BITX 2040 Build Update #2: Of Spreadsheets and VFOs

I continue to tweak the capacitors in my new BITX 20/40 VFO (scroll down to see it).  On Sunday I added a little relay that will switch in some additional capacitance to move the VFO about 500 kHz.  Without the additional cap, the VFO will be on frequencies suitable for 40 meters -- with the additional cap it will be on frequencies needed for tuning 20 meters. 

I calculated that I'd need an additional 220 pf to make this shift ( I later went with 100 pf).  In went the needed cap and relay.  It worked.  But there was a problem:  On 40 I had the desired 175 kHz frequency range.   But I found that with this arrangement on 20 I could only cover 95 kHz.   Obviously my variable air cap with 44 pf in series was being "diluted" by the additional 220 pf being switched in by the relay -- with the additional capacitance, the change in total capacitance produced by the variable cap (with series cap) was smaller in the 20 meter range than it was in the 40 meter range. 

Clearly, one solution was to play with the value of the cap that I had in series with the variable cap -- increasing it would increase the freq spread (both on 40 and 20).  But how much should I increase it?

By this point I was getting tired of all the manual calculations.  Time for a spreadsheet! I created one, and threw in the values of all the caps and of the coil,  and the resonant frequency formula.  I set it up to display and the resulting freq coverage. 

The freq ranges in the actual ham bands is a bit off -- there may be some stray capacitance and inductance in the circuit that is not being captured in my numbers.   But the important thing was the spread.  The spreadsheet allowed me to see that with a 100 pf cap switched in by the relay and a 74 pf cap in series with the variable, I could cover 180 kHz on 40 and 123 kHz on 20.  That's OK.  This little exercise shows the usefulness of spreadsheets in dealing with this kind of calculation.

You can see my spreadsheet here:
https://docs.google.com/spreadsheet/ccc?key=0Ak4BJL1-oWiJdElieDY5Y2xVWUtSNDl0anRYLVBBeGc&usp=drive_web#gid=0

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20/40 BITX Build Update #1: VFO Success

I've started construction on my second BITX transceiver, this one for 20 and 40 meters.  As with the previous rig, I decided to take the VFO first, but this time I pledged not to surrender, not to wimp out with a VXO or (worse!) a DDS.   No, this time it would be a real LC VFO.

I took seriously all the admonitions in the tech literature about the fickle permeability of ferrite and iron powder, so this time I used an old-fashioned air-core coil.  It is wound around a cardboard tube.  The tube was previously the bottom portion of a coat-hanger from the dry cleaner.  I wound 40 or so turns on this core, then measured the inductance:  5.6 uH -- that looked about right.

For the oscillator stage I used a Colpitts circuit very similar to the one in the original BITX schematic (but I am hoping I won't need the varactor diode fine tune mechanism).   I had on hand a nice Heathkit 19-146 pf variable cap with an internal 4:1 reduction drive.  Not wanting to pluck rotor places out of this beautiful part, I had to calculate the series capacitance that would yield a frequency spread of about 175 kHz.  It turned out to be 40 pf.  Then I had to figure out how much capacitance to put in parallel with the variable.  Well, it all ended up like this:

There was a bit of trial and error in the process of getting the VFO to cover the desired range.  A big help in all this was an on-line reactance calculator.  I found this one to be very useful:

  
http://www.1728.org/resfreq.htm

I found that the VFO is more stable if I reduce the voltage from 12 volts down to about 8.  Also, I found that when evaluating the stability, it is better (psychologically!) just to use a stable superhet receiver instead of the frequency counter.  The counter may appear to be jumping around a lot, especially if the signal you are monitoring is not very strong.  Just listening to it at zero beat on the superhet is very reassuring.

I followed the Colpitts oscillator with the FET buffer and two stage BJT amplifiers from page 50 of Doug DeMaw's QRP Notebook (page 50).  I now have the requisite 7 dbm signal.  And it appears to be quite stable. 

I plan using this with an 11 MHz IF, with the VFO running at around 3.875--3.700 for 40 meters and 3.175 -- 3.355 for 20.   I plan to use a small relay to switch in some additional capacitance to move the VFO down to the range for 20 meters.


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University of Twente's Online Receiver

Wow, I played with this on-line SDR receiver a few years ago and thought it was fantastic.   It is now even better.  I'm sitting here listening to 40 meters in the Netherlands.  Great stuff.   Check it out.  It is really amazing:

http://websdr.ewi.utwente.nl:8901/

Thanks to Bob, KD4EBM for letting me know about the updates. 

