Free Download of AADE Filter Design Software

Very useful when homebrewing filters. I am using it now to build crystal filters.  

http://www.ke5fx.com/aadeflt.htm

Thanks to KE5FX

LA6NCA Designs and Builds a Very Hybrid 80 Meter Transmitter (Si5351 and a 12A6 Tube) (Video)

Helge LA6NCA put out a really nice video explaining how he designed and built an 80 meter transmitter. 

I like how he put the Si5351 and the Arduino chip in what looks like a slightly expanded FT-241 crystal box.  Nice.  

I like the box and the chassis.  

I like his testing/tuning technique.  

The homebrew capacitor was a very nice touch.  

Where can I get some of those coil forms?  

And of course, the R-390 receiver adds a lot of mojo to the shack. 

Helge's web sites document an enormous number of great projects:  

Helge's page on the 12A6/Si5351 transmitter: https://www.la6nca.net/homebrew/tx_12a6/index.htm

Helge's main site:  http://www.laud.no/fykse/index.htm

Thank you Helge! And thanks to Hack-A-Day for alerting us to this. 

VK3HN's Amazing Summit Prowler 9 Homebrew Transceiver - A Masterpiece of Miniaturization (VIDEO)

I was wondering what Paul VK3HN was up to. Now we know: the Summit Prowler 9 transceiver. 

This is yet another amazing rig by Paul, with GREAT documentation.   

I was impressed by those bandpass filters.  I will try to do something similarly robust on my 17/12 rig. 

Paul's miniaturization of this rig is really astonishing.  I would go nuts trying to keep it this small. I just couldn't do it. 

Look closely at the boards he uses.  They look like printed circuit boards, but with all the components and all the soldering on one side.  This is very smart -- this makes it easier to troubleshoot and to change components.  

I was glad to see at least one NE-602 in there.  FB. 

The video is above.  Check out Paul's blog for more info: 

https://vk3hn.wordpress.com/2021/02/27/sp-9-a-compact-five-band-ssb-cw-qrp-transceiver/ 

Thanks Paul!

Split Stator Temperature Compensation Also Used in Yaesu FT-101

The eagle eye of VE3EAC spotted this (he also correctly pointed to a tiny broken "tine" as the cause of my  HP8640B woes).   I had missed the temp comp circuit.  Inside the Yaesu FT-101 VFO box that I used in my Mythbuster rig, there is a split stator capacitor and two temperature compensation caps similar to that recently described by Mike WU2D.  Very cool.  You can see the temp compensation cap in the picture (above). The red arrow points to the split stator cap,  the blue arrow points to to the two temperature compensation caps attached to it. You can see them all in the schematic below(in the lower left of the schematic). 

Old Military Radios at the Air and Space Museum Udvar-Hazy Center, and Autogyros

 

My son Bill and I were out at the National Air and Space Museum's Udvar-Hazy Center (out near Dulles Airport, where they display the really big stuff).  We spotted these old military radios.  The ARC-5 Command sets caught my eye.  Of course I was thinking about the great VFO parts inside those boxes...   The acknowledgement of the ARC-5's contribution to ham radio (on the card) was nice. 

 They also have an ART-13 on display.  

We had a lot of fun looking at all the planes.  We were especially impressed by the Autogyros. 

The Bensen B-6 Gyroglider seemed to be really pushing the envelope (of good sense!).   This was a an Autogyro with NO MOTOR.  It was towed!  No license required as long as you didn't release the tow line.   Note that it was designed in 1954 to introduce teenagers "to the thrills of flight at minimal cost." The headgear and goggles were key.  And the kit was only $100! 

An Analog LC VFO for my 17/12 Meter SSB Transceiver (VIDEO #1)

Here's my initial work on a VFO for my 17 meter -- 12 Meter Single Conversion Dual Band SSB Transceiver. The IF (crystal filter) will be at 21.4772 MHz. On 12 meters the VFO will run from 3.5128 to 3.4528 MHz. On 17 the VFO will run from 3.3092 to 3.3672 MHz.

The transistor I am using is an SK3050 Dual Gate MOSFET. I bought a bunch of these years ago in a panic when I heard that 40673's were getting scarce.

