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Showing posts with label SDR. Show all posts
Showing posts with label SDR. Show all posts

Monday, February 12, 2024

Dean's Amazing Homebrew sBITX

 
I was kind of making fun of  it during SolderSmoke podcast #250, but later that same morning I had a chance to watch the KK4DAS homebrew sBITX in action, in person, and I must say, it was very impressive.  This may be the only homebrew sBITX in the world (please correct me if I'm wrong).  

In the picture above you can see the amalgamation of traditional superhet with modern DSP.  Even for an HDR guy like me, the result is really cool.  Once again, I experienced waterfall envy.  And the sBITX receiver sounds great. 

Dean has written up his experiences with this rig in a blog post.  Check it out for more info: 


Thanks Dean! 



Sunday, December 17, 2023

Make Your Own SDR Software! And, "Analog Man" by Joe Walsh of the Eagles (WB6ACU)


The above video appeared on Hack-A-Day this morning.  ON THE SAME MORNING, Bruce KK0S happened to send me this version of Joe Walsh WB6ACU's song "Analog Man." This version has the lyrics.  Thanks Bruce. 


I am currently struggling with some DNS server problems.  Dean KK4DAS is helping me.  In spite of many years on the internet, this DNS problem has reminded me that, like Joe Walsh, I am an analog man.  I mean, just take a look at my Mythbuster rig: (1382) Mythbuster for Lamakaan ARC - YouTube

But there are limits to my analog fanaticism.  First, while Joe proclaims that he is looking for an analog girl, I very luckily found a digital girl.  Elisa is quite digital.  Second, even though digital tech is not my thing, I am willing to accept its usefulness.  I mean, there is so much we wouldn't be doing if we were all "analog men." Like going to the moon

This is a hobby -- it is all for fun.  Whatever floats your boat, right?  Still, Joe's song reminds me a bit of the old "SPARK FOREVER!" that you can still see on old QSL cards. That's kind of sad.  I just recognize that my comfort zone is more analog than digital.  

Friday, September 15, 2023

HB2HB -- A Contact with Denny VU2DGR (video)

At first I didn't realize it was Denny.  On September 11, 2023 at about 2330Z I had walked back into the shack after dinner.  I think DX spots showed an Indian station on 20 meter SSB.  Without realizing who it was, I tuned him in on my Mythbuster rig, heard the other station sign off, and quickly threw in my call.  Denny came back to me right away, and I think both of us then realized that we recognized the call of the other station. Wow, it was Denny, VU2DGR, the Wizard of Kerala!   At the time of the QSO, I didn't have my phone with me; after we spoke, I went to get it,  so the video above captures part of Denny's subsequent contact. (You can also at one point hear Guapo barking.) 

Denny has been running a wonderful station that combines SDR gear with and HDR tube type amplifier and a homebrew Moxon.  

Here is Denny's station. The transceiver is a RadioBerry.  the amplifier and power supply are on the other table.  


Here is the homebrew tube-type amplifier.  This is the part of the station that really puts the HB in HB2HB! That's the power supply on the left and the amplifier itself on the right: 


That amplifier has three 807s in it, with a 6L6GC: 



Here's a video on the RadioBerry transceiver. 


Finally, here is Denny's magnificent homebrew 20 meter Moxon: 


Thanks Denny! 

Tuesday, August 15, 2023

The Wizard of Kerala (India) -- Denny VU2DGR -- SDR and HDR

 
His signal was just booming in on 20 meter SSB yesterday evening.  It was one of the strongest signals I've heard from India.  I wasn't able to get through the pileup, but I heard mention of a homebrew station at his end...  Sure enough a look at his QRZ.com site shows that a LOT of solder has been melted in his shack.  Both SDR and HDR stuff.  Tube projects including an 807 amplifier made from "components collected from the scrapyard." And a homebrew 20 meter Moxon.  Check it out: 


FB Denny!

Kerala is on the southwest tip of India.  It is something of a hotbed of technological innovation.  My only Indian contact using my current series of homebrew dual-banders was with VU3TPW -- Renju is also in Kerala. 