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Circular Polarity and The Water Wheel in Dale's Moonbounce Amplifier

Bill:

 

I'll attach some pix of the feedhorn and LNA for you.

The importance of circular  feeds is that as a linear wave passes through the ionosphere, it undergoes Faraday rotation. So it may arrive at  the station you are talking to having been twisted 90 degrees. This  is a slow progressing process and  on  all bands except 23cM, may cause EU for example to be locked out for hours at a time for linear stations.

With circular polarity, Faraday is a non issue. The feedhorn almost all of us use is a VE4MA that has separate TX and RX probes. The circular polarity is synthesized as the linear wave propagates down the circular waveguide and encounters sets of  capacity stubs. The exact opposite occurs for waves entering the waveguide. The result is we get CW and CCW without having to use any relays (loss) and phasing  lines (loss).

My LNA has a noise figure of under 0.24dB and uniquely connects to a protection relay with no cable or adapters (loss).

The position of the feedhorn and its scalar ring is tediously adjusted by measuring the difference between sun noise and cold sky. W4SC developed a very accurate and repeatable process that uses an SDR RX for this.

I use  a modified C band satellite drive system known as a polar mount so I only need one motor drive to track the moon.

Anyway, hearing my own echoes off the moon was and still is the highlight of my amateur career. 

 

The photos are the feedhorn + LNA, My first water cooled 500W  tube amp, my previous 400W solid state amp (mounts right at the dish). My current design is 600W solid state and will also mount at the dish.

BTW, that little circle in the middle of the tube amp is a paddle wheel that turns as long as water is flowing. A tachometer on the wheel sounds an alarm and shuts down plate voltages   should the wheel stop turning.

I'll keep  you up to date on my BB RX progress- thank you again Bill.

Dale W4OP

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The NASA Juno Fly-by "Hams say HI to Juno" Video (very nice)

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The QRP Mojo Ceremony

More from Lobstercon (from N2HTT): 
 http://n2htt.net/2013/11/24/there-are-lobsters-in-the-woods/
And thanks to Pete, VE2XPL, for alerting me to all this. 

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Need help with part construction...

Please take a look and see if you can help me figure out how to make this thing.  The diagram is eschpecially illuminating.

 

 

THE DIE-CAST DROP-FORGED PLASTIC

TRICHOTOMETRIC INDICATOR-SUPPORT

          Inquiries concerning the mounting of the Trichotometric Indicator

          Support indicate that some difficulty is being experienced with the

          brackets which attach the support. As an aid toward fabricating the

          support brackets, the accompanying illustration is provided to show

          the type of material as well as the dimensional data needed. It will

          be noted that in attaching the bracket to the support a special ambi-

          melical hexnut is used. The application of this nut is unique in that

          any attempt to remove it in the conventional manner only tightens it.

          Because of this design, the nut must be fully screwed on before it can

          be screwed off.

 

DRAWN BY	FRED SPOON	SCALE ¼”=1 MILE
NO. 43906		FILE – BAR NONE

 Thanks to ZL2DEX for bringing this to our attention.

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On the Wavelength of Santa's Sled (with a nod to FA Wilson)

About a year ago, David, M0VTG, was reading "From Atoms to Amperes" by FA Wilson.   His thoughts turned to a seasonal application of Wilson's lessons....  Thanks David! 

WAVELENGTH OF SANTA AND HIS SLEIGH

We're going to need to know the following:

Total mass of the sleigh, reindeer, Santa and his presents, and the speed at which the sleigh travels. Assuming that the sleigh travels relatively close to the surface of the earth, the mass can be regarded as the same as the weight. Now assume each reindeer weighs 100 kg. Traditionally there are nine of them so total mass of the reindeer is 900kg. Say the sleigh also weighs 500kg and Santa and his presents weigh 400kg; then the total mass is 1800kg. To get round all the children who believe in him in one night would mean him travelling at a speed of say 1000kph (277.8 m/s). (Note that scientific notation for numbers used is that used on some calculators)

So mass (m) is 1800kg

velocity (v) is 1000kph (notice the not so subtle change from a scalar quantity to a vector quantity).

Max Plank came up with a formula: E = hf relates Energy to frequency using h (Plank's constant = 6.626 E-34 Joule seconds).

Albert Einstien (as everyone knows) says that E = mc² (where c is the velocity of light).

So it follows that hf = mc² and therefore, m = hf/c².

The momentum of a photon (p) is defined as mass x velocity or p = mv and as every radio amateur knows, wavelength (λ) is the velocity of light divided by frequency or λ = c/f (or f/c = 1/ λ).

So mv = hf/c² x c (velocity of a photon is c don't forget); so p = hf/c

Since f/c =1/ λ, then p = h/λ i.e. λ =h/p

Also since p = mv then λ = h/mv (This expression is known as the de Broglie wavelength - Louis Victor de Broglie)

Notice that the velocity of light does not directly feature is the expression. We can, therefore use it the calculate the wavelength of anything!

So the wavelength of Santa's sleigh is Plank's constant divided by the mass times the velocity or

λ = 6.626 E-34 J s / (1800 kg x 277.8 m/s) which equals 1.325 E-39 m - an unbelievably small number! Make up you own mass and velocity for the sleigh if like.

I defy NORAD to track such a short wavelength.

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"Snort Rosin" Seal of Approval for "Ferrari-esque" Italian Wire Cutters

And now for something (almost) completely different.  Rarely have wire cutters been described in such, well, almost erotic terms.  This definitely seems like the stocking-stuffer of the year for the SolderSmoke in-crowd.  And to think that I was pleased with a pair of $3.99 hemostats that I got from Amazon.

Hi Bill,

It's always nice to find something high-quality and inexpensive and today it happened to me so I thought I'd share my good fortune.

Having been in the professional radio repair business for 40 years (retired 2012), I very much appreciate quality hand tools.  On my bench at home I have an expensive pair of Lindstrom wire cutters but in the field I generally resorted to cheaper, not so high-quality tools (in case of inadvertent loss).  The problem at home is it seems like every time I need to grab my Lindstroms, they're not where I'm at so I've been on the lookout for a spare pair or two of quality cutters.  Well, today in the Fry's Electronic newspaper flyer I saw an ad. for Hakko brand wire cutters on sale for $2.99, regularly $4.99, a 40% saving.  Me being, shall we say, "thrifty",  this immediately got my attention.  I know Hakko markets some very good soldering related equipment, however until today I had no experience with their line of hand tools. 

So, between some appointments this morning I stopped at our local Fry's store and checked out the cutters.  I was expecting to find something typically cheap and made in China so imagine my surprise at discovering they are made in Italy!  The part # of this particular tool is CHP-170 and is mfg. by the CHP Tools division of Hakko.  The hand grips are palm-fitting and very comfortable with thumb and forefinger rests at the top of each for tool manipulation.  The design is what I would call "Ferrari-esque"; bright red with black accents.  Very pleasing to the eye.  Turns out that The metal parts are  high grade tool steel and Parkerized for low reflectivity and high wear and corrosion resistance.  What impressed me the most is the cutting surfaces; they mate perfectly.  So many inexpensive cutters have lousy mating surfaces, these don't.  With the cutting edges 'closed', shining a high-intensity light on one side results in -no- light 'leaking' by the mated edges.  That's first-class machining! 

IMO, even at the typical price of $5 or so, these cutters are a bargain, especially considering the quality (how does one say, "it is very good!" in Italian?).  So, if you or anyone you know is in the market for some great wire cutters, tell them that the Hakko CHP-170 has the "Snort Rosin" seal of approval, HA!

73.......Steve Smith WB6TNL
 http://www.amazon.com/Hakko-CHP-170-Maximum-Cutting-Capacity/dp/B00FZPDG1K

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"The Amateur Scientist" by C.L. Stong (FREE!)

This great book is available on-line:   You guys will really like it:

https://archive.org/details/TheAmateurScientist


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Renaissance Man Illustrator for Scientific American

C.L. Stong wrote the "Amateur Scientist" column for Scientific American for many years.  When I was a boy, my mom saved up to buy me the anthology of Strong's columns.  It had a big impression on me -- I still have a copy on my shelf.  I never gave much thought to the illustrations, but I now realize that they were responsible for much of the impact that that book had on me.  The cloud chamber drawing was one of my favorites.  Note the use of peanut-butter jars.  Yea!  
 
This morning an article on the Maker blog focused on the genius who did all those wonderful drawings:  Roger Hayward (I wonder if there is any relation to Wes and Roger -- all three are from Oregon and all three are technical geniuses.)
 
I found this very nice web site about Roger Hayward: http://scarc.library.oregonstate.edu/omeka/exhibits/show/hayward/introduction/introduction/
There are great illustrations in many places.  For the Scientific American drawings go to the 1960s section.

And check out this one:

From: http://scarc.library.oregonstate.edu/omeka/items/show/4456

 
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W4OP -- Earth-Moon-Earth and Another Barebones Superhet

Years ago I bought a Barebones Superhet from Dale Parfitt on E-bay.  Several years after that, having forgotten who I bought it from, I was asking questions about how to get it working on 17 meters.  Dale jumped in with some very helpful e-mails.  It took us both a while to realize that I was working on the receiver that he had built.  Dale is active in a really wide range of ham radio activities, everything from QRP to EME.  Check out his homebrew projects here (I really like his Solid State Drake 2-B!) http://www.parelectronics.com/par-homebrew-projects.php 
And his vintage projects here: http://www.parelectronics.com/vintage-radio-restoration.php
And here's what Dale has been doing with the Moon (that's his 15 foot dish in the picture): 

 

Hi Bill,

 

I thought of you today when I won a Bare Bones Barbados RX on eBay for $5. I am going to team it with a DDS VFO and a matching TX.Some parts are apparently missing, but i have a huge junk box and also know how to order from Mouser should the junk box fail me.

 

 

Right now I am putting my solid state 650W 1296MHz EME amp , Power Supply, meters etc. in its waterproof cabinet so I can mount it right at the dish and not incur any feedline losses.

 

1296 is probably the best EME band. Power is getting easier and easier to acquire (although solid state is around $5/watt), dishes are fairly easy to acquire or build and  perhaps most importantly, we all use circular polarity feeds with no relays/hybrids. Activity weekend can sound like 20M, with a number of stations just ragchewing on CW and SSB.

 

73,

Dale W4OP
for PAR Electronics, Inc.
http://www.parelectronics.com

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Thermitron (Tube, Valve) Op-Amps

It is kind of appealing.  I like it better than the 741.  This one you can take apart and see how it works.   Thanks Rogier!

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On the suffering of Geeks. Indeed, we suffer...

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11 MHz IF for new BITX 20/40 Dual Bander? Also: Cabinetry and Socketry

I am gathering parts and ideas for a BITX dual bander (20 and 40 meters).  I know Farhan used a 10 MHz filter for his "Simple SSB Transceiver."  But I was thinking of going a bit higher, to 11 MHz. This would allow me to run the VFO from 3.175 to 3.355 for 20 meters, and 3.695 to 3.875 for 40 meters. I'm hoping that I can do this with one single VFO (Farhan used two VFOs), perhaps with a reed relay switching in some additional capacitance for the other band. I'll also follow Farhan's lead and switch the Low-Pass and Band-Pass filters with DPDT relays.

I set up a simple spread sheet and looked at the VFO harmonics to see if any fell within the desired tuning ranges.  That looks OK. I have not looked at mixing products between VFO and BFO.  What do you folks think?   Would the 11 MHz IF for these bands work?  Or are there evil birdies lurking in my future?

I've gone ahead and bought another wood box for the new rig (I didn't even have to suffer through a second visit to the crafts store -- they are available on Amazon).  I also got a roll of copper sheeting at Home Depot.  This time I will prepare the box first, lining the inside with copper and preparing all the "socketry" (George Dobbs' word) before putting the PC board in.

 

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First Pictures of the Far Side of the Moon (1959!)

On October 7, 1959, the Soviets sent an "automatic interplanetary station" to the moon.  This, in itself, was an amazing achievement.  Even more amazing is how they managed -- using 1950s technology -- to photograph the far side of the moon and get the images back to the earth. 

The Soviet document on the Harvard site (below) says that the transmitter put out "a few watts" and used semiconductors.  There appears, however, to have been at least one vacuum tube aboard (the cathode ray tube used to scan the chemically developed photo negatives).  Frequency modulated analog video similar to FAX) was used to send the data.

http://articles.adsabs.harvard.edu//full/1962IAUS...14....7L/0000007.000.html

From Wikipedia:

Luna-3 was the first successful three-axis stabilized spacecraft. During most of the mission, the spacecraft was spin stabilized, but for photography of the Moon, the spacecraft oriented one axis toward the Sun and then a photocell was used to detect the Moon and orient the cameras towards it. Detection of the Moon signaled the camera cover to open and the photography sequence to start automatically. The images alternated between both cameras during the sequence. After photography was complete, the film was moved to an on-board processor where it was developed, fixed, and dried. Commands from the Earth were then given to move the film into a scanner where a spot produced by a cathode ray tube was projected through the film onto a photoelectric multiplier. The spot was scanned across the film and the photomultiplier converted the intensity of the light passing through the film into an electric signal which was transmitted to the Earth (via frequency-modulated analog video, similar to a facsimile). A frame could be scanned with a resolution of 1000 (horizontal) lines and the transmission could be done at a slow-scan television rate at large distances from the Earth and a faster rate at closer ranges.
The camera took 29 pictures over 40 minutes on 7 October 1959, from 03:30 UT to 04:10 UT at distances ranging from 63,500 km to 66,700 km above the surface, covering 70% of the lunar far side. Seventeen (some say twelve) of these frames were successfully transmitted back to the Earth, and six were published (frames numbered 26, 28, 29, 31, 32, and 35). They were mankind's first views of the far hemisphere of the Moon.

