Digital LO / BFO for the ZIA rig!

 

The 128X160 ST7735 Color TFT.

The 1st Step in the Resurrection Process is to build a replacement LO/BFO and that was done yesterday.

I had mentioned this project started on the wrong foot with a Black and White Nokia display and was quickly replaced with the ST7735 color display. However, that ST7735 was a 128X128 thus going to the larger 128X160 required extensive software changes to fit the old code on a larger screen. 

I put two LO's in the code so with a flick of a switch one could check for band activity on FT-8. That is a quick test as often the band seems dead, but a listen at FT-8 will show the band is alive and open to DX. As usual this code has LO memory.

BTW smack dab in the middle of the screen is a teeny tiny frequency readout with a small green dot. The plan is to include in the code -- split operation and that would show the transmit frequency. That is not fully operational as yet but certainly on the to do list. Try that with your analog VFO. 

Those with a super keen eye will spot what appears to be an open "blank" space right below the small frequency readout and to the left of my call sign. Well, it is not blank as built into my code is a timed 1kHz audio pulse train of about 7 seconds for Tune Up purposes. Hitting the momentary PB starts the pulse train which is fed into the balanced modulator and in the blank space appears the word "TUNE". You will not find that functionality in a Bitx rig!

The Green dot under the "A" is to show that is the active LO. Switching to "B", The "A" dot goes dark and a similar dot under the "B" goes from dark to Green. Yes, a simulated LED lamp.

I discovered yesterday that the original front panel must have been cut from a custom piece of PC board as it is slightly longer than 6 inches. I have nothing longer than 6-inches in stock so there will have to be a major rework of the original panel to accommodate the larger Color TFT. That is today's task.

Them that know can make things go.

BTW got a new batch of Nano V3's and these use the USB "C" connector. I also have been using a recent upload of the latest Arduino IDE. Finally, functionality that eases the pain of loading code and it is backward compatible with sketches written 10 years ago. Bravo Massimo Banzai!

73's

Pete N6QW

Resurrection of another Homebrew Radio.

[Just found out you can buy the Big Boy version of newly announced 500-watt Integrated FLEX SDR Radio for about $10K (with a few options). Sell the wife and kids, mortgage the boat and get on the Reservation List.]

Today we will cover another Resurrection Radio. This rig built close to 10 years ago has been hardly used. Was it a Turkey Radio? Often when I suggest a particular item is a Turkey, it is to disparage something I bought or built. You know... It's a real Turkey!

I built this Rig long ago but to this day am searching for a reason why it has been in a closet for nearly a decade Aside from one circuit element everything else was a proven circuit and used previously. This one circuit element was something entirely new to me.

Now I have homebrewed over 50 Transceivers with most of those being SSB and so you sort of get a feel of what works and what may be needed to have something work better. This was an attempt to see if there was something better

This rig bypassed the shelf of shame and simply put in the back of a closet.  It's been there for nearly a decade, and yet I haven't missed it. A true mystery as to the neglect.

So, last week I thought I would make one more attempt at making it work and to discern if there was some reason for the disfavor or was it a Turkey.

In fact, the build of this radio named the ZIA was documented in an extensive You Tube video shown below.

The current state of the ZIA shows I even have resorted to a bit of cannibalism

At some point I even started cannibalizing the radio for parts such as the Arduino, Si5351, the encoder, display etc. A place to start before doing anything else on this resurrection sojourn is to reinstall the taken parts. This puts the rig at the near original Baseline.

I should confess this project started a bit off on the wrong foot when I installed a NOKIA Black and White display which was very difficult to read. That was changed to a Color ST7735 display which made things very readable but somehow still did not turn this project into a go to or favored rig.

As you watch the video, this was shot during the peak of Cycle 24 and just listen to the DX stations on 20 Meters. You do not hear those signals during the peak of Cycle 25 a decade later. We were sold a bill of goods regarding the possibilities of Cycle 25! See yesterday's posting 

I will now identify the new elements. Drum Roll -- two TIA amplifiers. For those who may not know, the TIA or Termination Insensitive Amplifier is based on circuitry developed by Hayward and Kopski. My term ZIA is to reflect Impedance Insensitive Amplifiers.

In short, the Zin/out of the amp stage will not be affected (changed) by whatever you connect to the TIA circuit. The TIA configuration has its gain set by what resistance is initially installed in the build. You have the option of setting the gain from Tepid to really Hot! I set it for Hot!

Termination insensitivity has many benefits ranging from immunizing opportunities for self-oscillation, to reducing internal circuit distortions and finally inducing the maximum power transfer by providing a constant impedance set at 50 Ohms. In other words, it is the sliced bread of the electronics world. 

Our 1st chore is to build another digital LO/BFO board which I have started. From that point I will measure the sensitivity as compared to several "standard" receivers I have. 

Has the TIA circuit been oversold?

There is a huge chasm between Termination Insensitivity and Stage Gain. We all want both and simultaneously! Just because it is termination insensitive does not make for a superb amplifier stage. The resurrection will give us another shot to evaluate performance as I want to eliminate performance as a cause for the closeting.

