies are TUBES with enough voltage on them to really zap you.  So be careful in there.  This is an especially dangerous mix of transistor tech and tube tech.  With transistors you can work on them with the rig fired up.  With tubes, well, you have to be careful.

Part III tomorrow. 

CuriousMarc Repairs an old DISCRETE COMPONENT HP Frequency Counter

I really liked this repair video from CuriousMarc (aka AJ6JV).  This counter pre-dates the use of integrated circuits -- it is all discrete transistors.  Near the end, Marc mentions how this made this repair "like debugging a big integrated circuit, but with access to each transistor -- this made it quite satisfying."  I hear ya Marc -- with big ICs maybe all you would get to do would be to swap out a single IC.  There would not be much of a challenge there.  

With the older, discrete circuitry you get a good view of how Marc troubleshoots -- how he finds the precise points where the device is failing.  Note his use of the old HP paper manuals. I know this is an old guy thing, but I think the paper manuals (as opposed to the online versions)  just make the process easier.  Note too that Marc at one point had to go back to microfiche. 

The transistor tester Mark used was very cool. 

The whole physical structure of the HP device is very similar to my NYC HP8640B.  Thanks again Steve Silverman and Dave Bamford. 

I will look at Parts II and III of this series soon.  

Daylight Again on the Sunrise Net! Walter KA4KXX Builds a PTO

Dear Bill: 

I had never built a PTO, but after reading Farhan's Daylight Again Transceiver article I cobbled one together with parts and pieces I had on hand. My observations so far are as follows. 

1. The frequency-determining capacitors (shown on the schematic as three 470 pf) are very critical, so I feel the usual experimental cut-and-try technique is a must, even using all NP0 and C0G types. 

2. After I built the 2 MHz version like the article (see first photo), the stability was terrific, but when I tried building the companion Daylight Again crystal filter, I was only able to get a bandwidth of 1.6 kHz, which is too narrow for my taste in an SSB radio, so I decided to build the same filter design but with 11 MHz crystals, where I could easily achieve a 2.8 KHz BW. 

3. Therefore, now I needed a higher frequency VFO, so I merely reduced the capacitance (from about 1200 to 370 pf) without changing the coil and I am very impressed with the performance of my 4 MHz PTO (see second photo). The bandspread easily covers the entire 40M band, CW and Phone. 

4. However, whenever I transmit on the 40M Phone band, I like to first set my VFO within 10 Hz of the operating frequency. That way, if I talk for five minutes or so and get up to 15 Hz of drift (which is quite common with many radios when I operate portable outdoors in the sun and wind), it will not be noticable and I avoid receiving any "you are off-frequency" chastising. But the shortcoming I have with this PTO inductor is that the 1/4-20 bolt has a coarse thread, so it is very difficult for an old fellow like me to get within even 20 Hz of a particular frequency just using this common bolt. Therefore I believe a better choice would be the fine thread 1/4-28 two-inch brass threaded bolt which is available from industrial supply houses like McMaster-Carr. However, for CW use or those with a very steady hand, the 1/4-20 works well enough. 

5. I solved my fine tuning problem by adding a varactor circuit using a common 1N914 diode in series with a 100 pf capacitor, operating from 0 to 6 volts. Another advantage to adding this feature is that since I have not so far enclosed my PTO, I can mount the varactor potentiometer several inches from the PTO so my hand capacitance does not affect the frequency like when tuning with the bolt. 

6. An easy way to "do the math" in my case with the common Sanjian counters is to simply create a small lookup table listing half a dozen common frequencies and stick it on the radio. For example, 90% of the time in the morning I am tuned to my favorite SouthCars Net frequency of 7251, so using a BFO setting of 10,999.900, I simply set the PTO to 3,748.90 on the 6-digit 10 Hz resolution counter I normally use (see third photo). 

7. I am currently using my Daylight Again PTO on a daily basis with an NE602 receiver, and I am thinking of adding a locknut to the bolt so it does not wiggle when I jostle or move the radio, essentially giving me a crystal replacement oscillator that I can use for any single 40M frequency. To date I have been able to listen for hours at a time indoors without even any touch-up of the varactor fine tuning. 

