[ARC5] TCS Transmitter Tip

[WA5CAB at cs.com]

Putting diodes or anything else across the relay coil is an attempt to 
reduce the (usually small) spike on the relay supply line caused by the 
collapsing magnetic field in the coil.  Dave's reported problem is arcing across the 
contacts that make and break the B+ line.  Nothing hung across the coil is 
going to affect that.

That being said, I've never encountered this exact problem either here or 
aboard naval vessels.  But I've never actually operated a TCS off of the 
single dynamotor supply, either.  Does this happen in VOICE, CW or both.  If CW, 
check the VOICE-CW relay contacts that are supposed to short the modulation 
transformer secondary.  If they aren't making, that would potentially cause 
the problem.

Robert Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480

In a message dated 11/25/2016 12:15:44 PM Central Standard Time, 
dennis.monticelli at gmail.com writes: 
> Decreasing the lag time on break is very easy to accomplish.  Simply 
> putting a zener in series with the diode will dramatically reduce the lag by 
> rapidly collapsing the magnetic field.
> 
> Dennis AE6C
> 
> 
> On Fri, Nov 25, 2016 at 8:57 AM, Michael Hanz <aaf-radio-1 at aafradio.org> 
> wrote:
> >> It depends completely on the systems implications, Wayne.  A straight 
>> diode will add a significant time (milliseconds) to the contact break time, 
>> depending on the strength of the magnetic field in the pole and the air 
>> gap between the pole piece and the moving armature.  If it's just a push to 
>> talk function, it might be permissible.  If it's a telegraph key 
>> follower, you may be in trouble from a speed standpoint.  There is an  annoying 
>> lag-on-break in that case.
>> 
>> 73,
>> Mike  KC4TOS
>> 
>> On 11/25/2016 10:24 AM, Robert Eleazer wrote:
>> 
>> >>> Isn't it modern practice to put a solid state diode across relay DC 
>>> energizing coils?  Given electron tubes' higher voltages and thus their 
>>> resistance to spikes do we not need to worry about that?
>>>  
>>> 
>> 
>> 
> 
> 
> 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/arc5/attachments/20161125/a89cad0a/attachment.html>