I forgot to mention another important reference: Joe Carr's Popular Electronics VFO articles:

https://soldersmoke.blogspot.com/2017/04/vfo-tribal-design-wisdom-from-joseph.html

Thanks again to Dale K9NN for the bags of NP0 capacitors. And to Pete N6QW for the suggestion on the HT-37 main tuning cap.   Thanks to Mike WU2D for the great VFO videos, and to Frank Harris for his wonderful book on homebrewing.  And we can't forget the great reference books that guide so many of our projects: Solid State Design for the Radio Amateur and Experimental Methods in RF Design -- thanks to Wes Hayward W7ZOI and all of his co-authors.  

Boxing it Up: Tribal Knowledge from Pete N6QW on How to Make Enclosures for Homebrew Rigs

 

http://n6qw.blogspot.com/2022/02/2022-return-to-peashooter-build.html

Thanks Pete!  

Pete's Eclectic Approach to the Pea Shooter, San Jian counters on Analog VFOs, Non-Restaurant Menus

I liked Pete's comments on the various (analog, digital, mixed) approaches to homebrew: 

http://n6qw.blogspot.com/2022/02/2022-return-to-peashooter-build.html

http://n6qw.blogspot.com/2022/02/2022-peashooter-20m-compact-ssb.html

I too have San Jian digital counters watching the stability of analog VFOs (DX-100, HQ-100, Mythbuster). 

Variety is the spice of life!  

I also liked Pete's comment about the fellow who does on-the-air menu counseling for FTDX-3000 owners.  I sometimes run into guys on the air who want to do something similar with my simple homebrew rigs.  They start by making comments about my audio -- they will usually say it is "too high" or something like that.  Especially when I'm using the separate transmitter and receiver (which have to be "netted" imprecisely by ear), I have to explain that maybe resort to their RIT control would help.  If they persist, I sometimes have to tell them that how my rig sounds depends A LOT on the placement of the carrier oscillator relative to the passband of the crystal filter (most recently, the filter from the 1963 Swan 240).  Most of them have never had to do that kind of adjustment, so the "technical discussion" usually ends at that point, with my interlocutor saying 73, and presumably moving on to someone whose rig has menus to fiddle with.  (Recently heard audio techno term: "massaging the codec.") 

To each his own!    

A Thermatron (and Asperger's) Knack Story

Heroic stuff.  In more ways than one.  FB Mark.  

 https://www.aane.org/over-and-out/

How The Physics of Resonance Shapes Quantum Reality

Here is an interesting article that appeared in Wired.  It will resonate with many SolderSmoke listeners!

https://www.wired.com/story/how-the-physics-of-resonance-shapes-reality/#intcid=_wired-bottom-recirc_972910f0-7b0e-4a47-84bf-3a375ead6667_text2vec1-reranked-by-vidi

Differential Temperature Compensation Capacitors in the Hallicrafters HT-37 Main VFO Tuning Circuit

 

I've been watching with great interest Mike WU2D's excellent series on VFO construction.  His second video is especially interesting because he talks about how we can use a split stator differential capacitor to build a temperature compensation circuit that will allow us to "dial in" the proper amount of temperature compensation.  

The heart of this circuit is the split stator differential capacitor.  The stator is split; but there is a common rotator. As the rotator moves, the capacity across one part of the capacitor increases while the other part decreases -- thus the total capacity remains unchanged.  If we connect two capacitors of the same capacitance BUT OF OPPOSITE TEMPERATURE CHARACTERISTICS -- we can use this split stator cap to select just the right amount of temperature compensation.   Very cool.  Even cooler:  Mike actually built a split stator differential capacitor.  That, my friends, is dedication. 

I was sitting here this morning thinking about all this when it occurred to me that right in front of me was a capacitor that might be relevant to all this (see above).  I bought it on e-bay one year ago after Pete N6QW had alerted me to it.  It is the main tuning capacitor from an HT-37 transmitter.  What attracted us was the big anti-backlash mechanism.  But now I realized that it had another charming feature.  

Looking at it a bit more closely I saw a split stator differential cap just like the one that Mike had made.  Attached to the two rotors were two tubular capacitors.  The three caps are in parallel with the main tuning cap.  Bingo -- this is a temp compensation circuit.  

I checked the HT-37 manual.  The manual says that temp compensation is set at the factory.  OK.  But the schematic does not show the split stator caps and the two tubular caps (see below).  Could it have been that this circuit was added later perhaps to address drift? (We do see it in the HT-32B schematic -- see below.)

HT-37 VFO SCHEMATIC

Anyway, it was very cool to find this example of the circuit Mike was discussing.  In the photo at the beginning of this post you can see the three caps.  Below you can see the split stator cap in the background. 

In the comments a reader points out correctly that this circuit was discussed in the ARRL book "Single Sideband for the Radio Amateur."  Indeed, it is on page 51 of the 1970 edition, ARRL  gave credit for the circuit to Hallicrafters: 

HT-32B VFO Circuit

Joe Carr K4IPV (SK) also discussed this circuit.  In his article in Popular Electronics in August 1993, he too gave credit to Hallicrafters.  Carr also gave some detailed instructions on how to use the circuit to stabilize a VFO.  See pages 78 and  79 of the August 1993 Poptronics: 

https://worldradiohistory.com/Archive-Poptronics/90s/93/PE-1993-08.pdf

Podcast (Audio) Version of Bill's Talk to the L'Anse Creuse Amateur Radio Club

Tony G4WIF suggested that I make this talk available as an audio recording.  Good idea. Here it is: 

http://soldersmoke.com/N2CQRHomebrewing.mp3

6EA8s in the Mate for the Mighty Midget, and WA9WFA Re-Builds a Heath HW-12

I reported to Scott and Grayson that I had finally gotten around to changing the three aging 6U8 tubes in my Mate for the Mighty Midget receiver.  I replaced them with three more youthful 6EA8s.  This switch really seemed to perk up the old receiver.   I'm listening to 75 meters on it right now. 

Speaking of 75 meters, Scott sent me this picture of his latest effort:  re-building a Heathkit HW-12.  FB.  This is a way of experiencing (or re-experiencing) the construction of a Heathkit.  I did something similar, but much less complicated)  with a Heathkit VF-1.  Scott did a wonderful job taking this old rig apart.  That PC board looks great (see photo below). 

Scott's e-mail:  

Hi Bill and Grayson, I’m glad to hear of your good results with the 6EA8’s in your MMMrx! I had similar results when I finally got rid of the 6U8’s with their iffy performance and went with the 6EA8’s.  I did put a set of 6GH8A’s and tried it out, it worked, but I don’t have any data on performance improvements.  After completing the outboard power supply and audio amplifier, I’ve taken a break from my MMMRx and it’s sitting there on the bench. I’ll get back to it in a while.  

 

In the meantime I’ve started a new project where I’m re-kitting a Heathkit HW-12 eighty meter transceiver.  I have completed the disassembly process including the pcb.  I bought a Hakko vacuum desoldering iron for taking all (ALL) parts off of the pcb, and it’s bare now.   I’m planning to start rebuilding this coming week.  73 Scott WA9WFA  

Bill Talking about Homebrew Radio with L’Anse Creuse Amateur Radio Club (Michigan) -- February 2, 2022 (Video)

This was a very nice meeting.  We just talked homebrewing and why it is such an important part of ham radio.  Video above

Topics included:

-- Jean Shepherd

-- Being "Electrically Inclined" 

-- The Herring Aid 5

-- Radio Clubs around the world

-- The Shame Shelf

-- Making mistakes, releasing smoke

-- Errors in ham radio magazines and schematics

-- The importance of understanding the circuit

-- The Michigan Mighty Mite

-- Building a power supply for the HW-32A

-- The origins of the SolderSmoke podcast

-- Knack stories, the IBEW and what we all have in common

-- The importance of books

Thanks to The L'Anse Creuse ARC for the invitation. 

Video of SolderSmoke Podcast #235

Pete and Bill in LIVING COLOR! 

SolderSmoke Podcast #235 is available for download: 

http://soldersmoke.com/soldersmoke235.mp3

Travelogue:

6 weeks in the DR for Bill
One contact on uBITX. More SW listening.
Repaired my Chrome Book in Santo Domingo!
Christmas Present for All: James Web Space Telescope launch

Bill's Bench

-- Understanding the NE-602 (see blog post)

-- Thinking about a 17/12 dual bander.  Looked at old G3YCC Tx for circuits... 

-- Using Spurtune08. WB9KZY found it.  In the LADPAC zip file here:

https://web.archive.org/web/20091222012628/http://w7zoi.net/emlad08_123.html

-- Then Put G3YCC Acores SSB TX back in operation

-- Put W4OP Barebones Superhet on 17 with NE602 down converter.