8. Also, if continuous frequency readout is desired without building a noise filter circuit board, a separate power supply for the counter is a solution. For portable operation I use Lithium Polymer radio control model airplane batteries which are light, small, and cheap, so one 12V 2000 mAH battery for the transceiver (allows a half hour of transmitting at 15 watts) and a much smaller 12V 350 mAH battery with a series resistor to reduce the current and brightness of the counter has worked well for me. 

73, Walter KA4KXX 

Orlando, FL

The 17 & 12 SSB Transceiver -- Circuit and Build Info -- Video #4

I REALLY LIKE THIS RIG. IT IS LIKE A MAGIC CARPET THAT CARRIES MY VOICE ACROSS THE SEAS.

Cutting Display Hole sets off smoke alarm. Reverse Polarity Protection. IF and Crystal Filter at 21.470 MHz 50 ohms! TRGHS! Amp for VXO Carrier Oscillator/BFO. Mic Amp from uBITX. Transmit/Receive switching from mic connector. VFO: NO DIE CAST BOXES! HT-37 Variable Cap, Frequency Shift. BP filters from QRP LABS designs (G0UPL). TIA amp boards from K7TFC. Needed RF amp to hear band noise. BITX40 PA design, but RD006HHF1 instead of IRF510. Should I run receiver input through LP filter? Frequency Readout Story: How to use one San Jian counter on two bands.

Pete's Eclectic Approach to the Pea Shooter, San Jian counters on Analog VFOs, Non-Restaurant Menus

I liked Pete's comments on the various (analog, digital, mixed) approaches to homebrew: 

http://n6qw.blogspot.com/2022/02/2022-return-to-peashooter-build.html

http://n6qw.blogspot.com/2022/02/2022-peashooter-20m-compact-ssb.html

I too have San Jian digital counters watching the stability of analog VFOs (DX-100, HQ-100, Mythbuster). 

Variety is the spice of life!  

I also liked Pete's comment about the fellow who does on-the-air menu counseling for FTDX-3000 owners.  I sometimes run into guys on the air who want to do something similar with my simple homebrew rigs.  They start by making comments about my audio -- they will usually say it is "too high" or something like that.  Especially when I'm using the separate transmitter and receiver (which have to be "netted" imprecisely by ear), I have to explain that maybe resort to their RIT control would help.  If they persist, I sometimes have to tell them that how my rig sounds depends A LOT on the placement of the carrier oscillator relative to the passband of the crystal filter (most recently, the filter from the 1963 Swan 240).  Most of them have never had to do that kind of adjustment, so the "technical discussion" usually ends at that point, with my interlocutor saying 73, and presumably moving on to someone whose rig has menus to fiddle with.  (Recently heard audio techno term: "massaging the codec.") 

To each his own!    

Mythbuster Video #16 -- GLOWING NUMERALS! In Juliano Blue!

I added two San Jian frequency counters to the front panel. In addition to making the rig a lot easier to operate, they add a classy touch of Juliano Blue to the project.

I got my counters here: https://www.ebay.com/itm/224223678132

There is a limitation of some of the the San Jian counters: https://soldersmoke.blogspot.com/2021/02/a-problem-with-san-jian-plj6-led-counter.html

But this limitation didn't cause any problem with this rig:  In this case I just plugged in the IF frequency of 5.2397 MHz.  I connected the input to my VFO running around 9 MHz.  For 20 meter signals, I select the "up" option;  the San JIan counter just adds the IF frequency to the VFO Frequency.  For example 9 + 5.2397 = 14.2397 MHz .   For 75, I select the "down" option.  Here the San Jian just subtracts the IF frequency from the VFO frequency -- for example 9 - 5.2397 = 3.7603 MHz.  

The band select switch operates relays that select the proper band-pass and low-pass filters.  This switch also alternatively turns on either the 20 meter San Jian or the 75 meter San Jian. 

A Frequency Counter for the Hodgepodge -- An Analog Solution to a Digital Problem

Imagine my dismay when I discovered that I could not use my $5 San Jian PLJ6-LED frequency counter with my Hodgepodge transceiver.    The problem is described here: 

http://soldersmoke.blogspot.com/2021/02/a-problem-with-san-jian-plj6-led-counter.html

This video describes my solution.  I took some pleasure in using an analog solution to solve a very digital problem.   I know this could have been fixed with one or two changes to lines of code, but I liked doing it this way.  This was all kind of fun, and it allowed me to use yet another bit of circuitry that was sitting idle in the shack.  That is the whole point of the Hodgepodge project.  

