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Wednesday, January 8, 2014

First Light


Preston:  Your use of the term "First Light" is especially appropriate.  I got the concept from a wonderful book of that title by the author Richard PRESTON.  I pulled it off the shelf this morning, and, as my coffee was brewing, read this on the dust cover:

"First Light won the American Institute of Physics award in science writing. An asteroid has been named "Preston" in honor of First Light. It is likely someday to collide with Mars or the earth."

The book's glossary defines first light as: "A technical term from astronomy signifying the moment when starlight is allowed to fall on a new mirror for the first time."  The first light experience must, I think, be similar to the feelings we get when we first allow RF to fall on the front end of a new homebrew receiver.

Congrats on the S-107 OM.

73  Bill N2CQR
------------------------------------------

From Preston Douglas WJ2V:

I am happy to report that my little novice rig (well it's not so little if you weigh it) consisting of my restored circa 1960 Hallicrafters S-107 and circa 1959 KnightKit T-50 (with V-44) made our first QSO with a guy 20 miles away on Staten Island.  This was Saturday afternoon, in full daylight, on 40 meters.  He was also running vintage equipment (Heath) but running an SB-200 Heath linear.  I have no idea why he needed a linear on 40 meter CW, but he seemed happy with it.  I could easily hear his signal via leakage through my Daiwa cavity switch, so it was a pretty powerful signal.  The T-50 puts out maybe 20-25 watts full bore, but it certainly works fine, and got a 569 signal report.  The 9 part was obviously the important one.
 
I had just turned on the equipment, so the S-107 needed to be adjusted a bit during the QSO to allow for a bit of warm up drift.  It stabilizes ten or fifteen minutes after warmup.  I had to use a straight key as I have not yet built the little kit that interfaces solid state keyers with old rigs.  I'll get to it on a slow afternoon this winter perhaps.  But for now, a straight key is about the right speed for this setup.  T/R requires switching the antenna, the VFO to transmit, and the receiver to standby for transmitting.  Not exactly QSK. Since there are so many switches, it may not pay to add an antenna relay switch to this setup.  Besides, switching is part of the fun.  

I did not get set up in time for New Years, so missed the chance to operate SKN.

I learned about first light from Bill Meara's podcasts.  It refers to the first time a telescope is used, but, as he says, it applies just as well to a new (old) rig.

All of this was caused by a local ham offering a Hallicrafters S-107 for ten bucks. Even with the few bucks needed to put it right, I sure got my money's worth.  

Regards guys and Happy New Year,

Preston WJ2V
----------------------------------------
 
Earlier from Preston:
 
I am pleased to report my S-107 is restored to full function.  Based on the build up of filth on it before cleaning, it is also cleaner than it has been for many years.  The greasy dirt (I shudder to think what it was made of) in between the flutes of the control knobs has succumbed to a toothbrush and detergent.  Who'd have thought what a difference clean controls would make in the overall appeal of a radio?

The S-107 was purchased without negotiation from a local and fellow member of the Long Island Mobile Radio Club for ten bucks.  I cheerfully handed over a ten spot and drove home with this rig.  

On the bench, the tubes lit, and I could hear a couple of AM stations, but it made an awful racket with 60/120 cycle hum.  New electrolytic caps cured that.  The chassis felt "hot" to the touch.  Resistance checks on the HV-to-AC sides of the transformer confirmed that, thankfully, there were no shorts.  On advice of some pros on this list and elsewhere, I removed a cap and resistor from the AC line to the chassis that Hallicrafters thought was a good idea.  With a new three wire grounded plug, the chassis was now cold.  

Alignment was done with an old Conar signal generator (my $1 victory from an old hamfest) and trusty Tek 465 with frequency counter connected to its rear connector.  The double IF transformers peaked up, and so did the front end compression caps on all bands.  And now, the radio really receives CW and SSB!  With a simple dipole (my beam seems to have gotten sick from Irene and Sandy) I get good signals on 80, 40, and 20.  Maybe next weekend I will have time to try the upper bands during daylight hours.  But, the signal generator suggests they should be fine.

The ten buck receiver needed ten bucks worth of electrolytics.  And I needed to buy a little 20 buck kit of Bristol Splined wrenches.  (Nobody I thought to ask had a set to lend.)  They were needed because: Another Hallicrafters bit of wonderment is that the setscrews in the control knobs need to be turned with these unusual wrenches that look like, but aren't, hex keys.  Well, I suppose I can say I have the wrenches if I decide to restore another Hallicrafters.  I hear Collins has them too.

I think I mentioned that I had to restring both the band spread and main tuning with real dial cord.  Another three bucks, perhaps.  So, my ten buck receiver is still a bargain at around 40 bucks in all.  And, I had a lot more than 40 bucks worth of fun.  I spent part of the afternoon just listening to the receiver, it sounded so good.  You know how it is when you first listen to a new receiver.

Now, next thing will be to see how it does making contacts with a Knight T-50.  I know the T-50 is not quite QRP.  I probably puts out about 25 or 30 watts.  

This will be about as close to my novice station as I am willing to fall.  The original station had the T-50, but no VFO (which came with the T-50 I have now); but the receiver was an S-38E, which was, (collectors notwithstanding) a piece of crap.  And it's dangerous since it is really one of those transformerless AM radios in shortwave clothing.  No wonder I only made a handful of contacts with it as a novice.  I have no nostalgia for my old Hallicrafters S-38E.  I hear folks recommend operating it with an isolation transformer.  I have a better idea.  Don't plug it in.

I had so much fun with the S-107, though, I am starting to think about restoring an S-108 or an SX-110.

Preston Douglas WJ2V

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Sunday, January 5, 2014

BITX 20/40 BUILD UPDATE #4: 11MHz SSB Ladder Filter


As reported yesterday I have the 20 meter receiver portion of my BITX 20/40 rig up and running.  I decided to take a closer look at the crystal filter I built.  

Here is my method:  

1) Using an Arduino/DDS sig generator, I put 11 Mhz energy into the base of Q2 (the stage immediately prior to the crystal filter).   

2) Using my Rigol 1052E oscilloscope, I measured RMS voltage at the output of Q3/Q3A (the stage immediately following the filter).   

3) I looked at Vrms as I MANUALLY varied the input frequency in 100 Hz increments.

4) I took the results and plugged them into a spreadsheet.  I then used the spreadsheet to calculate the db drop from the peak Vrms value (So I wasn't looking at insertion loss, just the filter shape).  
I used 20*LOG(Vrms/276)

5)  I ended up with the chart displayed above. 

I have a few questions: 
1) What do you folks think about my methodology for evaluating the filter? 
2)  Where would you guys put the BFO frequency? 
3)  I know the ripple looks ugly, but the receiver sounds great.  Should I attempt to get rid of the ripple? 

Here is the filter I used (as prescribed by the AADE software):  I estimated Q at 10000 and used LM and CM values derived by the G3UUR method, and made no effort to match impedances going into the filter:   



Here is what GPLA predicted.  I estimated Rin and Rout values.  That probably accounts for the difference between the GPLA prediction and what I measured. 
  




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Saturday, January 4, 2014

BITX 2040 Build Update #3 Receiver Sounds Great!


There it is,  my second BITX transceiver, this one for 20 and 40.   Once I got the VFO sorted out, this one went together very quickly.  Obviously experienced gained on the first project was a big help.

I followed Farhan's advice and characterized the 11 MHz crystals in the filter.  Then I used the AADE filter design software to build a 3 KHz filter.  Using my Arduino DDS signal generator and the new Rigol 'scope, I was able to do a manual sweep across the passband -- it looked very close to what was predicted by the software. 

This morning I built the bandpass filter for 20. As soon as that was done, I fired up the receiver.  This was an amazing experience for me: a homebrew receiver that worked right away!  That never happened before.   I'm listening to 20 meters now.  It sounds great.  I even managed to demodulate and display some SSTV.  The VFO seems very stable.

I still have to build the RF amplifier stages, the bandpass filter for 40 and low pass filters for 20 and 40 (I know Steve Smith is watching!).  Then it will be time for cabinetry.   I guess I should put some paint or varnish on that walnut box.   Any recommendations?   I'll line it (on the inside) with copper flashing material.     

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Wednesday, January 1, 2014

Happy New Year! Straight Key Night

 
For the first time in years I got on the air on New Year's eve.  I fired up the HT-37 and Drake 2-B on 20 meters last night right at 0001 UTC  (well, with these rigs I should say GMT!).  There was a moment of stress when, as I was trying to adjust the key, the whole thing fell apart and the little ball bearings spilled out.  Yikes!  It was as if the radio gods were trying to tell me something.  It took me a few minutes to re-assemble my straight key, then I called CQ.  The HT-37 puts out a lot more power than I normally emit,  and it caused the Carbon Monoxide detector to go off, sparking a minor panic among family members.  (See, this never happens with QRP!)  With that resolved I had nice QSOs with K5KFK in Texas, W6VNR in California, and N1WPU in Maine.  This morning I worked WA0ZDE in Missouri.  The old HT-37 was drifting a bit, but Rick said he kind of liked that.  (I put a muffin fan on top of the transmitter -- that should settle it down a bit).   By the way, my key is a bit unusual: it is just a cheapo key, but I have it mounted on the base from a Vibroplex bug.  I never mastered the Vibroplex, and ended up giving the bug parts to HI8G in Santo Domingo -- Gustavo planned on using them to fix another bug that had been given to him years before by Fred Laun (K3ZO). 
 
Rick, WA0ZDE ( who I talked to on 20 this morning) sent me a VERY SKN photo collage (see below).  I see that Rick also tends to hold onto his gear for a long time. 
 
HNY to all!   GL in 14.  73! 
 



