Sunday, April 5, 2020

New Technology for 2020 ~ Improvise, Adapt and Overcome

What to do during the Pandemic?

This is a chance to get back on the air or to take up an interest in homebrewing your own rig. You can build this rig --it has only 10 devices and they cost a total of less than $5. It is called "The Simple SSB". Two VFO's, USB/LSB and a TUNE Function.

My good friend Bill, N2CQR has a project documented on the soldersmoke blog called the Quarantine -31. It is a radio receiver that is tuned up on the 31 Meter shortwave band. The photo he has on the blog looks like a 1930's ham receiver --al fresco on a metal chassis with plug in coils. So cool, Bill.

I have decided that I would post some simple schematics of projects that could be built with parts in your junk box. The first is a microphone amp using a single 2N3904. This same stage can be added ahead of an LM386 as an audio preamp. So you are getting a "twofer".

I have left the LT Spice info on the schematic so you can simulate the circuit yourself. Learning LT Spice might be a good time filler! 

Now this is where your reading skills come into play. R8 is stated as being a 10K Trim Pot so the capacitor connects to the center wiper. I got an email when this was 1st published from an irate ham that stated  it only had one volume level --loud. I have a word for him JERK! 

R8 is the mic gain control But the limitations of the simulation dictates doing it the way I did it. You could place two 5 K resistors in series and take a set of readings at their juncture and that would give ~ half volume 

I cannot resist my Italian roots and we have the word Quarantine that comes from Venice, Italy where in the 14th and 15th Centuries ships had to observe a 40 day waiting period to unload people and cargo as it was during the Black Plague Pandemic.

[The word quarantine comes from quarantena, meaning "forty days", used in the 14th-15th-century Venetian language and designating the period that all ships were required to be isolated before passengers and crew could go ashore during the Black Death plague epidemic . Thank You Google!]

#TOT --- Following him is with great peril to you personally and to all of us.

Pete N6QW

Wednesday, April 1, 2020

New Technology for 2020 ~ We are being challenged

The next two weeks will be bad!

That was a pronouncement made this week to all of us. Finally some realism in the assessments of what will happen. Thus WE are all being challenged to take specific actions to mitigate against this terrible scourge. In time it will be clear how this happened and how there was/is a failure of leadership at the very top; but for now --we must do our part.

Some Sobering Statistics for 13 States. In 5 days: 2X the number of cases and 3X the number of deaths. Social Distancing is vitally important!

To stay indoors and limit direct contact we can turn to our beloved hobby to have personal interactions. Time to visit on the air  with our ham friends world wide and to enjoy "rag chewing" about our favorite rig or perhaps sharing information about the current projects on our bench.

Speaking of projects on our bench I am now fixing things that somehow sorta worked but now is the time to making them work as designed. Just yesterday I did find the code error that kept painting over the readout on one of my rigs. I also fixed the issue of artifact displays when you went from seven digits to eight digits. Here is was the issue with this two band rig.

On 40 M the startup was 7.200.000. Good; but now you switch to 20 M and the startup is 14.200.000. Good! Now when you switched back the frequency read 7.200.0000. That extra Zero on the end really bugged me! Thus I figured out how to  have 7.200.000 and 14.200.000 always come on at boot up and/or changing bands. Wow that killed about two hours; but was very satisfying and fixed a problem that previoulsy I just sucked it up and lived with it.

How glorious it is to finally have fixed something that was really not right! I also find that most of the parts places are still delivering hardware. But as this pandemic grows that avenue may be severly impacted.  So you best right now go to the SolderSmoke Blog and in the right hand top corner find the Amazon link and get ordering.

I have also been thinking about actually coming up with a simple CW transmitter design that could be built with stuff you have around the shack. You can find crystals by searching for AF4K, Bry Carling. This Covid-19 may actually be the forcing function that renews a world wide interest in that binary form of communication.

Be safe: Get on the Air and/or Build Something.

Pete N6QW

Thursday, March 26, 2020

New Technology for 2020 ~ The AD9833 RF Generator Board

A New Toy on the N6QW Workbench!

3/29/2020 ~ Your uBitx may contain a critical part of the next generation of Covid 19 Ventilators.

3/30/2020 -- Double Balanced Mixers!

I am happy to report that Mouser now carries the ADE-1 Double Balanced Mixers and are available in single lot quantities for about $6 and some change. Nice! 

Just checking I went to the SolderSmoke Blog and searched in the Amazon block and typed in Double Balanced Mixers and this is what showed up ($1000)

It is a mixer; but probably won't work too well in my design. Guess it is important to be specific.

Pete N6QW


[I have a sudden interest in 3D Printers. Looking for recommendations firstly, on a good software package as that is probably more important than the machine itself and likely dictate what I buy. Given a robust software, secondly is a specific machine recommendation in the $300 to $400 range. My interest is in making knobs --big knobs.]

It seems like the University of Florida has been working on a ventilator design that uses plastic pipe and sprinkler valves. Such an approach would enable building such devices simply by making a trip to Home Depot. 

But then there is the issue of how to control the system. Boom hams to the rescue! According to what I just read on the reflector several hams have prototyped a control system to work with the plastic pipe / sprinkler valve ventilator. A posting on the reflector states today that  the involved hams will mate the Arduino / 2N3055 transistor control system with plastic pipe and sprinkler valves to breadboard a working model. How cool is that?

So while you are twiddling the knob on your uBitx that Arduino inside may be the heart of an international open sourced homebrew ventilator. That old adage is once again proven: Necessity is the mother of invention!

Just watch --- the emperor (with the nano particle sized e) will claim he invented it!

3/28/2020 ~ A new way forward!

We are now at 103K known Coronavirus cases in the USA and this is driving many changes in the way we do things that likely will be permanent!

Yesterday I made an inquiry of one of my XYL's Doctor's as she has an appointment coming up on April 7th. The office staff gave me instructions to download Zoom and that the appointment would be kept using the Zoom application. 

Payment for services will be by credit card and we already had setup prescription refills via the Dr. sending an email to our pharmacy. In the past seeing this Dr. was a bear! Her office had limited parking spaces and it was located 10 miles away. Man I foresee all future appointments being done this way. 

Ditto for her primary care doctor who will visit with you via a telemedicine application to determine what further action would be required. I happen to have a higher quality BP machine and a pulse oximeter so the Dr. can get some vital signs right over the internet.

Got an email from our dentist who is suspending his practice for a month -- not sure how you get your teeth cleaned via the internet; but someone surely is working on an application.

I discovered you can order "the college student staple food", Top Ramen via Amazon. The price is cheaper too. Funny story --on Monday I am getting a combined package from Amazon consisting of two items: A set of replacement probes for my Rigol DSO and a case of Beef Flavored Top Ramen. 

This Monday I will be all set --new DSO probes and Top Ramen! Just other day I received some high quality buttermilk biscuit mix from Amazon. 

It is likely in the future I will be doing more food ordering from Whole Foods and PillPak for the meds. What can I say other than Bezos is a genius: Stuff, Food and Medications all quickly delivered to my door. 

You have got to love technology! The stay at home order will change the paradigm! It saves gas too and is good for the planet. I am running some calculations on the gas savings versus the added delivery costs. That will be interesting.

Remember: #TOT, your life depends on it! Listen to the real leaders like Dr. Fauci and Gov. Cuomo!

3/27/2020 ~ Loaded the Code!

I just copied the code from the earlier link into a blank sketch and then of course you have to null out lines, add libraries, do the usual fiddling  and ultimately you should get a display that looks like this. You will note it says AD9850 because the author took that code from a prior project and repurposed it. [Thanks again DuWayne!]

For my use I will have to do some major surgery on this code; but this is a starting place. I want to limit the frequency range to 5 to 5.5 MHz and I don't like what was used for pin assignments --- but you can make it play as is.

I had an Uno R3 with an attached display and that is what I used. But in keeping with a small size you would want the Nano. We are moving forward...

