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Sunday, November 20, 2016
Homebrew Processor with Discrete Transistors and LEDs
I've been working with an Arduino today. Seeing this video makes me feel like such an APPLIANCE OPERATOR. FB OM! No store-bought mystery boxes for him!
Thanks to Steve N8NM for alerting us to the magnificent project.
More details here:
http://www.popsci.com/man-builds-huge-megaprocessor
Labels:
computer history,
minimalist computing
Saturday, November 19, 2016
Analog TO THE MAX! An Old School Readout for the BITX 40
Perhaps this was a reaction to a frustrating morning spent trying to get a 20x4 digital display to work with an Si5351 and an Arduino Uno via an I2C bus (I feel my blood pressure rising just due to the typing of those words). After much digital fiddling, I declared a "BASTA!" and looked around the shack for an antidote for the digital frustration. There on the bench was my fully analog BITX40Module rig, with its homebrew L-C analog VFO. It needed a better frequency readout. And this morning, it got one.
The pointer is Sharpie ink on a bit of PC board. It is held in place by superglue, suspended by a piece of wood about 1/4 inch off the chassis (to reduce dial parallax). The numerals are in Dymo tape -- there was not enough room for the "7" but I think I will be able to remember this.
Very therapeutic and satisfying.
The pointer is Sharpie ink on a bit of PC board. It is held in place by superglue, suspended by a piece of wood about 1/4 inch off the chassis (to reduce dial parallax). The numerals are in Dymo tape -- there was not enough room for the "7" but I think I will be able to remember this.
Very therapeutic and satisfying.
Labels:
BITX40Module
Tuesday, November 15, 2016
25 Watts From a Single IRF510
I should have tried this a long time ago. It works great. The power supply that I picked up at the Kempton Park rally many years ago happens to have a 25 volt unregulated output. Coincidence you say? I think not. TRGHS.
Farhan provides a really excellent description of how to do this:
http://hfsignals.blogspot.com/p/25-watt-linear-for-40-and-20.html
Labels:
amplifier theory,
Farhan
Monday, November 14, 2016
"Sideband Suzy" and the History of SSB
Farhan alerted us to a very interesting presentation on the history of single sideband: It was in episode 81 of Bob Heil's "Ham Nation" show. It starts at minute 22:
https://www.youtube.com/watch?v=xSF0WBdK1IQ&feature=youtu.be
Two things really caught my attention:
-- Note how OM Carson, way back in 1915, had figured out how to get rid of the carrier, but needed some way of eliminating the unnecessary sideband. He did it by using his antenna tuner as a filter. FB OM!
-- In the early days of SSB, when it was an exciting new technology, hams had regular "sideband dinners." At these events an award was presented. Kind of like an Oscar or an Emmy I guess. The award was the "Sideband Suzy" (see above). Kind of a classic figure... but half of Suzy was missing!
https://www.youtube.com/watch?v=xSF0WBdK1IQ&feature=youtu.be
Two things really caught my attention:
-- Note how OM Carson, way back in 1915, had figured out how to get rid of the carrier, but needed some way of eliminating the unnecessary sideband. He did it by using his antenna tuner as a filter. FB OM!
-- In the early days of SSB, when it was an exciting new technology, hams had regular "sideband dinners." At these events an award was presented. Kind of like an Oscar or an Emmy I guess. The award was the "Sideband Suzy" (see above). Kind of a classic figure... but half of Suzy was missing!
Labels:
Farhan,
Old radio,
phasing,
Phasing Rigs,
radio history,
SSB
Saturday, November 12, 2016
Putting a Heatsink on the BITX40 Module
The fan that I installed yesterday was driving me nuts. It was noisy, both acoustically and electrically. And I would occasionally get my fingers in the blades. Not good. While it did seem to keep the IRF510 from getting too hot, I knew that a real heatsink would do better thermally.
But how was I going to attach the sink to the transistor? That tab on the IRF510 goes to the collector, so if it touches a grounded heat sink, you get a short. A nylon screw and some mylar between the transistor tab and the heat sink is one option. But I didn't have a nylon screw. So I decided to just keep the heat sink electrically insulated from the chassis.
This project required me to refresh my memory on how to tap a 4-40 hole. I went back and watched the short video I made on the tribal knowledge that Pete had shared with me. Out came the Tap and Die gear and the machine oil. The process went very smoothly.
Here is what I did to get the heatsink in place:
1) After removing the original heatsink, I gently bent the leads on the IRF510 so that the transistors outer edge would be flush with the edge of the PC board.