Stay tuned and we may be on cusp of getting this rig back to a whole state and perhaps understand why it was relegated to the back of the closet.

Them That Know Can Make Things Go!

73's

Pete N6QW

Since we are talking about Numbers (only a 2nd posting), let's look at Sunspots

Several years ago, there were a few in the scientific community who touted that Cycle 25 would be amazing. Well, we are very near its peak and the results are anything but that. In a common vulgar vernacular, it was suggested a pair of 44DD's, and it turns out to be an anemic pair of 29A's.

The current chart from early May suggests we are at the peak and it's all downhill from there. The smoothed number is a peak of slightly better than 150.

In contrast, I was 1st on the air in 1959 (Cycle 19) and a comparable chart looks like this below. That smoothed peak is nearly 300 or 2X Cycle 25, thus my 44DD versus 29A analogy. In fact, a good comparison is to look at Cycle 20 sitting next to it which has a smoothed peak near 150. Hey scientists that is the comparison.

In fact, Cycle 25 is now seen as "common" and perhaps a miniscule less than Cycle 24.

This is data and perhaps an embarrassment to those few in the scientific community who suggested a revisit of 1959.

I have a more practical yardstick, and it has been named as an amateur tool. My Tool = My Ears. When I sit down in front of a radio (many of them high quality commercial radios), I simply do not hear the DX stations. 

Using the commercial radios (Drake R4C and Collins) eliminates the excuse from science --- well it's the homebrew radio you are using. Next is the science excuse -- it is your antenna. Wrong, for the few times when the band really is open, I work the DX.

So, guys we were handed a prediction (and that is just what it was) that likely was over optimistic and generated perhaps based more on guesswork than scientific work. Was it liking the view to that of earthquake predictions -- the big one is coming and after 100 years of nothing probability suggests it is near but maybe not just now. In the last 6 cycles we have not seen anything close. I may be wrong, but I believe Cycle 19 was the highest since 1755.

For me predicting spectacular solar cycles rivaling Cycle 19 is like relying on readings from a Nano VNA. Get a second source verification. Listen to your ears and use your DSO.

Them that know can make it go.

73's

Pete N6QW

The Magic Number is Three. Also, why we became Hams?

I have in hand several years' worth of Hard Data that supports the concept of three. Say What?

The number three is the number of continuous postings on the same subject before there is a huge dip in blog readership. Yesterday's blog was more evidence to support that concept. So, no more about the 40M Channelized Radio (#3 and a big dip was observed). 

Too bad as I did order a keypad from Jameco Electronics and will next implement channel selection with the pad as well as up down RIT tuning using two of the pads. But that will not be posted since that would be a fourth in that series and beside myself not too many readers would be interested in that posting.

The second part of today's posting is boring so you can stop here, and hope tomorrow's posting will be whiz bang, chock full of tribal knowledge and will untie the Gordian Knot. 

I was asked a question recently by a person who a ham is not, knows little about ham radio, and whose technical knowledge extends to the level of how to operate the TV remote control. The question was why did you become a ham?

I had to think for a moment and now several days later after noodling over that question have a more extensive answer that perhaps goes way beyond me personally and applies to most hams.

The noodling process arrived at a date in time where prior to that date is one set of answers and after that date a second set. What also was evident is that date also signaled a change in the age demographic.

So, while we have the magic number 3, somewhat arbitrarily we have the date of 1965. By 1965 we had radio communication for 70 years, single sideband was the communications medium, the market was flooded with appliance boxes and those born during the World War II years were out of college or conscripted to serve in Vietnam. So indeed, a pivotal year.

The Golden Era of Radio was from about 1930 to 1965, a mere 35 years and half the life span of radio itself. It was during that period that huge advancements were made in the technology and change in modes like almost exclusively from CW to AM and then SSB. The components shifted from Tubes to Transistors from high voltage to 12VDC and the all-important single signal reception. Need I also mention TV for the mass markets.

During our Golden Era who was attracted to radio? Lest we forget in 1930 there was a depression here in the US and hand building a simple crystal set was really cheap and offered a diversion from the misery. 

But the huge magnet for the youth was that a ham station could be a one tube transmitter and one tube receiver, built mostly from scrap parts. In effect ham radio for this youthful crowd was the social media of the day. Building these simple stations did not require a PhD in electrical engineering nor a laboratory full of equipment. Simple hand tools, a pine board, some wire-- and lots of guts is all it took. As a ride along -- youths could demonstrate not everyone could do this and, in many cases, show up their seniors.

A simple Ham Station

1 Tube Transmitter

Somewhat unabashedly I now offer a one tube CW transmitter from N6QW, and the project is described here.

We must turn to the psychologists to answer the question as to why we became hams and, in some cases, serious therapy is needed.

Many of us are introverts and fear direct social contact. You know too short, too tall, serious cases of acne, overweight, bald or just plain ugly. But behind a CW key or a microphone suddenly those "warts" are not seen. 

