XQ6FOD -- A GREAT Knack Story from Chile

Greg VK1VXG sent me this link.  I had a blog entry on this a few years ago, but I didn't do it justice.  This is a truly amazing and inspirational knack story, the story of Manfred, XQ6FOD. So many lines from this page resonated with me.  For example:

I always regretted having disassembled this radio. It was so nice, so compact... Everything was hand made, there was not a single right angle in it... I felt like a murderer after destroying it. But, I needed the parts...

I designed this thing during a family summer trip into Chile's beautiful deep south. The VFO part was designed on Chiloe Island, the IF and receiver circuit took shape at Futaleufu, Rio Cisnes, Puerto Aysen and Coyhaique, while the difficult RF power amplifier work was done on the return trip via Bariloche in Argentina. So this is an international design!  Once back at home, for the first time in my life I did a thorough computer simulation of the whole thing. I hacked around the program for two weeks, and then my poor Atari had to spend another two weeks crunching numbers. It found some potential problems. I improved gain distribution, corrected mistakes, and then went straight to designing the printed circuit board, without doing any real-world test.

Check it out:

http://ludens.cl/Radiacti/Radiacti.html

Oz QRP2QRP From Mt. Bullfight, Pyramid Hill, and Melbourne's Chelsea Pier

Paul VK3HN has obviously made an admirable effort here, and a visit to his very nice blog shows that he has a lot of true homebrew gear available.  We hope that he will haul some of that HB stuff up the mountain, perhaps to find Peter Parker operating from the Melbourne pier with a Beach-40.  As I type this I am listening to VK3IO on 40 meters, coming in nicely on my Barebones Superhet (kit version).

Dear Bill and Pete,

I would like to claim an entry in the SolderSmoke Homebrew To Homebrew
(HB2HB) log. Here's the story. On Sunday 24th April 2016 I drove two
and a half hours north east of Melbourne into the edge of the Great
Australian Dividing Range, to climb two summits, for the fun of
operating my 40 meter SSB QRP (5 watt) rig in a beautiful, RF-quiet
setting, and to activate two Summits Of The Air (SOTA) peaks.

My first summit was Mount Bullfight
(http://www.sotawatch.org/summits.php?summit=VK3/VN-002), in the
Rubicon Ranges, at 1,490 meters ASL not high by American or European
standards but a good heart-racing climb through thick Australian bush.
After a successful activation with good signal reports into Tasmania
(VK7), around Victoria (VK3) and New South Wales (VK2), I descended,
and drove about 2 miles up the valley to an adjacent SOTA summit,
Pyramid Hill (1,314 meters) where the activation also went well. Just
as I was finishing up with the chasers, Peter Parker VK3YE called me,
operating portable from his beloved Chelsea Pier, and we had a very
pleasant beach-to-summit ragchew QSO. The RF path is about 62 miles.

Peter was running his MDT double sideband rig, with 2 watts. I was
using my MST400, with 5 watts SSB. Both rigs are kit radios from OzQrp
(http://www.ozqrp.com/). Both are assembled by hams -- I built my
MST400 18 months ago and Peter was using the MDT rig that OzQrp
founder Leon, VK2DOB designed, built and kitted, the one he sent to
Peter for a YouTube review. So it was built by a ham, just not by
Peter.

Now, I know that there may be some, possibly even you Bill, who may
question the legitimacy of my claim on a coveted HB2HB log entry in
this particular case. I can assure you that we did experience the Joy
of QRP/P operation, Peter basking in the late afternoon Australian sun
on a beach and I on the mountain top. And to further add authenticity
to my HB2HB claim we discussed QRP, aerial experiments, and 'whats on
your bench' topics for a full 20 minutes.

However, I would not want to risk disturbing the wrath of the Radio
Gods with a dubious claim.

