[Elecraft] K3S PTT using DTR/DTS issue

Wed Sep 23 08:46:08 EDT 2015

No worries Don, I thought it should work as well. I'm just not keen on
having to repair/replace the I/O board on a rig I've had 1 week today using
the manual and supplied cable. Maybe I'm mistaken and I didn't smell
something in the rig. I've been in electronics since 1981 with formal
education and well before that as younger kid. Maybe I'm just getting old
and starting to smell things.... 

Jerry Moore
AE4PB, K3S - S.N. 010324
An Amatuer is - Considerate, Loyal, Progressive, Friendly, Balanced, and
Patriotic.

-----Original Message-----
From: Don Wilhelm [mailto:w3fpr at embarqmail.com] 
Sent: Wednesday, September 23, 2015 8:19 AM
To: ae4pb at carolinaheli.com; elecraft at mailman.qth.net
Subject: Re: [Elecraft] K3S PTT using DTR/DTS issue

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.
>>
>>    
>>
>>    
>>
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