The social interaction is judged by your signal strength, its clarity and since the brief exchange is limited to 5X9, 100 watts, dipole, Pete, Newbury Park and the weather you are there. Much practice with those few words is all that is needed for a perfect QSO. The LOTW affirms you made a contact and proof that you are someone.

That social affirmation extends today to how many $6K rigs you have in the shack, if you have two Mercury Amps and if your antenna system cost the price of a 2025 Toyota Camry LE ($33K). Social affirmations now come from flash the cash.

There was a huge gain in the ham population during the 1950's many of whom were veterans who were exposed to radio while in the service. For me personally I was about 10 years old in the early 1950's when I got my 1st CK722 transistor. BTW I didn't have acne, nor balding but was short.

So, what happened after 1965? Well, a lot including my first all expenses US Government paid trip to Vietnam. Of importance was the Japanese invasion into the ham market with those wonderful Rice Boxes that were not too expensive but had so many features. 

We must also look at retirements. Those who went to work in the aircraft and war related industries in 1935 as we headed to war were now in the retirement zone. By 1970 they had 30 years on the job. What would fill that void when they no longer had to punch in -- ham radio. Many of these same workers were knowledge workers with some level of technical skills. A perfect storm as they had money beyond what was earned on a paper route.

The year 1970 and beyond signaled an explosion in the electronics field with real RF transistors, early integrated circuits, digital displays, smaller and vastly more expensive radios. A fork in the road -- the radios with all of the latest and most desirable features were commercial and not homebrew and did I mention expensive. The market had shifted to those who could flash the cash. The target market was not the youth but those who could buy more and more. This started the decline of homebrew.

Suddenly microprocessors appeared on the scene and now another magnet for the youth. It was not the building or using a computer but the software. I bought my #1 son a Radio Shack Color Computer in 1980 and he taught himself assembly language. Today he is a software architect and soon to retire. It was the best investment I ever made -- he was always at home designing video games at age 14. Thus, the paradigm shifts from radio to computers. To this day the ARRL is struggling with how to fill the well with the youth. 

The need by the youth for social interaction has been filled with Tik Tok, X, You Tube and other social media platforms. You can just as easily contact someone in France using the computer or better yet smart phone as you once did through the use of 20M.

Thus, we have a hobby dominated by an older segment of the population that have cash and have a desire to say Mine is Bigger than Yours. This has been aided and abetted by the ARRL who made it where you have to know nothing to become a ham -- just money.

In about three weeks I will celebrate my 66th year of continuously being a licensed ham operator and hold an extra class license approaching 50 years. We had to know stuff!

Hope you had a good snooze.

BTW in 2021 I was a presenter at the GQRP Club Virtual Convention, and my subject was Valve CW Rigs. A page from the presentation and of importance is this chart and observe the time continuum of how our rig topologies changed.

This supports my date in time theory.

73's

Pete N6QW

The 40M Channelized Transceiver has been retrofitted with a Heathkit Crystal Filter!

You will absolutely hate yourself for ignoring my suggestion about buying a Heathkit Crystal Filter on eBay. There are 3 for sale right now for around $15 bucks. Do it and avoid the ruminations of a failure to act.

Yesterday I spent retrofitting the 40M Channelized transceiver with the Heathkit SSB Filter. The code changes took all of 5 minutes and the physical install of removing the Yaesu Filter and installing the Heathkit unit took about 90 minutes total. A good portion of that time was spent designing and milling a new bracket baseplate for the Heathkit and that was done on my manual milling machine.

The matching transformers have a 40:1 ratio achieved with a solenoid winding of 19 Turns tapped at 3 Turns. Those joined at the hip with the TIA topology that 40:1 transform will match 50 Ohms to the 2000 Ohm Zin/out of the Heathkit filter. It is truly a shame that many hams will only try one circuit like the TIA amps and miss out on the chance of experiencing other topologies. Remember mostlydiyrf.com sells a TIA kit and so you have a ready-made source for that bilateral stage amp. 

I also spent some time revamping the Color TFT display to emphasize some info like the frequency readout, by making it larger. We switched around some colors too.

I am pleased with the results. My next retrofit may involve a 3X4 keypad as I know how to take two of the pads and use them for up and down tuning of the RIT. Suddenly, we now are on the brink of an "uptown" rig.

Them that know can make it go!

73's

Pete N6QW

A Good Lesson Learned!

It is all about a strategy and having a mind that can see a path to gaining information without making it obvious that is not what you are doing. I am not describing myself.

In yesterday's post I mentioned that while it would be nice to have 12 Channels on the band switch, using the Color TFT chewed up quite a few of the pins and so 5-positions was a certainty with a possibility of adding just a few more without going to a pin expander or using the Mega 2560. Honestly that is what my brain was telling me.

Well, emails from three separate Blog readers suggested I could have a large number of positions using just one pin (Analog to boot) on the Arduino. So how can that be? 

