Podcasting since 2005! Listen to Latest SolderSmoke
Tuesday, April 23, 2024
EXCELLENT Video Series on RF Amplifier Design
Wednesday, March 13, 2024
Using the RF Power Amplifier of the BITX40 Module
Friday, September 29, 2023
"The Art of Electronics" #8 -- Why Not a Simple Emitter Follower as The AF Output Circuit?
Back when Dean KK4DAS and I were trying to find a suitable AF amplifier circuit for our High School Direct Conversion receiver project, we were debating what to use as the final. One option was the standard NPN-PNP push-push amplifier (like in Figure 2.53 above) -- an advantage with this one was that it would not require an AF transformer. But we decided that this circuit would add complexity to a project that we were hoping to keep very simple.
Another option was a simple common emitter amplifier with a transformer in the collector circuit. This worked, and was simpler. We ordered the transformers.
In the midst of all this, at the local radio club hams asked us why we just didn't put a single emitter follower at the output to handle the impedance transformation to an 8 ohm speaker (sort of as in Figure 2.52 above). They were convinced this would work. I was not so convinced and pointed out that we had never seen such a circuit in any of the ham radio literature. If this could be done, why hadn't the likes of Doug DeMaw and others used this circuit in their many, many rigs?
This discussion kind of ended there (we opted for the common emitter transformer circuit), but I have thought about it from time to time. A couple of weeks ago, when I got the second edition of The Art of Electronics, I found the above discussion of the use of this kind of emitter follower circuit. You can see why this circuit has not been used. Just to be sure, I built one in LTSpice. Sure enough, it takes way too much current.
Thank you, Horowitz and Hill!
Friday, September 8, 2023
Why Building for 10 Meters is Harder than Building for Lower Frequencies
Recently my trusty CCI EB63A .1kW amplifier has been in rebellion. On 10 meters, it now often insists on being an oscillator. It calms down nicely on 20 meters. But on 10, it has been a rebellious beast.
Why is this? Why would an amplifier that is well behaved and stable on 20 meters behave so badly on 10 meters?
I used LTSpice to explore the problem.
I looked at two ordinary wires. I gave them each a value of .003 uH. Very low. Then I joined them together in a transformer. I put a 1 volt signal into the primary and looked (in LTSpice) at how much of a signal appeared in the secondary. First, the result on 14 MHz. About 250 mV appears on the secondary.
Tuesday, June 7, 2022
SolderSmoke FDIM Interviews: A BRAVE HAM! Grayson Evans KJ7UM Presents a 50 Watt Amplifier to THE QRP GROUP!
Wow, talk about walking into the lions' den! Grayson Evans, author of "Hollow State Design" and guru of all things thermatronic, went to FDIM and made a presentation TO THE QRP GROUP on how to build a 50 watt amplifier with a 6146 thermatron. In New York that would have been called chutzpah. The QRP ARCI guys seem to have tolerated this QRO-heresy; I'm not so sure the zealots over in G-QRP would have been quite so tolerant.
Grayson gave a nice shout out to SolderSmoke's Pete Juliano.
And he offered some sage advice to those who live in fear of high voltage: "Don't touch anything with high voltage on it." Words to live by my friends. He even managed to call those who shy away from high voltage "wimps." This was all very reminiscent of the unforgettable safety advice he offered in his August 2021 interview on Ham Radio Workbench: "Try not to swallow anything, and don't sit on the thermatrons." I mean, who can argue with that?
You can listen to Bob Crane's interview with Grayson here (about 6 minutes total):
http://soldersmoke.com/2022 KJ7UM.mp3
Check out Grayson's Hollow-State Design Book 3rd Edition: tinyurl.com/hollowstatedesign3
Check out Grayson's technical blog:kj7um.wordpress.com
Sunday, June 5, 2022
JFET (Junction Field Effect Transistor) Video -- Part 1
Monday, April 25, 2022
75/20 - 17/12 Two Homebrew Rigs in Scrap-Wood Boxes
Wednesday, April 13, 2022
The 17 & 12 SSB Transceiver -- Circuit and Build Info -- Video #4
Saturday, December 4, 2021
Dean's Supercharged, 16-Watt, Furlough 2040, Simple SSB Rig
Tuesday, October 5, 2021
Dean KK4DAS Builds an EI9GQ 16 Watt RF Amplifier (and Noodles in the Process)
Tuesday, August 3, 2021
AFTIA! The Audio Frequency Termination Insensitive Amplifier from W7ZOI
Saturday, March 6, 2021
ZL2CTM's Simple SSB Transceiver
Friday, August 14, 2020
Tor LB4RG Builds an IRF-510 Amplifier
Click on the link to check out Tor's very FB and artistic video about his homebrew IRF-510 amplifier.
