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Monday, May 22, 2017

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.

Sunday, May 21, 2017

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.

Wednesday, May 17, 2017

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:

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.   

Tuesday, May 16, 2017

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:

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,


Greg, VK1VXG

Tuesday, May 9, 2017

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:

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!

Sunday, May 7, 2017

Still Photos and Slow-Motion Video from Shenandoah Rocket Launches

The above slow-motion video of launch #3 is pretty cool.    You can very briefly see a bit of the yellow parachute deploying. The best video from this flight is at the end, as the rocket floats over the farm buildings and comes perilously close to landing on top of one of the silos.  I put some snap shots at the end. Five other launch videos are available here:


Launch crew visible -  N2CQR with hat, Billy to his left. Randy's son (next to Billy) launches the rocket!

Smoke trail back to the launch pad.

MECO! And you can see the smoke trail up to the rocket

The view across the Shenandoah Valley.

Skyline Drive runs along that ridgeline

Here is a hunk of flame-proof wadding ejected by the rocket.

We were afraid it would land on the silo.  It was close.

GREAT BALLS OF FIRE! And a smoke trail.  

Part of the deploying parachute is visible.

Saturday, May 6, 2017

SolderSmoke Podcast #196 Rockets, Pete's EXPULSION, SDR, DiFX, '602 rigs, T.O.M.

View from rocket. I'm in front of the swing-set, with hat on. Billy to my left.

SolderSmoke Podcast #196 is available.
5 May 2017

Shenandoah Rocket Launch -- With video!

Pete and the QRPARCI HOF: We thank you for your support! 
Note the strange seasonality of these kinds of events... Always in the Springtime...
April is the cruelest month. Especially the FIRST DAY!  

Feel Tech Follow-up -- the DC blocking cap issue.

HBTV?  Roku Challenge? 

A tube of Desitin?  Why?

SDR Misadventures. 
SDR on a tablet  Just like WA7HRG
Pi Day   More RaspPi Linux observations  TOO HARD
The problem of Si5351 and updated libraries -- old sketches don't work!
My SDR question: If we go with direct sampling, no need for I and Q at front end  No image problem, right?  But why is there often a digital I and Q in the direct sampling receivers?

Getting RF in through the DDS jack.

Electric Radio:  Reading from the history of SSB.  And from the T.O.M. article
Joe Carr K4IPV : Homebrew Hero from Falls Church Va.  Any more info on him?

Pete's newest DifX
Pete's new digital scope.

Bill's NE602 RIG, Epiphyte History.
He put AADE crystal filter impedance match circuits in backward  That's why he needed RF amp. Duh.
The perils of a crowded box 
Building RF amp board (BITX Module design) for the NE602 rig.
NE602s do not put out a lot of power. uW
BITX Module Amp circuits very stable.
Chassis as the heat sink.
Mic amp?  We don't need no stinkin' mic amp!  But yes, we do. 741 on the way.

Parts on e-bay very expensive!  Back to the hamfests. On to Manassas!

Congrats to Tony Fishpool G4WIF, who received the Don Cameron, G4STT, Award for an outstanding contribution to low power amateur radio at the RSGB AGM meeting in Cardiff.

Designer: Douglas Bowman | Dimodifikasi oleh Abdul Munir Original Posting Rounders 3 Column