Saturday, May 27, 2023

Hans Summers G0UPL and his new QMX: The Bob Crane W8SX FDIM Interviews Part 1 (audio)

http://qrp-labs.com/qmx.html

We are very pleased and grateful to present this year's series of Four Days in May interviews by our FDIM correspondent Bob Crane W8SX.   Once again Bob did an outstanding job interviewing the FDIM participants. 

In this interview, the amazing Hans Summers talks about his latest QRP Labs kit, the QMX.  It is a combination of the QCX Mini and the QDX.  

Hans explains the M:  QMX. The M is for Marriage. Magnificent. Merger. Marvelous, many things like that. It’s what you get when you marry the mechanical and conceptual design of QCX-mini, with the SDR, multi-band digital implementation of QDX. Simply: QDX + QCX-mini = QMX. 

It has a very clever switching power supply that automatically adjust to prevent spurs and harmonics from the power supply from appearing in the band of interest. 

I was especially interested in his plans to implement an SSB option in future software updates.  Hans will use the same very complicated SSB generation scheme used in the trueSDX rig, but hopes to achieve higher performance and  improved signal quality due to the much more robust hardware of the QMX. 

Here is the interview: 

http://soldersmoke.com/G0UPL23.mp3

Here is the QRP Labs site about the QMX:  http://qrp-labs.com/qmx.html

Here is the QRP Labs web site: http://qrp-labs.com/

And here is a really wonderful and very current article by Hans on the evolution of QRP Labs and its rigs from 2010 right on up through 2023 and the QMX.  It is really interesting: 

http://qrp-labs.com/images/qmx/docs/fdim2023.pdf

Thanks to Bob Crane W8SX, Hans Summers G0UPL, and all of the FDIM organizers. 

Hans G0UPL-- Homebrew Hero

Wednesday, April 12, 2023

Farhan's sBITX -- Taking Orders! (Video)

It is really looking great.  Congratulations to Farhan for bringing yet another amazing rig to the amateur radio community.   

Order yours here: 

https://www.hfsignals.com/

Thursday, November 17, 2022

SDR Direct Sampling: The End of Homebrewing (as we know it)

I sometimes hear hams claim that our efforts to build simple direct conversion receivers are "very relevant" to modern technology and are "directly applicable" to today's communications techniques.  These hams will say that direct conversion receivers are at the heart of modern rigs. 

That's a nice thought, and it might have been true in the past, but I don't think it is true anymore.  

I think the future is what you see written on the black box (!) that encloses the receiver in the above video: "DIRECT SAMPLING RECEIVER."   In the recent past we did have two direct conversion receivers in the front end of SDR receiving systems.  These receivers produced I and Q signals that were fed into the computer (often via the sound card).  That was nice.  

But the writing has been on the wall for a long time.  There is no longer a need for all that direct conversion and I and Q.  Just put a fast Analog-to-Digital converter chip at the front end, convert the entire HF spectrum to a digital stream, and send that stream to your computer.  Or to another part of your "rig."  As in the ubiquitous 7300. 

I don't mean to be a Luddite here.  That big waterfall is very nice.  The receiver sounds great.  But I am a homebrewer and I prefer to build my own gear.  Ordering this black box on my phone,  having it delivered by Bezos to my front step, and then updating the driver, is not what I consider homebrew radio.  

A couple of things I spotted:  The Si5351 chip in the box -- at least one part was recognizable.  And the completely vertical skirts on all the SSB signals -- lots of 7300s out there.  

Hey, to each his own, YMMV, whatever floats your boat.  Just don't kid yourself into thinking that our beloved DC receivers are still somehow being used in these modern black boxes. 

Friday, October 28, 2022

SolderSmoke Podcast #241 Mars, Direct Conversion, PTOs and Glue Sticks, Anniversary of the BITX20, Multus Proficio SDR, Boatanchor Station, MAILBAG

The board I use to test DC RX circuits 

SolderSmoke Podcast #241 is available

Audio (podcast):  http://soldersmoke.com/soldersmoke241.mp3

Video (YouTube): (215) SolderSmoke Podcast #241 October 28, 2022 - YouTube

Introduction:

Back on Mars.  Opposition approaching.  I have a Mars filter.  And (like T.O.M.) a Mars globe. 

N2CQR DXCC done

SolderSmoke in the WayBack Machine

Sticker news

PARTS CANDY -- Don't Scrimp with a Crimp! 