-- Netting and audible spur problems 

-- Now working many stations with this old "split" TX/RX

Pete's Bench

-- The Peashooter

-- Dean's VWS build of your DC RX

-- Building a SSB Transceiver Doc

-- Homebrew Crystal Filters

-- The shrinking of the PSSST

-- PSSST on Hack-A-Day

Bad Dead Soldering Stations

-- My X-Tonics 4000 dies.   But it left behind a great box with ample socketry. 

Mailbag: 

AA1TJ Mike Rainey --- Again in the Hobbit Hole! 486 kc RX

Thomas K4SWL -- Radio Astronomy and the Raspberry PI 

WC8C Dennis Invite to the L'Anse Creuse ARC   FB  Fun

Todd K7TFC got boosted at Tektronix Beaverton Ore.  

What happened to Chuck Adams K7QO?  His work taken off the net.

W1MJA ex WN2RTH 

N7DA worked W7ZOI in Sweepstakes.  FB

Kirk NT0Z formerly of ARRL HQ

Farhan VU2ESE was up in the Pench Forest, trying to spot a Tiger! 

We spoke to Farhan's Lamakaan ARC in Hyderabad.  QO-100 beam down! 

Dean KK4DAS's 16 watter.   On SS blog

Scott WA9WFA  Bad 6U8s?   Ordering 6EA8s

Bruce KC1FSZ Peppermint Bark gift box

Mike WU2D:  Book by Frank Harris on Homebrew radio

Bob Scott KD4EBM So many good ideas and links 

Rogier PA1ZZ sending parts packages -- Thanks Rogier

SolderSmoke Podcast #235 NE-602, Azores Rig, Spur Problems, SSB Rigs, Peashooter, HB Filters, MAILBAG

SolderSmoke Podcast #235 is available for download: 

http://soldersmoke.com/soldersmoke235.mp3

Travelogue:

6 weeks in the DR for Bill
One contact on uBITX. More SW listening.
Repaired my Chrome Book in Santo Domingo!
Christmas Present for All: James Web Space Telescope launch

Bill's Bench

-- Understanding the NE-602 (see blog post)

-- Thinking about a 17/12 dual bander.  Looked at old G3YCC Tx for circuits... 

-- Using Spurtune08. WB9KZY found it.  In the LADPAC zip file here:

https://web.archive.org/web/20091222012628/http://w7zoi.net/emlad08_123.html

-- Then Put G3YCC Acores SSB TX back in operation

-- Put W4OP Barebones Superhet on 17 with NE602 down converter.

-- Netting and audible spur problems 

-- Now working many stations with this old "split" TX/RX

Pete's Bench

-- The Peashooter

-- Dean's VWS build of your DC RX

-- Building a SSB Transceiver Doc

-- Homebrew Crystal Filters

-- The shrinking of the PSSST

-- PSSST on Hack-A-Day

Bad Dead Soldering Stations

-- My X-Tonics 4000 dies.   But it left behind a great box with ample socketry. 

Mailbag: 

AA1TJ Mike Rainey --- Again in the Hobbit Hole! 486 kc RX

Thomas K4SWL -- Radio Astronomy and the Raspberry PI 

WC8C Dennis Invite to the L'Anse Creuse ARC   FB  Fun

Todd K7TFC got boosted at Tektronix Beaverton Ore.  

What happened to Chuck Adams K7QO?  His work taken off the net.

W1MJA ex WN2RTH 

N7DA worked W7ZOI in Sweepstakes.  FB

Kirk NT0Z formerly of ARRL HQ

Farhan VU2ESE was up in the Pench Forest, trying to spot a Tiger! 

We spoke to Farhan's Lamakaan ARC in Hyderabad.  QO-100 beam down! 