Just  finished listening to the daily briefing from NY Governor Andrew Cuomo. Now there is a straight talking "leader" and such a vast difference from the emperor (with a microscopic e) who essentially is misleading all of us.

You can listen to and believe the emperor;  but you do so at your own risk! Just look at the numbers of cases: that data is truth! We are past 100K cases --when do you stop listening to the emperor?

Why did he wait until now to invoke the war production mandate. Weeks ago he could have ordered GM to make ventilators. This is the problem of a lack of competence to lead!

It must be that the Trump properties are losing money and that is the rationale for opening the country by Easter.


But 1st, I see where the USA leads the world in the number of Covid-19 cases, at greater than 80K of our population. We now have surpassed the 1000 mark in number of deaths!

We must look to the emperor (with a microscopic e) as a potential reason as to why so many cases. From the outset he was in denial, calling it a Democratic hoax designed to make him look bad. 

It is well known that he was briefed on the impact of this scourge over two months ago. But instead of taking action, he frittered away precious time. The emperor chose to ignore the experts and to trust his gut. Well it seems his gut was wrong.

Anyone who listens to him or believes what he is saying --we'll check back with you in about two weeks to see if you are still alive! Good Luck!


Today my AD9833 RF Generator board arrived. I kid you not it is the size of a postage stamp. When the envelope arrived I thought at first that it was an empty envelope.

The link above has the key to unlocking its secrets! The plan is to fabricate a generator in the range of 5 to 5.5 MHz as this is a common VFO frequency for many of the OLDE Boat Anchors. I have a Ten Tec Omni C that has a drifty VFO and is a candidate for this jewel. Heathkit, Drake, Galaxy and National all used a VFO in the 5 MHz range.

I am working on the AD9833 as I await the PSN's to arrive from the UK or maybe Turkey.

See the link at the top, thanks to our good friend DuWayne , down in Riverdale, GA, we now have the "how to".

It is time to TOT!

Pete N6QW

Saturday, March 21, 2020

New Technology for 2020 ~ Lets Build a Phasing SSB Transceiver

LBAPT ~ Let's Build a Phasing Transceiver!

3/24/2020 ~ A bit of new hardware!

After a Skype session with ZL2CTM and also in an attempt to produce a quadrature output Si5351 --- I finally bumbled and stumbled through  many failures and now have something working (with a lot of help from around the world).

The idea of a quadrature output Si5351 has been around for some time, only I was not too successful in implementing the actual hardware -- until now. It gets harder as you get older! 

In my conversation with ZL2CTM he mentioned the idea of using a separate Arduino/Si5351 to generate the Quadrature outputs to free up the workload on the Teensy 4.0 which is running at 600 MHz and is fast. This then opens up the possibility of two displays. One could do an amazing spectrum waterfall piece and another would do just the frequency and other housekeeping tasks like Step Tuning Function, Sideband Select, etc.

One critical piece is the library that you use for the Si5351. Frankly this has me confused as I have four different versions of the Si5351 library and one caused you to have a 180 Degree shift an another a 45 Degree shift. I simply do not know why. But I guess the third time got me there.

This is all preliminary but having the separate Arduino /Si5351 Quadrature output is a piece needed for our Phasing Transceiver project. 

By the Way check out the LTC5599 IC from Analog Devices. It is a 30MHz to > 1Ghz SDR transmitter on a chip and can be had for about $11. One ham shared with me he has this working on 17M. 

Ahhh the new technology in 2020 is amazing!

If you are interested in hearing straight talk about the Covid-19 tune into one of the briefings by Governor Andrew Cuomo from New York. Listening to the emperor (with a small e) is a waste of time and riddled with misinformation (MOM).

I personally believe that blindly following the emperor (with a small e) puts you at a grave risk! You only need to observe the daily exponential growth in cases to see that opening the country by Easter is unthinkable.

Its like saying use a 47 Ohms resistor --it is ok just use a 1/4 watt. But the load requires a 100 watt. True same value wrong watt rating! Listen to Dr. Fauci and Governor Cumo. They know best!