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

Friday, December 27, 2013

SolderSmoke Podcast #157: Peter Parker on Phasing Rigs


SolderSmoke Podcast #157 is available for download.
http://soldersmoke.com/soldersmoke157.mp3

December 27, 2013

-- Santa Report:  Rigol Scope at SolderSmoke HQ.  Kites at VK3YE.
-- Project updates:   Bill's BITX 40/20 build. 
-- Peter finishing up BITX40  (in a big box)
-- BITX 17 (5 watts SSB) works JA, ZD7, ZS!
-- The mystery, elegance, and gentleness of phasing SSB
-- Phasing explained in 1970 ARRL SSB book
-- Phasing SSB: From Hallicrafters HT-37 to SDR
-- The SP5AHT Phasing Rig
-- I & Q for you:  The Binaural Experience
-- Direct Conversion receivers and Software Defined Radios
-- Simple DC receivers plugging into sound cards 
-- The joy of receiver building
-- 144 MHz aircraft bounce (Melbourne to Sydney)
-- VHF Across The Great Australian Bight  

HAPPY NEW YEAR TO ALL!




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Wednesday, December 25, 2013

Santa Arrives at SolderSmoke HQ! Rigol and Black&Decker


Santa Claus obviously heard my distress call when the TEK 465 gave up the ghost.  This morning it was replaced by a RIGOL digital scope.   I'm going through the tutorials.  Wow, lots of features.  A Black&Decker jig saw also arrived -- this will help in my cabinetry efforts. 

Last night just before dinner I talked to Kiyo, JH1MDJ, in Tokyo on 17 meter SSB with the 5 watt BITX.   I kind of broke through a small pile-up and we then had one of those "please repeat your power level... I can't believe that is 5 watts to a dipole" conversations.  

Happy Holidays to all!

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

Saturday, December 21, 2013

How they took the iconic Apollo 8 Earthrise Photo (Amazing Video)



I was ten years old and totally obsessed with the space program.  This video brought back a lot of the magic. Wow. You really have to see this one.


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

Where to send all those LM386 chips: Make them BEAM robot brains!



Over in the BITX20 yahoo group there have been some comments about the shortcomings of the widely used LM386 audio amplifier chip.  Many people don't like it because it is noisy.  I don't like it because it is a chip. (In my BITX rigs I have replaced it with a simple discrete component audio amplifier.)  So this morning I was pleased to find this video on the Maker blog that presents a very good use for all those LM386 devices:  We can turn them into robot brains!

Make's video and web page on this project are both very good.   One paragraph in the page kind of captures the reasons I dislike the LM386:

How It Works

The core of the “Herbie” circuit is the LM386 power amplifier chip. To simplify a bit, we can think of the chip as a “black box” with inputs and outputs that respond in predictable ways, and don’t have to completely understand what’s going on inside. 

 http://makezine.com/projects/sunbeam-seeker-bot/

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Friday, December 20, 2013

Christmas Eve Fessenden Memorial Broadcast on 486 KHz

Imagine it is Christmas Eve, 1906 and you are on the air, listening to the harsh buzz of Ol' Spark Morse Code.  Suddenly, in the headphones you hear a human voice and music.

Brian Justin  has set up an experimental station that recaptures that magical "birth of radio telephony" moment.   He will be on the air this Christmas Eve, Christmas Day and New Year's day.   Here is what W4DEX heard during last year's event:

http://www.w4dex.com/500khz/wf9xih/wf9xih_24dec11.mp3


Experimenter to Honor Early Wireless Pioneers with Longwave Transmissions

              Fessenden
As he has over the past several years, Brian Justin, WA1ZMS/4 -- as experimental station WG2XFQ -- will transmit voice and music on 486 kHz on Christmas Eve and Christmas Day and again on New Year's Eve and New Year's Day. Transmissions will begin at 0001 UTC and end at 2359 UTC. Justin, who may be better known for his microwave exploits on ham radio, will use an AM audio loop modulating his vintage-style, homebrew transmitter to honor Reginald Fessenden's Christmas Eve 1906 AM voice transmission.
WA1ZMS constructed his MOPA transmitter from 1920s-vintage components. [Brian Justin, WA1ZMS, photo]
"While his original transmissions used a set of carbon microphones in the antenna lead to modulate the signal," Justin explained, "WG2XFQ will be utilizing true Heising modulation in honor of Raymond Heising, who developed this early form of amplitude modulation during World War I.Justin constructed his 5 W master oscillator power amplifier (MOPA) transmitter using 1920s-vintage components. He said a modern 500 W FET linear amplifier allows him to meet his WG2XFQ ERP limit of 20 W. An RF engineer, Justin collects pre-1920 wireless gear and has a World War I Heising-modulated aircraft transmitter he's planning to restore. Justin was an active participant in the ARRL's WD2XSH 600 meter experimental project.

(From the ARRL Newsletter)

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Wednesday, December 18, 2013

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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Sunday, December 15, 2013

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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Saturday, December 14, 2013

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