Unfazed! Fight HISS-teria! Give the Si5351 a Chance.

 

Thanks to all who have contributed to our discussion of phase noise and the Si5351 chip.  Let me throw out some ideas -- some technical, others philosophical.

1)  We may be worrying about this too much.   In all of the homebrew or kit rigs we've built over the years, I never recall much concern about the phase noise specs of the LC or crystal oscillator circuit that we were using. What were the phase noise stats on a Heath VF-1? How about the phase noise stats for the little Hartley oscillator in those DC receivers we made?  No one even checked. Our rigs usually worked just fine.  We would have noticed if they were extremely noisy, but if they were good enough, we left well enough alone.  It doesn't really make much sense for us to now be suddenly very concerned about the phase noise stats of the various DDS and PLL chips that are replacing those LC and crystal circuits, especially when the measurements show that they are usually in the same range as our old familiar oscillators.   

2) The perfect can be the enemy of the good, and the "good enough."  We have a long tradition in ham radio of tolerating less-than-perfect or less-than-optimum parts.  Remember, the NE-602 has some shortcomings, but we use it. We use it a lot.  The IRF-510 wasn't even designed to be an RF amplifiers, but we have pressed it into service for our PAs.

3) We should be willing to give a new part a try, and we should be pleased if it proves useful.  We should be wary of untested claims re the unsuitability of a component.  We have to avoid the "works in practice, but not in theory" situation.   If something works well, doesn't create additional QRM,  is inexpensive, and fosters experimentation and homebrewing, we should be happy about being able to use it.  

4) All electronic components -- not just the Si5351! --  produce noise.  Resistors produce noise.  Look at this:
" We can infer... that if we install phase-quiet oscillators in transmitter and receiver, we ought to be able to tune our receiver to a frequency closely adjacent to a very strong signal from the transmitter without encountering anything like phase-noise hiss. Yet, after an exhaustive phase-noise cleanup at transmitting and receiving sites, we test our communication system only to discover that the transmitter still emits broadband hiss! The culprit is transmitted amplifier noise. Just about every modern transmitter or transceiver consists of a high-gain, linear amplifier strip that amplifies the low-level output of oscillators, mixers and phase-locked loops to hundreds of watts or a few kilowatts. Because amplifier circuitry is not perfectly quiet, the output of the transmitter contains noise (hiss) in addition to the amplified signal. Transmitted along with the desired signal, this hiss can degrade the noise floor of nearby receivers-just as transmitted phase noise can. Where does amplifier noise come from? Thermal noise, for one thing. Electronic components operated at temperatures greater than absolute zero generate random electrical noise. This noise is broadband in nature. Greatly amplified in an audio amplifier-or greatly amplified in a radio transmitter, transmitted as broadband radio noise, received and converted to audio-it sounds like hiss. Random variations in electron flow within active amplifier components (transistors and vacuum tubes) are another source of amplifier noise. Transmitted as broadband radio noise, received and converted to audio, it also sounds like hiss." Source: http://www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/qst/1988/03/page14/index.html

5) It seems that whenever a new technology or part comes along there will be those who issue dire warnings about how we can't or shouldn't use it.   When transistors came along, there were those who said that hams shouldn't homebrew with them because -- it was argued -- without spectrum analyzers we couldn't possibly come up with spectrally pure signals. 

6)  We have to be careful lest this obsession with perfection and extremely high tech standards be used as a rationale for not homebrewing, or (much worse) as an argument against homebrew rigs on the ham bands.   There is a bit of this going around.   Get on 40 meters with rig that drifts a bit or that is not "on frequency" to within 10 Hz and you will find out what I mean. 

7)  The Si5351 is a good part for our purposes. It does something new and VERY useful for us:   It can put out BOTH our VFO and BFO frequencies.   It makes it much easier for us to change bands and-or switch between USB and LSB.   Its phase noise figures are fine.  LA3PNA (citing measurements by KE5FX) notes: "The phase noise of the Si5351 is around -130dBc/Hz at 10KHz. This is quite decent, If compared to a Hartley or Collpits you would see little or no difference. Some of my measurements of published free running oscilators show phase noise in the -110dBc/Hz range!" 

-130 dBc/Hz at 10 kHz puts this part on the "good" curve of this chart. From (http://www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/qst/1988/03/page14/index.html

We should give this little chip a chance!   Give it a try! 

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

SolderSmoke 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

The KJURKN Receiver (video)

Shell, WA6KJN, has built some really cool homebrew rigs.  And an airplane. 

On his QRZ page Shell writes: "I have saved all my old homebrew gear. This is a tube SSB exciter using a pair of 6146's in the final. It has a Collins mechanical filter. Built in the 70's. It had a matching receiver also with a mechanical filter in the I.F."

Check out the QRZ page for meore inspiration (and some good ideas on towers):

https://www.qrz.com/db/WA6KJN/


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

Knack Story: Rupert Goodwins -- SolderSmoke in the Old Smoke (London)

Rupert with some sort of SDR rig

 

In addition to having a very cool name, Rupert Goodwins, G6HVY,  is a for-real tech guru:

https://en.wikipedia.org/wiki/Rupert_Goodwins

I was delighted when Rupert posted some sage advice about how to deal with my recalcitrant amplifier.   He managed to include a reference to Mr. Spock in his message, helpfully noting that some of these amp problems would challenge the Vulcan's logical powers.  That made me feel better.  I sent a few words of thanks to Rupert and got back this really great "Knack Story":  

Hi Bill,

 

Well, all I have on HF amp instability is anecdote and half-remembered theory. But I do like the sort of challenges that building RF on the bench brings up - a problem worthy of one's attention proves its worth by fighting back! 

I've enjoyed Soldersmoke (or should I say Soddersmoke) for years now, and even if I haven't bought the T-shirt, have bought your book. I first inhaled the demon fumes when I was barely into double digits, and the addiction kicked in hard - I fixed my first radio, a valve (tube!) FM 1950s broadcast receiver using a soldering iron that was actually one of my father's wooden-handled screwdrivers heated on the gas ring of the cooker in the kitchen. My parents were mystified but supportive...

London is indeed a hard place to play radio. But that makes it doubly pleasurable when it works: it rather feels like you're operating under cover, a special forces op sneaking the signal out under the noses of the regime. I once had a birthday picnic on Hampstead Heath where I brought my SOTA beam and fishing-pole mast: the local constabulary turned up and were also mystified but not quite so supportive... "What if everyone did it?" they asked. "Oh, if only..." I thought but did not say. 

 

I do hope you can pacify your errant amp. Sometimes these things can be fixed by brainpower, sometimes by just mucking around until they get bored before you do. But normally I find that I've learned a lot when the problem's solved. RF isn't black magic, it's a gateway into another world that's marvellous and enthralling, but ours to know. I read a really good paper by Freeman Dyson, where he said that Maxwell invented modern physics, because his equations were the first to show that the real world of how things work is both beyond our natural experience, but accessible through thought and logic. The real entrancing thing about radio is that it proves this - we can talk across the world by translating our knowledge into a tiny handful of otherwise inert bits and pieces that tap into something utterly beyond our senses. And it's open to anyone who cares enough to try. 

 

How cool is that? (I had to go and find that Dyson paper again - here it is, if you're interested:  http://www.damtp.cam.ac.uk/user/tong/em/dyson.pdf )

 

(I also have an unshakeable and unhelpful addiction for obscure but interesting radios, as my QRZ page confesses. And things I helped design and build when I was an engineer are now in the NSA and Bletchley Park cryptologic museum collections. That, as they say, is quite another story...)

 

Anyway, thanks again for emailing - I'm thrilled to hear from you, and perhaps, who knows, one day we may make contact the way God and Maxwell intended - via QRP on a lively band while dodging the noise and bouncing our photons off the Heaviside Layers. 

Best 73s,

Rupert, G6HVY

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

Rupert's QRZ.com page contains additional evidence of his Knack affliction and International Brotherhood of Electronic Wizards membership:

 

Other equipment here includes a Wireless Sets No 19 Mk III, an R1155, a Barlow Wadley XCR-30, an ICR-73, some PMR stuff on 4 metres, some old CB kit (shhhh!) and other obscurities. I like kit that has something different about it the 19 set, for example, is of course famous for its wartime role, but it was also the very first transceiver. The XCR-30 is really interesting, not only for being a high tech product of 60s apartheid South Africa (so a morally complex thing to own), but for having a very esoteric design that provides 0-31MHz coverage without bandswitching, very high stability and accuracy (you can generally pre-tune an AM broadcast station anywhere on the bands from the dial and be within 1KHz on switch-on, and all from a handful of transistors. There are stories to tell about all of my radios. 

Started in radio when I was too young to get my ticket, so was forced - forced, I tell you - onto CB radio, in the days when it was very popular and very illegal. Had a couple of crystal-TX, super-regen RX walkie-talkies (QRPp and RX so wide I could pick up Radio South Africa on the BC 11m band) to start with, thence bought a 'for conversion to 10m' populated CB PCB from a batch at Plymouth ARC Rally and just bunged a set of toggle switches on the PLL-02 divider inputs. This was the mid-late70s, when skip was high... Did the RAE ASAP after my 16th birthday, first legal amateur rig (I may have built things with 6V6s that may have made odd noises on the local Top Band AM Sunday morning net) was an Icom IC-2E. My richer friend, who was a G6E, had an FT-290R, which was obv. nicer but obv. deafer. "FT-290. IC-2E. I can hear him. He can't hear me." Used 19 sets at school, so have that addiction too. Since then, the hobby has been in and out of my life (like QTHs, wives, jobs and money), but the love of radio never has. 

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

I also understand that he once worked at a dodgy TV repair shop in the back streets of Plymouth and can still swap out a gassy PL509 with the best of 'em.

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

W1JSB's Very Cool Portable Rigs -- RadioSet-Go!

Brad Smith alerted me to this.  Very cool.   Hanz W1JSB is churning out some amazing trail-friendly rigs.   I really like the tinted-translucent front panel. 

Here is the site for Hanz's company:  http://radioset-go.com/

Here is his YouTube Channel:  https://www.youtube.com/user/w1jsb/videos


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

Amplifier Woes! Instability at Low Drive Levels! (Video)

I have to keep reminding myself:  This is not "plug and play." These are not appliances. 

After I got my 40 meter problems squared away,  I was doing some testing on my beloved 17 meter BITX.   I noticed something weird:   With the CCI EB63A amp feeding my 17 meter Moxon antenna, as I raised the output of the BITX17 driver, at one point (at about half the max input power) the SWR would suddenly spike. Then, as I raised the drive level above that point, the SWR would go back to normal. 

I looked at it on the 'scope.   I can see the signal go very ugly at the mid-level drive point.  In the FFT display, I can see that there is a strong signal at around 435 kHz.  The 18 MHz signal seems to be riding along on top of it.  Take a look at the video above.

Additional clues: 

I see no signs of the 435 kHz signal at the output of the BITX 17.  It seems quite clean.

This problem disappears if I replace the Moxon with a dummy load. 

This problem does not show up if I feed the EB63A with my almost identical BITX20.   And I use the same LP filter on both 20 and 17 in the CCI amp.

Any suggestions?  Has anyone had this kind of problem? 

Allison and Pete have been helping me with this.  Thanks to both of them.  

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