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.

Feedback on Farhan's FB Feedback Amp Video

As I said a couple of days ago, Farhan has put out a very informative video on amplifier design. During the video we can see him determine bias, feedback and load levels, then select component values. We then see him actually build the amplifier "ugly style" and use his Antuino to test it.  Fantastic.   

Watch Farhan's video here:  https://www.vu2ese.com/index.php/2020/06/18/feedback-amplifier/


I sent Farhan some of my reactions to the video.  In the hope of stimulating some discussion, I repeat them here: 

___________________

Wow Farhan, I really enjoyed your video and learned a lot.  You definitely have the Knack for explaining this stuff. 

I have been struggling to understand feedback amps for a long time.  I took up this topic on pages 187-190 of the "SolderSmoke -- Global Adventures" book.  I was more focused on the benefits of FB amps, and on how and why feedback affected input impedance.  

 I took notes as I watched: 

-- I liked the fulcrum analogy. 

-- Really wonderful how you describe the selection of components to get desired bias. 

-- Even better when you explain tapping down of RF coil to get 50 ohms to look like 200 ohms. Great stuff. 

-- Standardized on BNC.  FB! 

-- .1uF caps.  Love them!  No argument here! 

 

-- I copied your resistor list.  Will use it with Mouser. 

-- Saving the pigtails.  Indeed!

 

-- I like your ugly "resistors first" technique.  I may have to move away from Manhattan. 

--  Wow.  Ugly circuits IN SPAAAAACE!  FB!

 

--  2N3904   I always think it is EBC when looking at the flat end of transistor with leads facing down. Only had reverse pinout with PN2N2222.  EBC is my usual assumption.

 

-- I still have the big box of trifilars you left me.  I use them.  Thanks!

-- I like that VTVM in your Antuino.   Very handy. Want one!  Also, We need to get the Antuino to go down to below 455 kHz. 

-- I also like your dual Return Loss and SWR display.  I think in terms of SWR.  Return Loss sometimes messes me up. 

-- Didn't know about the Hold and Zoom feature on Antuino. FB.

 

-- Your measurement of the Q of the crystal was awesome.

  

-- I checked my soldering iron temp:  I'm at 480 C   A bit too hot. Will back off. 

 

-- Good description of need for an attenuator at amp output to keep it in Antuino's range.

 

-- As I watched you tug on the components after the solder cooled, I remember an old and silly admonishment from the ARRL Handbook:  NEVER  use solder for mechanical connections.  Ha!  They were WRONG!

 

-- Demonstration of the flatness of feedback was great.

 

-- I found your measurement of impedance using the SWR feature of the Antuino to be very useful.  Is there a chart relating the SWR/Return Loss to actual impedance values? 

-- Loved your description of how output impedance affects input impedance.  That is why you advised use of TIA amps in my DIGI-TIA.   But now I'm thinking that if I can accurately measure impedances of non-TIA amps, I can design L networks that will keep the crystal filter passbands ripple-free, right? 

-- Great explanation of the benefits of the 6 db pads at amp output.  Allison often recommends this. Now I know why. 

-- Wow!  Now I KNOW what that two-tone box you left with me is for!  Now I understand how it can be used to measure IMD on FB amps.  I pulled mine out just as you began to discuss yours.  Really cool. 

Thanks a lot Farhan for doing this.   These videos will be of long-lasting use to homebrewers around the world.  I hope we will see many more VU2ESE videos like this one. 

73  Bill 

Join up NOW!

From the front cover of the July 14, 1934 issue of Amateur Wireless.   This UK weekly magazine was the predecessor of Practical Wireless. 

Excellent Video from Farhan on Amplifier Design

Farhan has produced a really excellent video explaining the theory behind the feedback amplifiers that we use in so many of our circuits.  He takes us through the design and construction of these amplifiers, then uses his Antuino network analyzer to test an amplifier  and to measure input and output impedances.  

There is a lot of tribal knowledge and wisdom in this video! 

Check it out here:  

https://www.vu2ese.com/index.php/2020/06/18/feedback-amplifier/

Thanks Farhan! 

You must join the CONSTRUCTOR CRUSADERS

Wow. This 1934 front-page presages so many things that we talk about today. 

"The Constructor Crusaders,"  reminds me of "The Color Burst Liberation Army."

"Wear the badge and be in fashion," is clearly just another way of saying "chicks dig it," and brings to mind Pete's beret. 

Finally, "Constructor Crusaders will get the best out of radio!"  Well, that's what we've been saying all along.  

Note that as early as 1934 they were talking about TV:  "Radiovision."

Thanks to Scott KA9P for passing this to us. 

Lobes, Nulls, and "Gain Dipoles" -- Testing the Theory with WSPR

In the last podcast Pete and I were discussing dipole antennas.  We mentioned dipoles that were multiples of 1/2 wavelength and said the result could be a "gain dipole."  This provoked some head scratching.  Listener Riley asked for more info. See the comments section under this post: http://soldersmoke.blogspot.com/2020/05/soldersmoke-podcast-222-antennas.html. 

A short time later Pete was corresponding with Brad WA8WDQ who had questions about his antenna pattern.  Pete recommended using WSPR to test his antenna's effectiveness. 

These two exchanges got me thinking about the radiation pattern of my 135 foot doublet antenna, especially on 20 meters.  Where are my lobes, where are my nulls?   Following Pete' advice I turned to WSPR.   But first, a quick look at the PREDICTED patterns.

ON5AU has on his site a great article by antenna guru L.B. Cebik  W4RNL with exactly the info I needed.  Above is W4RNL's chart of predicted radiation pattern for 20 meters on a 135 foot doublet.  Note the orientation of the wire.

My antenna is oriented almost exactly north-south (broadsides to the east and west).  So with a standard north at top map, my pattern on 20 should look like that of W4RNL's chart.  What did I get from WSPR?   Here is the pattern for an hour or so of 250 milliwatt transmissions from my station using the 135 foot doublet on 20 meters (using homebrew balanced tuner): 

You can clearly see at least three of the four predicted lobes (NE, NW, SW). 

Now, part of this WSPR pattern could, I suppose, be the result of the geographic distribution of WSPR stations.  If there are just more of them in the areas where I am seeing lobes, the pattern could just be the result of geographic distribution.   I don't think that is the case, but to test this idea (a bit) I decided to look at the 40 meter pattern.  

Here is what W4RNL predicted (same north-south antenna orientation): 

And here is the WSPR map that I got, again using about 250 milliwatts for about an hour): 

I think this pattern matches nicely with the prediction.  You don't see the nulls that you see in the 20 meter pattern.  You do see some stations directly north of me (as predicted).  There does not seem to be a big disparity in the geographic distribution of WSPR stations.

One note on the use of WSPR:  I started out using WSPR in receive mode, thinking that the pattern I'd see would be similar on receive or transmit  due to the antenna reciprocity principle.  But I worried that the results could be easily skewed by higher power WSPR stations.  So I shifted to the transmit mode and limited my output to 250 milliwatts. 

Here is the W4RNL chart showing the patterns for all the bands: 

http://on5au.be/content/a10/wire/abd.html

Here is the azimuth chart for my location: 

Dilbert, Shep, Dex, Pete, Farhan, and Wes! N2CQR Presentation on Homebrewing to Local Radio Club

Dean KK4DAS asked me to speak to our local radio club, the Vienna Wireless Society.   It was a lot of fun.  I talked about my evolution as a homebrewer, some of the rigs I made, the moments of joy, and the tales of woe.   You can watch the presentation in the video above. 

I was really glad to be able to explain in the presentation the importance of people like Pete, Dex, Farhan, Wes, Shep and even Dilbert. 

I was also pleased to get into the presentation the N2CQR sign that Peter VK2EMU made for me.  Thanks Peter! 

Here is the URL to the YouTube video (also above): 
https://www.youtube.com/watch?time_continue=3414&v=VHSr-v4QO7Q&feature=emb_logo

And here are the PowerPoint slides I used: 
https://viennawireless.net/wp/wp-content/uploads/2020/06/VWS-presentation-Rig-here-is-homebrew.pdf

Jerry's Sproutie: A Short Wave Receiver (and a Limerick) by Jerry KI4IO

Jerry KI4IO is a really talented homebrewer;  I've called him the Wizard of Warrenton:  

https://soldersmoke.blogspot.com/2015/07/the-wizard-of-warrenton-jerry-ki4io.html

and 

https://soldersmoke.blogspot.com/2019/05/fdim-interview-with-ki4io-homebrew.html

Warrenton Va. is not far from me (and is the birthplace of Cappucio the Wonder Dog).  Once we are done with the pandemic I hope that Jerry and I can get together to talk about homebrew radio.  

Like me, Jerry recently turned his attention to the shortwave broadcast bands. He too went the homebrew route, but his receiver is a regen.  It is based on the Sproutie by Dave AA7EE. 

Here is Jerry's article detailing the project and the results: 

http://soldersmoke.com/KI4IORX2.pdf

Jerry had been scheduled to talk about antenna tuners at FDIM this year, but the pandemic caused the event to be canceled.  He shared with me a Limerick that he was going to include in the presentation.  Obviously we have similar feelings about automatic antenna tuners. 

In days of old

when hams we bold

and BALUNs weren't invented

We adjusted our C

and fiddled with L

and reflected power was prevented

KI4IO in his shack Feb 2020

Software for Computer Interface with NanoVNA: NanoVNASaver

In the UK, "brilliant" is high praise indeed.  So when Tony G4WIF told me that the NanoVNASaver software was brilliant, I took heed. 

Being able to use the tiny (nano!) device with your computer makes it a much more accessible and useful tool, especially for those of us with fat-finger syndrome. 

The photo above shows the NanoVNA measuring Return Loss and SWR  on my 40 meter dipole. You can see the identical Smith Chart traces on the two screens. 

Download and installation was very easy. I got my Windows PC version from here: 

https://github.com/mihtjel/nanovna-saver/releases/tag/v0.2.2

Other versions available from here: 

https://github.com/mihtjel/nanovna-saver

Coincidently, a fellow just today put out a video on how to use this software with the NanoVNA. 

https://www.youtube.com/watch?v=2S0dt0bYoLs

Thanks Tony! 

Alan Wolke W2AEW Explains the Vector Network Analyzer (VNA) (Video)

I told Alan that his video on VNAs was -- for me -- very timely.  The video popped up on YouTube on the day than my NanoVNA was being delivered.  TRGHS. 

Alan does a great job in explaining what the VNA does.  Particularly useful for me was his explanation of the VNA's ability to measure phase differences (through the use of directional couplers).  

I am having fun with my NanoVNA, happily measuring SWR and the bandpass characteristics of various filters.  Mine came with what looks like a guitar pick -- this is used as a stylus to hit the small boxes on the touch-screen.  A nice touch...   

I wish there was some good software for use with this VNA.  Apparently the nice software described by Joe Smith (yesterday's blog post) is quite expensive.  Is there a free alternative out there? 

NanoVNA, Millen Dip Meter, Kilo-Megacycles, and Measuring the Speed of Light (Video)

Yesterday my NanoVNA arrived.  This morning I was looking for info on how to use it and I found this really wonderful video from Joe Smith.  

Wow.  Joe gives a really useful intro to the capabilities of this amazing little device. He even reaches back in time and compares NanoVNA results with those obtained by a Millen Grid Dip Meter.  He pulls out of his junk box an attenuator that is so old that it is marked in "Kilo-Megacycles."  (Shouldn't we revive terms like that?)

Joe also gives us a taste of what it is like to live and work in the GHz range.  He warns us never to touch the SMA connectors on our NanoVNAs (too late Joe).  And -- get this -- he uses a torque wrench to connect the little SMA coax connectors to the NanoVNA.  I'm not kidding.  A torque wrench.   Joe connects surface mount capacitors and inductors that have their values specified not only in picofarads and microhenries, but also at the specific frequency at which they were measured.  

My understanding of the Smith Chart was greatly improved by watching Joe's video. 

Icing on the cake:  Joe wraps up the video by using the NanoVNA to MEASURE THE SPEED OF LIGHT.  Great stuff.  Thanks Joe.  

