[Amps] SB-200 QSK mod info

[Paul Christensen]

Vasily,

Nice set of measurements.  From what I can see, each relay is switching 
quite fast with the RF output relay lagging the RF input relay and bias by 
roughly 0.5 ms.  This shouldn't be a problem with any modern transceiver. 
>From past measurements, transceivers like the Icom 7700/7800, and K3 all 
supply RF > 9 ms after amp key line closure.  Still, for someone who seeks 
perfection, it may be a concern in that the event order is misplaced due to 
electromechanical delays.

You can solve the problem with hardware, but that will add more circuit 
complexity.  One possible solution would make use of CMOS 4538 dual 
monostable chips that allow you to trigger events on the leading or trailing 
edge of a pulse.  In the past, I've used those in several applications and 
with a bit of care taken, CMOS can be relatively immune to RF.  Of course, 
you could always create delays in other ways using R/C combinations that 
drive say...a transistor switch.

Another solution is one I developed a couple months ago.  It uses either an 
Arduino Nano or 16F88 PIC microcontroller to precisely control all switching 
elements.  However, it also adds another layer of protection beyond just 
proper sequencing:   RF is sampled before each switching event to ensure 
that hot-switching never occurs.  As the microcontroller detects a fault 
condition, the microcontroller inhibits the switching event and then pulses 
one of two timing error LEDs -- one for leading edge faults, the other for 
trailing edge faults.  So, it can be a valuable timing diagnostic tool in 
the absence of a scope.  Probably the most beneficial attribute of a 
microcontroller in this application is that timing fixes are changed 
strictly through USB port uploads.  The hardware is fixed; only the code 
changes.  The code also supports 3-stage dynamic EBS "hang" bias, with hang 
time adjustable between 0 - 255 ms in 1 ms increments.

The C++ code and logic flow chart is posted on my QRZ.com page.  Structured 
logic is used and each line of code is documented to allow for easy 
modification.  The first set of "S-QSK" boards have arrived and I'm now 
starting to validate the PCB layout.  On my QRZ.com page, you will see that 
the board is incredibly dense for its small size but this allows the board 
to be installed into most any amp.  A Remote RF Sensor is also being tested. 
This allows an amp builder to place the RF sensor away from the 
microcontroller board, if desired.

Paul, W9AC

> ----- Original Message ----- 
> From: "k3it" <gokoyev+k3it at gmail.com>
> To: <amps at contesting.com>
> Sent: Wednesday, March 27, 2013 1:09 AM
> Subject: [Amps] SB-200 QSK mod info
>
>
>> Back in February I bought a W7RY SB-200 QSK board from a link on this 
>> list.
>> The mod is finished now and I posted some scope traces and  info here
>> http://uncle-ziba.livejournal.com/9102.html .  I believe there is small
>> issue with the relay sequencing,  but I may be wrong.  Please let me know
>> if timing looks OK to you.
>>
>> 73!
>> Vasiliy K3IT
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>