Linear Tuning in the HT-37

I just kind of like this picture.  This is the HT-37 dial that came with the HT-37 VFO assembly I recently bought.  Note the retro designation: KILOCYCLES.  And note the nice, even, linear spacing of the VFO. This VFO runs 5 -5.5 MHz.  The circuit is a series-tuned Clapp.  That circuit seems to be one of the secrets of getting linear tuning -- to avoid the common situation of having all the upper frequencies kind of bunched together at the end of the capacitor's tuning range.  I notice that this circuit was used in the Galaxy V VFO and in the VFO of the Yaesu FT-101, both notably linear in their tuning.   

Another HT-37 VFO -- No Temperature Compensation Trimmer Capacitor?

Is that thing beautiful or what?  That is the VFO assembly from an HT-37.  This one includes the fly-wheel mechanism.  It tunes 5 - 5.5 MHz.  I'll probably replace the tube with an FET, but mostly keep it as is for use in a future transceiver.  It is built like a battleship.  Hallicrafters did not mess around with the solidity of VFO construction.  

I was a bit disappointed when I did not see the split stator temperature compensation trimmer cap that was present on the Hallicrafters variable cap that I bought back in February 2021: 

https://soldersmoke.blogspot.com/2022/02/differential-temperature-compensation.html  

I took a look inside my own (beloved) HT-37 and saw that it too lacks the temp compensation trimmer that came with the February 2021 variable cap.  Could it be that the February 2021 seller had the source wrong?  Could he have in fact been selling me the variable cap from an HT-32?  Or could it be that Hallicrafters added this split stator temp compensation capacitor to later versions of the HT-37?  

Hallicrafters patented the split stator temp compensation circuit (U.S. patent #2718617).  Chuck Dachis says in his book about Hallicrafters that the company had perfected this circuit by 1957.  

An HT-32B transmitter was selling for $725 in 1963.  That's $7020 in today's money.   Wow, and that is just for the transmitter!  

Software, Hardware, and Rockets -- T-Zero Systems (videos)

There is a lot of really cool stuff in these videos.  I am a hardware guy, devoted to HARDWARE Defined Radios.  But these videos are a reminder of the importance of software, of the things we could never do with our older, analog technology.  

Watching him build his rockets, I even get ideas for my comparatively low-tech workshop: that small jig-saw that he used to cut the rocket fins looks like something I really need. 

This fellow is a professional rocket scientist who likes the work enough to take it home as a hobby.  It looks like he is working in Florida.  

Watching the videos and hearing him discuss the joys and frustrations of his endeavors reminds me a lot of what goes on in ham radio homebrewing. He often seems to have the same kind of haunted, obsessed look in his eyes that we are so familiar with.  That is what Jean Shepherd must have looked like when he couldn't get his Heising Modulator to work properly.  Oh, the humanity!   

Here it the YouTube channel: https://www.youtube.com/c/TZeroSystems

Here are some videos and stills of our 2017 rocket launches from Virginia's Shenandoah valley: 

https://soldersmoke.blogspot.com/2017/05/still-photos-and-slow-motion-video-from.html

Go WERRS! 

IGY! Science and the Vanguard Satellite in 1959 (video)

The International Geophysical Year (1958-1959) was a very scientifically productive period.  It is really amazing how much we learned from tiny satellites like Vanguard.  Like the shape of the Earth!  Great stuff in this video.  

Very cool telescopes and cameras set up around the world to monitor the early satellites.  And there is a quick mention of ham radio efforts to monitor the new spacecraft. 

Thanks to Josh G3MOT for sending this to us. 

Go IGY! 

A Surprisingly Good Movie from the Late 1960s: "The Ham's Wide World" (Video)

I found this movie to be surprisingly good.  Narrated by Arthur Godfrey, it features Barry Goldwater, and a lot of other hams.  There is a homebrewer too!  Lots of  old rigs we know and love:  a Drake 2-B, a couple of Galaxy Vs, a Benton Harbor lunchbox, Heathkit SB-series rigs, many Swans, and was that an HQ-170 that I saw in there?  There are also many cool antennas, including a 15 meter quad set up by a bunch of Southern California teenagers. 

Near the end, when they visit ARRL Headquarters, we briefly see none-other-than Doug DeMaw, W1FB!  FB!  

Please take a look at this video and post comments about the rigs, antennas, and radio amateurs that you see in the film. 

Apollo 11 in Real Time

https://apolloinrealtime.org/11/

This web site presents all the data received from Apollo 11.   They are presenting it in the sequence it happened, exactly as it was 53 years ago today.  Today's clock is synched with clock from 53 years ago. I just tuned in today -- they are at the 6 day point in the mission.  Armstrong and Aldrin are on the Lunar surface, resting.  Collins is in orbit, sleeping.   

This is exactly the kind of thing we need to have playing in the background as we build things in our shacks.  Thanks to Peter O'Connell VK2EMU for sending us this wonderful link.   https://apolloinrealtime.org/11/  

 

Putting a Real LC VFO in My Ceramic-Resonator, Direct Conversion 40 Meter Receiver. LC JOVO! (Video)

This is the DC receiver that I built back in 2017-2018. I had used a ceramic resonator in the VFO. That receiver was on the cover of SPRAT magazine. It may not have deserved the honor -- recently Dean KK4DAS and I discovered that the ceramic resonator VFO drifted rather badly. So Dean and I are now building real LC analog VFOs. This is kind of an aside to a Virginia Wireless Society -- Maker Group project. This video shows my receiver working yesterday on 40 using the VFO that was recently thrown together.

More details on the original project (that used the ceramic resonator) here: 

https://soldersmoke.blogspot.com/search/label/DC%20Receiver%20Build

 The VFO circuit comes largely from W1FB's Design Notebook page 36.  I followed most of the conventional tribal wisdom on VFOs:  NP0 caps, often many of them in parallel.  Air core coil (in my case wound on a cardboard coat hanger tube). 

For C1 I used a big variable cap (with anti-backlash gears) that Pete N6QW advised me to buy on e-bay. Thanks Pete.   L1 is on the cardboard tube.  I only built the oscillator and the buffer -- I did not need the Q3 amplifier.  (The water stain in the upper left is the result of a heavy rain in the Azores around 2002 -- water came pouting into the shack.)  

I think the VFO is more stable than the Ceramic Resonator circuit. But I want to go back and give the ceramic resonator circuit another chance...  Miguel PY2OHH has some really interesting ceramic resonator circuits on his site. Scroll down for the English translation: https://www.qsl.net/py2ohh/trx/vxo40e80/vxo40e80.htm

Dean KK4DAS commented that VFO construction is as much an art as a science.  I agree -- there is a lot of cut and try, a lot of fitting the components you have on hand into the device you want to end up with.  You have move both the frequency of the VFO AND the tuning range of the VFO.  Mechanics (in the form of reduction drives) is often involved.  And, of course you have to apply lots of tribal knowledge to get the thing stable. You could, of course, avoid all of this by using an Si5351, but I think that moves you away from the physics of the device, and is just less satisfying. 

So,  JOVO!  LC JOVO!  The Joy of VARIABLE Oscillation!   

Hex DX! First Long-Haul Contact with the New Hex Beam - VK4KA on 20 SSB

This morning at around 1345 UTC I had the chance to try out my new Hex beam on some "down under" DX.  9,548 miles, 15,222 km    The DX Spot page told me that VK4KA was on 14.255 MHz.  QRZ.com said the beam heading for me was 270 degrees.   He was quite strong.  He was working a fairly huge pileup, going through callsign numbers.  He was on the 6s when I tuned in, so I had some time to test the Hex beam.  Above you can see a rough front-to-back test.  Below you can see a comparison with my old 75 meter doublet.  

A few minutes after the second video, in spite of the pileup I called VK4KA and made the contact.  I congratulated him on his homebrew Moxon.  https://www.qrz.com/db/VK4KA

It was fun to reach Australia with the new antenna. 

Jean Shepherd and Studs Terkel Talk About Radio on "The Big Broadcast" Sunday night 7pm-11pm

 

I'm home recovering from the second COVID vaccine booster (I feel OK, just a bit tired).  Our local public broadcast station, WAMU, announced that on Sunday night (July 17) from 9 to 11 pm EDST they will rebroadcast a 1962 radio show featuring Jean Shepherd and Studs Terkel.  They will be talking about the impact of radio on society.   

Here is the link:   https://wamu.org/show/the-big-broadcast/

Looks like they will make an mp3 available after the show.  

I like "The Big Broadcast" and often tune in.  

James Webb Telescope's Deep Field -- What Would Be Behind A Grain of Sand Held at Arms Length. Click on the Picture

 NASA’s James Webb Space Telescope has produced the deepest and sharpest infrared image of the distant universe to date. Known as Webb’s First Deep Field, this image of galaxy cluster SMACS 0723 is overflowing with detail.

Thousands of galaxies – including the faintest objects ever observed in the infrared – have appeared in Webb’s view for the first time. This slice of the vast universe is approximately the size of a grain of sand held at arm’s length by someone on the ground.

Hex Beam at N2CQR

 

I got my K4KIO Hex Beam up on the roof yesterday.  I think it looks pretty good!  It is in the same spot that I had my beloved Moxon.  Curse you Nor'Easter!   

Putting this thing in the air made me appreciate the relative simplicity of the Moxon.  It had just four poles, not six.  It weighed just nine pounds, not 25.  It was significantly smaller.  On the other hand, that antenna just gave me one band -- I have 20, 17 and 12 on this one, and I could add three more. Also, this one is a lot more rugged, and is likely to survive the next Nor'Easter. 

It was fun spinning it around.  First QSO was DX on 20 SSB:  EA1HDZ.  This morning I spoke to KP3CQ in Puerto Rico.  Later,  I was listening to ZS3Y -- he was faint until I tried him on long-path.  He was transmitting on the long path and was much stronger when I pointed in that direction.  

I kept the 75 meter doublet -- I just put it on another tripod.  So I will be able to continue to use that antenna for 40 meter AM contacts (I've been having a lot of those lately).   

Surface-Mount Solder Smoke -- Is THIS Really Homebrew?

I was recently noting that the assembly of IC, CPU-based projects doesn't seem like real homebrew radio.  I realize that there is a danger here -- there is a tendency in ham radio to reject the new and to stick with the old.  "SPARK FOREVER" was the rallying cry when CW came along.  There are still a lot of AMers who refer to SSB as "Single Slop Bucket." So, with that in mind I point the blog to the above video.    He is using complicated ICs that probably have thousands if not millions of transistors.  But he is definitely making something new. And he releases some real solder smoke in the process.   FB.  

It is probably not for me, but others may like it. Like the old song says "Different strokes for different folks." YMMV.