Bill's Bench

School DC RX projects -- in Hyderabad and Northern Virginia. 

Direct Conversion Receivers -- Keeping it Simple, Learning a Lot.  A step beyond the Michigan Mighty Mite. Do we really need 100db?  Do we really need to shield VFOs?  Farhan's super-simple and stable Colpitts PTO.  Audio amps, 1000-8 transformers and rolling your own LM386

PTOs and Glue Stick PTOs.  Paul Clark WA1MAC. Brass vs. Steel bolts.  #20 thread vs. #28 thread.  Backlash Blues. The best Glue Sticks. 

2 meters and the VWS.  Bill has a Baofeng. 

SHAMELESS COMMERCE:  MOSTLY DIY RF

Pete's Bench

20th Anniversary of the BITX20   Pete's early BITX rigs. 

Computer Woes

The Multus Proficio SDR rig

Simple SSB in China  BA7LNN

Things of beauty: Tempo One, NCX-3 and a SBE-33

MAILBAG

-- NS7V is listening.

-- Graham G3MFJ sent SPRAT on a stick.

-- Nick M0NTV  FB Glue Stick and 17 Shelf videos.

-- Dino KL0S HP8640 Junior

-- Mark AA7TA   Read the SolderSmoke Book

-- Steve EI5DD Connaught (Ireland) Regional News

-- Dave K8WPE  Planting the seeds of ham radio interest

-- Peter VK3YE Ruler idea on PTO frequency readout

-- Michael AG5VG Glue Stick PTO

-- Tobias  A polymath with UK and Italy connections.  And cool tattoos.

-- Alain F4EIT   French DC receiver

-- Michael S.  was in USMC, working on PCM/TDM gear

-- Alan Yates writes up Amazon transformer problem

-- Todd VE7BPO,  Dale W4OP, Wes W7ZOI

-- Farhan VU2ESE sent me an sBITX

-- Todd K7TFC   The Revenge of Analog

-- Jim Olds    Building QRP HB gear  


The Multus SDR rig Pete discussed

The older rigs Pete mentioned


My version of DC RX that Farhan is working on

My PTO with VK3YE's ruler frequency readout


Saturday, August 27, 2022

SDR on a Breadboard -- But Isn't This an Old-Fashioned Fantasy?


Nice video, but I'm afraid it is a bit of an old-fashioned fantasy.  It would be nice to think that our beloved analog mixers and direct conversion receivers still have a place in the SDR world.   That may have been true a few years ago when we were using soundcard-based SDRs.  But today we just put an Analog to Digital Converter at the antenna, do "Direct Sampling," create a digital stream, and sent it to the CPU for processing, right?   

Sometimes we think that we can show younger people how our older tech (Direct Conversion receivers) is STILL relevant in the age of SDR radio.  But I can just hear them scoffing at this notion, pointing out that I,Q-to-soundcard front ends have gone the way of the dinosaurs, and all we need now is an ADC and a CPU.  

But hey, I am an HDR guy.  Am I missing something here?  

Thursday, July 7, 2022

Would this Really Be Homebrew?

 
Hack-A-Day has an interesting post about an FM Broadcast radio project.  I took a look.  The Github page has the schematics for the hardware.  For me, the thing is, there is just not a lot there.  It is a bunch of chips.  The FM Tuner IC is the heart of the project.  With that one you have to dig down to see that it is a digital processing chip:


All of the action -- all of the magic of radio -- is locked inside those little SMD chips.  I suppose if you were skilled enough to write the software or to significantly modify it,  you'd get closer to the experience of homebrew radio,  but very few of us have those kinds of skills -- we just download the software, then struggle to get it into the chips. 

And sure, you could struggle to solder those chips to a PC board, but really, why bother when 99% of the components are already inside the chips?  You should just buy a board with the chips on them and with the software already loaded.  There you have it:  the store-bought appliance is really, really close to the supposedly homebrew receiver. 

But hey, to each his own.  This is a hobby and it is all for fun.  I just think I have more fun with old-style, analog, discrete component HDRs.  YMMV.     