The best is yet to come.   Especially for those of you who like waterfalls.... Stay tuned. 

A Problem with the San Jian PLJ6-LED Counter

I had hoped to use this handy and cheap little frequency counter to add some glowing Juliano Blue to the frequency readout on my Quarantine Hodgepodge rig.   I've used these boards with my BITX20, my HA-600A,  and with my DX-100/HQ-100 rigs.  But guess what -- these boards do not work with the BITX40 module board that is the heart of the Quarantine Hodgepodge.  And the reason why is interesting. 

Here is what happens:  First, you plug in the IF frequency of your rig.  In my case 12 MHz.  You connect your VFO output to the signal input on the PLJ6.  You power up the PLJ6.  You then have to select one of two IF frequency options.  One of these options ADDS your IF frequency to whatever it detects at the signal input.  In my case, for a 7.2 MHz signal it would detect a VFO signal at 4.8 MHz. If it were to ADD this signal to the IF freq,  it would readout 16.8 MHz.  And it does.  But obviously that is wrong.  So you go to the other option -- this one SUBTRACTS the designated IF frequency FROM whatever it finds at the signal input.  So here we get 4.8 - 12 =  -7.2   Almost perfect right?  But here is the problem:  The PLJ6 can't handle negative numbers!  So it displays 000000.  Not helpful. 

Here is the manual: 

https://www.mpja.com/download/35057tebasic%20manual.pdf

I didn't have this trouble with any of the other rigs because none of them required the use of negative numbers.  My BITX 20 for example had an IF of 11 MHz and has the VFO running a bit above 3 MHz -- so the PLJ6 just adds the IF to the VFO signal and Bob is my uncle.  Similar problem-free addition takes place with the other rigs. 

I found some discussion on this problem on the internet.  Here is one: 

https://groups.io/g/BITX20/topic/bitx40_and_plj_6led_frequency/4330098?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,0,4330098 

Some of the respondents didn't seem to understand the problem.  Others hint that the ability to handle negative numbers was as some point in the code for the PLJ6 device,  and may somehow be accessible, but no further info is provided. 

I have already worked up a possible solution, but I'm interested in how you folks would approach this problem.   Any thoughts or suggestions?  I will reveal my solution in the days ahead.   

Shuji Nakamura -- The Inventor of Juliano Blue LEDs

He is the 2014 winner of the Nobel Prize for Physics.   He is the person who figured out how to make blue light LEDs through the use of an Indium Gallium Nitride semiconductor.  I was reading about him this morning in "Conquering the Electron" by Derek Cheung and Eric Brach.  Thanks to Nakamura, the numerals on all my frequency displays glow in a pleasing Juliano blue.  Three cheers for Nakamura! 

More on him here: 

https://www.trumpf.com/en_US/presse/online-magazine/nobel-price-winner-nakamura-wants-more-light/

Glowing Numerals for the Lafayette HA-600A (With Jeweled Movements)

 

I really like this receiver.  I have strong sentimental ties: it was my first SW receiver.  But the frequency readout situation was kind of rough -- depending on where you put the Main Tuning cap, your Band Spread dial could be WAY off.  

China to the rescue!  Specifically the very nice San Jian PLJ-6 frequency counter boards.  I have used these in several projects.  I like them a lot. I get mine on e-bay.  They are very cheap.  Here is the manual with specs: 

https://www.mpja.com/download/35057tebasic%20manual.pdf

As I did with my BITX20, I put mine in an Altoids-sized box.  I got to use my Goxawee rotary tool with circular metal blade to cut the rectangular hole.  Hopefully future efforts will yield neater results, but the flying sparks were fun;  they made me feel like one of those car-part  "fabricators" on cable TV. 

To tap the VFO frequency, I just put a bit of small coax at the point where the 10 pf cap from the VFO circuit enters the first mixer.  I ran this cable to the unused "Tape Recorder" jack on the back of the Lafayette -- this connects to the input of the counter.  I attached 11 volts from the power supply to an unused terminal on the accessory jack of the Lafayette -- this powers the counter.

Having a counter on the VFO proved very illuminating -- in more ways than one.  I measured the Center Frequency (CF) of my IF to be at 456 kHz.  I set the PLJ-6 to display the VFO frequency MINUS 465 kHz.   For AM broadcast signals, this worked fine:  I'd tune the signal for peak S-meter reading.  This meant that the carried was right at the CF.  