Well, you set up that Analog Pin, so it is reading an Analog voltage which is changed with a switch. The internal Arduino logic would then test the voltage read (allowing for a small range of voltage) and then if the test is met you would load a specific value of frequency into the Si5351.

A0 is the One Pin Analog Read

It is like the old "if" and "then" statements.

IF the read Analog Voltage is between 2.4 and 2.6 volts THEN load 10378500 into the Si5351.

[I have not done any analog voltage reading with the Arduino, but I seem to recall you actually can't directly read voltages but only values and so there possibly may be a conversion involved. I am certain I will be corrected if what I said is incorrect.]

10378500 - 3178500 (LSB BFO) = 7200000 on the display so you would be at 7.2 MHz with 10.378500 MHz loaded into the Mixer stage.

Friend K7TFC (mostlydiyrf.com) was one of those who contacted me, and he uses this exact method of One Pin Analog with one of his products. In essence it is a resistive ladder approach where say 5 VDC is applied at the top of the ladder and the Band Switch connects to the ladder rungs and reads that voltage.

But he also shared several different ways of the resistor ladder approach. One uses all of the same value of resistance so that as you cycle through the band switch each position changes the resistance by the same exact amount. Assume ten resistors each 50k at the 1st position you would have 500K and at the 10th position 50K. The same scheme using different values i.e. 10K, 27K, 33K etc. would give the same effect but a little more work to establish the voltage reading at each rung. 

Another K7TFC scheme was to use momentary push buttons to replace the manual band switch.  

This caused me to think that with 7 Pins to the Arduino you could also use a 3X4 Keypad yielding 12 frequencies.  See https://www.n6qw.com and the remote VFO for the Ten Tec Triton II. A Keypad on the radio front panel would give it the air of sophistication not often seen in homebrew radios. 

A really uptown approach (akin to a really high-class hooker) would be to have a larger touch screen display with a smaller Keypad array as part of the screen and then no band switch or push buttons needed. Possibilities and lots of them. 

Them that know can make things go!

Happy Memorial Day! Never Forget! Some of those who gave their lives for our freedom were not citizens and chose to serve in exchange for citizenship. I guess today they still would get deported. Hmmm those making today's rules did they ever serve our country? We all know of at least one who didn't.

73's

Pete N6QW

A Channelized 40M SSB Transceiver

The subject of today's posting was mentioned in yesterday's blog and now you can see it 1st hand. I converted the 60M five channel radio to 40M. Here is the Proof of Life.

40M Channelized Radio

Just think with this sketch a channelized commercial radio could be modified so it is both Channel and VFO operated.  There are such radios now on eBay. (Some are reasonably priced.).

The eBay radio listings are from Canadian Marconi and from Hallicrafters.

There are other possibilities like modifying a 23 channel SSB CB transceiver using this channelization approach and that could result in a very nice (and cheap) 10M rig. 

There are some hidden gems in this design. Take for instance the BPF as it was a 40M BPF tuned down to 60M by the addition of two fixed caps and retuning 5 trimmers. 

Back to 40 Meters involved desoldering the two caps and a trimmer retuning. About 2 minutes of work as it was designed that way initially using LT Spice. Moving it to 20 M involves desoldering two more fixed caps and a retuning of the trimmers. 

Tribal Knowledge at work here and a look at the Appendix of SSDRA. Hayward often used the same inductor for his BPF's and just moved the cap values. Your Nano VNA will not tell you that directly and EMRFD does not have that Appendix. Looking at the chart in SSDRA is most helpful at the initial design stage.

I still have the LPF that needs a rework and then we can check into the Jefferson Noontime Net on 7204 kHz running QRP. Truth be known the net control is in Fresno and uses the Half Moon Bay SDR receiver site. Fresno is closer to me than the SDR site -- so in effect the rig has to cover a greater distance to be heard. 

[There was mention of a 12-position switch covering more channels, but implementation involves an engineering trade-off. You would need 7 more pins (or a pin expander) to use the 12 versus 5 as many of the Nano Pins support the color TFT. Going to an LCD would free up pins or using a Mega 2560 has the additional pins needed. 

A 12-channel switch arranged for 8 channels could be easily done with the existing Nano. In case you are wondering the code uses an Array and the switch position essentially calls up values in the array which is loaded into the Si5351.]

Them that know can make things go!

73's

Pete N6QW

Your Next Appliance SDR Box will have one of the these

I must be a magnet for anything SDR as a page from Digi-Key showed up on my smart phone. (LINK)

A new device from Analog Devices essentially is an SDR Transceiver on a chip and of course you need the FPGA to do the number crunching. Right now, the frequency range is 30MHz to 6GHz but in time, we will see the lower frequency end drop to cover the HF bands. 

There are some additional refinements, like BW, as it can be selected for narrow or wide and the narrow is 12kHz -- we would probably like 10Hz -- in time my friend.

The price point is $500 in single lots but beyond this chip not too much more in the box. Final Done: A rig would be in the $3K to 4K range and this would position it in the market with the competition.

