[Amps] Universal Sequential QSK Board

[Paul Christensen]

> with the QSK circuit on LZ500ZB and/or have words of wisdom? I wonder if
> the QSK circuit has been played with and I can't operate it like this.
> (I'm really knew to "QRO" stuff).

Anyone wishing to either add or modify their amp's T/R circuit to support a 
true sequential QSK system may want to look at the Universal S-QSK Board I'm 
developing.  More background info is available on my QRZ.com page.

http://www.qrz.com/db/W9AC

This is not a commercial product and I have no desire to get into the order 
fulfillment business.  I am having some PCBs built and will decide how to 
best proceed with distribution.  However, no date has yet been set for board 
availability.  I'm not even sure there's much of an interest in such a 
device.

Sequential amp QSK is just one of many applications provided by the board --  
as well as fast T/R switching of classic Tx/Rx separates, and switched 
timing of receive preamps.  Either an Arduino Nano or 16F88 PIC chip may be 
used as the controlling microprocessor.  C++ code has been written for the 
first two applications.  The code supports 2 and 3-state bias systems as 
well as programmable EBS "hang" bias as an option.  All system timing is 
performed exclusively by the microprocessor.  Advanced programmers can 
program direct to a PIC, and forego the Nano.  However, programming changes 
don't get much easier than with the Nano.  Grab a mini USB cable and upload. 
It's that simple.   Users should have no trouble customizing the code by 
studying my flowcharts and the C++ comment fields.  Don't like the way my 
code operates?  The code can be quickly modified to adapt to your own needs 
and ideas.

Some features already implemented:

1) Nano or PIC microcontroller plugs into the S-QSK motherboard and uses 
screw-down (or molded) Phoenix-style I/O connectors.  Each I/O connector can 
be unplugged from the
motherboard for easy assembly and servicing;

2) Programming a Nano requires no special hardware programmers to burn the 
code into the microcontroller.  Just grab a USB cable and upload like a
photo from your camera.  Advanced programmers can substitute a 16F88 PIC 
inside the Nano PCB footprint;

3) Four input channels; eight output channels;

4) Optically isolated I/O for maximum RFI immunity.  Photo-Darlington 
transistor array on the input and PhotoMOS relays on the output;

5) Each input can be selected for dry contact closure or fed from a 
solid-state open collector -- or other solid-state switching device;

6) Each output can be selected to float or reference circuit ground.  Each 
output can be jumper-selected to function as a current sink or current
source;

7) Main and Remote RF samples with BNC and header pin connectors.  RF is 
converted to a DC level and conditioned into a photo-coupler.  It will sense 
RF well below 100mW;

8) LED status indictors on RF sample and all output lines for quick visual 
code validation after re-programming;

9) Uses a +12V into a DC-DC converter, bootstrapped to the +12V supply to 
provide +24V to vacuum relays (big thanks to W8ZR for the idea);

10) Two switchable on-board relay coil accelerators (if desired);

11) Since this is a universal QSK I/O board, it can be populated with only 
the circuits of interest, thereby saving on construction cost and assembly 
time;

12) C++ developed for use with an amplifier T/R and bias system.  User 
supplies the bias switching device inside the amp.  Optional bias hang time 
adjustable in software;

13) C++ code also developed to use the device to time classic separates 
(e.g., Collins 75A-4 with a Johnson Viking II).  This is the QSK "Control 
Box"
mode.  When used with PIN diodes (production board in development), 
super-fast and silent QSK switching is possible.  In this configuration, the 
input can
be any straight key, bug, or electronic keyer.  Minimum interconnecting 
cables between Tx and Rx.  In fact, I have no cables between a Drake R4C and
T4XC.  With PIN diode isolation and care in construction, it's possible to 
listen to your own transmitted signal for the sidetone;

14) Precise control and delay of all steps in adjustable 1 ms. timing 
increments;

15) Significant fault protection built into the code (e.g., hot-switch 
protection).  Before anything can switch in between switching steps, RF is 
first sampled and judged with the state of the input key line.  Both lead 
and tail LED fault status indicators can be used to determine exactly when 
hot-switching tried to occur;

16) Can be used to time/switch transmitted RF with beverage preamps.  Since 
multiple I/O is provided, just write the code to match your requirement;

17) Failed or burned up Nano?  No problem.  Thousands are out there and 
you're not at the mercy of a single vendor to supply you with a replacement 
chip that uses proprietary code.

As you can see, the board offers a lot of flexibility to support many 
RF-sensitive switching applications.  Again, info will become available on 
my QRZ.com page as development continues.

Paul, W9AC