Dean KK4DAS's 16 watter.   On SS blog

Scott WA9WFA  Bad 6U8s?   Ordering 6EA8s

Bruce KC1FSZ Peppermint Bark gift box

Mike WU2D:  Book by Frank Harris on Homebrew radio

Bob Scott KD4EBM So many good ideas and links 

Rogier PA1ZZ sending parts packages -- Thanks Rogier

NASA Video of Moon Orbiting Earth (Looks Fake, but Is Real)

https://scitechdaily.com/this-is-real-nasa-camera-a-million-miles-away-shows-moon-crossing-face-of-earth/

FLASHBACK: The Herring Aid 5 Direct Conversion Receiver and Frank Jones (Video)

The Radio Gods seem to be pushing me towards Direct Conversion receivers.  This week I was speaking via Zoom with the very FB L'Anse Creuse Amateur Radio Club in Michigan.  My Herring Aid 5 tale of woe came up (see video above).   Then Dean KK4DAS was sharing video of the amazing fidelity of the Pete Juliano Direct Conversion Receiver.  Then I started thinking about Frank Jones W6AJF, and the story (fictional) of his build of the Herring Aid 5 by Michael Hopkins AB5L: 

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

I gave Frank a board for the Herring Aid Five redux from the April 1998 QRP Quarterly and challenged him to build one up. It took maybe two hours and that includes his own touches which included refusing to buy any parts.

For the transformers, he calculated the turns ratios from the impedances and tested a bunch of TV set pulls 'till he found something close. But he made the output 1:1 because his Brandes phones are close to 1000K Ohms as it is. 

He was willing to use toroids, but not to buy one, so I gave him an Amidon circular and he calculated the values of the 18 specified units. Then he wound them on unidentified cores from my junk box after learning the permeability of each with his homebrew dip meter. 

A store bought Zener was out of the question so he mixed and matched regular diodes with transistors hooked up as diodes until he got close enough to 10 volts. The mosfets came out of a TV tuner and Frank will use any plastic bipolar that says "C" or "D" on it for a 2N2222. 

Of course it worked the first time. He rigged up a patch to a pair of Class A push-pull 6L6s so Christie could hear it and she said it was "Also cute but bigger than the other one." 

Now a real QRPer would cry at that, but not Frank who sees no advantage in miniaturization at all. In fact, he mounted the whole thing in an old case from a Collins 6 and 2M transceiving attachment he junked out for the parts and no two knobs matched as Frank thinks matching knobs slow you down in a pileup. He wanted to take it back to his own shack and try it out with his breadboard MOPA and pair of 100THs because he does not run QRP, saying it "transfers the burden to the other guy."  

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

Frank Jones was one HARD CORE HOMEBREWER.  No store-bought Zener diodes or toroidal cores for him! 

All of the SolderSmoke Herring Aid 5 articles can be found here: 

https://soldersmoke.blogspot.com/search?q=Herring

Thomas K4SWL -- SOTA Activation on Bearwallow Mountain, North Carolina (video)

Thomas put out a very nice video of his recent activation of Bearwallow Mountain in western North Carolina.  Really nice.   It was fun to see the QSOs and the logging as he did it.  Very cool that he worked Christian F4WDN --- Jack NG2E also worked F4WDN on a recent activation in the Shenandoah area of Virginia. 

More details on the activation here:  

https://qrper.com/2022/02/summits-on-the-air-pairing-the-elecraft-kx2-and-chameleon-cha-mpas-lite-on-bearwallow-mountain/

Thanks Thomas! 

Barefoot Ham Radio -- PA2OHH's Wonderful Web Site

I first saw the link to Onno's site on Peter VK2TPM's blog.  And at first I confused it with the site of another great homebrewer Miguel PY2OHH.   This is all very IBEW:   On the website of an Australian ham,  I spot the web site of a Dutch ham living in Spain and briefly confuse him with a Brazilian homebrewer with a very similar callsign.  TRGHS. 

Onno PA2OHH has an inspirational approach to the hobby that he presents in a  really wonderful website.   Here is his intro to Barefoot Radio: 

Barefoot technology and Barefoot power!

Barefoot technology or simple, non-professional radio technology and real Barefoot power or harmless QRP power, that is what you will find here. There are some complex designs but many designs are simple radio amateur circuits. They will never be used professionally!
These simple circuits and rigs can give you much fun: home brewing, portable activities during holidays, etc.
Batteries and inverted V dipole antenna's with a fishing rod as the center support are all you need to make many QSO's.

Much fun!
Barefoot technology and Barefoot power can give you much fun, but is not perfect... There are disadvantages like VXO control instead of a VFO, direct conversion receivers that receive both sidebands and simple frequency displays that are not so easy to read. But working with such simple equipment is often more exciting than working with a much better commercial transceiver.
Perhaps that you cannot believe that you can make many QSO's with QRP power of only 1 watt. Indeed, some practice is needed in the beginning so do not give up too soon. Every boring standard QSO becomes an exciting experience with QRP power!