Here is Joe Smith's YouTube channel:  
https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg

Now I have to get the software to use the NanoVNA with my computer. 

Lightning Strike on the Washington Monument

Here in the DC area, the monument is very frequently in view.  I have been up to the observation deck.  We were here for the earthquake that damaged the structure.   On Thursday night someone made a good video of lightning hitting the monument.  

This particular storm was flashing through my window, and was visible during a Zoom class through the windows of persons elsewhere in the area.  

This lightning storm took out one of NA5B's amazing Web SDR receivers.  I think it was only the LF receiver.  I am sure Mehmet will have it back on-line soon.  

Here is an article on the topic: 

https://www.popularmechanics.com/science/a32781804/watch-lightning-strike-washington-monument/

Duga-2 The Big Soviet Woodpecker Antenna (Video)

https://www.bbc.com/reel/video/p0864g3p/the-secret-soviet-radar-hidden-in-chernobyl-s-shadow

No Main-Tuning Reduction Drives in Stock Drake 2-Bs -- But why no mod articles?

Alan Wolke W2AEW and I were recently discussing our Drake 2-Bs (again!). Both of our receivers have reduction drives between the main tuning control and the string mechanism that moves the main tuning capacitor.  I wondered if these were the results of modifications by previous 2-B owners.  I vaguely recall that my Elmer -- Hilmar WB2NEC -- had done this sort of mod. 

OM Wouter ZS1KE sent me this very illuminating photo of the inside of his Drake 2-B.  No reduction drive.   So Alan and I obviously have modified 2-Bs.

One thing that puzzles me:  I can't seem to find a single article that describes this apparently common mod.  Does anyone know of an article in the ham magazines that might have described how to do this?  

Thanks again Wouter!  

"The Radio Collector" A TV Series from 1985

Here is a really nice five part series of PBS TV programs about the history of radio and about restoring old radios.   I got a kick  out of W6AM's description of the "exam" that got him his first radio license -- you will find that story at the end of the first episode (above). 

Here are all five of the progams: 

https://www.youtube.com/playlist?list=PLLTogcYJemH5Oc_W8Q4gsae4a0zHvi5L8&fbclid=IwAR1H1Eq1vqMb_-MntRvPId5f_UpU5h-KJVtz2Wj8ijbTmSusr1BmGvcAROk

And here is the background info (from the YouTube Channel): 

The Radio Collector from the California Historical Radio Society

5 videos 156 views Last updated on May 25, 2020

The 5-part PBS series from 1985, “Radio Collector” was nominated for a Los Angeles Area Emmy for Best Informational Series. Radio Collector was shot in 1985 on 3/4″ video, a marginal format that boasted 240 lines of resolution. It was edited 3/4″ to 3/4″ using a control track/insert cuts-only editor, then that 2nd generation 3/4″ was transferred to 2″ at KOCE in Southern California where the credits were added. KOCE sent it to PBS and it was available to all member stations, and it has been aired on many stations. Mike Adams' students in Radio-TV-Film at California State University, Fullerton, were the camera operators, musicians, etc. Twenty eight years later CHRS President Steve Kushman transferred a copy of a copy of a copy of the master which went from 2nd generation 3/4″ to 2″ to 1″ to Beta SP to his computer. The story has held up well, and of course many of those profiled here are silent keys/valves. Mike’s inspiration for this series was the original “This Old House,” thus “This Old Radio.” Enjoy

Adam N0ZIB's FB Station (and UGLY Michigan Mighty Mite)

Bill and Pete, 

Thanks for the work you put into your podcast. I’ve been listening to it on my commute and while at work (I’m a welder/fabricator). Fantastic content.  Keep up the great work.  

All your talk about Farhan and the Ubitx convinced me to order one.  I welded an aluminum case for it and upgraded to the Nextion 3.5” screen. Also added a tuning knob from a Heathkit SB-401.  So far I’m really enjoying this rig. Plan to add an audio amp (to drive a larger speaker) and a CW filter to it this weekend.  In the station picture I sent I also show my paddles made from a hacksaw blade and stainless steel hardware. It’ll send 25 WPM before it gets a little sloppy.  My QCX 40 is also pictured.  I have a commercial rig too but find I’m not using it very often. 

