[Elecraft] Fool proof kill switch = deadman timer?

[Fred Jensen]

Correct meJimif I misunderstand, but it sounds like you are looking for 
a truly fail-safe way to make sure your remote doesn't go into 
continuous transmit, and to recover it after the control-link returns 
and is stable.

"97.213(b) Provisions are incorporated to limit transmission by the 
station to a period of no more than 3 minutes in the event of 
malfunction in the control link."

Just assuring your I'net modem is on aUPS doesn't seem to meet that 
need.  The way(s) I've seen it done on remotely controlled mtn-top 
VHF/UHF base stations on a network linked by radio, microwave, and VOiP 
include two parts:

1.  A simple RF sensor with3 min timer that resets to zero every time 
the RF drops.  It interrupts the power, and must be reset via the 
control link.  I've seen some that self-reset after some period [like 10 
mins] with a limit on the number of times it will do so.  Most used the 
NO contacts such that the relay has to be energized to power the 
transmitter.

2.  An interlock that prevents keying of the transmitter unless the 
control link is active.  This was usually accomplished with a 
sub-audible tone [CTCSS] that either keyed the remote transmitter 
itself, or enabled keying by some other means.  No control tone = no TX.

3.  Recovery from remote power failures with K-line equipmentmay require 
a couple of little robots [maybe Lego's?] to punch the PWR switches. [:-)

I believe #3 can be solved on Elecraft equipment with one of the lines 
in the AUX cable.  #'s 1 and 2 are *not* the same thing.

73,

Fred ("Skip") K6DGW
Sparks NV USA
Washoe County DM09dn

On 5/29/2017 8:20 AM, Jim Miller wrote:
> In considering remote operation options I'm still struggling with how to
> implement a kill switch that is foolproof.
>
> Last night we had several power glitches that left our Comcast modem hung
> up. There was really no service outage in the area so all it took was
> unplugging and replugging the modem to restore it. Of course it took nearly
> 5 minutes to completely come alive with internet service active.
>
> This happens often enough that it makes me concerned that if internet
> service is interrupted while I'm operating remotely I wouldn't be able to
> kill the transmitter output.
>
> So I'm wondering if a better option is to have a deadman timer to kill the
> K3 and amp output. Not sure what criteria I would use to reset the deadman.
> I'm sure a Raspberry Pi or similar could be programmed to do the work.
>
> Suggestions welcomed!
>
> jim ab3cv
>