More info: http://www.svengrahn.pp.se/trackind/luna3/Luna3story.html#Film

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A British Bicycle (and Workshops)

Experiments in Speed from SpindleProductions on Vimeo.


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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.   

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Naval Gun Turret as EME Dish Mount (VIDEOS)

Hack-A-Day ran a story on EME pioneer Zoltan Bay.  In the comments section someone posted this memorable video about a moonbounce station in Central Kansas.  Wow.  Putting using naval gun as an AZ-EL rotor for the dish is really thinking outside the box.   Then deciding to put the whole thing atop another tower...  Great stuff.



Here is another moonbounce video. VE2ZAZ was using a smaller antenna (!) and JT65. FB.

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M0XPD's Digital Analog BITX -- Best of Both Worlds

Paul, M0XPD, has built a very interesting version of the BITX rig.  His is on 40 meters.  It features plug in bandpass and IF filters (great idea!) and uses DDS technology for both the BFO and VFO stages.  Good going Paul!  More details here:
http://m0xpd.blogspot.co.uk/2013/11/rising-to-challenge.html

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Standard Computer Crystals for 17 Meter SSB VXO and IF Filter

Pete Juliano, N6QW, is an electronic  genius.  The ideas in his SPRAT article will be of great use to all those who share in Doug DeMaw's devotion to VXOs and reluctance to spend money.  I'm really tempted to go back and re-do my BITX using Pete's 11.52 MHz computer crystal super-VXO and 4.9152 IF (I could then take my expensive 23.1 MHz crystals and put them back in my Doug DeMaw Barebones Superhet).  I also like Pete's DPDT reed relay crystal switcher too.  Three cheers for Pete Juliano, Doug DeMaw, and SPRAT!  And thanks to WB9FLW for reminding us of Pete's articles.

Hi Bill,

 

Your BITX17 really has me fired up! I came across an interested Super VXO by Pete N6QW for use on 17 Meters.

He uses standard computer xtals (4.9152 MHz for the IF) and (3 - 11.520 MHz freq doubled in the VXO)

This gets you on 18.120 to 18.150 using these two standard xtals.

See Link Below:

 

http://www.jessystems.com/SPRAT%20Article.pdf

http://www.jessystems.com/Images/23%20MHz%20VXO.jpg

http://www.jessystems.com/vxo2.html

http://www.jessystems.com/switchedxtalvxo.html

Thanks for all your efforts they are much appreciated!!

Best Wishes,

Pete WB9FLW
 

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Beautiful French Aerial Photography Project. UPstagram! (Video)

We've put cameras in kites and rockets, but I think this is much cooler.

More details (and pictures) here: http://hackerloop.com/upstagram/

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BITX Build Update #19 Layout, VXO, Bal Mod, Filter, PA

The files of the BITX20 Yahoo group were very useful to me during my BITX build.  So I have decided to make a contribution myself.  I uploaded a few drawings today.  Here is how I laid out the circuitry on my 8 inch by 11 inch copper clad board.  I included the isolation (Manhattan) pads for one of the bidirectional amps.   

Here is the VXO.   I built is on a separate board, but I could have put it on the main board. 

Here is the balanced modulator and crystal filter. 

 

Here is the power amplifier circuitry.  Amazingly easy to stabilize. 


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BITX (and W2AEW) on Hack-A-Day

The guys over on Hack-A-Day ran a little follow-up article on the BITX-17.  Check it out:
http://hackaday.com/2013/11/13/bitx-a-return-to-hackers-paradise/#comments

They also had an article about Tek-Wizard Alan Wolke earlier in the week:
http://hackaday.com/2013/11/11/diagnose-and-repair-a-yaesu-ft-7800-ham-radio/

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New Book About Heathkit Gear

Jeff Tranter, VE3ICH, has a new book out -- it is about Heathkit Test Gear.  (Hey, I had that VTVM on the cover!)  This book looks like it deserves a place under the Christmas trees of SolderSmoke fans.   The book is available from Lulu.com, and Santa (or Mrs. Claus) can use the discount coupon below (Coupon code: CORNUCOPIA.)

http://www.lulu.com/shop/jeff-tranter/classic-heathkit-electronic-test-equipment/paperback/product-21272772.html

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Save 20% on SolderSmoke and other Lulu books (through Nov 15)

http://www.lulu.com/spotlight/soldersmoke

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That wonderful first contact, when the new HB rig is still on the workbench...

