Showing posts with label Telegraph Key. Show all posts
Showing posts with label Telegraph Key. Show all posts

Diode Spark Killer for Semiautomatic Key

swing hell yes
lots of swing is a pain to copy
but
a bit of swing, is a horse of a different color
add a bit of a chirp and some drift
cans on head
pre war receiver
turn down the lights
sit by the glow of the tubes and dial lamps

  © W8ZNX
I'm not sentimental, I'm just as romantic as you are, so I agreed with Mac W8ZNX that "a bit of a chirp and some drift" is not a drawback, it is an attribute, trait of a telegraph radio station, especially the Glowbug one. Just a bit, not too much, and how big this bit should be, I prefer to choose myself.

Well, I used to use a Straight Key, then learned a BUG, and everything was fine until I used a cathode keying of a rock bound oscillator or a differential keying of my Magic Eye MOPA transmitter. When I tried to manipulate the high impedance grid circuit of the TNT oscillator, I got a pretty nasty instability of note, specifically at the dots generated by semi-automatic key (dot contact spring, you know).

Quick patch and further explanation:



germanium diode and early speed-x bug



As I see it, the dot contact spring produce a micro spark, discharging the bypass capacitor sporadically, so that every time the exciter starts to oscillate, it has unpredictable remaining voltage on the tube grid. This effect is negligible on dashes (non bouncing contact), as well as in case of cathode keying (low impedance circuit).
Anyway, additional germanium diode on the BUG contacts solved the problem and I got exactly what I want - "a bit of a chirp and some drift", not too much.

WARNING: Can reduce clicks and improve the signal even if you use a cathode keying or rock bound oscillator.

Second Life of Dead MFM Hard Drives - Iambic Paddle

Homebrew Iambic Paddle Just finished my first in life "Instructable" at the D.I.Y. host site instructables. It is short sketch about Iambic Paddle which has been made using a spare parts from the dead MFM HDD drive. I got a lot of fun posting to that site, and I think that it should be good idea to post more detailed article here. Frankly, this homebrew project is not a Pure Glowing Bug, but I'm not so puristic today.
Well, let me explain - why I decided to use HDD heads as a levers in this Iambic Paddle Project. For many years I've collected computer spare parts for no reason, just because I have a big, nearly endless Junk Box and it was impossible to me to throw such high-tech toys in the trash. But one morning I found that my Junk Box is full and The Time of Trash Bags has come. It was a hard work, but under the tons of debris I found the treasure - my first homemade Z80 Sinclair Spectrum and five old 5 inch MFM hard drives from my second computer.
As you remember, these drives was a big rounded shaped boxes, ideal as a chassis for any homemade electronic projects, tube glowbugs as well as solid state stuff. Another interesting things - powerful electromotor and magnetic cylinders itself, thick shiny discs which are so usable as a dial or scale part, looked much better than a CD in this role. And last but not least - yes, precision bearings on the easy to mount axis in magnetic head's block. What a beautiful hardware! When I opened and totally disassembled these hard drives, I realized that I literally had a very new telegraph key, usual one lever, dual lever iambic paddle or even straight key - not so important, it is easy to make any kind of telegraph manipulator using these nice spare parts. Watch this video demonstrating a working Iambic Paddle and take a look at step by step constructing process here: