SolderSmoke Podcast #197: Farhan, Fame, 'Fest, Testgear, SSB History, Dishal Dystopia, QRP CW, MAILBAG

SolderSmoke Podcast #197 is available:

http://soldersmoke.com/soldersmoke197.mp3

Up in NYC, met Dave W2DAB. got Steve Silverman's HP 8640B Sig Gen.

Farhan's visit to SolderSmoke HQ

Got me a TEK1401A Spectrum analyzer

Farhan at "Geekfest" @W7ZOI   http://w7zoi.net/Farhan-visit.html

BITX40 Modules.  5,000 already.   1,000 a month.

The BITX pronunciation problem. 

QRP Hall of Fame.  I suspected April 1 reprisal!    "I am unworthy" 

Like in Wayne's World: https://www.youtube.com/watch?v=lBEn3a4TIUw

Dusting off my Tuna Tin 2, Herring Aid 5 and Farhan's key from India.

The Manassas Hamfest:  OLD crystal gear.   20's and 30's stuff. Leon Lambert RX and Philmore Fixed Crystal Detector. 

 Reminder of how YOUNG the radio art is.

RELATED:  Bell System 1953 Transistor Documentary.  11 year old Pete and his CK722.

Bought some good stuff from Charles AI4OT.

Armand WA1UQO gave me a big collection of Electric Radio.  So much history and HB wisdom in there. Frank Jones and Lafayette Radio.  Jim Lamb and 1930s SSB.  

Is the CK-722 the source of Pete Juliano's affinity for Juliano Blue?

Was Wes Hayward already using Juliano Blue?

"Your rig sounds real good for a homebrew rig!" 

"Well, your rig sounds pretty good for a Yaesu!"

Related topic: Going over the Waterfall:  The SDR Superiority Syndrome.  Feathering.

ARRL Arduino Book   by Popiel.    Very nice.  Right level.  Lots of good info.

BENCH REPORT:

Pete's Dishal Dystopia --  Is the perfect TRULY the enemy of the good enough?

Bill's  NE602 RIG: 

Replaced OLED.  Blue one seems noisier.  Shielded it with  copper flashing.

Made me yearn for bigger boxes WITH A HOOD!

DOCUMENTING WITH LTSPICE

MAILBAG:

Special Thanks to our correspondent in the Dayton Xenia Metropolitan area -- Bob Crane W8SX.

Jack Welch, AI4SV 5R8SV -- Our Man in Antanarivo -- Sent me a GREAT BOOK "I, Libertine" by Frederick R. Ewing.   EXCELSIOR!

https://qrz.com/db/5r8sv

Bruce KC1FSZ https://www.qrz.com/db/kc1fsz  Building Scratchbuilt BITX.  On the way put the VFO where the BFO should go and had a DC RX.  FB

Greg, VK1VXG   Suggestion for WA8WDQ on Arduino serial plotter

http://www.instructables.com/id/Ultimate-Guide-to-Adruino-Serial-Plotter/

Ben KC9DLM  Mercury PTO.  In a syringe!   No thanks! Maybe add some high voltage and selenium.  And a radium dial!  Yea!

http://webshed.org/wiki/Mercury_PTO

KY3R's metalized cigar boxes!  FB On Blog.

Richard WB2PEF has revived his Doug DeMaw 8P6 rig.  FB.  But bothered by PTT thump.

Update on Dave AA7EE (from Mike KC6SAX)

AI4OT and N2CQR

N2CQR AND W2DAB

KI6SN's 89-Cent Project Box Chassis

Eric 4Z1UG had a great "QSO Today" interview with Richard Fisher KI6SN.  Richard mentioned his method for making project boxes.  The commercial versions are getting very expensive, and the used ones are now hard-to-find at hamfests.  So use Richard's technique to roll your own! 

Details here: http://arsqrp.blogspot.co.il/2016/03/the-89-cent-homebrew-metal-project-box.html

FB.  Thanks Eric.  Thanks Richard.