In this video, YC0AFF in Indonesia seems to be having as much fun with his new BITX as I've been having with mine.  I think there is something special about those early contacts, when the newly finished (or not quite finished!) rig is still on the workbench.  Designed in India and built by radio amateurs all around the world, the BITX has become a global ham radio phenomenon, reminding us that we form an International Brotherhood of Electronic Wizards.

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An Amazing French Workshop (Video)

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Knack-to-the-Max! Early Moonbounce

The link below will take you to an amazing collection of QST articles describing the early days of EME or "moonbounce."  Very interesting.   I was really blown away when I found out that Ross Bateman, W4AO, (pictured above, on the left) did the very first amateur moonbounce work from the small suburban Washington town that I live in now -- Falls Church, Virginia!

I am trying to find OM Ross's old address or more info about him.  If anyone has an old callbook, could you please look up Ross Bateman, W4AO, aka W4XNB?   He worked at the National Bureau of Standards. 

The moonbounce story is filled with interesting technology and characters and clubs.  Sam Harris and his Rhododendron Swamp VHF Society sounds like our kind of group!  Scroll through the OK2KKW web site and you will come across our esteemed Doug DeMaw and Bill Orr. 

http://www.ok2kkw.com/eme1960/eme1960eng.htm

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Zoltan Bay and his Chemical Moonbounce Detector

In March 1944, Bay recommended using the radar for scientific experimentation, including the detection of radar waves bounced off the Moon. The scientific interest in the experiment arose from the opportunity to test the theoretical notion that short wavelength radio waves could pass through the ionosphere without considerable absorption or reflection. Bay's calculations, however, showed that the equipment would be incapable of detecting the signals, since they would be significantly below the receiver's noise level.

The critical difference between the American and Hungarian apparatus was frequency stability, which DeWitt achieved through crystal control in both the transmitter and receiver. Without frequency stability, Bay had to find a means of accommodating the frequency drifts of the transmitter and receiver and the resulting inferior signal-to-noise ratio. He chose to boost the signal-to-noise ratio. His solution was both ingenious and far-reaching in its impact.

Bay devised a process he called cumulation, which is known today as integration. His integrating device consisted of ten coulometers, in which electric currents broke down a watery solution and released hydrogen gas. The amount of gas released was directly proportional to the quantity of electric current. The coulometers were connected to the output of the radar receiver through a rotating switch. The radar echoes were expected [11] to return from the Moon in less than three seconds, so the rotating switch made a sweep of the ten coulometers every three seconds. The release of hydrogen gas left a record of both the echo signal and the receiver noise. As the number of signal echoes and sweeps of the coulometers added up, the signal-to-noise ratio improved. By increasing the total number of signal echoes, Bay believed that any signal could be raised above noise level and made observable, regardless of its amplitude and the value of the signal-to-noise ratio.²⁶ Because the signal echoes have a more-or-less fixed structure, and the noise varies from pulse to pulse, echoes add up faster than noise.  From: http://history.nasa.gov/SP-4218/ch1.htm

During the war, Zoltán Bay protected Jewish colleagues from Nazi persecution. In 1998, the State of Israel honored him as Righteous Among the Nations for his actions and listed his name at Yad Vashem.


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SolderSmoke Podcast #156 -- Special Echolink Interview

 

Podcast #156 is available: 
http://soldersmoke.com/soldersmoke156.mp3

Special hour-long interview with Peter Parker, VK3YE
-- Early experiences with radio
-- CW
-- DSB Gear
-- Simple gear, and gear that is TOO simple
-- VXOs, Super VXOs and Ceramic Resonators
-- Building receivers
-- Chips vs. Discrete
-- Making the leap to SSB
-- The Knob-less wonder and the BITX
-- No need for a sophisticated workshop
-- Advice for new phone QRPers


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BITX Build Update #18 -- BITX in a Box?

I've really been enjoying using my BITX17 without an enclosure.  Having all the electronics exposed on the workbench really accentuated the homebrew nature of this rig.  But obviously it was time to box this thing up.  At a local craft store, I found a wooden box that is exactly the right size for my BITX copper clad board.  I put the BITX in the box yesterday.  I kind of miss the exposed electronics.  

The far left control is AF gain.  The need for a few inches of wire to the pot has introduced a bit of AC hum.  I'll try to knock this down with better shielding on the lead to the pot.