For SSB, things were a bit different.  I set the BFO knob  to be RIGHT AT 465 kHz when the dot is in the center position.  With the BFO there, I could tune in SSB signals.  The suppressed carrier would be right at the center of the IF passband, with the audio information above or below the suppressed  carrier frequency.  But it didn't sound good this way -- it sounded better if I would tune an LSB signal 2 kHz down from the center, then adjust the BFO down about 2 kHz.  This put most of the the audio in the peak portion of the IF filter(s) curve.  Doing it this way means that I have to remember that the number displayed on the PLJ-6 is 2 kHz down from the actual suppressed carrier frequency of the transmitting station.  I can live with that.  

I am going to leave the Lafayette on the corner of my workbench so that I can easily tune in hams  and SW broadcast stations.  Having modified the product detector and added the digital frequency readout makes listening to this receiver even more pleasing.  The jeweled movements are as smooth as ever. 

So 2021 is off to a good start on my workbench.  HNY to all!  

Chip Replaced, GSC 6000 Counter Fixed

 

This thing has been half-broken for a long time.  I needed to get the input for 40 MHz - 650 MHz working    I got the a replacement SP8630B Plessey divide-by-ten counter chip on e-bay, and yesterday I extracted the old chip and put in the replacement.  I took great care NOT to solder this one in upside down (as I had done with another chip replacement in this counter). I used solder flux and solder wick to gradually get the pins free of the board. (You can see the old chip in the picture above.)

As to what happened to the original SP8630B chip,  John over on the Vintage Test Gear Facebook page wrote: 

The Plessey SP8630A/B is an ECL divide by 10 prescaler, with a upper working frequency of 600MHz. That generation went out of production in the late 1980s. Plessey was bought by a Canadian company now called Micrel. You may be able to find one from one of the specialist obsolete component companies, but it may be dead on arrival. Those ECL ICs had a fairly high mortality rate if they are very old.

It is the old story of "metal migration". In early semiconductors very small impurities in the silicon structure cause minute bits of the metallisation to leach out into the essentially non-conducting silicon insulation. Many old devices, although they have never been used, were found to be very leaky and this degrades the gain of the active devices. The worst types are the very old Germanium transistors.

As the semiconductor scientist learnt more about the super cleanliness required and the better purification of the metals the problem tended to improve. The Marconi company I worked for back in the 1980s had a real problem with comms satellites failing after a few years of service. Of course you can't go up there and swap out the faulty devices. Accelerated ageing of a backup satellite showed that some devices just stopped working after being subjected to high and low temperature cycling, which is a common problem with satellites in orbit!

I am liking this little machine more and more.  It is very simple -- no microcontroller, just a collection of gates.   I discovered that the main main crystal oscillator is actually built inside a little oven to keep the temperature stable -- oscillator and the oven stay on as long as the counter is plugged in, even when the device is switched off.  I calibrated the counter with WWV and with my HP8640B and with my little Feeltech sig gen counter.   I wish I knew how to calibrate the counter in the Rigol DS1102E oscilloscope.  

Arduino, Si5351, GPS linked atomic clock, GPS disciplined frequency counter and more...

Wow, it has been a while since I first talked to Rick, N3FJZ.  Above you can see his QSL card.  And here is a link to a SolderSmoke blog post (with videos) that describes our Homebrew to Homebrew contact:

http://soldersmoke.blogspot.com/2015/10/hb2hb-n3fjz-n2cqr-si5351-and-bitx-tias.html

The e-mail below shows that Rick continues to melt solder, bringing into his rigs some very cool technology:  atomic clocks, GPS modules, and color displays.  That's a long way from the original PTO Direct Conversion receiver that he first heard me with.  FB Rick! 

--------------

Leif, 

I've made great progress on my Arduino Mega 2560 based rig controller I call the ZX-Front-Panel. I just finished a feature I always wanted which is a built-in *GPS disciplined frequency counter*. It uses the 1-pulse-per-second timing output from the GPS module to create a frequency counter with atomic-clock accuracy. It's on the solderless breadboard with the rest of the ZX-Front-Panel right now, and even so, it can count up to 30MHz with no trouble! and it should be able to count up to 100MHz or more if built on a ground plane with a little shielding. The best part about it is that it only required one additional chip (a 74LV8154 32-bit counter $1 from Mouser) in addition to the existing parts already on the ZX-Front-Panel; i.e. the Arduino Mega 2560 ($10), the Ublox NEO-6N GPS module ($15), the display ($25), and the Si5351 PLL RF Oscillator ($8). 