2) I put a strip of thick tape (Gorilla Tape) along the lower side of the heat sink. This will keep the heat sink from shorting to the chassis.
3) I placed the heatsink where I wanted it, and carefully marked where the mounting screw (through the transistor's tab) should go.
4) Drill! Tap! (see video) https://www.youtube.com/watch?v=LuqliWT1k5A
5) I applied some heat sink compound (or Desitin!) and then attached the transistor to the heatsink.
6) I put a few drops of glue between the heatsink and the board and the chassis, just to mechanically stabilize it a bit.
7) Bob's your uncle.
It seems to work great. The MOSFET stays cool. even after long "old buzzard" transmissions. And I notice no stability problems. It was fun to put to use some tribal knowledge and refresh a mechanical skill.
But how was I going to attach the sink to the transistor? That tab on the IRF510 goes to the collector, so if it touches a grounded heat sink, you get a short. A nylon screw and some mylar between the transistor tab and the heat sink is one option. But I didn't have a nylon screw. So I decided to just keep the heat sink electrically insulated from the chassis.
This project required me to refresh my memory on how to tap a 4-40 hole. I went back and watched the short video I made on the tribal knowledge that Pete had shared with me. Out came the Tap and Die gear and the machine oil. The process went very smoothly.
Here is what I did to get the heatsink in place:
1) After removing the original heatsink, I gently bent the leads on the IRF510 so that the transistors outer edge would be flush with the edge of the PC board.
2) I put a strip of thick tape (Gorilla Tape) along the lower side of the heat sink. This will keep the heat sink from shorting to the chassis.
3) I placed the heatsink where I wanted it, and carefully marked where the mounting screw (through the transistor's tab) should go.
4) Drill! Tap! (see video) https://www.youtube.com/watch?v=LuqliWT1k5A
5) I applied some heat sink compound (or Desitin!) and then attached the transistor to the heatsink.
6) I put a few drops of glue between the heatsink and the board and the chassis, just to mechanically stabilize it a bit.
7) Bob's your uncle.
It seems to work great. The MOSFET stays cool. even after long "old buzzard" transmissions. And I notice no stability problems. It was fun to put to use some tribal knowledge and refresh a mechanical skill.
Labels:
amplifier theory,
BITX40Module
Friday, November 11, 2016
My Extroverted BITX40 -- On (but not in) a Box
I kind of like this arrangement -- it has the "three dimensional" feel of an old tube rig. This obviously wouldn't be good for portable operations, but I am not planning on going portable. There is a lot of room under the chassis. I could put a digital VFO in there and put in a switch so that I can easily go from digital to analog.
Labels:
40 meters,
BITX40Module,
Farhan,
India
Thursday, November 10, 2016
Two Gel Cells and a Heat Sink -- BITX40 Power Hack
I blame Pete for this. And Farhan. Pete has been leading us astray with all his talk of high power linear amplifiers ("Two 813s kid, that's all you need!"). And Farhan practically pushed us beyond QRP limits by placing a separate DC power connector for the IRF510 final amplifier on his new BITX 40 Module board. Farhan writes:
There are jump-points from where you can add more modules like the DDS, more bands, better audio amplifier, etc. Imagination is your limit. You can separately increase the power amplifier's supply voltage to 25 volts to be more than 20 watts of power : You will have to add a better heat sink. The mods are on the way! (from hfsigs.com)
A while back Chris KD4PBJ sent me some very nice heat sinks -- one of those would fit quite nicely on the PA side of the BITX40 board. And I just happen to have two 12V Gel cell batteries. One will power the board and the two together will power the IRF510. With 20 watts out to my dipole I feel confident that I will WIN the upcoming ARRL Phone Sweepstakes (in my category: Homebrew VFO, Northern Virginia).
There are jump-points from where you can add more modules like the DDS, more bands, better audio amplifier, etc. Imagination is your limit. You can separately increase the power amplifier's supply voltage to 25 volts to be more than 20 watts of power : You will have to add a better heat sink. The mods are on the way! (from hfsigs.com)
A while back Chris KD4PBJ sent me some very nice heat sinks -- one of those would fit quite nicely on the PA side of the BITX40 board. And I just happen to have two 12V Gel cell batteries. One will power the board and the two together will power the IRF510. With 20 watts out to my dipole I feel confident that I will WIN the upcoming ARRL Phone Sweepstakes (in my category: Homebrew VFO, Northern Virginia).
Labels:
amplifier theory,
BITX40Module,
Farhan,
India,
Juliano -- Pete
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