[CW] Misc. Info regarding keyer circuits and key filtering circuits

[kremper4-mailman at yahoo.com]

That choke/capacitor filter brings back memories!  One can make some beautiful (albeit mostly useless) bell-like notes with those filters. (B-o-o-i-i-i-n-n-n-g-g-g!)  But as Dave mentions, watch out for the LC kick. Get yourself across a straight key with such a filter and you're certain to get a wake-up call!
   
  Paul / N1FB
  

David Ring <n1ea at arrl.net> wrote:
  Key shaping filter suitable for high power (and other) transmitters:

1 henry choke in series with keyline
1 mfd capacitor to ground across keyline
2000 ohm resistor to ground across keyline

(My notes say 1 henry choke - but my notes during this period of life
were very accurate. This is indeed the size of a filter choke - but
the prices today are outrageous! The 1 mfd capacitor will make many
transmitters have a 15 to 25 ms decay time resulting in a beautiful
bell decay. The 2k resiistor is "non-polarized" and functions to
ground high voltage transients to ground - remember this was the
vacuum tube days of high current switched suddenly!)

A metal oxide varistor of 220 V may be used for the typical 120 volt
key lines found on ships of USA registry. The typical medium
frequency transmitter (410-512 kHz 600 watts output) had a 120 volt
positive @ 175 ma circuit, while a typiical HF 2 to 25 MHz A1 Wireless
Telegraph transmitter had a 200 volt negative at 360 ma keyline. Thus
the use of a 2 k resistor to shunt keying transients as it was "non
polarized" and could be used with both positive and negative key
lines.

The only fast relays that I knew that would handle these types of key
lines were the Magnacraft Electric Company (Chicago, IL) W132-GPCX-3
mercury wetted contact relay with a 250 ohm coil and designed to
switch with 12 vdc. I never used this relay because I thought it
wasn't heavy enough.

The relays I used with the C P Clare Part No. HGJM-51111M-KSQ relay
and the similar series relays. The HGJM series relays were rated at
2A (switched current) at 500 Vdc maximum and 100 Volts-Amperes
(apparent power - similar to watts) - both the 5 vdc and 9 vdc
relays would give no trouble as long as there was a 2 k ohm resistor
across the output to supress transients from the relay coils in the
transmitters.

One other fast relay was the square relay that was about 1-1/2 inches
long and 3/4 inches high and 1/2 inch wide - which is still sold to
this day be RadioShack. We would turn this relay upside down and
glue it to the inside of our keyer boxes. It worked well even though
they were only rated 200 volts at 2 amps.

I hope someone finds this interesting and perhaps someone will find this useful.

73

David Ring, N1EA
=30=
_______________________________________________
CW mailing list
CW at mailman.qth.net
http://mailman.qth.net/mailman/listinfo/cw