Check out my video series covering the ZX-Front-Panel development progress. The first link below will bring up the video page on my website with the latest video at the top, so you'll have to scroll down a bit to get to the earlier development stages. Check out the rest of the website too for the schematics of my Bitx / TIA inspired rig design (which I call the ZX-SSB-II) that I used an early version of to make my first HF HB2HB contact with Bill (N2CQR) back in 2014 or so (Bill and Pete, via the Soldersmoke podcast, were my inspiration to build my first SSB homebrew rig). 

YouTube videos: http://www.remmepark.com/circuit6040/ZX-SSB-II-Front-Panel/ZX-SSB-II-Front-Panel.html#video 

Homepage: http://www.remmepark.com/circuit6040/index.html

Dean AC9JQ and I have been communicating via emailing about his progress in building his own copy of the ZX-Front-Panel, and I'm very excited to learn that he might be thinking about producing a future homebrew rig featuring the ZX-Front-Panel as its controller/VFO. The best thing about the ZX_Front-Panel is that ounce you install the sketch into the Arduino Mega, you don't need to modify the Arduino sketch itself when you build your rig; i.e. the SSB crystal filter's center frequency (the I.F. frequency), the Si5351's clock output drive level, the display brightness and contrast, and the Si5351 crystal correction factor (crystal trim) are all configurable, real-time, right from the ZX-Front-Panel's user interface, and once set, can be saved to the Arduino's non-volatile EEPROM to be automatically loaded on the next power-up. Also, since it has a GPS module, it features a UTC/Local real-time clock with atomic clock accuracy too. 

Anyway that's all for now, take care Leif. 

73 Rick.

Blowing the Dust Off of KW4KD's Homebrew Station from the 1970s

KW4KD CW TRANSMITTER

I got on 40 meter SSB over the weekend and spoke to Jim KW4KD.   He was on a modern commercial rig, but then he told me he had some homebrew gear on his shelf...  Wow, it is magnificent.  A complete CW station (with homebrew keyer) AND an SSB rig. I immediately launched a campaign to get Jim to fire that gear up and to provide opportunities for more HB2HB contacts.   Here is his description of the equipment:

Hi Bill,

It was a blast to get to chat with you too.

Just listening to the audio on this end, I can tell you’ve put a lot of time and effort into getting what you have there up and running.

Never once touched the dial on this end. So your radio gets a A+ for stability too.

Read your Bio on QRZ and sounds like you’ve been a few places, and seen a few things, and that unto itself would make a great contact . But for me, the fact that you are out there building, and I ‘m getting to hear the fruits of your efforts, is ham radio at its best.

 

Attached are pictures of the gear that made up my station back in the 70’s.

FWIW: At that time my call was WB4YQC.

(But for the record, these shots were taken today.)

In those days I had two setups (Both on 40 mtrs).

A CW station, using separate Xmtr & Rcvr, And a SSB xcvr.

By themselves the CW xmtr ran 8 to 10 watts, and the SSB unit probably hit 5 Watts peak (on a good day).

Like you, I had a separate linear. But in my case I used a pair of 6DQ5’s (TV Sweep tubes) that would run about 180 watts input, (Nothing Solid State, that I could afford, could make that kind of power back in then). The linear is still here, but stashed away in a closet somewhere, so not shown in today’s set of pictures.

As an Add-On for the SSB unit, I built a Frequency Counter, and used it as a digital dial.

The counter is unique in that it supports two inputs (one for the VFO, and the other for the Xtal BFO). In the 2 input mode, the counter is an UP/Down counter.

The Xcvr’s BFO runs at 9Mhz, while the VFO runs at ~2Mhz. So the counter counts up on one pass, and then down on the 2nd. At the end of the 2nd pass, it updates the Display with the final tally. (i.e, the effective TX/RX freq)

The cases for the Xmtr & Xcvr were designed by me, but were built by a friend who had access to a metal brake. Internally none of the units are especially pretty, as the were always works in progress.

I’ll have to dust off the linear. Its been at least 40 yrs since its seen AC.. Not sure what kind of shape the electrolytics are in.

Probably need to apply power slowly. I’ll see if I can round up an Autotransformer.

As far as posting on your blog, if you think it will encourage others, I’d be flattered if you did;

However, before anybody asks, (assuming that they might) there’re no schematics. Everything was built from sketches made on envelopes and napkins, which have long since disappeared. And even if they did exist, not sure today that you’d be able to find some of the ICs & transistors that the units use.

Again, it was my pleasure to catch you on the band today, & look forward to getting to hear you again.

73  Jim (KW4KD)

KW4KD CW TRANSMITTER WITH HB KEYER

40 Meter CW receiver on Left

40 meter SSB transceiver with freq counter

G3ZPF's Knack Story: Debunking Tech Fairy Tales, Surviving Nixie Tubes and Ferric Oxide

Bill:

I'm finding the book very entertaining, and am currently about halfway
through it. Like you there were a few electronic 'fairy tales' that I
was suckered into and I was pleased to see your debunking of them. My
professional training was structural engineering so anything electronic
I picked up along the road, and was thus an easy mark for misdirection.

I still remember the first time I realized that teachers sometimes don't
understand what they're teaching, but just repeating what they were
told. At age 11 we were using a thin tube with a slug of mercury and was
told that at -273c the air under the mercury would have zero volume. I
knew it was BS, but was too young to know why. A decade later I worked
it out for myself, by accident really, and I still feel slightly
resentful about being misled. Turns out that -273c is a 'convenience'
(aka a fudge factor) which makes the combined gas law work :-p

The first electronic fairy tale I encountered was "the feed impedance of
a half-wave dipole is 72 ohms". Taught to me while studying for the UK
radio exam, and trotted out repeatedly in the RSGB magazine.

This magically mutated into 50 ohms when the Japanese rigs started to appear,
which made me a tad suspicious, and when my very young self finally
scraped enough cash together for the ARRL handbook I spotted the graph
showing variation of feed impedance with height.

I was devastated. I remember wondering why all the old guys at the club
(who I spent most Sunday mornings listening to on 160m AM as an SWL)
didn't know this.

In that instant I saw that all my hours of climbing up & down ladders;
cutting and pruning my very low dipoles to get 50ohms (bear in mind how
changeable and usually awful the UK weather is) had been utterly pointless.

From that point on I used doublets + open wire feeder. Up the ladders
just once and all tuning done in the shack in a comfy chair with a coffee
in one hand using a PROPER balanced ATU, not some shonky single ended
thing with a balun on the back.

Of course I found out about saturating balun cores the painful way (a
T200 core stays very hot for a very long time), and accidentally
discovered the current balun (which I called the idle-mans balun) at a
time when nobody distinguished between a voltage balun and a current one.

I took my inspiration from the 'coax round a ferrite ring' method of
stopping TV coax braid from conducting my RF into the TV. Fast forward
20 years and current baluns are the way to go. Its tough being a visionary.

I remember spending a weeks wages (back in the 70's) on a Fairchild
9H59DO prescaler chip for my TTL freq counter. Like you I hate chassis
bashing and the counter only went in a box after I'd had so many jolts
off the 150v rail to the nixie tubes I figured it was box-it or die :-)

The circuit of the counter was 'designed' by me lifting the simplest
version of each part of the circuit from dozens of peoples designs &
just hoping it worked. By the time I'd finished I had learned enough to
know I was lucky it did work....and what a mess spilled Ferric oxide
makes on a pale grey bedroom carpet.

When GQRP first started up a bunch of us locals used to have a 10m net.
Primarily for ragchews but also to give the newly licensed types at the
club their first ever CW QSO on air. We were all sufficiently enthused
to build a 2w xtal controlled 10m CW TX. Using a 2n3819 in the PA & 2w
meant the matching was easy to 50 ohms.

We were all within a few miles of each other so 599+, so one guy built a
half-watt version. Still 599.

I decided to go for it. Grabbed my sig genny off the shelf. It had a 50
ohm output. Lightbulb moment. Set it to 1microvolt outputans keyed the
aerial with it. 539 all round, albeit with some chirp and drift. Well, it
was a valve sig genny.

1uV across 50ohms is qrpppppp. Thats when I realised the million miles
per watt is no challenge at all when radiating extremely low powers over
short distances.

Might  be harder today though. Back then we could hear the receiver
noise floor on 10m. Not much chance of that now.

But I confess I was always far more interested in operating than
building. Never had the luxury of a workshop. Always tucked into the
corner of a bedroom. If I couldn't hold it in one hand and drill it with
the other it couldn't happen.

I remember hearing that Kennedy had been shot at the instant it
happened. I was on 20m listening to a pair of USA hams rag-chewing and
they both had the TV on. I rushed downstairs to tell my parents who told
me I was talking nonsense "or it would have been on the news". Took a
couple of hours for it to appear on our TV news.

I used to love chatting to the USA novices on 15m CW back in the late
70's. Some of those guys were real pros. You could hear them coming back
to your CQ while screwing the trimmers on their xtals to get co-channel.

I still treasure a letter I have from one youngster. It was his first
QSO outside the USA. He tells how his mom got so excited she ran into
the road telling all the neighbours her lad was talking to England.
.....yes the one in Europe :-)

Life seems a lot more cynical these days.

Even to this day I find the concept of my voice turning into electrons
which throw themselves into space and sometimes hit another piece of wire
in another country and reproduce my voice genuinely 'magical'. Sadly my
grandkids don't 'get it'. They're happy with Skype, facetime, and TXT.

The closest they came to interest was the eldest grandson (at age 10)
saying "grandad, can I have that telegraph key when you're dead?".
Sensing my surprise he added "I'm not interested in morse, but it looks
kinda cool". Now he's 20. Bought his first apartment, and his first BMW.
Making his way in the world and glued to his iPhone.

It would be kinda nice to get back onto 160m AM, but sadly the
electrical 'crud' levels in the UK are S9+ down there :-(

I spent 30 years in front of a TS930, which was able to produce proper
AM because where most rigs had one xtal filter it had pairs of them. You
slide the filters over one another to get narrower passbands for CW and
if you slide them past each other you can gget DSB or AM.

Thanks for taking the time to write your book. You've lived a very
varied and interesting life. I wrote a SciFi novel back in 1980 but at
that time there was only one scifi agent in the UK and she didnt like
it. Maybe I'll get it onto kindle one day.

I was expecting a lot of free time in retirement, but between the 3
grandkids and my 94 yr old mom I have less time than when I was working.
But despite the dodgy knees and eyesight its the best job ever :-)

Regards,

David  G3ZPF
www.g3zpf.raota.org
www.raota.org

Video of Curiously Strong Altoids Tin Frequency Counter

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

A "Curiously Strong" Frequency Counter

I got a six digit San Jian frequency counter for use with my BITX20.  I was trying to figure out how to put it in a box and mount it on the rig when I realized that the counter fits almost perfectly in an Altoids tin.  THE RADIO GODS HAVE SPOKEN. 

I found the counter on Amazon.  I use an eight digit version with my BITX17.  But I think the six digit version is better (it fits in an Altoids tin!)

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Glowing Blue Numerals! A Frequency Counter for the BITX17 (VIDEO)

These little frequency counters from China have a lot of potential.  And they add a dash of digital color to an otherwise bland analog hamshack.  I got mine on e-bay. 

My BITX17 has now been "accessorized" with 
1) A rotatable Moxon antenna (big improvment!)
2) A 120 watt Communications Concepts Linear amplifier (another big improvement) and
3) This digital frequency readout.  

What next?  

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

SolderSmoke #171 DC RX in QQ, Power Supplies, Small Screens, 12 Buck Counters, HW8 Error?, KX3 RX

SolderSmoke Podcast #171 is available: 

http://soldersmoke.com/soldersmoke171.mp3

Bench Report: 
Pete's Small Screens (in Color!) 
Si5351s
Bill's Graph Paper Frequency Readout
Bill's Broadened Barebones Barbados RX.  DIGITIZED! 
Another AD9850 DDS using M0XPD Kanga UK Shield
New 13 dollar Color Display (Prettier than Graph paper!) 

Pete and Ben's Article in QRP Quarterly Available free here: 
http://www.qrparci.org/qqsample/qqsample.pdf

The DEEP SPIRITUAL REWARDS of DC Receivers 
The Importance of Good Power Supplies
SPRAT Article on HW8 Design Error
Latest Edition of Hot Iron
Elecraft KX3 -- Has one of the best receivers in the world  

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20