Very Nice. Also, check out Tor's FB SolderSmoke hat.
https://gopro.com/v/bQ1JGOXRrRqrQ
And here is an update from Tor"
https://gopro.com/v/gv19pDDqQnO1a
Monday, June 22, 2020
Feedback on Farhan's FB Feedback Amp Video
As I said a couple of days ago, Farhan has put out a very informative video on amplifier design. During the video we can see him determine bias, feedback and load levels, then select component values. We then see him actually build the amplifier "ugly style" and use his Antuino to test it. Fantastic.
Watch Farhan's video here: https://www.vu2ese.com/index.php/2020/06/18/feedback-amplifier/
I sent Farhan some of my reactions to the video. In the hope of stimulating some discussion, I repeat them here:
___________________
Wow Farhan, I really enjoyed your video and learned a lot. You definitely have the Knack for explaining this stuff.
Saturday, June 20, 2020
Excellent Video from Farhan on Amplifier Design
Farhan has produced a really excellent video explaining the theory behind the feedback amplifiers that we use in so many of our circuits. He takes us through the design and construction of these amplifiers, then uses his Antuino network analyzer to test an amplifier and to measure input and output impedances.
There is a lot of tribal knowledge and wisdom in this video!
Check it out here:
https://www.vu2ese.com/index.php/2020/06/18/feedback-amplifier/
Thanks Farhan!
Wednesday, March 4, 2020
N3FJZ's Al Fresco. BITX-inspired, TIA. 50 Watt, SSB Rig (Video)
The last blog postings on Rick N3FJZ were in 2015. Rick sent me a very uplifting reception report, then we had a pretty amazing Homebrew-to-Homebrew contact.
Paul Taylor VK3HN yesterday alerted me to a new YouTube video that shows the progress Rick has made with his homebrew SSB rig.
This is a great example of true amateur SSB construction. Rick is making use of a combination of digital and analog technology. He is adapting circuitry developed by others and using it to meet his needs. During the development stage he is keeping the circuit open (Al Fresco) so that he can easily work on it.
FB Rick.
Thursday, February 20, 2020
Tribal Knowledge: More on Tapping Metal
Back in 2014, when I was putting together my EB-63A solid state amplifier, I had to learn how to tap aluminum so that I could attach my transistors to the heat sink. I did short YouTube video on how I did this (with tales of woe!). This video turned out to be amazingly popular -- more than 27,000 views! Apparently there is a great thirst for this kind of knowledge out there. Recently someone in Alaska came across my video and shared with us some more useful information on how to tap metal. Here is some tribal knowledge from Paul KL7FLR:
Hi Bill and Pete,
Stumbled over Bill’s YouTube video about tapping in Aluminum and I would like to add my experience doing such. I have probably tapped over a 1000 holes in various metals, cast iron, steel, aluminum, bronze and brass from 0-80 to ¾-20. Each metal poses its own problems and solutions. There was nothing in error with your video or the method you presented.
My comments:
What causes broken taps is the tap is not being perpendicular to the work. A hole not perpendicular to the work, a worn/dull tap (this applies to the drill bit too) and lack of lube.
Every hole to be drilled and tapped must be perpendicular to the metal. A hand drill electric or battery will not be perpendicular unless two other people can spot the drill operator. Not possible when you are alone in the shop.
Any serious homebrewer should have a drill press. A small bench drill is very inexpensive. Even the $69 Harbor Freight model is adequate for the average ham’s workshop. I see these items at flea markets and on Craigslist all the time cheap. Estate sales not so cheap but sometimes on last day you might get a bargain. Adjustable from 500 to 3600 rpm will cover all the normal sizes of drills. An x-y table could be added ($$) for added accuracy if desired. (search x-y table for examples and sources)
The size of hole you drill makes a difference too. Most drill charts assume you are tapping at 75% of thread contact. This is amount of the male thread of the bolt/machine screw threads contact the female thread in the piece. This is about the max you can expect without some precision tooling that won’t be in the average home shop. 75% provides maximum strength of the fasteners. So unless you’re working on something that requires strength like a tower support bracket or the wings of an airplane you don’t need 75% as 50% thread contact is more than adequate. So when the drill chart shows that a #43 you can instead use a #42 or a 3/32 drill. A little bit larger hole will be a lot easier to tap threads.
