Videos from Mike AG5VG -- His Homebrew BITX Rigs

Here are two great videos from Mike AG5VG showing his two homebrew receivers in action.  (The transmitter portions of Farhan's circuit will come later.) See yesterday's post for more details. 

On the video above (40 meters) 

-- I love that speaker.  

--  The enclosure and the reduction drive for the VFO is really great.  FB OM. 

-- Very cool that Mike captures a 40 meter QSO with "Wild Bill" ZS6CCY in South Africa, someone who we've spoken to many times, often on the long path, sometimes from Mozambique. 

-- I like how Mike demonstrates the effect of removing the antenna.  You can definitely see what we mean when we say you should be able to "hear the band noise."   

  

Above you see the 20 meter receiver in action.  You can see one of the physical benefits of using a wooden base:  You can easily mount connectors, switches and tuning controls using just pieces of copper-clad board screwed into the wood.   This is what I am doing with my latest BITX 15-10 rig. 

For the tuning of the VFO, it looks to me as if Mike has a large "main tuning" control in the center, with a smaller "fine tuning" or "bandspread" control off to the left.  Does that smaller control work with a varactor diode or with a smaller variable cap?  Also, to the right of the main tuning control we see a 3 pole switch.  Is that switch putting additional L or C into the VFO circuit to move the frequency around?  These techniques would all be quite valid;  Mike demonstrates that there are many ways to skin a cat (or tune a VFO!) 

Mike:  Please send more info. 

South African Homebrew: ZS4L's "Griffin" 40 Meter SSB Transceiver

 

That's William, now ZL4L, and his homebrew 40 meter SSB transceiver.  He has given the rig a wonderful name from Greek mythology:  The Griffin (see below).  I talked to William this morning on 10 meter SSB.  I mentioned my homebrew rig and to my surprise (this doesn't happen much) he asked for more info.  Then he told me about his own homebrew creation, The Griffin.  FB William! 

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

From William's QRZ.com page (https://www.qrz.com/db/ZS4L):  

I have always wanted to build a homebrew transceiver-and recently I completed my pride and joy-a 40m SSB/MCW transceiver-I call it the ZS5WC "Griffin"..

"Griffin"..-well --if you know greek mythology you will find that it defeated much greater adversaries in battle.(to cut a long story short..)
The parallel I am getting at is..Big commercial rigs can be taken on by a rig constructed at home-and with great success!.
Sure, it does not have the bells and whistles of a 1000mp-but the TX audio is good, the RX is great , and the SMILE factor-even with all the little quirks is off the scale!..
Basically it is a single conversion superhet-4 tuned BPF stages,ATT, Gain control stage ahead of 1st Rec. Mixer/Bal. mod (NE612) , Xtal 10mhz homebrew filter,2 transistor feedback amp, second gain control stage,2nd mixer/BFO (NE612)-On TX to PA board-4 transistor pre-amp, IRF510 mosfet PA, LPF and RX /TX relay. ON RX to TL072 audio pre-amp, Spits to AGC/S-meter amp-(741 and BC107's) and audio amp TBA820m.
ALC is done on AGC board as well with BC107 back to back to AGC bc107.
The S-meter drive is developed in the emitter leg of the AGC BC107-simple series pot to calibrate-no zero pot is required..(Works great!)
There is a volt control PCB too, with RX/TX switching.
On the main PCB there is a phase shift osc. for MCW and sidetone. Alc is adjustable from front panel from 1/2 watt to 5 watt.Rit is included in the Hartley osc. circuit and readout is done with a pic and two line LCD disp.(from AADE.com..)
Freq. drift from warm is 200Hz down in frequency then swings round and stabilises close to start freq.
Rit is good for around 5Khz swing.
Amp keying is available on the back panel, as well as an aux. 12 supply-(To run a homebrew noise squasher and amp..)

https://www.qrz.com/db/ZS4L

An Especially Good (Old) SolderSmoke Podcast

February 22, 2008    

-- We were in Rome.  

-- I read a 1931 QST ad sent to me by my fellow "Hambassador" David Cowhig, WA1LBP; David was in Okinawa when he sent it. 

-- I describe Wes Hayward's comments about Pat Hawker, G3VA. 

-- I talk about getting on the air with my HW-8 (after fixing it!), re-tubing my Drake 2-B, and putting up a 30AWG antenna in Rome. 

-- I describe meeting up with Roman hams (including amplifier manufacturer I0ZY!) and visiting the local radio club.

-- The Science Museum in Florence, Italy. 

-- DSB from Rome with my NE602 rig. 

-- Tony Fishpool and Graham Firth's Test Gear book. 

-- An important corollary to Murphy's Law. 

-- Listening to SolderSmoke from safari, under the Southern Cross in South Africa. 

-- Ron Sparks calls in from Dubai. 

You can put on a playlist of all the SolderSmoke podcasts here: 

(12) Videos of the SolderSmoke Podcast - YouTube

 

Old Smoke: SolderSmoke's Early Theme Music from W8MOJ, Boatanchors in South Africa, and Homebrewing in Dubai

Over on the SoulderSmoke YouTube channel I have been putting up some podcasts from days-gone-by.  Recently they have been from our last days in London and our earliest days in Rome.  We have had a nice series that includes "Echo-calls" from Andy ZS6ADY  in South Africa, talking about old tube radios (Boatanchors) in that country.   Soon we will start a series that includes Echo-calls with Ron Sparks AG5RS, who was homebrewing in Dubai. 

But these early podcasts begin and end with some very distinctive techno-music from Mark O Johnson, W8MOJ.   Here is our old blog post that describes Mark's musical contribution to SolderSmoke.  Thanks Mark!  https://soldersmoke.blogspot.com/2011/01/tech-details-on-soldersmokes-theme.html

SolderSmoke Podcast #73 Jan 2, 2008 -- AA1TJ Circuits and Poetry, Mixers, CW, Straight Key Night at WA6ARA, Boatanchors in South Africa with ZS6ADY (Part 1)

This is the first in a series of four podcast that include Echolink conversations with Andy ZS6ADY about old tube radios (boatanchors) in South Africa.  Click on the YouTube link above to listen. 

January 2, 2008 SPECIAL NEW YEAR'S EDITION AA1TJ's circuitry and poetry. Homemade tubes. Book Review "Early Radio" by Peter Jensen. The Vatican's antennas. Google Earth flight simulator. Mixer madness continues (now in LTSpice). Mars-asteroid collision? Bollywood: The BITX-20 connection. BANDSWEEP: Straight Key Night at WA6ARA. ECHO-GUEST: Andy, ZS6ADY, South African Boatanchor fan. MAILBAG: Jake N4UY(NOVA QRP), Steve G0FUE (Bath Build-a-thon), Nigel M0NDE

No Main-Tuning Reduction Drives in Stock Drake 2-Bs -- But why no mod articles?

Alan Wolke W2AEW and I were recently discussing our Drake 2-Bs (again!). Both of our receivers have reduction drives between the main tuning control and the string mechanism that moves the main tuning capacitor.  I wondered if these were the results of modifications by previous 2-B owners.  I vaguely recall that my Elmer -- Hilmar WB2NEC -- had done this sort of mod. 

OM Wouter ZS1KE sent me this very illuminating photo of the inside of his Drake 2-B.  No reduction drive.   So Alan and I obviously have modified 2-Bs.

One thing that puzzles me:  I can't seem to find a single article that describes this apparently common mod.  Does anyone know of an article in the ham magazines that might have described how to do this?  

Thanks again Wouter!  

QSX! Hans Summer's New SSB Rig Revealed in South Africa

I liked this video.   I liked Hans' description of his mechanical skills, and the way he has at times become a "human CNC machine."  

This seems like a much more sophisticated rig than the QCX.  I may be wrong, but  QCX seemed to be essentially an analog phasing rig with a narrow CW audio filter.  I kind of expected the SSB version to be a QCX with broader filter, but QSX is a different,  more sophisticated, SDR rig. 

Once again, three cheers for Hans Summers.  We should all pay him to go to those summer conventions -- every time he does, something new and important for ham radio comes out of the trip.  

SolderSmoke Podcast #193: BITX 40, OLEDs, KWM-4, Noise Abatement

SolderSmoke 193   28 Jan 2017

http://soldersmoke.com/soldersmoke193.mp3

Report from Pete on BITX 40 Session with California radio club.

Update on the BITX40 Module Revolution
-- Check out the BITXHACKS page.  Send in contributions.
-- BITX20 mailing list very active.
-- Raduino!
-- Interview with Farhan with W5KUB --   Eliminating the commercial gear.
-- BITX 40s on the beach in Australia.  FB

Bench Reports:

Pete:
-- Color Displays!
-- KWM-4
-- OLED MADNESS!

Bill: 
-- Fixing up the old HT-37   HT37 to HT37 QSO with W1ZB
-- Dabbling in VHF with Ramsey Aircraft band receiver.  NOT FUN.
-- Going all IC with Si5351 OLED NE602 rig.
-- BANDSWEEP
-- OLED Noise and the Active Decoupling solution.

Using LTSPICE as a diagnostic or understanding tool.

Of Waterfalls, Homebrew Rigs and Casual Critics on 40 meters. Words of Wisdom from W8JI.

LEXICON:  HAYWIRE   TOMBSTONE    BIKESHEDDING from Todd K7TFC

Some great recent interviews by Eric 4Z1UG:
Ian G3ROO  Origins of ROO   Regen at age 8
Hans Summers G0UPL     Balloons!   NO COMMECIAL GEAR
David White WN5Y          ELECTROLUMINESCENT  RECEIVER EXPLAINED
Rob Sherwood NC0B 

MAILBAG: 

Chris KD4PBJ's BITX 40 with improved stability
Jerry W0PWE built a DIGITIA!  Very nice.  Worked Keith N6ORS and heard me! TRGHS
Mike AB1YK's Al Fresco Scratch built BITX.  But give that LC VFO another chance Mike!
Steve N8NM 30 meter rig with salvaged CB LC VFO. FB
Keith N6ORS Franken SDR rig with parts from the 1980s.  FB
SKN Bandscan from Mike WA6ARA  I worked W1PID Jim!
What is Mikele up to?
Rocking Johannesburg and Kirghizstan via local repeaters:

 http://www.sarl.org. za/public/local/GoogleRepMap. asp?Lat=S%2026%2011%2008&Lon= E%2028%2008%2049

A Message from South Africa

Hi Bill,

 

I am Pieter callsign ZS3AOR. I came upon your E-Book at Amazon and downloaded it to my Kindle and man, I really enjoyed reading about your endeavors with everything.