Is the drive to open by Easter purely a personal desire -- surely the Trump properties are tanking right now? Some sobering food for thought. 

Pete N6QW


Fellow Hams --we are on our own! The lack of leadership at the top has put us all at risk. There is a huge difference in "playing a president" and being one. A real leader would have taken immediate and decisive action -- he took a golfing trip! 

It is really easy to spot the true "leaders" in the fight against CV-19: Cuomo, Newsome, Inslee.

Just observe --- the $2 Trillion Stimulus package will benefit the rich, the emperor's friends, and the large corporations. BUT those who need it the most will only get the crumbs. Who are the Republicans kidding?

I have coined two new Acronym's MOM and #LTCTOT. A clue: MOM is not about your mum. It is Master Of Misinformation --wonder who that is?  

CV-19 Blues Crush

Caveat Emptor ~ I may  really be in the weeds this go around. But, Hey, 20%  of the USA population are home bound so maybe we can collectively do it together.

Firstly I bought two of the QRP Labs Phase Shift Networks which are in route to me. I did a bit of further examination and there are two mods that will be required. (This is not a kit project!). The first issue is to decode how to connect to the inputs which I will need to pursue further study. But there are two other identified "hurdles".

The first hurdle aside from interconnection is that the PSN has a narrow band width of perhaps about 1500 Hz which will really piss off the 40 Meter FLEX Radio guys. But this 1st go around is proof of concept and then I will need to see how to make that wider.

The 2nd hurdle is that the PSN is not bidirectional -- it was made to chunk in a receiver. Use in a transmitter requires some significant modifications. So there is some electronics on the board that SUM the I and Q channels to produce an audio output for the receive mode. That part of the circuitry will have to be bypassed so it can feed the I and Q Channels on the RADIG Board. Now on the front end of the PSN we will have to build an interface that takes the single ended output of the 2N3904  Microphone amp and splits it into two signals to feed the input side of the PSN. My first thought would be to use something like a modem coupling transformer to create a balanced input. There likely will be development needed here.

So before you buy a set, you might want to see how I fare. But this is the fun and it is a time killer. I think that in about a week the total US will be in lockdown. 

I have tried to contact Hans Summers about these two issues and have not heard back --so I might try a different email.

So those of you who thought this was a hoax --we are here because the emperor (with a miniscule e) is in denial. The last thing anyone should do is believe him or any of his claims. #LTCTOT! In essence we are on our own and the emperor (with a microscopic e)  has written us off! So let us observe the safe practices and LBAPT!

Pete N6QW

Tuesday, March 17, 2020

New Technology for 2020 ~ A simple way to build a Phasing SSB Transmitter

PWKSCDS -- I just realized I made a very bad assumption. It came to me in a dream!

3-20-2020 ~ The emperor's buddies strike again!

[But 1st. Some people are saying that 3 Republican Senators got advanced notice of the CV-19 impact and sold huge chunks of stock BEFORE the market crash. Sounds like the swamp got a bit deeper. I sure would have liked to have been privy to that info so I could have sold  my few shares of stock and not taken a hit. Shame on them!]

[3/19/2020, 6:43 PM PST. California has essentially been shut down with most businesses to close by midnight. You are permitted limited travel (like taking a walk) and you can buy groceries; but that is about it. Aren't you glad that you now have a project to work on while you are holed up?]

A Phasing Rig must have struck a couple of nice chords. Today I got two  inputs from "down under". One VK ham (Thanks Greg!) has provided me a source for homebrewing your own audio phase shift network which is found at this link.  and the spreadsheet for the calculations at this location 

This work was done by PIM PA2PIM

The second input (Thanks Stephen!) made me aware that in the G-QRP Club SPRAT #120 someone did the heavy lifting and translated the 'toob" SSB jr. to an all Solid State version. Now that would be nice. That source also referred me to a project by   Fred Johnson ZL2AMJ called "The Tucker Tin #2". 

Lea Earnshaw, ZL1AAX, (founder of Southcom Intl and Kachina Radio) published a nice book called The Transistor Radio Handbook and in there is a very excellent simple Solid State Phasing Transmitter. So it can be done with little hardware!