But this gets brings us too a bigger question: the need for a cabinet that shields.  Obviously the wood shields it only from dust.  I know there are some benefits to putting this thing in a proper metal box.  The AC hum would be less of a problem.  Also -- listen to this -- in the morning, before 17 opens, I can hear -- faintly -- the WWV transmission on 5 MHz (recall that the IF in this rig is 5 MHz).  And if I ever build an external linear amp for this rig (I might), I guess a proper metal box would help prevent the kind of oscillation that often drives me crazy on these kinds of projects.

So, what do you guys think?   Stick with the wood, or put it in a metal box?   Any thoughts on putting metal shielding material around the inside of the box (thick aluminum of tin foil)?    

(The other black control knob is for a rotary switch that will allow me to select among two or three crystals for the VXO. )

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40% Off SolderSmoke Book!!! Through 4 November

And on all Lulu books.

Just use the coupon code FALLSALE40 at checkout.

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Arecibo Birthday

Thanks to Bob Crane for this birthday alert:

The Arecibo Observatory opened on this date in 1963. At a diameter of a thousand feet, it's the largest single-aperture telescope ever built. It's also got the largest focusing dish in the world, which gathers electromagnetic waves from space. Located near the city of Arecibo in Puerto Rico, it's close to the equator, which enables it to "see" (via radio waves) all the planets in the solar system; within six months of its opening, it enabled scientists to study the rotation rate of Mercury and determine that it rotated every 59 days, rather than 88 as was previously thought. It's also been used for military purposes like locating Soviet radar installations by tracking their signals as they were reflected off the moon. It's provided the first full imaging of an asteroid and also led to the first discovery of planets outside our solar system.

In 1999, it began collecting data for the SETI Institute; SETI stands for "search for extraterrestrial intelligence," and the organization looks for deliberate radio or optical signals from other planets. The Arecibo Observatory also sends data over broadband to the home and office computers of 250,000 volunteers, who, through the Einstein@Home program, donate their computers to be used for data analysis during periods when they would otherwise be idle. A year ago, three such volunteers in Iowa and Germany discovered a previously unknown pulsar, 17,000 light years from Earth.

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Brooklyn Bike Generator -- Want one!

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The New "Gold Standard" in QRSS Grabbers

Bill 

I just discovered Scott Harden's "QRSS Plus" grabber aggregator...

http://swharden.com/qrss/plus/

Check it out - it is the new "Gold Standard".

73, Paul

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An Interesting Idea for Checking Crystal Filter Passbands

Today at 9:37 AM

Hi Bill,

Just listened to your last soldersmoke blog with reference to xtal filter checking using a DDS and scope. What do think of this idea to check filter performance?

http://www.qsl.net/7n3wvm/Fil_Meas.html

 Logical, relatively easy to build and NO digital electronics to deal with. 

Best 73

Rick G6AKG

PS keep up the great work, love the Blogs.

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Slide Show of BITX 17 Build

As I was building this rig, I periodically stopped and took a picture of the board.  I think the resulting slide show is kind of fun.  Check it out:  There is a button to launch the slide show.

http://www.flickr.com/photos/106886073@N04/sets/72157637045750216/

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Book Review: "Bunch of Amateurs" by Jack Hitt

The title held a lot of promise, but the subtitle ("A Search for the American Character") hinted at the main problem that I had with the book:  the author (perhaps driven by his editor) seemed to be struggling to prove that there is some uniquely American elements to amateur science and technology.  Early on, Mr. Hitt, makes the preposterous claim that "the rest of the world doesn't have amateurs."  He goes on to write that "In Europe and on other continents, the word hints at class warfare... Amateurs may be taken seriously, but, almost by the power of the word, are kept in their place: isolated outside some pre-existing professional class, some long-standing nobility.  In America, amateurs don't stay in their place or keep to themselves."   

What a load of rubbish!  This claim directly contradicts what many of us have been finding out in the quintessentially amateur world of amateur radio:  as we travel around the world (in person, or via the ionosphere) we find, all around the globe,  guys who have followed shockingly similar paths to ham radio.  From Sudan to Switzerland, from India to Indiana, the story is much the same.  And I'll bet you'll find similar similarities in just about every serious sci-tech hobby (astronomy, photography, etc.).  To claim that there is something fundamentally exceptional about amateurism in the U.S. is, I think, ridiculous.  Mr. Hitt should have spent some time looking at the amazingly diverse and vibrant world of British amateur science and technology.  That alone would have prevented him from straying into these silly claims of American amateur exceptionalism. 

But, all that aside, there is a lot of interesting material in the book.  I liked his description of John Dobson and the amateur telescope builders.  And, somewhat surprisingly, Hitt's description of the DIY Biology movement (these guys are playing with genetics and cooking up new organisms) seemed to capture very well the creative joy and satisfaction that amateurs find when working (just for fun) on their projects.  I was kind of surprised when I found myself identifying with the DIY Biology folks. Their basement labs sounded a lot like our radio shacks.   