Dino's HW-8 Mods

Bill -

Enjoyed the recent Hamvention interview with Ed Hare and your comment about him and a Heathkit HW-8 QRP rig.  I recently rescued the HW-8 I bought on eBay that had been sitting in my project queue for several years.  As I was refurbishing the rig I found that John KC9ON (http://kc9on.com) has several HW-8 mods that are very reasonably priced and I incorporated in the the refresh.  They included replacements for the audio amplifier and the T/R relay, the “miniYAK” electronic keyer that I installed internally and built-up a external control dongle for the keyer.  Cleaned up the additional audio filter that the previous owner had installed (ancient MFJ CWF-2 op-amp filter, surprisingly still available from the MFJ Vectronics brand, model VEC-820K) and did a complete realignment of course.  The T/R replacement includes provision for a red and green LED that indicates that the rig is in the receive mode (green) and transmit (red); I was able to mount them directly behind the relative output meter using a piece of plastic drapery hardware (always pays to keep that kind of stuff!).  Finally installed a fresh S-meter mod.

RF output is ok on all the bands except for 15m and I still need to figure that out.  Getting rid of the old Molex power connector and replacing it with a Powerpole was a real plus I thought.  Have swapped out the PA transistor with several different types but the one the last owner substituted in seems to be the best (ECG488).  Have to admit I’ve never been a devoted QRP guy but love the community for it’s technical bent but since I’ve been looking for some new challenges I thought this would be a enjoyable one.

As you’ve pointed out Mike Bryce’s HW-8 handbook is a must have for anyone updating their radio and there is also a seminal 2-part article series in CQ magazine that probably started the mods craze; they appeared in the August and October 1977 issues of CQ.

Here are some pix of the clean up process and shows I’m not afraid to drill holes in a boat anchor to make it more useable!

73 - Dino

Here’s the new audio board installed:

The additional audio filter with the new 5-pole selectivity switch put in by the previous owner…had to add some audio coupling caps and clean up all the wiring.  The plastic piece over the meter was from some old drapery hardware and it now holds the RCV/XMT green/red LEDs:

I replaced the original S-meter mod with a proper terminal strip (old parts were just hanging in the air).

Here’s the solid state T/R circuit that replaced the mechanical relay:

Les Moxon, G6XN

I was on 40 SB tonight talking to Don KC5YR. He is the creator of the web site known as the Moxon Antenna Project: http://www.moxonantennaproject.com/   That site had this great picture of OM Les Moxon, inventor of the wonderful antenna that bears his name.  I also found this old QSL card that shows some of Les's homebrew gear.  Les has been a Silent Key for many years now, but his legacy lives on.

FDIM: Bob Crane Interviews Ed Hare W1RFI

I always associate "Ed Hare" with that picture of him holding an HW-8 in the ARRL lab.

I was supposed to edit this one a bit at the beginning, but I forgot.  Sorry about that Ed. 

Thanks to Ed and to Bob Crane for the interview. 

http://soldersmoke.com/FDIM17W1RFI.mp3

Stay Thirsty My Friends --- A Very Inspirational Article

There is no real connection to radio here, other than the fact that some of us are in this guy's age group, and that we have had a few Dos Equis Guy memes on the blog.  But do yourself a favor and spend a few minutes with this article.  You will be glad you did. 

http://www.politico.com/magazine/story/2017/06/02/most-interesting-man-world-friends-barack-obama-215215

Thanks to Larry K8MU for alerting us to this.

Stay thirsty my friends.

Put Yourself on the BITX Map

On Jun 9, 2017, at 4:53 PM, Doug W wrote:

Seeing the topics for regional operator lists got me thinking.  If words are good, pictures are better.  I set up a google map that you can add yourself too to help visualize where everyone is located.  I was going to add people that responded to the other topics but out of respect for privacy (and my laziness) this should be entirely opt in only.  The map is only accessible with the link below.  The interface is reasonably intuitive but I will do my best to explain how to add yourself.

go to

https://drive.google.com/open?id=1Oa_egVdStSJBF5C7mpS6MXrkces&usp=sharing

type your address in the search bar on the top of the map (the box with the magnifying glass to the right)

hit enter or click the magnifying glass
verify the location displayed
click add to map at the bottom of the box that pops up
now click the pencil/edit icon at the bottom right of the box
change the highlighted address to your call sign and click save at the bottom left of the box
you can also add more information to your spot if you choose to
bookmark the link and check back as more people add themselves

I am making this sound much more complicated than it is.  If anyone can describe the process better please do.

FDIM: Bob Crane Interview with Preston Douglas WJ2V

WJ2V with Chuck Adams and Zack Lau

Our ace journalist in Dayton Ohio caught up with QRPARCI President Preston Douglas, WJ2V. 