I admit that neither radio was scratch-built, on copper board
ugly-style, or had the form of a wild birds-nest of separate modules
and interconnections, with parts loosely screwed onto an Italian
chopping board or a discarded lump of wood. Indeed, neither can it be
claimed that both operators built their rigs. So I will take a
rejection of my request with acceptance and dignity, acknowledging
that you are duty-bound to maintain the highest of standards, and that
entry into the SolderSmoke HB2HB log is not to be granted without
proper consideration.

I do understand that you may feel that accepting this QSO could set a
dangerous precedent and risk opening the flood gates to a tsunami of
dubious HB2HB QSO claims from hams using minimal assembly rigs, like
some of the Elecrafts. Who knows, some individuals might even be
tempted to claim HB2HB QSOs from VHF FM hand-helds after managing to
screw on the rubber-ducky antenna. Even unboxing a shiny new
Yae-com-Wood is, to some, a form of 'handiwork'.

Bill, the decision is yours. Peter VK3YE and I look forward to your
decision. Judge wisely.

73 from down under, Paul VK3HN, with agreement to this claim from Peter VK3YE.

Details of this day of activations are on my blog at:https://vk3hn.wordpress.com/

Peter's MDT review is at:  https://www.youtube.com/watch?v=2OtZeFkb1xw

A Lot of Soul in the Barbados Receiver

After a rather frustrating period working on the Hallicrafters S38-E, I decided to do something different, maybe work on something that isn't known as a "widow maker."    So pulled off the shelf an old Doug DeMaw Barbados Superhet Receiver.  "Barbados" sounds much nicer than "widow maker."  This design and this particular receiver have quite a history: 

-- DeMaw presented the receiver in the June 1982 issue of QST.  It uses six 40673 dual gate MOSFETS, an op amp for the audio, and a 250 Hz crystal lattice filter at 3.579 MHz using (YES!) colorburst crystals.  The local oscillator was a VXO. Doug's was for 20 meters, but his article provided a lot of info on how to put it on other bands.

-- I built one in 1997, building it for 20 CW.   That project is described here:

http://www.gadgeteer.us/RXHB.HTM

-- Sometime around 2000 I bought another one.  This one had been built on a FAR Circuits board by Dale Parfitt, W4OP.  Dale had used 5 MHz rocks for the filter and had used a varactor tuned circuit for the LO (with a DC-DC converter to increase the range).   I put it aside.  It sat on shelves in several countries for a number of years.  (I even have a THIRD one, a partially stuffed board that Michael Hopkins (the guy who wrote those great stories about Frank Jones coming back to life to retake the 5 meter band)).

-- I started working on it again around 2005. We were in London by then.  I put it on 17 meters using a capacitor-tuned VXO running up at around 23 MHz.   I did a quick and dirty broadening of the crystal filter by simply changing the capacitor values in the filter.  This worked, but obviously it needed refinement.  As I asked questions about this receiver, Dale Parfitt came to my rescue.  It took us both a while to realize that he was advising me on the receiver that he had built.  That was kind of cool.

-- I used the receiver with my first homebrew SSB transmitter.  I had them both running with separate VXO's, with crystals switched from the front panels.  I'm sure there were no other rigs like this on the air anywhere in the world.

-- By 2011 we were back in the US and I put my old homebrew SSB station back on the air.

-- In October 2014 I was building my first BITX rig.  I built it for 17 meters using a 23 MHz VXO.  I took the crystals out of the Barebones receiver.  Later that month I used an Arduino/AD9850 DDS arrangement as a digital crystal replacement: 

http://soldersmoke.blogspot.com/2015/01/digitizing-barebones-superhet.html

It worked, but it looked hideous.

-- By January 2015 I had learned a lot about how to characterize crystals and build filters.  I decided to take a shot at properly expanding the frequency response of the 5 MHz Barbados filter.  I measured the characteristics of the crystals and got the proper cap values for a 3 kHz filter.  When I tested it, the width seemed fine, but the ripple was more than I had expected.  Kind of disappointed I moved on to other projects.

-- Which brings us to today.  Escaping from the S38-E, I decided to put the Barbados receiver on yet another band.  With sunspot numbers in decline, I opted for 40.  And I wanted this to be an analog, L-C VFO project. No DDS, no PLL.  It would be all L and C for me, thank you! First I played around with the idea of running the VFO up at around 12 MHz, subtracting the 7 MHz sigs to get to the 5 MHz IF. But then I did a sweep of the filter.  First, there was a nice surprise -- the width AND the ripple were fine, just what I wanted (I must have had a measuring problem when I checked the ripple before).  And the skirt was MUCH steeper on the high side than on the low side.  This is why these filters are often called Lower Sideband filters.  You get better opposite sideband rejection if you use them as LSB filters.  

With the skirt situation in mind, I realized that running the LO at 12 MHz would not be a great idea. Our rule of thumb tells us that if we SUBTRACT the signal with the modulation from the signal without the modulation, we'll get SIDEBAND INVERSION.  So 7 MHz LSB would end up as 5 MHz USB.  Not great.  Plus, it is hard to get a VFO stable at 12 MHz.

So I opted to run the LO at around 2 MHz.  There would be no sideband inversion, and it would be easier to get the oscillator stable.   Wary of the threat of harmonics and spurs, I ran the receiver for a few days using an Arduino AD9850 at 2.125 MHz - 2.300 MHz.  It worked fine.

I now have the receiver running with a real Colpitts VFO.  The inductance is provided by an adjustable, shielded coil at around 1.5 uH (it was on the board) in series with a 3 uH toroid (type 6 yellow).  The feedback caps are at 2200 pf with a 1020 cap in series.  The main tuning cap is a small air variable with 73 pf max.  This only lets me tune about 40 kHz of the band, so, in a variation on the old Main Tune -- Bandspread technique, I have a rotary switch that adds capacitance in parallel with the main tuning cap.  I can now tune from 7.141 to 7.300.  The tuning rate is fine and I didn't have to mess with a reduction drive. 

More Barbados receiver blog posts here:

http://soldersmoke.blogspot.com/search?q=barbados

Kind of amazing that DeMaw designed this thing 34 years ago.  A lot of soul in this old machine.   

The Solder Is Smoking at N6QW!

It is very good to see the solder flowing again in the Newbury Park Laboratories of Pete Juliano, N6QW.  Check out that postage stamp-sized display.

More details on Pete's newest rig can be found on his blog:

http://n6qw.blogspot.com/2016/05/a-new-ssb-transceiver-from-n6qw-with.html

Putting Junk Mail to Excellent Use: Tony G4WIF's Proto-boards

Tony's Version of Audio Section of N6QW's LBS Receiver

Tony Fishpool, G4WIF writes:

I’ve been intrigued by Pete’s matrix pad method. Of course, few of us have the machinery to mill them as Pete does, but etching is a possibility. Now some of Pete’s boards clearly have a lot of noodling behind them. His boards are quite big with little areas of pads and space between. The layout for the whole project has clearly been considered in advance.

I wanted a board that I could make modular, take little time to etch and adapt for the circumstances. These “proto-boards” are the result.

The project is Farhan’s “sweeperino” and one board is for the Si570, and the other the AD8307.

The Si570 board is now complete and working:

The PCB method is pure Chuck Adams. His videos on YouTube describe the toner transfer method better than I could.

The only difference for me is that my glossy paper comes free from travel agent brochures.

Just express a passing interest in Viking River Cruises and you will never pay for PCB paper ever again!

There is a free printing only version of the software I use, so if SolderSmoke listeners want to use the proto-board design, I will happily email them the files.

Kind regards

Tony G4WIF

A 12AU7 Atop a Raspberry Pi

http://makezine.com/2016/05/06/warm-tube-tone-is-just-what-the-raspberry-pi-has-always-been-missing/

I don't know what to say.   One moment I find myself thinking that this could represent "the best of both worlds."   A minute later I'm thinking that this thing is a horrible chimera.  And it has a whiff of audio fool-ism about it, don't you think?  Will it work better with oxygen-free cables and gold-plated fuses? 

Still, overall -- pretty cool.

Polyvaricon Reduction Drive

Oh man, we need more of these.  Many more.  Unfortunately, this may be the only one.   I pulled this out of an old piece of mystery-gear given to me back in 1994 by my friend Pericles HI8P.   Look at that:  dual turning rates, solid construction, and very small.   This device seems destined to go into my W4OP-built Barebones Superhet (in the background).

Farhan's Cool BITX 40 (video)

I especially like the wood base and the transparent front panel.  But we have to send Farhan a D-104!

Check out the video of this rig in action:

https://www.facebook.com/ashhar.farhan/videos/10153914094442107/

Farhan posted:

The BITX40 has a redesigned crystal filter at 12 MHz that contributes to a very clear signal. Note the clarity on SSB and the absence of noise due to the three poles of filtering. This was charminar net on May 2, 2016. I couldn't break-in. Probably because the tiny plug mounted mic was too far away from my mouth.

Un-modifying an S-38 in 1966, and the Urge to Build

Michael mentioned this article in the Comments section under yesterday's post.  March 1966 issue of 73 magazine.  Page 26.  Just click on the images for easier reading.   Or you can find the article here:

http://archive.org/stream/73-magazine-1966-03/03_March_1966#page/n27/mode/1up

More S38 wisdom from 73 here:

http://archive.org/stream/73-magazine-1976-11/11_November_1976#page/n89/mode/1up

That's the November 1976 issue, page 88.

I miss "73".

Hallicrafters S38-E Saved! it is not a "Pig with Lipstick." It Sounds Good! (Video) (And Radio Moscow recordings)

You guys know how it is:  You get tired of struggling with an old piece of gear.  You put it aside, thinking that you might never work on it again.  But it sits there in the corner, sort of looking at you.  A few days or weeks or years pass and you think, hey, I'll take one more quick look at this thing to see if I can get it going.

That's what happened to me this weekend with the Hallicrafters S38-E.  I hooked up the isolation transformer and put a fuse in the primary. I checked the wiring of my rewound antenna coil primary and found that I had connected it wrong.  Duh.   I then found that the antenna tuned circuit tracks fairly well with the tuned circuits in the local oscillator. 

I hooked it up to my 40 meter dipole and fired it up.  As evening rolled around the shortwave bands started to perk up.  The Chinese Broadcast stations were there, as was that fire and brimstone preacher Brother so-and-so.   But then I tuned into Radio Havana Cuba and the guy was talking about homebrew shortwave antennas.  Could it be?  Yes indeed.  It was Arnie Coro CO2KK.  The Radio Gods had spoken!  They clearly had wanted me to get this old rig going.

I still have a few things to do:  I need to fix the front panel light.   I want to put in a three-wire (with ground) AC cord.   Perhaps a real BFO (the original circuit seems to run out of steam with strong SSB signals).  And I need to spruce up the alignment on the 1.7-5 Mc and 13-30 Mc bands.

I think Pete and I may have been too harsh on this old receiver (calling it a pig with lipstick and all that).   It is clearly not a great communications receiver, but it is nice for casual shortwave listening. 

And here is a bonus treat for you guys: Remember Radio Moscow in the bad old days?  Yesterday I found a site with good recordings of some of their 1965 broadcasts.  This is  just what you would have heard coming out of an S38-E in 1965:

http://www.wnyc.org/shows/radio-moscow/listen/ 

1625 Tubes and Si5351 Chips: JH8SST's FB Rig

Peter has been helping Jun JH8SST and other Japanese hams get their Si5351 synthesizers working with various displays.   Jun has had some great success as you can see in the above video.  I really like the combination of old (1625) and new (Si5351) technology.

Jun is a long-time homebrewer who as built some amazing stuff.  Check out the pictures on his QRZ.com page:

http://qrz.com/db/JH8SST

And look at his cool 128x128 TFT display:

Other videos here:

https://www.youtube.com/channel/UCcY94imiTswpjPcfcUIbNcg

KC9KEP's Superhet Receiver with HOMEBREW 455 kc IF Transformers

No store-bought 455 kc IF cans for Big Nick!  FB OM.  Great stuff.

We have featured Big Nick's beautiful work twice before:

http://soldersmoke.blogspot.com/search?q=kc9kep

More of his videos here:

https://www.youtube.com/user/KC9KEP/videos

Be sure to check out his coil winder.

Reduction Redux: Searching for Some Smooth Spin

OK, here is yet another picture of my Mighty Midget's Mate receiver, this time with yet another main tuning dial. I gave up on the large reduction drive on the right -- it worked fine but was very stiff.  I cracked open a smaller version of this very common Japanese-made reduction drive, but in this smaller one I was kind of surprised to find  a Jackson Brothers drive in there.   I now had three of these beauties available -- all of them worked fine but with considerable difference in ease of turning.  I picked the one that was easiest to turn.  

I had to cut the main shaft of the beautiful Hammarlund 35 pf variable cap that I am using. This was dangerous, because of the risk of messing up the delicate bearings.   I stayed out of trouble by putting the tip of the shaft in a vise and then cutting the shaft with a small coping saw.  This prevented any force from being transferred to the bearings.  It worked. 

I was careful to try to line up the shaft and the reduction drive as closely as I could. 

I needed something to serve as the tuning indicator.  I used one of those small CDs that often carry the drivers for cheap electronic devices.  It fit nicely.  A standard sized CD was too big. 

The final element was the knob itself.  I had an old Drake 2-B knob in my junk box (who sent me that?).  It was perfect and added a nice touch of soul to this old-new machine.

I built this receiver in 1998 and when I finished it I thought it was pretty good.  But it is much better now.  It has a nice 455 kc Toyo Crystal-Mechanical filter.  The tuning ranges on 40 and 75 now line up perfectly with the phone bands.  It now has a fuse in the power supply. And the tuning is now SMOOTH.

   

Always Listen to Pete! Second Thoughts on the S38-E

After working a bit on the Hallicrafters S38-E receiver, I am forced to admit that Pete was probably right about this receiver when he warned me that I'd be putting lipstick on a pig.  For those of you who have a sentimental attachment to this receiver, please don't take offense -- I understand.  But while I had one of these as a kid, I never really BONDED with it. That Drake 2B was stiff competition for my radio affection. So I can be more objective about this thing.  And I now think Pete was right. 

Problems: 

-- It is mechanically rickety.  It jiggles around mechanically and, as a result, electrically.

-- The front end is no match for Northern Virginia RFI.  All it has between the antenna and the converter tube is one puny LC circuit.  Not enough.

-- The LO mixer and the LO are stuffed into one 12BE6 tube.  The IF amp and the BFO cohabitate in another tube. In each case there  just seems to be too much going on between one plate and one cathode. 

-- The whole AC/DC transformer-less thing is kind of nuts. You have to get used to TWO ground symbols on the schematic: one symbolizes B- (and is not attached to the chassis).  The other is to chassis ground.  Turns out that my E model is not really a "widow maker" -- they have a 470K resistor and a cap between B- and chassis ground, so the damage you could do to yourself was quite limited.  Still, it is all kind of goofy.  I have an isolation transformer on the chassis, ready to move this receiver into the 1960s if the spirit ever moves me.  KB2WIG commented:  "At closing time, I don't care if the S38 has lipstick."  

As I worked on this thing, I began to realize that the little homebrew 6U8 receiver I have next to it on the bench is a much better receiver.  So I began to lose enthusiasm for putting lipstick on the S38-E.  At least for the moment.  I do like the cool 1950s place names on the S38-E's front panel:

Java
USSR
Vatican
Singapore
Edmonton (!)
Congo
Milan
Iceland
Angola
And of course, the CD (Civil Defense) frequencies. (For when you wanted to do some shortwave listening while ducking and covering. )

But for  now, me and the S38 are on a break. 

A Reduction Drive for the Mighty Midget's Mate Receiver

This morning I put a reduction drive onto the main tuning cap of my 6U8 Mate for the Mighty Midget receiver.  Before I had been directly turning the 35 pf variable cap.   The tuning rate was a bit too high for easy tuning of SSB stations.  This drive went in nicely and it does reduce the tuning rate considerably, but it feels a bit tight.   Is there anyway to loosen up one of these drives?

Meeting up with ARRL CEO Tom Gallagher, NY2RF

On April 12, Tom Gallagher NY2RF was in DC and was kind enough to make some time in his schedule for us to get together and talk about radio.  As we mentioned on a recent podcast, Tom, who has recently taken over as Chief Executive Officer of the American Radio Relay League, is a true FB ham.  He has a restored Drake station that he keeps on the air, and was recently talking up the Michigan Mighty Mite during his interview with Eric 4Z1UG in the "QSO Today" podcast.  And he is a SolderSmoke listener.  It was great to finally meet Tom.  We are all lucky to have him at the ARRL.

Pigs, Lipstick, and my old Hallicrafters S38 "Widow Maker"

I blame Grayson for this.  After getting my old 6U8 superhet running nicely on 80 and 40, my attention turned to an old Hallicrafters S38-E that had been relegated to the car port (Armand saw it out there, looking abandoned.)  I didn't like it because of its "transformer-less" "widow-maker" power supply. I was afraid to even GIVE it away for fear that someone would electrocute themselves.  But Antique Electronics Supply had an isolation transformer, so the order went in.

I have to rewind or replace one of the primaries on the input antenna coil.  This was a victim of the original cheapo power supply.  Apparently the antenna terminal got grounded when the chassis was "hot."  POOF -- smoke was released.    

The bands do seem to sound better through thermatrons... And there is an undeniable 3-D aspect to working on these old rigs.

So yes, in a certain sense  REAL RADIOS GLOW IN THE DARK.

.............

Bill, I think that as long as you don't work on it in the car port in your bare feet you'll be fine!  Good luck with it and don't blame Grayson too much.  I think it was destined to come back in the house eventually.  The radio gods have been whispering in your ear!
 Ciao! & 73, Armand

............

Bill:

I’ll take the blame, no problem!

S38 is nice to work on, plenty of room, no magnifying glass required.  But I have to admit I am not a big fan of working on low cost AC line powered “raft-anchors” (too little for a boat).  Definitely give it a isolation xformer and replace the filter cap(s).  If it doesn’t weight 50+lbs, a bit lightweight for me.

If you need a good thermatron homebrew project (and who doesn’t really), I’ll send you plans for a nice 4-thermatron (including compactron) AM/CW 20/40M 5 watt transmitter I am finishing up (90% of the work is “finishing up”).   Designed from scratch.  Actually works.  Uses a new construction technique I’ve been working on. 

Grayson

..........

Hi Bill,

As I read about your next project – kept thinking –you can put lipstick on a pig BUT it is still a pig. I had one and put an isolation transformer on the front end –but found I was showing signs of carpal tunnel syndrome on my left hand as I kept retuning the radio because it drifted so much. Have fun.

Pete

Pete:

I don't know.  Simplicity is a virtue, and this thing is pretty simple: RF amp, mixer, LC oscillator, detector, audio amps.  Broad as a barn door with just two 455 kc IF transformers for the filter. Lots of room on the chassis. 

As for drift, my little 6u8 RX with LC oscillators in both LO and BFO settles down very nicely. 

Bill

...............

Hi Bill,

 I surely didn’t mean to denigrate your next homebrew project and perhaps it was that the one I had was a  dud in the lot.

 But I then moved up to the SX-99 and was in tall clover. Besides today we have some things we can do to enable “tamer” oscillators. So why not? You need to team that up with the M^3 and make some contacts.

 Pete

.............

