[Elecraft] K3S PTT using DTR/DTS issue

[Don Wilhelm]

I was making the assumption that the situation in the K3S was similar to 
what would happen if you tried to connect two RS-232 ports together as 
would happen if you used a "Y" cable.  I know that will not work, and 
because one driver can be trying to drive a positive voltage on the 
signal at the same time another driver is driving with a negative 
voltage.  Not only will that not work, but the drivers can damage each 
other.
But then I do not have detailed schematics.

Lyle has responded that he has connected both the USB and an RS-232 
adapter with no problems (he should know since he is one of the K3S 
designers), so the implementation in the K3S apparently has designed in 
protection for that situation.

Sorry if I caused alarm unnecessarily.

73,
Don W3FPR

On 9/23/2015 7:13 AM, ae4pb at carolinaheli.com wrote:
> The manual doesn't indicate that you can't have both the USB and RS232
> connected at the same time. In fact the manual states that you can connect
> the RS232 specifically for PTT. The RS232 isn't going to be used for rig
> control, only PTT. If this is an unacceptable configuration on the K3S then
> the book needs to be properly written.
>
> I'll pull the covers at lunch and see what the smell is.
> -----Original Message-----
> From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Don
> Wilhelm
> Sent: Wednesday, September 23, 2015 12:25 AM
> To: ae4pb at carolinaheli.com; elecraft at mailman.qth.net
> Subject: Re: [Elecraft] K3S PTT using DTR/DTS issue
>
> Jerry,
>
> Did you have the USB connection to the K3S still connected while you also
> connected the USB to Serial adapter into the RJ-45 dongle?
>
> If so, that is a "No-no".  RS-232 (whether from the internal K3 USB to
> serial adapter or from an external adapter) is a one to one, point to point
> protocol.  It must have *only* one driver on the signal lines.
> If you connected both at once, you had two drivers on the signal lines, and
> those two drivers would "fight with one another", possibly causing damage.
> When one driver is trying to send a mark, the other trying to send a space,
> those two signals are of opposite polarity and can cause damage to one
> another.
>
> So whether you damaged your external USB to serial adapter or if you damaged
> the internal USB to serial adapter in the K3S is indeterminate - damage
> could have been done to both.
>
> 73,
> Don W3FPR
>
> On 9/22/2015 10:42 PM, ae4pb at carolinaheli.com wrote:
>> So my new K3S is running well and I'm setting up my software and see
>> that it can do digital modes and control PTT using a comm port. I open
>> my owners manual, page 20, which says I can use that connection for
> control and PTT.
>> I'm already using the USB for control so will just use it for PTT. I
>> have a USB to serial adapter so I install it, plug in the RJ47
>> connector to the rig, mate the DB 9 connectors and immediately smell
>> burning components, Quickly disconnect the DB9.
>>
>>    
>>
>> I was previously using this serial adapter successfully on a YAESU
>> FT-897D before I sold the rig to get the K3S.
>>
>>    
>>
>> So now the questions:
>>
>> 1.   Why did this apparently experience an issue? I see nothing in the
>> manual to indicate this requires anything but a standard connection.
>>
>> 2.   How much damage has been done to my brand new k3S using the supplied
>> Elecraft cable and a known good previously good USB to Serial cable
>> (MFJ I believe).
>>
>>    
>>
>> I'm heartsick. Being the type of person who checks and double checks
>> things I can find nothing wrong with what I did and yet apparently
>> I've damaged something.
>>
>>    
>>
>> Tomorrow I'll pull the cover and check the board.
>>
>>    
>>
>>    
>>
>> Jerry Moore
>>
>> AE4PB, K3S - S.N. 010324
>>
>> An Amatuer is - Considerate, Loyal, Progressive, Friendly, Balanced,
>> and Patriotic.
>>
>>    
>>
>>    
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Elecraft at mailman.qth.net
>>
>> This list hosted by: http://www.qsl.net Please help support this email
>> list: http://www.qsl.net/donate.html Message delivered to
>> w3fpr at embarqmail.com
>>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html Message
> delivered to jermo at carolinaheli.com
>
>