The type of tap will also influence the difficulty of tapping threads. The typical hardware store tap is a straight 3 or 4 flute taper tap. The chamfer of a taper tap is 9 threads making tapping much easier. This is the tap for hand tapping. The plug tap has a chamfer of 5 threads and is best used in a tapping head or fixture. The bottom tap is for tapping threads in a blind hole, usually after started with a taper tap. That increases the pucker factor x10. The normal taper tap cuts as it is rotated in a clockwise direction or counter-clockwise for left hand threads. The cuttings will clog the tap and you must back the tap out frequently to clean the cuttings from the flutes preventing the tap from seizing and possibly breaking the tap. Breakage is easily done with the smaller taps but also will happen to a larger tap too. There is a style of tap called a spiral point tap. It will push the cuttings up to the top of the hole and not clog the flutes as easily as the straight flute taps. I still back it out and clean it out of habit. These don’t cost any more than the hardware taps. A 4-40 is about $2.90 the last time I bought one.
Avoid “carbon steel” taps. These will break easier than “high speed tool steel” taps and they are usually a few cents cheaper too.
Lubrication is necessary. Bill’s use of 3-in-1 oil is a good lube but “Tap Magic 20016A Aluminum” fluid is better for tapping aluminum and regular “Tap Magic” for everything else. https://www.amazon.com/Tap-Magic-20016A-Aluminum-Yellow/dp/B00065VEUO
The metal you are tapping can be an exercise in patience. “Hardware” store aluminum comes in various grades from crappy to real crappy. They are of an alloy best suited for the extrusion process and are not wonderful for the tapping process. Aircraft grade aluminum is nice stuff to work with but not cheap. Comes in many grades from 1000 series to 8000 to match the application. Grade 2024 is communally found and is easy to work with while 7075 works like steel. Since most of us won’t be buying a 21 foot stick of aluminum or a 5x8 foot sheet we must take the hardware store grade into account when tapping holes and lean towards the 50% thread engagement, plenty of lubrication and lots of patience. I frequent several aluminum boat building firms and they let me pick through their scrap piles and I’ve made frequent donations of a case of soft drinks or a can of coffee to the break room fund and have also paid the going scrap price for the scrounging privilege.
Worn taps: These get dull with use and will break at the worst possible time and in an expensive workpiece. Broken taps can be removed but are time consuming and require some expertise in doing so. Best to retire them when worn. I used to keep a chart of how many holes a particular tap had been used and at 35 holes for the small taps they got retired. 50 holes for taps larger than ¼”. I once spent over a week of evenings extracting a worn tap from a locomotive cylinder casting. Never again! As my mentor said many times, “dull tools cause accidents and ruined work”.
Clamp the work to be tapped stationary if possible. You don’t want it moving around thus inviting a broken tap. Use some method of a tap guide (as Bill did with a block of wood, not great but better than nothing). I use what is called a “Piloted tap wrench”, https://www.amazon.com/Set-Wrench-Piloted-Spindle-Capacity/dp/B077SVQD4S .
Picture is of my setup.
Step 1: Work clamped securely to table at desired hole location.
Step 2: Drill hole.
Step 3: Use piloted tap wrench to tape hole.
Step 4: Done.
Friday, January 31, 2020
WA2EUJ's NXP RF Power Amplifier Design Challenge Entry -- Won First Place Prize!
Congratulations to Jim WA2EUJ. First Place the NXP Design Challenge.
You can buy the board here:
https://sites.google.com/site/rfpowertools/home/nxp-mrf-101
Thanks to Pete Eaton WB9FLW for alerting us to this.
Monday, November 6, 2017
Jan's FB Slovakian SMD TIA Boards
Saturday, September 16, 2017
The Road to QRO Perdition
I want to start out by saying that this is NOT my fault. I have been TRYING to do QRP things. Remember my recent Tuna Tin 2, Herring Aid 5 rig? I am aware of the ever-present threat of expulsion from the QRP HoF. We all remember what happened to poor Pete back on April 1, 2017.
But sometimes people just deliberately put temptation in your path. That is what happened this week. Our old friend Rogier KJ6ETL (formerly known as PA1ZZ) sent me the very LARGE chunk of aluminum that you see in the picture above. Look at that thing. It is practically begging to be turned into a very QRO push-pull amplifier.
At first I told myself that it would be impossible to tap the big heat sinks on the sides. How would I get the drill in there? But then I realized that I can just put the threads in from the outside. I can almost smell the machine oil. And the heat sink compound...
Thanks lot Rogier. This is all your fault.