Plan to start building the simpleceiver soon and maybe a bitx 17 too. Your podcast played a big part in convincing me to pick up a soldering iron again.  You guys are awesome.  Keep it up.  

73’s

Adam

N0ZIB

(Pete noticed that the main tuning knob on Adam's uBITX was NOT from Heathkit but was instead from a Collins KWM-2 or 32S3.  He advised Adam that the knob would sell quickly on e-bay.  It did, and will finance additional N0ZIB homebrew projects.  We are thinking of adding these knobs to our SolderSmoke Retirement Fund Portfolio.)   

Adam continues: 

I was listening to your older podcasts and heard several discussions about the Michigan Mighty Mite.  So this jumbled up mess probably doesn’t look like much but I built one. I need to order a 40 meter crystal and actually build it again on a board(with the coil rewound for 40) but my “proof of concept” build was a success. Using a variable cap from a Hallicrafters S20-R and the crystal holder from a Heathkit.  

QCX SSB -- But How Much QCX Remains?

Hack-A-Day carried a very nice video describing recent efforts to turn Hans Summers' amazing QCX CW monoband transceiver into a multi-mode, multi-mode (including SSB) rig (see above).   This is project will greatly interest QCX and SDR fans.  

But I wondered how much of the old QCX is still there after the modification.  Not much, it turns out.  

Here is the bloc diagram of the QCX.  It is essentially a phasing rig, using the same principles as my venerable HT-37 transmitter and my version of KK7B's R2 receiver: 

Yesterday Paul VK3HN sent me the schematic of the new multi-mode, multi-band version:  

Notice how different it is.   I thought that perhaps the new rig would keep something of the I-Q circuitry of the QCX, but it does not.  This is not a criticism, just an observation.  

But here is something that harks back to a topic we've been debating on the blog and podcast.  Notice that the top diagram is a bloc diagram.  There is a lot of circuitry in most of those boxes -- lots of resistors, capacitors, inductors, and transistors.   There is a schematic diagram under that bloc diagram.  But look at the second diagram.  While it looks like one, that one is NOT a bloc diagram. That IS the schematic diagram.  Most of the circuity has been sucked into the chips.  

While many will prefer the rig described by the second diagram, I remain an HDR guy, and don't really like seeing the circuitry disappear into the ICs.  But, to each his own.  This is all for fun.  Congratulations to the guys working on the new rig. 

AJ4SN Homebrew

OM Stan AJ4SN reports that his operating position is on the left. The workbench is on the right.  FB. 

More here: https://www.qrz.com/db/AJ4SN

I like the Turner +3 Transistorized microphone. 

Thanks to Ed B. for the link. 

An Amazing Catalog of Circuits from HA5KHC

HA5KHC is a club station in Budapest, Hungary.  The photo above shows a portion of their worshop.  The link below is for their really amazing collection of links to ham radio circuits. 

http://konstruktor.ha5khc.hu/linkgyujtemeny/linkgyujtemeny.htm

Tribal Wisdom from KE3IJ

Lots of homebrew wisdom on OM Rick's web site.  Excerpts: 

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

Why am I not on the air as much as I'm tinkering with toy radio circuits? Well, if some of the hams reading this don't mind my saying so, the manners of many of the people using the bands these days leaves so much to be desired that I often find more pleasure in futzing around with "minimal" QRP [low-power] ham-band transmitters and receivers, as well as good-old AM broadcast receivers, than in getting on the air anymore. 

So I've found a certain twisted fascination with trying to build the simplest pieces of junk possible, and seeing what I can pick up with them. I usually start by drawing a rough schematic on paper, then tack-soldering a haywire "spider-web" of components, as a 'first pass,' and then I rebuild the circuit more neatly once its design is finalized.

It still amazes me that we can connect some modified "rocks and sticks" together (that's basically what copper wire, silicon transistors, etc. really are, when you think about it) and hear voices and music magically appear out of nowhere...

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

He has many regen circuits.   And his Drake 2-B dial skirt looks just like mine.  

Visit Rick's site:  http://ke3ij.com/radios.htm