Pete: I KNEW  you would try to get a synthesizer of some sort inside the S38-E.  But I say NO!  I had a lot of fun getting the LC oscillators in my 6U8 rig to tune exactly where I wanted them to tune.  You know, play around with the cap in series with the main tuning cap to change the tuning rate (better than removing plates -- they are hard to put back on!).  Then changing the values of the L and C elements to get the thing to oscillate in the desired range.  Then wrap it all up with some Dymo tape on the 1/2 CD "tuning dial."   Sure, I know, that would have been a few keystrokes on the Arduino, but somehow this old way puts you closer to the physics, closer to the electrons. Take a look at the e-mail about Wooden Boats, VFOs and PTOs on yesterday's SS blog. 

The "widow maker" potential of the S38-E was apparently on the minds of the guys who designed the cabinet. The whole box and the front panel are all very carefully insulated from the chassis.  Plastic nuts!

Nice looking pig, by the way.  She may appear on the blog soon. 

73  Bill

Wooden Boats, VFOs and PTOs -- Recovering Lost Arts

Photo from radiomuseum,org

I couldn't resist posting another great message from Rick Campbell, KK7B.  This one was sent by Rick to the r2pro mailing list.  Rick mentions the Collins Permeability Tuned Oscillator.  More info on this magnificent bit of old tech can be found here:

http://www.radiomuseum.org/forum/design_excellence_the_collins_pto.html

Rick writes:

Great stuff here on different approaches to designing-building-experimenting with stable VFOs. Some of it is a mature art, and some really is a lost art--but that's good.  There's nothing quite so gratifying as recovering a lost art while taking advantage of modern tools and techniques, and perhaps exchanging ideas on some new-fangled communications medium.

If you ever want to see folks having a blast recovering a lost art, head to a wooden boat festival and watch the kids learning from old codgers who can do magic with a little bit of centuries old technology.  Just don't mistake it for reenactment--some of the new boats these kids are designing, rowing and sailing may include some venerable tools and techniques and give an aesthetic nod to classics, but they are lighter, easier on the environment, easier to transport, and much much faster than historic craft.

We can do the same with our radios.  Spend as much time designing and building your VFO as I spent designing the small sailing rig for my little boat--or convert an old Collins PTO to solid state.  For highest performance use a mix of old and new--I use hand stitched 1968 sails from the Schatteaur Loft in Seattle on my bigger old boat.  Old radios are a treasure trove of parts and technology, and since 1959 well-designed HF gear has been stable enough for SSB.

I measured one of my converted old Collins 2.5 to 3.5 MHz PTOs at 18 Hz per hour drift.  It was originally built in the mid 1950s.  Some problems were solved long ago, and the techniques and solutions hold up well over time.

As with the kids studying old wooden boat techniques and then taking their new creations out on the Salish sea, it is well worth our time and effort to spend some time studying how our forbears constructed a good VFO a half century ago.  It's not just the schematic: the construction, materials, temperature coefficients...all are important, and the quickest way to come up to speed is to study old stuff that works well.

Good stuff, and have fun with the experiments.

Best Regards,

Rick

K.P.S. Kang's Pixer Superhet

K.P.S. Kang (VU2KR and VU2OWF) has been contributing ideas and circuits for many years from his QTH in Punjab India.  He is the source of what became known as the VU Transmitter circuit:
http://www.zerobeat.net/g3ycc/week1.htm

Today I spotted a recent blog post by OM K.P.S. on a simple superhet receiver he is working on.  He has a knack for describing the design considerations (needed gain, IF selection, etc.)
Check it out:

http://smallwonderqrp.blogspot.com/2016/04/pixer-empirical-hf-superhet-receiver-i.html

and

https://plus.google.com/111066147552844651495/posts

WSPR Party Balloons Make it Across the Pond

		Hans Summers April 15 at 11:25am
VE3KCL/QRP Labs S-9 balloon finally reached Europe! What a crazy way to cross the Atlantic. Crossed Portugal, now into Spain. France is next! 16mW 30m WSPR signal was reported in ZL and VK (19,000km DX). Who says you need 5W on HF WSPR? 73 Hans G0UPL http://qrp-labs.com