PA3CLQ's Leuke Linken Nr. 363


Rotary snow plows on Donner Pass

A fascinating video of 1920s technology that still works:

Visit at:


"Owney Day" at the National Postal Museum:

If you have an interest in RPOs, please visit the RailwayPO group at

Happy Veteran's Day, Dr. Frank R. Scheer, Curator Railway Mail Service Library, Inc.
In the 1913 former N&W Railway depot along Clarke County route 723 117 East Main Street Boyce, VA 22620-9369 USA


Bug Debounce / Descratcher using LMC555 - Continued from PLL Nr. 360

How do you define "bounce"?

Milt k4oso


I decided to go with the kit from Jackson Harbor Press at:

The trouble with bugs is that if you get them to stop bouncing at ONE speed, they will tend to bounce at other speeds.

I like to set mine for about 16 - 18 wpm, and I am happy to QRS for the guys who run down around 10 - 13 wpm any time, but that is when I run into more bounce

and it requres more skillful use of the bug to keep it from bouncing.

If you slap too hard, or try to go too fast for the setting it will tend to generate more bounce.

Fun nevertheless!

73 - Bry AF4K


There are two sources of bug noise, commonly referred to bounce and scratch.

Bounce is caused by the Dot contact actually bouncing when they makes contact.

Look at the second to the bottom trace on:

This is the Dot start zoom-in, notice the first long bounce, follow by two more shorter bounces.

The higher frequency noise is probably the two contacts scratching together a little.
A similar pattern is show on the scope shots here:

There is also pivot scratch, which may show up as noise on the Dash input.
What Bry may be indicating is that the first Dot may have extra bounce depending on how hard the key is hit to start the Dot pendulum in motion.

I noticed the first Dot issue when making my scope shots.
John KN5L


Very good, John.
Actually, there are several sources of key noise and some have little to do with the actual contacts as you pointed out, John.
Yes, contact bounce happens on the leading edge of the contacts making and is literally one contact bouncing off the other.

The spring contact, typically, has too low of a tension.

The pre-tensioning devises help because of two things.

It compresses the spring contact to point of higher tension.
That, in fact, compresses the tension range the contact goes through when making a dot.

A stiffer dot "U" spring can, usually, accomplish the same thing.

It can occur on the trail edge as a contact bounces back upon release, but less often.
As pointed out, contacts scratching together is another source.

Here, contact material is often involved.
Here, contact smoothness, material surface resistance and lack of or varying tensions.

Some materials hardness can actually cause this.

Yes, some metals are softer then others. Ideally, the two contacts will burnish themselves when operated.

Burnishing is polishing, not filing.

It moves material, does not remove material.

Harder materials can clean themselves, but softer materials move about a minute amount.
Another source of 'noise' is the pivoting points not keeping keeping the dot bar or dash bar at a steady ground potential.

A recent key I had acquired had sort of a unique problem.

It would miss/drop the first dit after a dash, occasionally.

I put a little flexible clip lead from the dot bar to a good ground and the problem went away.

There is a tiny spring that goes from the dot bar to ground.

The ground side was not making as good of a contact as needed.

The dot bar was getting it's ground from another source that was not reliable.

I tightened the screw that had that spring's ground and fixed.

I have had other keys with a problem of the dot bar maintaining a consistent ground and, often, a flexible clip lead between the dot bar and ground/base confirmed suspicions.
The debounce circuits have been used for years.

They can/will cover up the problems, but not solve them.

In some cases, it is more economical then actually solving the problem because some problems require part changes or replacement.

It is not fun having the problem, but rewarding when you can solve it.
Joe V31JP


Dit contact bounce usually is caused by two things, Either dirty contacts, or improper setting of the dit stop screw.

The lever is pushed to the dit side and when the vibration stops the contact should JUST BARELY stay closed.

Adjust the screw so the contact just opens and turn back until it just closes and lock it down, once set the speed can't affect this setting.

This has worked for me !

Try it.

Fifty years of "bugging" on the air !

My radio is Ham Radio...CW is Real Radio
73, John...K8JD


I have added two new post assembly Oscilloscope images to

The second of the bottom image indicates that there is little change with bounce or scratch after several hours of enjoyable SKCC QSOs,
thanks everyone.
The bottom image measures both Bug weight and speed.

The weight, or symbol Space versus Dot periods, was adjusted close to 1:1 or near 50% duty cycle for continue Dots with the Bug.

The weight is the one critical Bug adjustment of the E and C screws referenced on the Vibroplex adjustment document

The Symbol Space plus Dot period is 151 ms.

The speed can be calculated with:

WPM = 1200 / dotDuration = 1200 / (151 / 2) = 16 WPM
John KN5L



[MWA] QRS CW Ops Tests Wednesday/Thursday
For those of you interested in doing slower CW (or sending more CW by hand), you should join in this week's CW Ops test, which will be QRS in celebration of the new CW Academy graduates.

Very Special Slow-Speed CWops Tests Wednesday/Thursday
Loosen your seat belts everyone--we're going to have some slow-speed CW fun.
We will have Very Special Slow-Speed CWops Tests on 12 November.

We will again be welcoming enthusiastic CW Academy graduates to the wonderful world of on-the-air CW.

These guys and gals are the new blood and future of ham radio.

Our job is to make them feel welcome and eager to come back for more.

To help the tentative make the jump to full-fledged CW aficionados.
CWops Tests rules are at

We will have our normal three sessions, 1300-1400Z Wednesday, 1900-2000Z Wednesday, and 0300-0400Z Thursday (Wednesday night).
CWops Tests exchange.

Members: Name and CWops Member Number.

Nonmembers: Name and State, Province, or DX Country Prefix.

CW Academy graduates: Name and CWA.
Everyone please limit speed to 20 WPM maximum.

CQ at 20 WPM.

Even when you are working someone you normally work at 35 WPM, please send no faster than 20 WPM.

When you answer someone CQing at less than 20 WPM, answer at his speed.

When someone answers your 20 WPM CQ at a slower speed, match his speed.
Thank stations by name.

Make the new guys feel welcome.
If appropriate, help stations by explaining CWT exchange.
If someone wants to rag chew, rag chew for a bit.
Send lots of FBs and other encouragement.
Us working us—we do that all the time.

Please make a special effort to work the new guys.
Send a welcoming QSL card or email to each new station worked.
Our Very Special Slow-Speed CWops Tests are not just for CW Academy graduates.

Please talk about the event at your local clubs.

Encourage CW-tentative hams to get on and have fun. Help, encourage, mentor.
Mark your calendars.

Very Special CWops Tests 11/12 June.

The graduates are our new blood.

They are the hams who will carry on the CW tradition.

Let's make a very special effort to get on and make the graduates feel welcome.
Let's infect them with the CW bug.
*The first rule of CW is to have fun and to share the fun.

This week, more than ever let's share the fun with our Very Special Slow-Speed CWops Tests.
Special note.

I have it on good authority that W1AW will be active.

The Old Man will be sending *W1AW/5 HIRAM MS* at *20 WPM* or less.

It will be a thrill for our new guys to work W1AW.
Minnesota Wireless Association mailing list
To post a message:
List Help:

MWA Official Web Site:

CW Exuberantly, Hank, W6SX CWops Tests Manager

My simple website about Gigantic DF-Antennas

Part 1 "DF-Antenna Wullenweber Array"

Part 2 "DF-Antenna USSR Variants"

Part 3 "DF-Antenna USA Variants"

Next Part 4 "USSR OTHRA DUGA 1,2 & 3" at: