SolderSmoke Podcast #179 SPECIAL TENTH ANNIVERSARY EDITION

SolderSmoke Podcast #179 is available:

22 August 2015

http://soldersmoke.com/soldersmoke179.mp3

YESTERDAY MARKED 10 YEARS OF THE SOLDERSMOKE PODCAST

-- A clip: The first minutes of SolderSmoke #1

-- A trip down SolderSmoke memory lane.

-- The SolderSmoke lexicon -- words and phrases we use (a lot).

BENCH REPORT

-- Pete's antenna project.

-- Pete's new Blog:   http://n6qw.blogspot.com

-- Bill's big amplifier problem fixed thanks to Allison KB1GMX.

-- Six digit freq readout with an Altoids case.

THE Si5351 PHASE NOISE CONTROVERSY

-- ALL oscillators make noise.

-- Keeping things in perspective:  It is 100 db down!

-- Observations and tests from LA3PNA, NT7S, and K0WFS:

http://k0wfs.com/2015/08/21/si5351-phase-noise-and-thd-tests-using-an-agilent-e4402b-spectrum-analyzer/

http://nt7s.com/2014/11/si5351a-investigations-part-7/

-- Try it, you'll like it!  The benefits trying things on real rigs.

NEWS

Interviews on "QSO TODAY" with Eric 4Z1UG.

Horrible band conditions.

Looking at Saturn with telescope.

MAILBAG

Another recruit for the CBLA:  Paul KA5WPL.

Ron G4GXO on Bell-Thorn and Eden9 SSB rigs.

Rupert G6HVY on Kon Tiki radio and Mr. Spock.  

Mikele's Croation BITX rigs.

Dean AC9JQ's TIA.

Bryan KV4ZS will build an LBS receiver.

Dave Anderson give Pete good antenna advice.

Steve Smith moves in from the garage.

Pete has built  12 SSB transceivers.  Intervention time? 

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

Going through a phase (on phase noise)

There seems to be a bit of hysteria on the alleged phase noise problems of the Si5351 chip.  The library yields some words of wisdom that help keep things in perspective:

ARRL Handbook (2002) page 14.5: "You would be excused for thinking that phase noise is a recent discovery, but all oscillators have always produced it."

Experimental Methods in RF Design page 4.12 "At first glance, phase noise sounds like a esoteric detail that probably has little impact on practical communications.  This is generally true."  (EMRFD does, however, go on to discuss the problems that arise on both receive and transmit from EXCESSIVE phase noise.)

Our old (young!) friend Thomas LA3PNA e-mailed on this subject noting that the Si5351 chip produces less phase noise than many Hartley or Collpits oscillator designs.   He provides a link to measurements (far better than mine!) of the noise from the Si5351:

http://nt7s.com/2014/11/si5351a-investigations-part-7/

NT7S puts it this way:

I believe that the plots speak for themselves fairly well. If you compare these results to the receivers in the Sherwood Engineering receiver table, I think you'll see that the Si5351 acquits itself quite nicely for such an inexpensive part. Personally, I think the Si5351 is eminently usable for many receiver applications, except perhaps the most high-performance. Certainly for the price, it's going to be extremely hard to beat. I hope this motivates those sitting on the fence to decide if the Si5351 will meet their needs.

Be careful in evaluating statements saying that the Si5351 phase noise is 3-6 db worse than an Si570.  This makes it sound like there is a LOT of noise coming out!  But again, it is important to keep things in perspective:  The noise from one chip might be -156 dbc/Hz while the "worse" chip might be -150 dbc/Hz.  That's still not enough noise to make a lot of noise about.  

The ARRL handbook recommended a very simple check for excessive phase noise:  Set up a very strong signal in the band of your receiver.  Then slowly tune to the signal, listening carefully for any build-up in noise as you approach the signal.  I did this, and I didn't hear any.  As for transmit, well,  as Pete points out, I think the spectrum police on 40 meters would let us know if our signals were broad or noisy!  The ARRL Handbook notes that in a transmitter, "This radiated noise exists in the same proportion to the transmitter power as the phase noise is to the oscillator power..."


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

Si5351 Phase Noise? A Tale of 3 Oscillators

Si5351 at 16 MHz

 

There is still a lot of talk about the supposedly horrible phase noise of the Si5351 chip. In a recent episode of a popular (and very good!) podcast about homebrewing, the podcasters talked about this in the context of some megawatt AM shortwave broadcast stations that had oscillator phase noise problems and were wiping out large portions of the HF spectrum.   I don't think those stations were running Si5351s, but the listener was left with the impression that these handy little chips are very noisy with lots of spurs and will inevitably produce horrible dirty, spectrally impure signals. 

 

This has not been our experience.   Following Pete's lead, several of us are using the Si5351 to generate both VFO and BFO signals in our transceivers, with good results. The receivers sound very good and we have not heard complaints of "broad" or "noisy" transmitted signals.

 

I decided to dig into this a bit.  This was also an excuse for me to use the FFT and screen capture features on my Rigol 'scope.  

 

I now have THREE BITX transceivers in the shack.   My BITX17 uses a VXO at round 23 MHz (IF at 5 MHz)/  My BITX20 uses a classic LC VFO running around 3.5 MHz (IF at 11 MHz).  Finally, my BITX40 (DIGI-TIA) uses the dreaded and much reviled Si5351 running at around 16 MHz (IF at 9 MHz).   I thought that these three rigs would provide a good opportunity to test the scurrilous claims about the Si5351.   

 

As a simple first test, I put my Rigol scope in FFT mode and just put the probe at the VFO Mixer's LO input.  The screenshot above is the FFT for the Si5351.  It looks pretty clean to me.  The 'scope is looking at 15 Mhz above and below the VFO signal.    

 



VFO at 3.5 MHz

 

Next I measured the output of the BITX20 VFO at the same point (input to the VFO mixer).  (I had to change the vertical range, but the horizontal was unchanged.)  Here you can see the second harmonic (just because at this low freq it is within the freq range setting of the 'scope).  It doesn't look much different than the Si5351.   



VXO at 23 MHz

 

Finally, here is the BITX17 VXO at 23 MHz, again at the input to the VFO mixer.   It looks remarkably similar to the Si5351, don't you think? 

 

More on this to come.  The ARRL Handbook (2002) has a good discussion on phase noise. I am digging into this and hope to do some more tests.   For now, I think we should reserve judgment on the utility (for us) of the Si5351.  



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

An Enthusiastic Recruit for the Color-Burst Liberation Army



Hey Bill and Pete

Man, I am loving the podcast! 

It is absolutely what I need, and what ham radio needs today!!!

I am at about episode 168 trying to catch up.

I would really like to build a Mighty Mite.

In fact, going on the record,  

I AM GOING TO BUILD THE MICHIGAN MIGHTY MITE.

If you have any crystals left could you please send me one.

I've got a 9 year old boy that's home schooled and I want to make this electronics hobby a stepping stone to a higher learning experience. 

I got in to ham radio to learn electronics and somewhere along the line I just learned how to send and receive CW and how to pass multiple choice question tests. Somehow along the way I lost my love of radio. I still have a nice modern day rig, but it has no "soul". I heard that comment in one of your episodes and it really rang a bell with me and when it rang I said,

 "Oooh, that's Awesome! "

I want a radio experience with soul!

I think that maybe why folks still use CW. It's a mode with soul. I know you champion SSB, but home brewing a CW transmitter and receiver has got to be a truly soulful experience.  And its one I intend to have as one of my own.

 I too want to enjoy the "Joy of Oscillation ".

With you guys inspiring me, I am sure this will be a wonderful adventure. 

THANK YOU! THANK YOU! THANK YOU!

For your guidance and inspiring work in the field of homebrew radio.

Sincerely,

Paul Hodges

KA5WPL 

P.S.

The chemistry of you 2 guys on the show REALLY remind me of Click and Clack. You guys really work well together! 

PLEASE DON'T STOP!

73

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

Paul:  Consider yourself inducted.   There are, however, some conditions:

1) You MUST build the MMM and make it oscillate (thus experiencing the JoO).

2) You MUST send a picture or (better) a video of your MMM in operation.

3) You have to give me permission to put your e-mail (below) on the SS blog.

4) You have to send me your address so I can issue you a for-real SS 3.579 crystal (with mojo).

Deal?  73  Bill

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

Deal,

I'll do my best to get video, at the very least I'll get pics.

As for making it actually oscillate, well if the "radio gods" let it be then I'll be having some good vibrations going on in the shack. Hope to have it going before first snow...of 2015...

Also, being inspired as I am, I made a CW contact with 5 watts since I emailed you last. 

Thanks for helping me get the fun and excitement and the adventure back in to ham radio!

Sincerely,

Ka5wpl

P.S.

Please send a card if you have one with the crystal. 

PPS  Also why not initial it if you've got a small enough pen :)

73

----------

Paul's Knack Story is here: http://www.qsl.net/ka5wpl/

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

Star Trek Propagation Prediction

Thank you Brad Smith.  Live long and prosper OM.

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

Another BITX DIGI-TIA -- AC9JQ's (video)

Wow, Dean's BITX with Termination Insensitive Amplifiers (3 of them) sounds really nice. And this is with a homebrew ladder filter (see below).

 

I also like the way Dean makes his enclosures -- he uses scrap aluminum and 1/2" angle.  This might cause me to abandon the wooden cigar boxes.

  



Dean will now add the driver and PA stages and plans on following Pete's suggestion by making this a 20/40 rig. 

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

VK3ZZ's Magnificent Rigs

 

Oh man is that beautiful or what?   Thanks to Peter Parker for the alert.   This is yet another reminder that Australia remains a bastion of homebrew enthusiasm and expertise. 

 

This is the work of Ross, VK3ZZ.   Read more about this rig, and the other creations of this Electronic Wizard (including an impressive AM rack), here:

 

http://www.qrz.com/DB/VK3ZZ

 

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