Friday, June 17, 2022

SolderSmoke Podcast #238 -- SolderSmoke Shack South, Cycle 25, Chiquita Banana Radio, RCA, HQ-100, Mate Mighty Midget, Sony SWL RX , Mailbag

SolderSmoke Podcast #238 is available:  http://soldersmoke.com/soldersmoke238.mp3

TRAVELOGUE:  

Cathartic decluttering:  Bill preparing for future winter travel to Dominican Republic.  Will build SolderSmoke Shack South.  Dividing everything up:  Rigs, parts, tools, supplies, antennas, test gear.  Everything.  

OUR SPONSOR:  Parts Candy.  
https://www.ebay.com/usr/partscandy  Premium quality test leads! Hand cut, hand crimped, hand soldered, these will become your new favorite test leads GUARANTEED!

PETE'S BENCH:

-- Cycle 25 better? – Out here on the left coast – it is not evident
-- Chiquita Banana and the US Navy in early ‘wireless” operations.  Why RCA was created by the US Navy in 1919.
-- Update on the MAX2870 –someone has written the code to make it work with the Raspberry Pi and the QUISK SDR software
-- Field Day prep

SHAMELESS COMMERCE DIVISION:
 
Bill needs your help:  
-- Please watch his YouTube videos.  The longer the better!  Success based on hours watched. Great to have on while you are working in the shack. Just go to YouTube and search for the SolderSmoke channel. Or:  SolderSmoke - YouTube
-- Please put links to the SolderSmoke blog on your websites and blogs. 
-- How to USE the SolderSmoke Blog: Propagation, shopping, other sites... 
-- Please put comments under the articles on the SolderSmoke blog.  We like comments and dialogue. 

BILL'S BENCH:

-- Repair of the Sony ICF SW1 shortwave receiver.  Bad electrolytics.  Number Station receiving device? 
-- HQ-100   Q-Multiplier. BFO Switch. AVC.  Noise Limiter limitations.  Dave K8WPE: Old Radio Lessons.
-- MMMRX: Detector circuit. Alignment. Muting. On the air (40 AM with DX-100) 

MAILBAG: 

-- Bob Crane W8SX -- Great interviews at FDIM. On the SolderSmoke Blog. Thanks Bob! 
-- Dave Bamford W2DAB -- Stickers on the Upper East Side of Manhattan.  FB Dave! 
-- Farhan VU2ESE:  LADPAC software now available through W7ZOI' site.  
-- Lex PH2LB: Stickers in a Netherlands pub.  
-- Dave K8WPE Michigan Mighty Mite links.  Old Smoke idea. On the SolderSmoke blog. 
-- Rich WB4TLM was in the electronics class of CF Rockey W9SCH. FB. 
-- Dean KK4DAS Working on  his dad's HQ-170A. VWS maker group on mixers. 
-- Grayson KJ7UM -- Mixology article in ER. 
-- Pete Eaton -- Farhan's new analog rig: Daylight again!  Standby for more info from Farhan. 
-- Will KI4POV New HB Al Fresco single conversion superhet.  FB. 
-- Alvin N5VZH. Shep's "I Libertine."  Yes.  I laughed, I cried,  It changed me. 
-- Chuck KF8TI.  Mr. Wizard!  
-- Steve N8NM on the mend after some routine maintenance. 
-- Ben AB4EN is listening and likes the podcast -- Thanks Ben. 

May 1939 QST


Wednesday, June 8, 2022

SolderSmoke FDIM Interview: Jack Purdum W8TEE on the Challenges of Decoding CW by Software

 

In his interview with SolderSmoke correspondent Bob Crane, Jack Purdum made some very interesting comments about the challenges of decoding CW with software. He notes that W1AW's code practice CW is perfect, but that below 18 wpm, they deliberately insert a "Farnsworth Delay" that increases the spacing between words -- this complicates automatic CW decoding.  

Jack also talked about the distinctiveness of different CW operators.  Jack  noted that W1AW has no real "fist" in this sense:  "It has the personality of a stick!" 

Jack mentioned that Pete Juliano had been reading book on SDR radios that Jack and Al Peter recently published:  https://www.amazon.com/Software-Defined-Radio-Transceiver-Construction/dp/B09WYP1ST8/ref=sr_1_1?crid=2KPYAMPOW5P6J&keywords=DR.+Jack+Purdum&qid=1654598559&sprefix=dr.+jack+purdum%2Caps%2C40&sr=8-1  

Here is our correspondent Bob Crane's interview at FDIM 2022 with Jack Purdum: http://soldersmoke.com/2022 W8TEE.mp3


Thanks Bob.  Thanks Jack.