 

The way you explained for instance the inner workings of transistors and mixers and problems associated with it is really  good.

 

Subsequently I downloaded the August Podcast and I am hooked with you and Pete.

 

Kind regards from the Namaqualand region of South Africa (Northern Cape Province)

 

Pieter  ZS3AOR

 

 

 

Pieter's Workbenches

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

BITX Build Update #20 -- Switchable Crystals, South Africa QSO

I got tired of popping the hood and manually changing my VXO crystals.  First I tried to switch the rocks using a rotary switch on the front panel, but I think the leads were too long and the output was kind of squirrely.   So I dug around in the junk box and found a 12 volt double pole double throw relay.  I put the crystal sockets across the two poles and ran leads from the armature terminals to the crystal terminals. I use the rotary switch to activate the relay.  I cover about 41 kHz of the 17 meter band with the two crystals. 

17 meters has been in great shape.  On November 16 I had a very nice contact with Syd, ZS1TMJ in Glenwilliam, South Africa.  That's about 8000 miles on 5 watts SSB.   

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

Big Data and the Square Kilometer Array

All of this is very interesting, but SolderSmoke readers will probably find the last ten minutes most interesting.  

http://www.youtube.com/watch?v=dzlwhP5JejA

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

Hard Core! Wisdom and Ideas on Toroids

Gerard ZS5AAC

This morning the BITX20 mailing list has an interesting discussion of toroidal cores. I especially like Gerard's use of the cores from old CFL bulbs. Farhan wraps it up with a great explanation of why we use ferrite cores in broadband transformers:
------------------------------
Over the years I built quite a few BITX's. In the beginning I used the
toroids salvaged from CFL lamps. These worked quite well for the mixer
coils. For the filter coils I used 6mm bakelite slug tuned coils that were
stripped from old PYE radios. Wonder if anybody else experimented
along the same lines. I build my BITX's Manhattan style and they work from the start with few minor tunings. Happy BITX'ing, Gerard, ZS5AAC.
---------------------------------------
Bob
The purists may attack us on this, but what you propose is very
possible. I have been using a wooden-core toroid for several years as part of an antenna tuner.

http://qrp.webhop.net/Pictures/Webcam-1293651325.jpeg

http://qrp.webhop.net/Pictures/Webcam-1295140555.jpeg

I'm also using small plastic and wooden beads as toroid cores for
several other projects. Half inch long sections cut from thick-wall (schedule-40 or schedule-80) PVC pipe also makes good toroidal forms. Beauty of using non-metallic cores is that the core can be split to allow winding wire through the slot without having to thread it through the hole.

http://qrp.webhop.net/Pictures/Webcam-1289957121.jpeg = 1.4 uh

Bending an inductor back on itself in toroidal form concentrates the
magnetic field in the center, whether the core is metallic or non-metallic. This gives you similar self-shielding properties when using either type core material.

With non-metallic cores you no longer have to worry about core saturation, so running high current finals is not a problem.

Key to doing this is being able to measure inductance of 5 turns, 10 turns,
and 20 turns, so you can calculate and plot the effective AL of your wooden core toroids. Once you know this value you can make up a chart to tell how many turns are required for a specific inductance.

Twisting wires together to make a transmission-line for bifilar or
trifilar windings is interesting because the impedance of that transmission line might affect performance of your transformer. It may require a bit of experimentation with an SWR bridge to tell when you have the best balance between twist pitch, wire diameter, and insulation thickness.
Arv - K7HKL
---------------------------------------------

Robert, Arv,
There are two types of coils used in the bitx - the broadband
transformers and the RF coils in the bandpass filter and oscillators.
You could easily substitute the rf and vfo/bfo coils with just about
any kind of coil - as long as you are hitting the same inductance and
Q. But there is a catch : a few years ago, I finally got down to
measuring the Q of the nylon tap washers that I had originally used.
The q was quite modest at 70. Wes made independent measurements with similar results (his paper is on www.w7zoi.net under technical stuff). In short, for good performance use good old air coils wound on a
cylindrical formers if you don't use toroids.

About the broadband transformers. These need a material that has very
low loss, very high permeability. The reasoning is like this :
1. We need an transformer's inductance such that the reactance is
at least 200 ohms at the lowest frequency. This puts the inductance at
around 30uH at 4MHz.
2. If we achieve 30uH through lots of turns (say 100), each turn will
exhibit capacitance with it's neighbor and the large number of turns
will add up the capacitance so that the coil will provide enough
self-capacitance to resonate at an unintended frequency in HF leading
to pretty bad mixer performance.
3. The only way out would be to achieve the required reactance with
lower number of turns. This means using ferrites.
- farhan VU2ESE

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