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BITX BUILD UPDATE #17 Arv's Discrete AF AMP

I've been kind of cheating with the audio output from my BITX17:  I've been using one of those little battery-powered computer speakers.   It sounded fine, but hey, this is supposed to be a homebrew project right?  I've already noted my ideological objections to the use of the LM386 CHIP.  The files of the BITX20 yahoo group provided a very promising and completely discrete AF amp circuit by Arv Evans, K7HKL.  I used a 2N3906 and a 2N3904, with a 2N2222 driving them. It works like a charm.    Not a bit of feedback or motor-boating.  It sounds great.  I've already had a contact with it:  Jack, W7YUM is a builder of big amplifiers out in Salt Lake City.  He seemed very impressed with the BITX concept so we may have a Utah BITX in the works. 

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Words of Wisdom (on Amplifier Stability)

From "A Simple SSB Transceiver"  by Ashhar Farhan:

"What if your transmitter is unstable?  Don't curse your fate.  All transmitters start out as unstable beasts. Relax."   Farhan goes on to provide some good pointers on how to tame the beast.  

I've had very good luck with the PA in the BITX  -- very little cursing of fate on this project. 

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BITX BUILD UPDATE #16 -- FIRST QSO!!!!!!!!!!!

 

Wow, it is very clear that the radio gods are pleased with my BITX efforts!  I had my first QSO on the new rig today.  And it was with a station in my old home, the place where I got my start in 17 meter homebrew phone:  THE AZORES!  CU7MD.  Very cool.

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BITX Build Update #15 -- Necessary Mic Amp Mod

I was having trouble with the mic amp on my new Manhattan Discrete BITX 17.  I had it wired as per the schematic, but it just wasn't working right -- I was getting very little DSB out of the balanced nodulator, but everything worked fine if I 1) unbalanced the bal mod or 2) injected audio (from a sig generator) directly into the audio in port of the balancec modulator.  Clearly something was wrong in the mic amp circuit.  I noticed the collector voltage seemed quite low.

Some quick Googling revealed that others had struggled a bit with this problem also.  Nicolae's note was especially illuminating and useful: 
http://users.tpg.com.au/nfieraru/Electronics/BitX20_Mic_Preamp.htm

As Nicolae noted, the 10K value may have worked with lower gain transistors.  We must remember that BITX was (very admirably) designed for minimal cost and maximum use of scrounged parts.

I swapped the 10K resistor for a 39K and all is right with the world.  The band is not yet open here, but I bravely called a European aeronautical mobile station, hoping that he would be my first QSO on this rig.  I think he heard me, but no QSO (yet!).

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BITX Build Update #14 -- STABILITY!

Good news on the BITX.  I think I have solved the low frequency oscillation problem in the power amplifier.  I tried running the PA off a separate power supply -- the oscillations disappeared leading me to conclude that the feedback was taking place via the power supply lines.   I put a 22 uF cap to ground from the top of the PA's RF choke.  With this cap in place I can dispense with the separate supply kludge. The amp is stable.

This morning I also resolved a different stability problem.  I'm using a relay for T/R switching.  One set of contacts controls the DC power, the other set was supposed to disconnect the receiver input from the antenna/lowpass filter when on receive.  But I had positioned the relay too far from the LP filter and RX input, so I ended up with this long piece of coax that was hanging off the PA output terminal and carrying lots of RF on transmit.  Yes, this led to oscillations.  I thought about repositioning the relay, but I think part of the problem is that even if optimally positioned, the long unshielded contact levers inside this relay would be radiating a lot of RF and causing stability problems.   So instead I put a small reed relay very close to the PA out and RX in connections.  It carries the signal to the receiver when in R mode, and disconnects the RX when in T mode, without any long coax lines or unshielded relay levers.   It works.

I still have a few things to do:
-- I need to build a proper speaker amplifier so that I can dispense with the amplified computer speakers KLUDGE.
-- I need to get a 3 pole double throw switch and some crystal sockets so that I can switch crystals from the front panel.  Three rocks will cover all of 17 meter phone.
-- I have to build a case for this rig.  I'm thinking wood, with tin or aluminum sheeting glued to the inside (for shielding).  


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From Bits to Atoms -- Software vs. Hardware

I thought this was pretty good.  On Hack-A-Day.

http://hackaday.com/2013/10/18/guest-rant-from-bits-to-atoms/#more-105097

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