Congratulations to Preston and QRPARCI for a successful FDIM event. 

Pete and I will heed his warning! 

Listen to the interview here:

http://soldersmoke.com/FDIM17WJ2V.mp3

Thanks Bob! Thanks Preston!

Old Timer Needs Soldering Help

I believe Harold is in Elk Grove California.   Is there anyone out there who could help him?  If so, please send me an e-mail at soldersmoke@yahoo.com


Bill

I'm a very elderly ex-ham living in Elk Grove and my current project is putting together a World War II military surplus IFF. This requires that I solder cable to small circular connectors and I no longer possesss the eye-hand coordination to do this. Do you jnow of any ham who can help me with this-he or she would be reimburses, of course Thanks for you your help

73s Harold S Meltzer ex W2OZX.

The Leon Lambert Crystal Radio

Above you see another gem from the Manassas hamfest.   I didn't know what this was.  And I don't think the seller knew what it was either.  I think I gave him 5 bucks for it (as it turns out that is close to the original 1925 price).  It was only in the course of looking up yesterday's Philmore Fixed Crystal Detector that I happened to spot a picture of this thing.

There is not much to it.  That nice dial is mechanically connected to a sweeper arm that runs along a big coil.   The galena and cats whisker were apparently held in place by the Fahenstock clips on the front.   Leon Lambert made these things in Witchita Kansas around 1924.   He started making them without the fancy wooden box, but one report says he found a good source for the enclosures:

In 2004 Dale Davenport wrote:

Leon Lambert's crystal sets show up maybe as or more often than most other brands from that time period apparently, particularly in the Midwest, There are quite a few variations though: some have a little metal tag tacked on, usually on top front center, some do not have a tag at all. Detectors vary some as well and I've seen them with Erla fixed detectors. One thing is more or less constant it seems, and that is the little wooden boxes they are mounted in. I cannot verify the story other than from observations, but was told quite a number of years ago that the boxes the Lambert sets are mounted in were used to ship sticks of chalk, packed in saw dust, to schools. Lambert supposedly had a deal with someone with the local school system to acquire these as they were emptied. I have owned one example, and have seen other examples of these sets that show some pressure marks on the flat sides, near the corners, where they apparently were packed in bundles, and the strapping tape used to secure the bundles left an impression. This seems to indicate that the story might be true and they might be leftover marks from the box's days as a chalk shipping box.Has anyone else heard the story or can anyone else offer more details on this theory?  From: http://www.antiqueradios.com/forums/viewtopic.php?t=36735

Here's a picture of the unboxed version -- you can see here where the galena went:

From: http://www.gifarmer.com/radio/crystal.shtml

And here we see Leon himself:

From: http://makearadio.com/index.php

More info: http://www.radiomuseum.org/r/lambert_long_distance_2.html

http://www.radiomuseum.org/r/lambert_crystal.html

The Philmore Fixed Crystal Detector

I was at the Manassas, Virginia hamfest on Sunday.  An old timer had a box of crystals for sale.  It was obviously the kind of "box of rocks" that many of us have in the shack.  There was a very wide variety of crystal packages in there, perhaps the widest range of possible styles.  In  among the modern computer crystals and WW II FT243s, I found one from the earliest days of broadcast radio.  The Philmore Fixed Crystal Detector is really just a chunk of galena with a phosphor bronze cat whisker held in place by a spring. Philmore apparently went ahead and found a "sweet spot" for you. 

N2HTT was working with on of these last year: https://n2htt.net/2016/01/17/a-complete-digression/

Of course, I liked the New York City connection.

I will see if this old thing still inhales.

KM4FNQ's FB Michigan Might Mite

Bill:

transistor: 2n2219a metal can with homemade aluminum heat sink
resistors: 27 ohm 2w 5% metal oxide; 10k ohm 1/4w 5% carbon film
polyvaricon capacitor: from an old am radio 9pf to 149pf
capacitor: 0.047uf polyester film (473)
coil: 1.25in. pill bottle with electric motor magnet wire: 0.017in.
       primary: 45t, tap: 15t, secondary: 6t
crystal: hc49/u 3.57 mhz

key: momentary-on switch from radio shack going-out-of-business sale

board: fr4 1oz copper, 3inx4in

pads: me-squares from qrpme.com

dummy load: six 300 ohm 3w metal film resistors

next step: low pass filter.