March 19th, 2020 ~ More CVHI Projects.

Here is the bad assumption that I made: That hardware building skills still abound. Wrong! The hardware building skill level today, in our hobby, has been outstripped by those with software skills. Hardly anyone scratch builds stuff today and an even very smaller percentage builds "toob" gear

It would be a simple matter for me to go to my stock of aluminum chassis boxes, dig out the Greenlee Chassis punches, drill a few holes with my floor mounted drill press and I would have the chassis for the SSB Jr (below) . The total elapsed time --about 1 hour. Not many hams have those skills nor the tools to use a chassis punch today.

I also have several power supplies that would power a tube transmitter. Scratch that idea --no one would build it and most hams only have $1.95 Walwarts. Too hard!

Don't Give Up Just Yet!

But let us not give up on the quest to build a phasing SSB transmitter and ultimately a phasing transceiver. The "hard nut to crack" was the Audio Phase Shift Network. But then I discovered today that you can buy one from a very reputable supplier. Boom! Hans Summers and his QRP Labs sells the Polyphase Network  for an amazing price of $11. It is intended to be added to a receiver block so may require some modifications; but PWKSCDS.

So gang what if we undertake using two of the PSN Networks in a transceiver and brew our own phasing rig using these networks? We could actually take the SSB Jr schematic building blocks to create comparable solid state building blocks and at this stage I envision a low part count rig. I would start with the transmitter first as we could use the Web SDR receivers for the other end.

After I finished the block diagram it hit me -- quite possibly only a single PSN may be required and only the Mic Amp and Audio Amp are switched at a common port. That would make for a huge simplification. Sideband reversal would be done as normal by switching the outputs out of the PSN to get either USB or LSB. 

My intent would be to design the rig as we go along and some modules exist already. I have circuits for an excellent simple 2N3904 microphone amplifier as well as the Bi-Directional RF Amp stage (2N2219), plus RF Driver Stage (2N2219A) and IRF510 Final. 

Using the already proven RADIG Board would mean even less development required. We is on a roll!

The Audio Phase Shift Networks would be purchased. The Tough Nut is no longer as the RADIG takes care of the RF Phase Shift and the Balanced Modulators

Enter the Si5351 where one clock would supply the RF for a basic transmitter and a second clock could provide frequencies to heterodyne that signal to other bands. Sounds like I am designing the rig as I type. (I am!)

This may all be a bust; but a solid state rig with one of the critical components purchased at a reasonable price may result in more hams having an interest to build one while in CVHI. 

This might even encourage some hams who read this blog with circuit board experience to design boards that could be commercially manufactured. This is an option  for those hams who always start by saying where can I buy the PC Board?

Yes this could be done with Tayloe Detectors/Mixers; but what fun is that. We are starting on a journey to build a modern day 1950's Transmitter/Transceiver.

Pete N6QW

CVHI = Corona Virus Home Isolation

A Little Laughter is Good Medicine!

The GE SSB Jr. 3 Tube Transmitter

I suggest you visit the N4TRB Wesbsite where you can download the complete Article from the GE Ham News #205. Below is the Schematic for the SSB Jr.

I will see if I can find some substitutes for the audio transformers. Now think beyond what is possible and use the Web SDR receivers as a simple station. You can be heard on 40 Meters with just 5 watts. 

This is a great CVHI project and the parts are common (once I find you the transformer substitutes) Ebay and Antique Electronic Supply has everything else you need!

CRHI = Corona Virus Home Isolation.

We could start a whole new revolution of home brew Phasing Transmitters. We also need to think about a NET frequency so we can have our own exclusive net. I believe 7.285 MHz is the recognized 40m QRP Frequency -- so either find some crystals OR look to the AD9833 Oscillator Board as a source for VFO control. The AD9833 Board and Arduino Nano can be had for less than $10 and are available on Amazon. Couple that with a cheap LCD and we are uptown.

For those inclined to really tinker -- this could be transported to a solid state version. But having a tube rig would be a blast.

Let the parts hunt begin.

Pete N6QW

Wednesday, March 11, 2020

New Technology for 202 ~ The Iowa Hills Software --- Hilbert Transforms

March 16, 2020 ~ Time Killer

Go to and tune into Podcast SS #219. This is good for 1.5 hours and may help pass some of the time you now have as the USA closes down for business. 

I am having a difficult time reconciling what I am seeing on the ground and what we hear from the emperor (with an extremely small e). This is going to get worse! Note: "He is responsible and it happened on his watch!"

There was a line at the grocery store this morning at 5:30 AM and the store didn't open
until 6 AM. Friends that is 0'Dark 30!

How are your stocks doing today? Are the Russian hackers at work trying to penetrate our national health agencies? The emperor (with a very small e) probably will most likely claim it is the deep state who did this. At around 1PM eastern the DOW was down about 2000 points. So emperor (with a very small e) how is your metric doing????

This actually may be a really good time/place to pick up women. But it probably is money is the big draw moreso than the ability to cook!

Pete N6QW

March 15, 2020 ~ This Sucks!

Today in California they closed the bars, night clubs, wineries, and brew houses. That means no more watching girls pole dancing. 

Most of the public and parochial schools in the major metro areas (SF, LA, SD) are closed. I expect the senior centers will be shut down on Monday.

Gatherings are limited to no more than 50 people. We are also told that if you are a senior citizen you must self isolate yourself by not going out in public.

Today our local grocery store (Albertson's) which is one of their flagship stores was out of the following:

  • No Paper Towels or Toilet Paper
  • No Clorox Wipes or Clorox Spray
  • No Bread
  • No Butter
  • No Pasta or Macaroni
  • The Soup stock was down by 75%
  • Canned vegetables were down
  • But Plenty of Beer & Wine but given todays proclamation that too will be gone
  • Water was in short supply.

The good news story is that I have a shack full of waiting projects, lots of parts and plenty of solder.

Pete N6QW

Today's Question:

Is the stable genius tanking our country? How did your 401K do today? Some people are saying his shortcomings are showing! Where is the leadership we so desperately need? Tomorrow will be another "bumpy ride" as more cases surface.

The Iowa Hills Software:  Hilbert Transforms

So what I am about to share with you comes from someone who knows very little about the Iowa Hills  Software. Yes, it is a case of the blind leading the blind.

For those of you deeply into mathematics, or a high level software architect, the subject of Digital Signal Processing and Hilbert Transforms is much like Massimo Banzai starting by saying "The Arduino is a simple tool to make things happen". Mr Banzai of course is the face of all things Arduino just so you know. Bob if you are reading this, then time to engage "the snooze control".

The Hilbert Transform dates back to 1905 so it was not invented in Silicon Valley and I encourage you to do the Wikipedia thing and look up Hilbert Transforms. It made my head hurt...

The Hilbert transform is important in signal processing, where it derives the analytic representation of a real-valued signal u(t). Specifically, the Hilbert transform of u is its harmonic conjugate v, a function of the real variable t such that the complex-valued function u + iv admits an extension to the complex upper half-plane satisfying the Cauchy–Riemann equations. The Hilbert transform was first introduced by David Hilbert in this setting, to solve a special case of the Riemann–Hilbert problem for analytic functions.

So the bottom line is that someone who wanted to do digital signal processing reached back in time and had a Eureka Moment -- use Hilbert Transforms. 

The Iowa Hills Software essentially takes all of what you see in the Wikipedia page and compresses it into a Simulator where you simply move some cursors around a graph to form the type of filter you want. 

Since we are using the I and Q approach (90 Degrees out of phase) which is processed at audio frequencies, then we must do the phase added option where we run the simulation twice. One is at + 45 Degrees Phase Added and the other at - 45 Degrees Phase Added. The span between the two is of course 90 Degrees.

But wait -- long ago and for those of you who once owned a Central Electronics 10A (with a BC458 VFO) or perhaps like N2CQR who has a pristine hallicrafters HT-37 (in addition to his restored S-38E) this idea of I and Q was done with hardware --HDR as Bill says. 

Essentially resistor and capacitor networks provided the 90 Degree shift in the audio signals. This was (and is) problematic as the hardware networks drifted over time and required a lot of constant fiddling. 

Anthony Vitale, W2EWL, came up with a SSB transmitter all fitted inside and using much of the original Military ARC-5 transmitter components to produce a compact Phasing SSB transmitter, Now that was advanced technology for the late 1950's (March 1956 QST). Many units built from his design found their way into Mobile SSB transmitters.

But now with the advent of creating phase shift networks digitally, the problem of drift and changing component values is simply GONE! 

The Iowa Hills Software now lets you create the digital filters and provide the all important 90 Degree Phase Shifted Values so that you can create nearly perfect I and Q Data Streams. Couple that with powerful microcontrollers like the Teensy 3.5, 3.6 and 4.0 with the integral CODEC board you now have a very capable SDR transceiver in a very small platform. 

Let us not breeze by that too quickly -- the same hardware used in my front end is bilateral -- so one set of hardware does all. My ADE-1's are used on both transmit and receive. 

Another simplification which I have as yet to implement (it is me having some cockpit problems making that happen) is to generate the quadrature RF signals directly from the Si5351 at the operating frequency. 

This is impactful in that you could make the Si5351 into a Two Meter SDR transceiver. Right now my Si5351 outputs at 4X and that is frequency divided by the 74AC74. This has two limitations where the 160 MHz end of the Si5351 would limit the upper operating frequency to 40 MHz and the 74AC74 drops off the radar at 95 MHz. 

Zl2CTM has provided me some code to directly generate the two out of phase RF signals. But I keep getting error messages about my variant of the Si5351 that is stashed in my library directory. Just need to fix that and test drive the higher limit frequencies possible by eliminating the 74AC74 and the 4X frequency multiplication. 

So ok what about those of you who are ardent CW operators and want a CW filter. Below is a plot of a potential CW Filter where I chose the Center Frequency of the filter to be 500 Hz and the 3 dB Band Width to be 500 Hz. 

At 60 dB down the BW is 1 kHz. If I remember this correctly the shape factor is the ratio of these two and so we have a 2:1 Shape Factor. For the purist that probably is too large and some would like to see perhaps a 1.6 to 1 shape factor. That might be possible --I just didn't fiddle with the numbers -- hey this took me all of 5 minutes. 

Note worthy along the left hand top edge are some blocks to check. The last one is Coefficients. Checking that block will produce 115 coefficients that appear along the right hand side of the plot. The normal default when you select Phase Added under the Pass Band Tab is +45 Degrees. Run the coefficients at this setting and then under the File Tab -- save the coefficients with the added title  +45. Now look at the Help Tab and just below that and to the right is the Phase Add block. Use the down arrow to make that value - 45 and rerun the Coefficients and save that with the added title -45.

These values with a bit of added information are embedded into the Arduino Sketch and instant filter 

Next week I hope to test drive this filter in a Teensy 3.5. Hopefully I will also make a video so you can listen to the filter on the air. But a real test is to find a CW contest weekend and see how well it holds up. In my mind the chosen 500 Hz BW is a compromise between having a narrow CW filter, yet not so narrow as to present some issues like ringing or significantly reduced audio volume because of a very narrow BW.

Keep in mind this is very new to me and I may have some incorrect assumptions … the long journey starts with the 1st step. The on the air test is the key. I haven't figured out how to make this transmit CW --just another day at the home office.

The value of having two Teensy 3.5's is that I can use one as a test bed and the other as "standard" when I want to operate the rig. I only need to exercise care that I plug Teensy 3.5 Pin #1 into Socket Pin #1

Ok Bob, snooze over!

Pete N6QW

New Technology for 2020 ~ Improvise, Adapt and Overcome

What to do during the Pandemic? This is a chance to get back on the air or to take up an interest in homebrewing your own rig. You can bui...