Monday, June 6, 2022

SolderSmoke FDIM Interviews: Hans Summers G0UPL Talks about the QDX and His New Balloon Tracker

 

Thanks to Bob Crane W8SX for getting us this wonderful interview with Hans G0UPL.  Its really amazing to hear Hans talk about how many QDX rigs and Baloon Trackers have been sold by QRP Labs, and how quickly they sell.  Really great.  Hans's comments on the realities of the parts shortage was also very interesting. 

Listen here (about 7 minutes):  http://soldersmoke.com/2022 G0UPL.mp3

U4B Balloon Tracker 

SolderSmoke FDIM Interview with Farhan VU2ESE -- The sBITX is Coming!

Bob Crane W8SX --  our correspondent in Dayton/Xenia --  once again collected interview with FDIM presenters. Thanks Bob!  Here is his talk with our friend Farhan:  

http://soldersmoke.com/2022 VU2ESE.mp3

Here is a great post on the sBITX (May 30, 2022) from Farhan's web site: 

https://www.vu2ese.com/index.php/category/uncategorized/

Here is Farhan's amazing presentation on the sBITX at the 2021 FDIM: 

https://soldersmoke.blogspot.com/2021/11/farhans-amazing-knack-story-from.html

Saturday, May 7, 2022

SolderSmoke Podcast #237 is available: TV Show! No! W9YEI's 1939 TV. 1712 Rig. HQ-100. New SDR Rig and Book. JF3HZB's VFO Digital Dial. FIELD DAY! PSSST. MAILBAG


SolderSmoke podcast #237 is available:  http://soldersmoke.com/soldersmoke237.mp3


Travelogue -- New York City!  Stickers!
And about that trip to Los Angeles for the SolderSmoke Cable TV show... 

Well, it fit in well with SolderSmoke's UNFORGETTABLE appearance on the Oprah book club.
And TechieTatts? Daughter worried about listeners rushing to get tattoos -- A risk we were willing to take.

https://in.pinterest.com/padmakumar10/techie-tatts/

This episode is sponsored by PartsCandy.  GREAT test leads: https://www.ebay.com/usr/partscandy

Bill's Bench

Tracking down Johnny Anderson's 1939 or 1940 homebrew TV receiver.

https://soldersmoke.blogspot.com/search?q=Anderson
Working with Joh DL6ID.
Jean Shepherd's January 1973 description.
FlickLives web site and Steve Glazer W2SG have lots of info on Shep and his friends.
Internet allows us to look at TV articles that were being published.
We've concluded: Probably 1939 or 1940, using an RCA 913 1 inch CRT tube. 

Lots of ideas from IRE Journal, QST, and Gernsback magazines.
Quite an achievement! Amazing how much pre-war TV progress there was.  

17-12 rig
All boxed up and working DX!
Figured out how to display both 17 and 12 on the same LED. https://www.youtube.com/watch?v=kAmmFZyFu8w
Drain protector for speaker cover. Copper tape to cover horrible cabinet making.
I think I need a Hex Beam.

Hammarlund HQ-100
Needed some maintenance.
I started to look more closely at it.
Got the Q-Multiplier to work -- it really adds a lot on CW.
Makes me feel guilty about all the QF-1s...
Using the 100kc calibrator with a 455 kc crystal as a BFO,
keeping Q multiplier below oscillation point.
Moved the BFO switch to the front panel. Helps a lot.
Need to fix the S-meter AVC circuitry.
Much more sturdy than the S-38E.
S-38E 1957-61 $54.95 5 tubes.  AC/DC.
HQ-100 1956-60 $169  10 or 11 tubes.  Power supply,  regulator.
You get what you pay for.  

Pete's Bench

Jack Purdum and Al Peter's new SDR rig and book (featured on the SS blog Amazon ad).
JF3HZB's beautiful digi VFO.
Backpack antenna for Field Day?  
Pipsqueak Disaster -- Too simple?
Peashooter Eye Candy.
Build Something Different.