73 de Ken  KM4FNQ

LTSpice .asc file for the Organic Chip NE602 Rig

A link to the .asc LTSpice file for the NE602 rig  appears below.   Perhaps some brave soul  more skilled in LTSpice than I am might want to turn this drawing into a real simulation.  Some of the parts (like the NE602s) have actual simulated components behind the drawings.  Others (like the relays and the LM741 and LM386) are just drawings.  But go ahead and flesh this thing out.  Who knows, it might come to life in the PC and start making QSOs on 40!

Here is the .asc file:  http://soldersmoke.com/NE602 Rig.asc

My Organic Chip Rig with an LTSpice Schematic

CLICK ON IMAGE TO ENLARGE

This is a rig that came together through a process of Spontaneous Construction.  It started out with an innocent effort to get  an Organic Light Emitting Diode display to work with an Si5351/Arduino combination.   Then I figured I'd make a superhet receiver with it.  Then Pete said I should make it a transceiver.

Most of my earlier transceivers so closely followed the schematics of Farhan or others that it didn't really make sense for me to prepare a new schematic.  This one was different.  So I decided to prepare a proper schematic.  I tried a few of the free-ware CAD or drawing programs, but each of them had a learning curve at the entrance. So I turned to LTSPICE.  I have already climbed that learning curve.  

The results appear above.  Click on the image to make it bigger.   I'm sure there are errors in there.  And I think some of my parts choices might be less than optimal.  But it works well.

The filter was deigned with the help of AADE software.

The idea of using two NE602s with a filter between them came (I think) from the Epiphyte.

The band pass filters were designed with ELSIE software.

The RF power chain is mostly from Farhan's BITX40 module, with the pre-driver and driver modified for a bit more gain.  Farhan's amp is the most stable power amplifier I have ever used.  It hasn't given me any trouble, even at 20 Watts. Strongly recommended.

The microphone amp is derived from the 741 op amp circuit used in the (in)famous Wee-Willy DSB rig.

The receiver AF amp also comes from Farhan's BITX40Module.

Please let me know if you spot errors or have suggestions for circuit improvement.

A link to the .asc LTSpice file appears below.   Perhaps some brave soul  more skilled in LTSpice than I am might want to turn this drawing into an actual simulation.  Some of the parts (like the NE602s) have actual simulated components behind the drawings.  Others (like the relays and the LM741 and LM386) are just drawings.  But go ahead and flesh this thing out.  Who knows, it might come to life in the PC and start making QSOs on 40!

Here is the .asc file:  http://soldersmoke.com/NE602 Rig.asc

Juno Spacecraft Looks At Jupiter

https://sciencefriday.com/segments/jupiter-surprises-in-its-closeup/

KY3R's Metalized Cigar Box Rig Enclosures

Bill, 

Bob, KY3R, here. Haven't written to you in a few years (although do manage to run into you most years at the Vienna Wireless Society hamfest ). 

Anyway, was watching your visit with Farhan, and you mentioned your penchant for building projects into wooden hobby boxes, and using copper  flashing for shielding. I want to share my solution. 

I snatched up any old cigar boxes I come across. For shielding I use "metal repair tape." This is the stuff used for joining or repairing dryer lint vent ducts, and it is available at any hardware store. Very lightweight, and you just cut the desired lengths, peel off the backing, and press onto the inside of the box. The only drawback is that it is aluminum and doesn't take solder very well, but it is easy enough to add one or two short lengths of wire from the circuit ground plane to a terminal bolted down onto the case interior. 

The attached photos show my current project--a Por Larranaga cigar box in the process of being converted into a home for a BitX-40! I haven't yet fully decided exactly how to position the unit in the box, but as shown in one of the photos, it fits with plenty of room for later mods. As for other decisions, I toyed with the idea of painting or covering the outer box, but I am leasing toward leaving the original cigar box labeling. Arguably adds a bit of "soul," plus who needs a clean panel and all that fancy stenciled lettering anyway. I'll know which knob is which!

73, and as always, thanks to you (and Pete, of course) for your continued work on the SS podcast.

Bob Keller, KY3R

The Transistor! 1953 Bell System Film -- Great Stuff!

Thermatron fans beware!  There is some trash talking of tubes in this 1953 Bell film.  But there is also a lot of recognition of the contribution made by our beloved valves.  I especially liked the report on the historic 1915 phone transmissions from Arlington, Virginia. ( I drive past the transmitter site every work day).  FIVE HUNDRED TUBES combined to send the human voice from Arlington to both the Eiffel Tower and to Pearl Harbor, Hawaii.  FB OM!  59!

I was disappointed, however, that this film failed to recognize another momentous 1953 achievement in sold state electronics:  In that year, 11 year-old Pete Juliano built his first solid state amplifier -- an audio amp using a CK722 transistor.  Read about it here: http://soldersmoke.blogspot.com/2015/03/pete-juliano-homebrwing-with.html

The fact that Pete was homebrewing solid state circuits at the time that this film was made is a reminder of the vast experience that he has, and of how much technological progress we have made in such a short period of time.

Farhan gives me a Spectrum Analyzer and W2AEW Provides the Tutorial (Video)

At Dayton, Farhan very kindly bought me a Tektronix Spectrum Analyzer.  (I joked during his visit that this device might help me stay in the good graces of the FCC.)   This morning I decided to learn more about this device.   I Googled "Tek 1401A" and was immediately directed to a YouTube tutorial.  I was pleased to see that it was from our old friend Alan Wolke W2AEW.  I knew that the Tek analyzer and I were in good hands. TRGHS.  Alan expertly laid out the functions of the device.  I am confident that I will soon be analyzing the spectrum of my homebrew rigs, and that they will all be found COMPLETELY FREE of spurious emissions.

Alan's tutorial is instructive for all those getting started with spectrum analyzers. 

I need to find a manual and schematic for the 1410A.

Thanks Farhan.   Thanks Alan.   And three cheers for Beaverton, Oregon!

Indonesian BITX: Check out the BRITX

Pretty cool,  don't you think?

Here is the Google translation of the "about" portion of OM Dian Kurniawan's blog:

Electronics is something very interesting. In it are stored many miracles of His creation. The almost limitless opportunities for creativity make electronics an art medium. Countless things are ultimately made easy and possible with electronics.... Feel free to start. Life starts from a cell. Let's keep working for a better life. Salam.

It is obvious that OM Dian has THE KNACK and is a member of the International Brotherhood of Electronic Wizards.   Does anyone know his callsign?

There is a lot of very cool stuff on his blog, including some mind-blowing applications of small, color displays.  Check it all out:

https://diankurniawan.wordpress.com/

FDIM: W8SX Interviews Mike Bryce WB8VGE

Mike Bryce's many contributions to the radio art and QRP definitely puts him in the Homebrew Hero category. I have Mike's "Hotwater Handbook" (about the legendary HW-8) on my bookshelf.  Our intrepid SolderSmoke media team (Bob W8SX) spoke to Mike at FDIM 17.  His comments on the joy of a good troubleshoot, and on the pernicious, unfixable nature of many recently marketed appliance radios really resonated with me.   

Mike has special expertise on Heathkit gear:  https://www.theheathkitshop.com/index.html

Listen to the interview with Mike here:

http://soldersmoke.com/FDIM17WB8VGE.mp3

KEEP THAT GREEN FLAME BURNING MIKE!

FDIM: W8SX Interviews W8TEE on Facelifts for SSB Rigs

Our intrepid correspondent Bob Crane interviewed FDIM speaker Jack Purdum W8TEE.  Jack made some very intriguing comments on his efforts to enhance the beloved BITX transceiver.  CW! AGC! Speech processing! Woo hoo!  We await more details on how to acquire the board that Jack describes.

Jack is a very accomplished guy who has made many contributions to the radio art, most recently on Arduino microcontroller projects:  https://www.qrz.com/db/W8TEE   

Listen to Bob's interview with Jack here:

http://soldersmoke.com/FDIM17W8TEE.mp3

Thanks Jack! Thanks Bob!

Here are is the manual, bill of materials, and schematic for Jack's board:

http://soldersmoke.com/W8TEEschematic.pdf

http://soldersmoke.com/W8TEEmanual.doc

http://soldersmoke.com/W8TEEbom.doc

Homebrew Peppermint BITX: KC1FSZ Goes Scratch-built and Sweeps a Filter

Hi Bill/Pete:

Congratulations to Bill on the award.  Very well deserved!  

