[GreenKeys] Testing 255A Relay

[Charles Days]

I have had my 19 for some 50+ years, I didn't have it long when I decided I had to do something with the polar relay and if I wished to extend the data loop (2) that the relay(s) were essential for me..

So I found a military polar relay test set from John Meshna in Lynn, MA. I power it with the DC available at the 19, I have the large regulated power supply. I set about testing all the relays I could find for small money. Almost all were out with the critical sensitivity adjustment.

For my installation, I wanted to use relays or at least their covers that were metal to avoid any noise and possible influence from RF in the shack. Some, older relays use a brass cover...

An important note is that the internal magnet can and will loose strength. Several of the relays the magnet was removed and taken to a "Magneto Shop" and recharged. I allowed some time to pass for the magnet to normalize, some magnets refused to charge despite maxing the current on the charger. Those relays are "parts" relays.

The test set also generates a signal that pulses the relay for balance.

I suggest that the magnet may have deteriorated and the relay come out of balance as well as a sensitivity loss. The simple adjustment cannot accomplish this.

I keep several calibrated relays on hand.

A mal adjusted relay or one with sensitivity loss will introduce distortion, combine that distortion with any distortion from a mal adjusted selector and the usable range diminishes dramatically, combine still further distortion in the radio path and coming from the transmission source, the TD or keyboard, there is practically nothing left but errors.. The relay does, in sense, act like a 23hz (FWIR) filter, short duration noise pulses that would get repeated with solid-state are not recognized because of the mechanical inertia.

Chas

WA1JFD
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/greenkeys/attachments/20230209/24c8eff3/attachment.html>