MAILBAG

James W0JKG CBLA -- Others are building MMM too!
SM4WWG // Jörgen  Wonderful message.  Joined GQRP.  No longer "wrong."
Dennis WC8C Libraries for Max2870 board.
Jack NG2E  Progress on the Right to Repair movement. 
Jim K9JM  Someone cutting into our business with Solder candles!  
Chuck  WB9KZY Correctly identified the location of the IBEW sticker.  As did Dan Random.
Dave Bamford (who lives nearby) suitably impressed. 
Farhan wrote to us about a video on Don Lancaster.  Homebrew keyboards!  Yea!
Dean KK4DAS  QRP to the Field.  HB2HB 40 SSB   QRP  I feel virtuous.  
Todd K7TFC likes my ingenious use of the drain screen as the speaker protector on the 17-12 rig. 
Todd  had good thoughts on granular approach to homebrewing as seen in the Don Lancaster video.
Lex PH2LB HORRIFIED by my reverse polarity protection circuit.  This is a touchy subject! (as is WD-40!)
Rogier PA1ZZ sending great info on SWL and numbers stations.
Jesse N5JHH -- The guy who made the IBEW stickers -- Liked the NYC stickers. 
Steve N8NM has a new antenna article on his blog: https://n8nmsteve.blogspot.com/
Randy AB9GO Agrees -- Can't GIVE old 'scopes away. 
Dino SV1IRG Liked the 17-12 rig videos. 
Steve Hartley G0FUW Murphy's Law of Enclosures. 
Ralph AB1OP FB on the 17-12 Rig. 
Roberto XE1GXG --Our correspondent in Guadalajara. Petulant, irritable people on the computer scene.

Have some gear looking for a good home:   Tek 465 'scope from Jim AL7R W8NSA.   SBE Transceivers.  Windsor Signal Generator.  Let me know if you are interested and can either pick up or arrange shipping.  



John Anderson W9YEI Homebrew Hero

Tuesday, March 1, 2022

Dennis WC8C's FB Homebrew 6 Meter Rig -- Any Ideas or Suggestions?

 
Dennis WC8C is the event coordinator for the radio club in Michigan that I recently spoke with.  He mentioned to me that he was working on a homebrew 6 meter rig.  FB Dennis.  I see lots of tribal wisdom in your approach, especially in your decision to do this in a stage-by-stage modular form. 
Dennis's rig is obviously a work in progress, so if anyone out there has any helpful hints (especially on the carrier suppression and on the testing for spurs and splatter) please share them with him via e-mail or blog post.  

The files on Dennis's rig are on GITHUB: https://github.com/soligen2010/6_Meter_Transceiver

Thanks Dennis!  
----------------

This is my 6 Meter homebrew transceiver, currently work in progress.  It is a single conversion super –heterodyne design.  I constructed each stage independently with SMA connectors.  This is so I can re-make sections as needed, and will allow me in the future to swap sections to experiment with alternate designs.  The VFO and BFO are controlled using a SI5351 with an Arduino micro controller.  I currently have separate SI5351 modules for VFO and BFO because I suspected issues with cross-talk.  These issues may not actually be real, so once I am happy with the performance, I will test again with just one module to see if it is OK.  The Power Amp is still on the to-do list, so output is well under 0 DBm

The Blue boards were designed by me and ordered on-line.  The other boards I etched myself.  Construction is mostly surface mount because I find it easier than drilling all the holes.  SMD components are mostly 805 and 1206 size. Transistors are SOT23.

The Band Pass filter is a 5 coil design made with air-core inductors.

3 bi-directional termination insensitive (TIA) amps are used (blue boards).  Total RX gain is about 44db.  Total TX gain is about 16db.  Each board has its own independent RX/TX switching circuitry (mosfet based) and is fed with +12.5, GND, and RX/TX logic signal from the Arduino (3V logic and up will work)

The Mixer and modulator are both Diode Ring mixers.

The 12 MHz SSB filter is a crystal ladder filter similar to the one used in the uBitx.

The Mic and audio pre-amp (also a blue board) is made on a modified TIA amp board.  I had 10 of these boards made, and the needed circuitry was largely the same, so I modified the board with a rotary tool and jumpers.

The Audio amp is a PAM8403 module and drives a headset.  I did make some modifications to the module so it runs in-spec and to eliminate the power on audio pop.

The challenges I have been having are mostly related to spurs, splatter, carrier suppression and TX audio quality.  I have been gradually tweaking these things to improve operation before I start on a power amp.  My IF is 12 MHZ, and I was using the LSB side of the crystal filter because it is sharper (VFO 62 – 66 MHz) but have recently changed over to the USB side of the filter (VFO 38 – 42 MHz).  This eliminated the spurs I was seeing near the pass band.  I still need to make some adjustments to the crystal filter as it is too broad.

I still have some splatter and audio quality seems low, but I am starting to doubt my test setup.  I see the splatter on the RTL SDR, but I don’t see it on the Tiny SA.  The spatter happens at ~160 KHz intervals.  I am hoping to find someone local with a better spectrum analyzer to help me verify if it is the rig or my SDR dongle/test setup.

The modules to the side of the picture are my rejects/experiments.  The one covered in copper shows how I eventually will shield all the modules.  I 3D printed a cover for the board, when wrapped it with copper tape, soldered to the bottom ground plane.  The one shown is a diode ring modulator.  For some unknown reason the carrier suppression is rather poor.  I had previously made a junk-box modulator that had much better carrier suppression.  I don’t know why it is better than the one I more carefully made for the radio, but until I figure it out, I am using the junk box version.  The junk box modulator uses unmatched schottkey diodes, whereas the “final” one uses a 4 diode SMD package because I wanted them matched – I thought this would be better, but maybe not.

Saturday, February 19, 2022

Pete's Eclectic Approach to the Pea Shooter, San Jian counters on Analog VFOs, Non-Restaurant Menus

I liked Pete's comments on the various (analog, digital, mixed) approaches to homebrew: 

http://n6qw.blogspot.com/2022/02/2022-return-to-peashooter-build.html

http://n6qw.blogspot.com/2022/02/2022-peashooter-20m-compact-ssb.html

I too have San Jian digital counters watching the stability of analog VFOs (DX-100, HQ-100, Mythbuster). 

Variety is the spice of life!  

I also liked Pete's comment about the fellow who does on-the-air menu counseling for FTDX-3000 owners.  I sometimes run into guys on the air who want to do something similar with my simple homebrew rigs.  They start by making comments about my audio -- they will usually say it is "too high" or something like that.  Especially when I'm using the separate transmitter and receiver (which have to be "netted" imprecisely by ear), I have to explain that maybe resort to their RIT control would help.  If they persist, I sometimes have to tell them that how my rig sounds depends A LOT on the placement of the carrier oscillator relative to the passband of the crystal filter (most recently, the filter from the 1963 Swan 240).  Most of them have never had to do that kind of adjustment, so the "technical discussion" usually ends at that point, with my interlocutor saying 73, and presumably moving on to someone whose rig has menus to fiddle with.  (Recently heard audio techno term: "massaging the codec.") 

To each his own!    


Wednesday, January 12, 2022

Looking at the Galaxy's Spiral Arms with a Dongle, a Raspberry Pi,and a Homebrew Antenna


I told Farhan that the world NEEDS a homebrew Raspberry Pi observatory at Lamakaan in Hyderabad. They are on it.  

This looks very do-able.  And fun.  And UHF.  And SDR. And Raspberry Pi. 

I'd like to build one too.  I was encouraged by the video demo -- it was done in Alexandria, Virginia, very close to where I live. 

A while back I was lamenting to Dean that I reluctantly threw away a DISH or DIRECT TV  satellite TV antenna.  I worried that I had discarded something that would have been useful for radio astronomy.  Turns out I didn't need it.   This video and the associated .pdf shows how to look at the galaxy with a simple homebrew (Home Depot!) horn.  



Thanks to Thomas K4SWL of the SWLing Post for alerting us to this. 

Sunday, December 12, 2021

Hack-a-Day: Has DIY become Click-and-Buy?

https://hackaday.com/2021/12/11/has-diy-become-click-and-buy/


Hack-A-Day today asks about the boundaries between DIY construction and the use of purchased, completed electronic components.   This is closely related to our long-standing discussion of what really constitutes "homebrew." 

Is it really homebrew if you buy a bunch of  already-stuffed PC boards and connect them together?  

Is it really a homebrew receiver if 90% of the components are inside one chip? 

Is it really homebrew if most of the signal processing is done in your computer (that you definitely did not build)? 

The comments below the article are interesting.  There we see some of the same arguments used by ham radio operators who are more inclined toward click-and-buy. They argue that since none of us are making our own resistors and transistors, we are ALL therefore click-and-buy people, so we should just get over it and pull out the credit cards. Some commenters carry this to extremes and ask if the real homebrewers are out there mining the copper for their wires.  

The debate seems to spill over into the software area:  One person asks if it is really DIY if you are using software libraries that contain code written by someone else.  Or to be truly DIY should you write all of your own code in assembly language?    

There is one very insightful comment about hams who are inclined to disparage the homebrewing that they did in their youth.  We often hear this:  "Oh, I used to build my own gear, but now-a-days I just buy commercial transceivers -- they are so much better."  As if homebrewing was a folly of youth, something that they grew out of (and up from) as they became able to afford the latest ham radio appliances.  As if homebreweing were a regrettable thing that was done only out of necessity.   This is, I think, sad.  

I think I'm a lot closer to the traditional concept of DIY than I am to click-and-buy.  I still prefer LC oscillators to Si5351/Arduino combos.  I prefer traditional filter rigs to SDR rigs.  And I prefer to make my own crystal filters.  I don't like to use ICs unless I really understand what is going on inside them (so I can be comfortable with an NE602 or an LM386, but I'm not comfortable with a CPU chip that may have millions of transistors in it).  But I am not homebrewing my own transistors nor am I mining copper. 

What do you folks think about this? 

Tuesday, November 2, 2021

Farhan's Amazing Knack Story: From a Boyhood SW Receiver to the Design of the sBITX SDR


The presentation starts at about the 4 minute point. 

I think if I were only allowed to watch one YouTube video in the next year, I'd make it this one. 

In this amazing RSGB video, Ashhar Farhan VU2ESE takes us back to his earliest days as a radio amateur.  He tells us about his very early desire to build radios, his early projects, and his personal evolution as a designer and builder,  from a simple DC receiver, to the BITX, the Minima, the uBITX and now the hybrid HDR/SDR sBITX.  

There is a lot of  homebrew wisdom and tribal knowledge in this video. And we learn so many hitherto unknown details about the rigs that have become so important to us:  

-- Farhan had the EMRFD book with him on the famous flight from Sweden to India during which the BITX was designed. 

-- We learn about the origins of the BITX oscillator circuits, and that the VFO and BFO are essentially the same.  

-- I was really pleased that Farhan included a picture of my HB BITX17 rig in his presentation. 

-- Farhan discusses the difficulties he faced in obtaining needed parts in India. 

-- We actually see the nylon washers that Farhan used in the original BITX. 

-- Farhan discusses his early system for measuring coil inductance. 

-- In addition the huge contribution of EMRFD,  Farhan talks about how he was helped by Pat Hawker G3VA's writing, and the ARRL's SSB Handbook. 

-- Farhkan talks about his Tex 465 'scope and his building of a Spectrum Analyzer. 

-- We see his evolution to dual conversion. We see the conceptual birth of the Minima and the birth (thanks Wes!) of the TIA amps.  I didn't know about the HF-1.  Then Farhan designed the uBITX and now the sBITX.  

 -- Farhan talks about his practice of taking the pictures of new rigs with the new rig sitting atop the book that was most important in its design and construction.  FB. 

-- I was really blown away by Farhan's presentation of how the uBITX advertisement was inspired by and in many ways based on the Heathkit ad for an HW-101.  Amazing. 

-- I learned a lot from Farhan's discussion of SDR theory.  I pledge to spend more time with this.  I really like Farhan's hybrid HDR/SDR approach. 

-- But I have a question:  Farhan seems to say that we'd need a big expensive GOOGL computer to do the direct sampling HF SDR.  But doesn't the little RTL-SDR do just that?  Without a GOOGL?  

-- Great to see Wes's AFTIA being used in the sBITX.  

-- Really cool that Farhan has his mind on VHF transverters when designing the sBITX.   I liked use of the TCXO module to free up one of the Si5351 clock outputs.   FB.  And great to include an idea from Hans in this rig. 

Thanks very much to Farhan (who stayed up until 3 am to do this!) and to the RSGB for hosting.

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