I just watched the video that Bill made with Farhan and I really enjoyed it.  As usual, lots of useful information there.

Farhan’s demo of the Sweeperino was particularly timely because this past weekend I was doing something very similar.  

As I’ve mentioned to Bill before, I am working on a scratch-built BITX to accompany the Peppermint BITX-40 module rig that I’m running right now.  I took Pete’s advice and started from the audio end.  After building the audio amplifier, product detector, and first/last pair of IF amplifiers, I was able to connect the VFO where the BFO is supposed to go and enjoy a pretty reasonable direct conversion receiver.  It works great!!  My first working receiver.

So my next step was the crystal filter.  I puzzled over all of the different articles, tried to follow the G3UUR method, sorted crystals, etc. and finally put the whole thing together.  But all along I’ve had this doubt that I could have possibly followed all of the steps closely enough to achieve the precision needed for a 3.5 KC SSB filter - it just didn’t seem possible.

Last week I decided to try to “sweep” the filter.  This was a multi-day undertaking in itself.  I pieced together the microprocessor, an AD9850, a TIA amplifier, the RF power detector from the SSDRA book, and some software that generates the necessary frequency sweep and collects power readings.  The picture of the test rig is included below.  It’s not much to look at.

With low expectations (and wires that are too long), I ran a few seeps and then downloaded the data onto my computer for analysis.  No fancy software here, I’m just using Excel.  When I put the data into a line chart in Excel, what emerged from the jumble of seemingly random numbers was a thing of beauty: a 3.5 KC passband right below 12 MHz. It’s the next stage beyond the Joy of Oscillation:  The Joy Of Selectivity!

It’s even showing about the right insertion loss.  Note the setup is very primitive and noisy so the fact that I can’t measure anything below -8dB isn’t surprising, you can ignore that part.

But I’m starting to get the feeling that this might actually work.  Onto the diode mixer …

73s,

Bruce KC1FSZ https://www.qrz.com/db/kc1fsz

VU3XVR's BEAUTIFUL Morse Keys

Truly a thing of beauty.  Farhan gave me one of these.  They are crafted by VU3XVR.  It is enough to turn a phone-guy like me back to CW.  Thanks Farhan!  

Here is VU3XVR's site:

http://vu3xvr.blogspot.com/p/morse-key.html

FDIM: Listen to Bob Crane Interview Hans Summers, G0UPL

Bob Crane, our intrepid correspondent at the 2017 Four Day in May event, caught up with Homebrew Hero Hans Summers G0UPL.  Hans's amazing web sites have been the inspiration for many projects in my shacks.   My favorite so far was his QRSS transmitter using an LED based multivibrator circuit to generate a shark fin pattern on grabber screens.  That was fun.  I am now really tempted to send one of Hans's WSPR transmitters into the stratosphere using party balloons. 

Listen to the interview here:

http://soldersmoke.com/FDIM17G0UPL.mp3

Visit Hans's QRP-Labs here:

https://www.qrp-labs.com/

Thanks Bob!  Thanks Hans!

Video: Farhan in the SolderSmoke Shack! BITX, JBOTS, McDonald Straw Sig Gen, uBITX, Sweperino and more!

Thanks again to Farhan for visiting us.  It was great to see his reaction to my humble implementations of his great designs.  I got him to sign my BITX17.  This was really a fantastic day for me and for my family.

Farhan Visits SolderSmoke Headquarters

Wow, today was an important day in the history of SolderSmoke.  Our friend -- and newly minted member of the QRP Hall of Fame -- Ashhar Farhan VU2ESE came to see us.  We had a great time.  I showed him all the many devices that I built based on his designs. 

We shot a video of the shack visit. I will post it to YouTube in a few days.

Thanks for coming to see us Farhan.  And congratulations on the richly deserved Hall of Fame Induction.

Homebrew History is Made: Farhan @ W7ZOI

Thanks to Wes W7ZOI for sending me the link to his page describing the visit of our friend Farhan.  I think this visit was a historic gathering of homebrew heroes and their groundbreaking rigs. Read all about it here:  http://w7zoi.net/Farhan-visit.html

Please help me convince Farhan to visit SolderSmoke HQ before returning to India!   Send him (or me) e-mails, texts, tweets, or just post messages of support below this post.   

