[Elecraft] KAT500 as a remote-controlled tuner

[Jack Brindle]

The answer is yes. But then it won’t tune and the cores will overheat from excess power trying to use a now-invalid solution. You must disable the amplifier to perform a tune or anytime the ATU needs to do any switching. It determines when it needs to do that (say from a QSY where it needs to go to a different solution). If you have fixed-frequency operation and can guarantee that the ATU won’t need to change the relays while power is high, then your analysis may be correct. Why risk it?

So what is wrong with hot switching? You get arcs across the relay contacts greatly reducing their lives. Having to replace the relays isn’t fun, but having to replace a coil because the relay won’t make contact is even worse.

There is a reason we designed the key line interrupt into the ATUs.

Jack, W6FB


> On Nov 3, 2018, at 5:44 PM, ANDY DURBIN <a.durbin at msn.com> wrote:
> 
> I live in AZ so I know what UV does.  What I don't yet know is if the KAT500 is smart enough to inhibit tuning with an  input power level high enough to damage the L C switching relays.
> 
> 
> If the answer is no then the obvious follow up is  - why not?
> 
> 
> if the answer is yes then a keying inhibit is not needed to protect the KAT500.
> 
> 
> Andy, k3wyc
> 
> 
> 
> 
> ________________________________
> From: Jack Brindle <jackbrindle at me.com>
> Sent: Saturday, November 3, 2018 12:58 PM
> To: ANDY DURBIN
> Cc: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] KAT500 as a remote-controlled tuner
> 
> The keying interrupt must be provided by the ATU in order to avoid hot switching the ATU relays when it tunes. This cannot be determined anywhere but in the ATU, thus it must provide the break.
> That key line break is pretty important to the life of the ATU.
> 
> Jack, W6FB
> 
> 
> 
>> On Nov 3, 2018, at 12:17 PM, ANDY DURBIN <a.durbin at msn.com> wrote:
>> 
>> "Someone asked me recently whether a KAT500 could be remote-controlled"
>> 
>> 
>> It wasn't me that asked but I have been considering using the KAT500 as a remote tuner as I need higher power capability than my current MFJ-993BRT.  However, my approach was going to be to buy just the KAT500 board and find/build a suitable enclosure.  I'm a bit surprised Elecraft does not offer the KAT500 board packaged as a weather resistant remote tuner.
>> 
>> 
>> As to needing AUX cable and keying interrupt -
>> 
>> 
>>     - KAT500 does not need AUX cable to operate but if you want to help it along it's far better to give it the TX exact frequency rather than just the band.
>> 
>>    -  What other remote tuners provide keying interrupt?  In any event, the SWR seen at the remote tuner could be quite different from the SWR seen at the amplifier and may not be a good indication of whether the amp should be keyed.
>> 
>> 
>> The keying interrupt should be based on SWR seen at the amplifier output.  I actually already have that wired using my LP100A.
>> 
>> 
>> 73,
>> 
>> Andy k3wyc
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