For the average homebrewer, this would be a huge hill to climb and likely most applications would be from commercial manufacturers in Chine (China) as they are faster, better and cheaper with more modern factories and lower labor rates. You can tariff all you want but FBC is a response to a TW (Tariff Whim).

Keep your eye on hackaday as likely some hams from Europe will be the 1st to build a ham band SDR using this chip. Immediately, the Chinese will steal the design and start mass producing the new SDR radio. I will go out on a limb and predict that US will be left in the dust as we simply lack the skill set and manufacturing capability to put this new device in a design and/or product!

Now I want to share a current project on the bench that involves a built radio that has been gathering dust. About 5 years ago I built a 60M radio using a surplus filter from a Yaesu Radio. The Filter Cf was 3.180MHz and was formerly housed in a FT-101 filter board. With an LO in the 8.5 MHz range a high side injection into a DBM yields 60M. 

My twizzle on this project was to not use an encoder for tuning as the 60M band is channelized into 5 distinct channels and all USB. That was not too difficult but not "slick enough" as I had no requests for the code. I soon found out that the 60M is like a wasteland and not too many stations. Thus, another project on the storage shelf.

I actually liberated some parts from that radio, most recently, the small ST7735 display, that was initially used on the JF3HNB circular display. Acquiring the 3.2-inch ILI9341 display freed up the ST7735 now meaning a reinstall in the 60M radio. This prompted me to think beyond 60M. Suppose you built a channelized radio for other bands -- like 40M.

In my recent experiments with the Hybrid rig has centered on 40M. What this revealed, like it or not, 40M has become channelized. Nets now roost on the following frequencies: 7.074, 7.147, 7.155, 7.185, 7.192, 7.204, 7.208, 7.235, 7.240, 7.245, 7.255, and 7.260. If you have kept count that is a 12-position switch.

The retrofit involves code changes, BPF changes and LPF changes. In all about three hours of work. A good project for this long Memorial Day weekend. Stay tuned. Before you hit the send button I am looking at a clarifier control for when some of these nets move a kilohertz or two.

[No Pete is not suffering from early onset dementia with a suggestion for a channelized radio. Think operations like POTA or SOTA where but a few frequencies are used and since you have to lug the gear to the picnic table or up that hill, small size and light weight are a consideration. I regularly check into the Jefferson Noon Net at 7.204 MHz running only 3 watts. A channelized rig would work here.]

Them that know can make things go.

73's

Pete N6QW

Now what do you do?

You are an elite member of a very small group (0.01%) who actually takes to heart some of the suggestions I make on this blog. There you go, you bought the Heathkit Crystal Filter for less than $15 and the burning question is how to install this filter in a circuit? 

The P3ST IF Module is a great starting place as shown below.

The 500 Ohm resistor smack dab in the middle of the schematic is for simulation purposes representing a 500 Ohm Filter. To use this schematic for the Heathkit Crystal Filter you simply insert the Filter where the resistor is shown and modify two of the filter matching transformers. 

The original primary (L3) is set for a 50 Ohm to 500 Ohm transform. L3 is changed from 6 Turns to 3 Turns so now that 50 Ohms looks like 2000 ohms to the input side of the filter. The secondary remains at 19 Turns thus 361/9 = 40 since the 2000 to 50 Ohms is a 40:1 transformation. On the second transformer, the secondary is likewise changed to 3 Turns and you are there.

The 2N2222A's are biased HOT so you need heatsinks. The P3ST uses relay steering so that this module is used both on transmit and receive. I refer you to the https://www.n6qw.com website for full details of the P3ST build. 

NOW for a big caution about using the Heathkit in a single conversion design as the Cf is 3395 kHz and 2nd harmonics are close to the 40M band (2X3395 = 6.790 MHz) and a loose BPF might see some of that 2nd Harmonic. Whereas the 4th Harmonic (4X3395= 13.58 MHz) is less of problem on 20M. 

The real nut to crack is 40M as the LO for a single conversion at the Low side say for 7.2MHz yields 7.2 - 3.395 = 3.805 MHz LO -- 2X3.805 = 7.61 MHz -- again too close to the Band Pass. A high side LO is better as that would be at 10.595 MHz and less of a risk. Don't hit that send button too fast. W7ZOI has a software program called "spur finder" and it will spit out all of these combinations.

That said this schematic is ideal for a dual conversion rig where the 1st conversion is to 8.3 MHz and a second conversion with a 5MHz LO drops you at 3395kHz.

You now have a way of integrating this filter into a PROVEN simple circuit using a small number of components.

Them that know can make things go!

73's

Pete N6QW

Unveiling a best kept secret.

Who doesn't like knowing the best kept secret which I am about to unveil. So here goes.

I will always suggest for those considering a homebrew SSB or CW transceiver and who for them, is a 1st time outing on such a project to use a commercial crystal filter. Once you have successfully built the complete radio, then is the time to get on with the science project of homebrewing a crystal filter. One problem at a time is always a good approach

So, what is the best kept secret? It is a Heathkit Crystal Filter found in many of their rigs. Many can be had for under $15 like this one.

I guess the low price is based on that these filters are of a low frequency like 3.395 MHz and a set of BFO crystals will cost more than the filter. Most of the Filters have a Zin/out of 2K Ohms.

Actually, the filter is the best kept secret part. With an Arduino and a Si5351 for about $20 you get the whole digital LO and selectable BFO RF sources. The added bonus no drifty analog VFO!

Now the low Center Frequency of the Heathkit filter makes things a bit tricky in single conversion designs. But it is a great choice for a dual conversion rig. There is that 3rd clock on the Si5351 that will yield a heterodyne frequency. Think of a 1st conversion in the range of 8.3 MHz and with a 5 MHz LO the IF is 3395 kHz. This is the HW-101 frequency scheme. 

As an example, if we have our 5 MHz LO at 5.2MHz and the BFO at 3396.5 kHz and the 1st conversion frequency at 15.7965 then 7.2 MHz would be copied. The LO would tune in reverse so that a 7.3 MHz signal would use a 5.1MHz LO frequency to yield 7.3 MHz on the display.

How to match the pesky 2K impedance to 50 Ohms? A solenoid winding of 19 turns tapped at three turns would do it as 3^2 = 9 and 19^2 = 361. We have 361/9 = 40:1 and 2000/50 = 40:1 -- all on a FT37-43 core.

If you check https://www.jessystems.com and look for the Tri-Band Transceiver link you will see the use of the Heathkit Crystal Filter ($15).

Them that know can make it go.

73's

Pete N6QW

A visit with an old friend.

All of us have experienced a visit with an old friend. Most often it is like putting on a pair of old comfortable shoes. Your feet love them, and it just feels right. But you also note that the age factor has somehow entered the equation.

You know it is like that old girlfriend that at one time certainly had a "perky pair" but with the cruelty of the time factor are now simply a "dumpy duo". But it is the wiseman who realizes the big picture and not one single frame. 

So, it is with homebrew radios that are over five years old. In 5 years, the technology has moved through two generations and what was leading edge is now the trailing edge; but that does not mean that old rig is still not useful. 

The other day I pulled out a rig I built some five years ago, and this was like meeting an old friend. I find myself cycling through these old radios because either my antenna is broken or my prediction about Cycle 25 was correct. 

Dismal is the propagation and overnight we have gone from a perky pair to a dumpy duo. In plain simple terms we have been sold a bill of goods about how great Cycle 25 will be. I heard several discussions about this just yesterday on 20M and so it is not just me or my antenna. Thus, a good time to look over past work as there is no propagation!

This particular rig was built for one purpose -- it was to test homebrew and commercial crystal filters. With about 3 minutes of work on the Arduino sketch a new filter frequency is accommodated. The only other chore is to install appropriate matching transformers.

But there are two other bonuses to this approach. The first is that the rig serves as a benchmark. The only thing changing is the filter so like a trip to the eye doctor is B better than A and the second is to test "odd ball" filter frequencies in a known test jig. 

One homebrew filter sounded really great and then using my R4C I tuned across the passband and listened to the opposite sideband, and it was there. This told me that I had an issue with the filter itself and/or placement of the carrier oscillator on the filter slope. The R4C had a 1-inch antenna so the opposite sideband was really strong!

[Sidebar. Has anyone noticed that we don't hear much about Nano VNA's these days -- hmmm the novelty must have worn off and another whiz bang gadget is gathering dust at the end of a workbench.]

The rig is nothing special but does have some unique features. The Mic Amp was my 1st attempt to use a PNP transistor and the bilateral IF module is the Plessy circuit. The Driver stage uses the one out of EMRFD and I believe is much like a 13-year-old YL pretending to be 18. 

I never ever did see the gain out of that stage like was predicted and there are about a half dozen of my transceivers that have that in the design. I have stopped using it. Just because it is in EMRFD does not mean it is the gold standard. Get over it as there are other designs. 

40M at 5 AM

Typically, I see about 4 watts out of this radio with the IRF510 in the Final slot. I use the Half Moon Bay SDR receiver site as a listening post, and I was easily spotted 300 Miles away on 40M with an S7 signal level.

Them that know can make it go.

73's

Pete N6QW

No more Midway stuff. A great place to spend $800.

If I had $800 in pocket change (I don't) this would be the place to spend it. This truly is where the technology is taking us. A perfect example of an all band, all mode radio. Regrettably it did not come out of some garage in Campo, California or Port Hadlock, WA or Jerome, AZ, or Arnold, PA, but out of Chine (China). At 20 watts, it is more than QRP and a serious candidate for POTA and SOTA ops.

PMR-171 Transceiver

If you click on the link above, I am not specifically touting this radio, but more of the concept of what it is saying it can do and at the price point. How come FLEX, Elecraft or some of the US Boutique suppliers do not have something like this? The answer is simple -- they cannot meet the price point. A KX3 from Elecraft starts at $1500. 

There is another problem and that is the US engineering capability is not used to FBC (Faster, Better, Cheaper). Gone is the hands-on capability that often starts at age 10 where there is endless experimentation and learning. Heck, you have to know nothing and no Morse code requirement to get an extra ticket! Look at the so few who homebrew radios -- ask why and you get a lack of learned skills for the answer. Such skills are what drives innovation. Thus, a simple axiom: No skill base, no innovation.

 

Thus, it is offshore locations, principally Chine (China) that are bringing forward products that have a huge world and US Market potential. Let's face it -- most of the components are made in Chine (China) and what technical approaches the Chinese lack, they simply "liberate". I actually think sources in the Ukraine could put a rig like this on your operating desk. 

I doubt seriously a US Manufacturer can do it for under $1000. Despite what's his name touts, US Manufacturers simply are not geared for FBC, and it is not something you pick up at a seminar in Muscatine, IA, and implement at a plant in Lake Charles, LA, one week later. 

So, assuming the PMR-171 is not vaporware and operates to the published specifications then this is the next generation of radios to replace the IC-7300 (which is made in Japan).

Them that know can make it go.

73's

Pete N6QW

Meet the Moaning Bird. A Staple on Midway Island

I promise-- this is the last posting about Midway Island (Sand Island).

Midway Island Moaning Bird

My 1st night on Midway (1963), I was quartered in the old wooden BOQ, built during the island buildup program just prior to Pearl Harbor. The building smelled awful and included a population of very large rats. I caught a 13-inch-long rat (nose to tail) in my room using an industrial sized rat trap.

The old BOQ housed the very junior officers (like me), the schoolteachers and other civilian contractors. My next-door neighbor, a civilian contractor, seemed to have connections with the ladies of the isle. Back to the 1st night there and about midnight I heard this eerie sound and concluded it was one of the ladies of the night visiting my neighbor. Listen to the video and see why I reached that conclusion.

Well as it turned out it was not a lady of the night but one of a unique species of birds that occupy Midway. After the rat incident, I managed to get assigned to the new concrete constructed BOQ and no more rats. But with the screened windows open at night, you did hear that same sound.

One other bit of info about my neighbor was that he was a ham and, in his room, he had a Collins KWM-1 with a wire antenna strung out to an Ironwood tree. I was hooked when I saw his rig as I made a promise to myself to one day own a KWM-1. I did keep that promise and have several. That neighbor had the best of all worlds: A drink at the O Club was $0.25, he had a Collins KWM-1 and visits with the ladies of the night. He also made a ton of money! 

His company (Page Communications Engineers) was installing Tropospheric Scatter Radio Relay stations across the Pacific. The antennas were Sterba like Curtain Arrays on 300 ft towers. We all knew the why of that communications link. It was only 20 months after 1st being assigned to Midway that in May 1965, I was at the terminal end of that radio system.

Them that know can make it go.

73's

Pete N6QW

The Fish and Wildlife Service (FWS) has let Midway slip into a state of decay.

Yaesu FTX-1 Field

A new offering for you POTA aficionados, a mere $2500 for a 100-watt radio that can be operated as a 5-watt radio without the amp strapped on the back. I think it was a hot seller at Dayton this year

I was appalled to see the state of decay of my 1st Duty Station on Midway Island. It happened on the FWS watch.

There is but one way to reverse this terrible process. We need what's his name to turn Midway Island (Sand Island) into a Namesake Golf Resort. The island does have an 8000-foot air strip with a 3000-foot overrun and an easy hop from Oahu. 

A side bonus would be to restore the Rhombic Antennas so ham DXpeditions could operate from Midway. What better place to use the $5M Gold Card. 

BTW the snorkeling and scuba diving are superb as Midway is surrounded by a coral reef. 

You might also like to do an Internet search on the 1964 Midway Island Bird Abatement Project. Some 22,198 Gooney birds were removed from the runway areas as bird strikes were a serious problem. The removal was not a relocation.

When Midway was open to visitors following a deactivation as a Naval Base, the FWS set up a ham station so guest operators could operate from Midway. The visitation program is now defunct. This is a photo of that station.

Them that know can make it go.

73's

Pete N6QW

Birds of Midway Island with a Bonus of being a rare DX Station!

QSL Card from Midway Island

 Gooney Birds of Midway Island

Midway Island is actually Midway Islands, comprised of two distinct islands those being Sand Island (1440 acres at low tide) and Eastern Island (the smaller at 450 acres). In 1963 these two islands had distinct call signs starting with KM6. Two club stations existed on the islands with KM6BI on Sand Island and KM6CE on Eastern Island. Individual hams had KM6 call signs. Short story Midway stations (all 7 of us at the time) were a distinct radio entity and considered rare DX.

In 1963 I was a newly commissioned Ensign assigned to Midway and at that time was 21 years old. My first day on the Island I visited the Officers Club and was asked to show my ID. The bartender was an off-duty sailor who starts by saying: we don't serve underage dependents, and I said I am not a dependent where he said I need to see your ID. The next morning when we held "morning quarters" I could see the stark look of terror on that sailor's face when he discovered I was his Division Officer. 

At this time, if you were a licensed ham and changed your physical station location you were required to change your call sign. My call sign issued 4 years before my assignment to Midway was K3IXU and the move to Midway generated KM6DD, a first-time issue of that call sign and my Midway call sign. Today there are many KM6 stations mostly in California. You no longer can visit Midway as it is a protected wildlife sanctuary -- but if you could the call sign is KH4. There are about 100 people on Midway today.

At first, I was excited about my assignment to a rare DX location and of course its historical significance that came with the island that occurred only some 21 years earlier. It took only about a week to discover that Midway was like a prison sentence. 

You couldn't leave the island; there were limited facilities and only six single women on the whole island -- all schoolteachers. Of the six the two younger ones were booked for dates months in advance the two older ones were protected by nature and the two in the middle were in their late 40's, somewhat unattractive and looked shop worn. These schoolteachers were accorded "officer status" and lived in the BOQ (Bachelor Officer's Quarters) and ate in the officer's mess. 

One of the two teachers in the middle group was also the home economics teacher. After about two weeks on the island at dinner one night she saunters over to the four-person table where I was sitting and introduces herself. She then asks the usual questions: where are you from etc. and then says I am the home economics teacher. Her next statement was I bake a lot of cookies so if you like chocolate chip cookies I am in room XXX. I thanked her for the offer and made a note about not going to dinner at that particular time ever again. Gulp she was my mom's age and really dumpy looking! Good thing I was a ham as I had a great hobby for a remote rare DX island.

BTW during that 13-month tour of duty I read 120 books and that was a diversion from the Home Economics teacher who undoubtedly had more than cookies on her mind. 

The hobby side of ham radio was secondary to the mission of the Midway primary ham stations and that was phone patches Later I became custodian of KM6BI, and we were on the air 24/7 as there were 3000 personnel on Midway and ham radio was the connection to the outside world. BUT that was my 1st taste of the rudeness of some hams. 

Often when calling CQ with specific emphasis on stations with phone patch capabilities at a desired location we would get a response from a strong station and after a brief signal report exchange, I would say here is the phone number. The response back was I don't have phone patch capability I just wanted a signal report from Midway. Often the person sitting right there in the shack who wanted the phone patch was horrified that they had queued up to get on the phone patch list and were in contact with a ham who could make a local call only to get such a big disappointment. Regrettably such contacts were often with stations on the east coast and in the 2-call area. A whole new meaning to NY Rude!

Midway of course is the home to the Gooney birds where two species exist in the island -- the Laysan and the Black Foot. There are birds on Midway that exist nowhere else in the world. So, yes bird watching yet another diversion from chocolate chip cookies.

There was a good deal of scientific study of the birds including one while I was there. The US Navy banded six Gooney birds and took them to Seattle where they were released. Three days later they all showed up on Midway -- they had a navigation system superior to anything the Navy had. Oh, another documented curiosity is that Gooney birds' nest within 1/2 yard from where they were born. That also is documented -- a built in GPS.

Like the Tale of Two Cities, my tour was the best of times and worst of times. The Navy Exchange (PX) carried but two sizes of everything. Yes, you guessed it: Too Small and Too Large. Sears catalog sales did a booming business on Midway. The Bank of America had a branch on Midway so you had checks and bank drafts where you could simply mail order and include a check. I even bought a VOM kit from Allied Radio using that system -- it was fast -- about a 3-week turnaround.

One thing I enjoyed was standing OOD duty. A Civil Engineer Corp officer is a staff officer and normally does not stand duty as the OOD. Because of the small number of officers on Midway this was an exception. Why I liked OOD duty was that I would inspect the main galley and ate a meal there. This duty I took seriously, and I made a full inspection and always gave high marks to the staff on the report that was submitted up the chain of command. The chow really was superb! 

Typically, the last item on the duty list was a complete tour of the base at 2300 Hours. After my 3rd OOD tour, the Commissary Officer suggested I make a stop at the main mess hall as my last stop. I did that and awaiting me was a bag of hot fresh donuts -- what a way to end my tour. I learned a valuable lesson during my Navy years -- you treat people right and you get the benefits. Many of my fellow officers hated inspecting the mess hall and eating a meal there. Too bad guys, no donuts for you.

The not so good part of the OOD tour was those damn teenagers. The base XO had a teenage son who was always sneaking off to abandoned bunkers on the island for a bit of party time with the several YL teenagers on the island. The XO's XYL would call the OOD to find her son. The abandoned bunkers were great for what he was doing but dangerous because of their instability. I usually found him and suggested he go home. Now the tricky part how to include that in the incident report without identifying him. The code words used: unidentified teenagers were removed from abandoned bunkers. I guess the XO's kid never met the Home Economics teacher.

Them that know can make things go.

73's

Pete N6QW