WA8WDQ's Automated Filter Scanner (and a tip from VK1VXG)

Bill, Pete,

Thought I'd share today's activities.  Using Bill's excellent wire stripping technique, I was able to finish assembling my 7 MHz bandpass filter.  At this point, I'd normally terminate the filter then hook up the signal generator and oscilloscope to manually scan/observe the filter's response.  But today, I took a different tack.  Using the AD9851/Arduino signal generator I built last year coupled with the W7ZOI AD8307 Power Meter I built this year, I wrote some additional Arduino code to scan a block of frequencies while using the Arduino's A/D to record a level at each scanned frequency, thus characterizing the filter's response.  I also used a W7ZOI unidirectional TIA to boost the generator's output to within the full scale range of the A/D.  This setup is similar to the popular PHSNA project that has gained attention over the last couple of years.  The Arduino formats the data as CSV then feeds it into Numbers (the Mac Excel equivalent.) for plotting (see attached but please forgive the labels/legend on the plots as I didn't take the time to format them).  Unfortunately, my Arduino UNO is low on RAM so I'm only able to save a max of 100 scanned frequencies.  Even with the lack of resolution, as you can see, the output is definitely useable to get a sense of the filter shape and roll-off.  I'm now motivated to write some plotting code so I can get a more real-time output in lieu of the spreadsheet.  The output of the AD9851 seems pretty flat within several MHz as is the TIA, so the accuracy should be pretty good within moderately sized scan blocks.  Adding additional external FLASH (or moving to a bigger Arduino like the Zero) will fix the low resolution.  FYI - Arduino behavior when RAM is low can be very erratic!  It started crashing when I got close to the max available :(.  

If you haven't as yet, definitely check out the PHSNA project.  They've added a boat load of features beyond just scanning filter response . . . and at a fraction of the cost of a spectrum analyzer with a tracking generator.

Brad  WA8WDQ

Hi Bill,

I'm having trouble posting a comment in response to Brad, WA8WDQ's

automated Filter scanner project, and I'm hoping you wouldn't mind

passing this tip along.  It might be of use to other readers too.

Recent versions of the Arduino software include a Serial Plotter feature

that lets you graph directly from your arduino.  By making use of this

feature Brad wouldn't need to save data on the uno - just send it back

to the computer and graph in realtime.  It is a little primitive, but

still usable. I believe the plot window is 500 datapoints wide.

There is a nice tutorial on how to use it here:

http://www.instructables.com/id/Ultimate-Guide-to-Adruino-Serial-Plotter/

If you're in a hurry  and can survive with a bit of inaccuracy in your

sweep measurement you can also get away with using a simple diode

detector RF probe.  This is good enough for a "yep, that filter does

what I want" measurement, but not for measuring exact loss or 3db

bandwidth etc.

Hope that helps,

73s

Greg, VK1VXG

An NE602 SSB Design from China: The KN-Q7 by BA6BF

Allison KB1GMX alerted us to this rig.  Pete and I had been discussing with her various designs for SSB transceivers.  I recently completed an NE602 rig.

I really like the KN-Q7 (click on the picture above for a closer look).  The T/R switching is much simpler than my use of three DPDT relays.  It even seems simpler than the Epiphyte's switching of the BFO and VFO frequencies.  I also like the analog VFO and BFOs inside the 602s, but I think Pete would use an Si5351.  The AF amp muting circuit is kind of neat. 

I questioned the need for the extra IF amp for the receiver.  My rig just uses the two NE602s and an AF amp circuit from the BITX40 module (2N3904 and an LM386), and with this I can hear the band noise floor on 40.   But Allison points out that different bandpass and crystal filter have different losses, so with these components some additional gain may have been necessary. YMMV.

Here is the kit manual:

http://www.qsl.net/bd6cr/knq7amanual.pdf

Here is a video of VK2TPM putting his KN-Q7 on the air:

It is interesting that Peter notes a need for additional mic gain.  Some of the NE602 rig designs run an electret mic right into the NE602 balanced modulator with no mic amp. For a few days I had my amplified D-104 mic running into the NE602 in this way.  I too found that I was having to "loud talk" into the mic.  I put an LM741 mic amp in there and it fixed the problem. I wonder if later versions of the KN-Q7 included a mic amp.  I will check on this later.  

Three cheers for designer Shi Ke, BA6BF!