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

Check out Onno's site:  https://www.qsl.net/pa2ohh/

Mike WU2D -- VFO Video #3

Mike WU2D continues to show us how it is done.  I hope to make all my future VFOs using the techniques he describes.  Thanks Mike. 

Exorcism Lite -- Spur Suppressed on 17 meter Transmitter -- Split TX/RX Station On The Air

I spent most of January in the tropics, away from my workbench.  This seems to have had a good effect on my 17 meter split TX/RX project.  As I was leaving, heading south,  I was thinking about several difficult options to deal with my spur problem (see previous blog posts). I thought about turning the transmitter into a transceiver by building a receiver board.   I thought about putting San Jian frequency counters on both the transmitter and the receiver, then doing a visual numerical "netting" by just putting the two devices on the same frequency (I actually ordered 3 San Jian counters).   The counter option was even more complicated than it at first seemed -- I would have to build a converter to shift the RX VFO frequency up.  VK2EMU suggested a tube type "Magic Eye" (interesting idea, but also complicated).   This was getting out of hand. 

When I got back home, I took a new look at the problem.   I decided to take one more shot at suppressing the 8th harmonic of the carrier oscillator.  I had already built a new oscillator and buffer using the circuit from Farhan's BITX20.  And I had put it in a metal box.  Now I decided to do three things: 

1) Tighten up the low pass filter at the output of the buffer by moving the cutoff frequency lower (to around 7 MHz) thereby getting a bit more suppression at 41 MHz

2) Try putting a series LC shunt circuit tuned to 41 MHz  at the output of the carrier oscillator (between the oscillator and the buffer). 

3)  Reduce the voltage to the oscillator/buffer.  I have this on a pot, so I can adjust it down to the point where the remnant of the harmonic is no longer audible, while keeping the main carrier osc signal sufficiently strong. 

It seemed to work.  I could now hear the desired frequency for spotting, without the confusing tone from the spur.  

Why had I been able to do this back in 2002 in the Azores using a simple trimmer cap to ground?  My guess is that I was using my Drake 2-B as the receiver.  The trimmer cap to ground may have reduced harmonic output.  And I was probably cranking back the RF gain on the 2-B to the point where I could hear the desired signal but not the remnants of the spur.  I have no RF gain control on the Barebones Barbados receiver that I am using in this project. 

So, what's the lesson from all this?  Well, if you are faced with a serious technical problem, and you find yourself considering complicated and difficult solutions,  go to the Dominican Republic for about a month (especially if it is January or February), and then take another look at the problem when you return.  If you are unable to travel this far or for this long,  taking a walk or taking a weekend break from a troublesome problem will likely have a similar mind-clearing effect. 

The video above shows part of a February 1, 2022 QSO with Gar WA5FWC using the split TX/RX 17 meter rig.  Gar is an amazing long-time SSB homebrewer who got his start with phasing rigs back in the day. 

The NCDXF/IARU Beacons (very useful website)

 

So there I was, innocently checking the lower end of the tuning range on my now 17 meter SSB Barebones Barbados W4OP receiver.  I had it tuned to the bottom of the 17 meter phone band.  All of a sudden I hear YV5B in CW.  It was obviously a beacon transmission. 

I had forgotten about these beacons.  Some quick Googling brought me to a very up-dated web site: 

https://www.ncdxf.org/beacon/

The site shows exactly which station is transmitting at any given moment.  There is also a very handy map display giving beam headings and distance from your location.  

So far, I'm only hearing YV5B and VE8AT.  I hope to hear more once the Coronal Mass Ejection is behind us. 

Check it out.  Leave your receiver on 18.110 MHz.  Let us know what you are hearing.  

Three cheers for the NCDXF and the IARU! 

Mike WU2D Shows Us How to Do Temperature Compensation in Homebrew LC Analog VFOs

In several of the articles that I have seen about the homebrewing of VFOs the authors seem to throw up their hands when the subject of temperature compensation comes up.   They seem to just say, "This is hard.  Not for the faint of heart.  Good luck with that!"   But in this great video Mike WU2D shows us in very practical terms how to do temperature compensation of VFOs.   This is really great news for those of us who prefer old style coils and caps to Si5351 chips.  Thanks Mike!