[TowerTalk] Universal Sequential QSK Board

[Paul Christensen]

I'm in the process of finalizing development of a sequential QSK board that 
can be used for many applications where both RF sensing and precision 
sequential timing is required.  Examples include: control of external 
devices such as preamps, active antennas, or external relays that need to 
have power removed during transmit.  Code has already been written and 
tested for use with sequential amplifier QSK/EBS systems, QSK switch for 
classic Tx/Rx separates.  A similar product is produced by DX Engineering 
(Model TVSU-1A - Time Variable Sequencer Unit) but to the best of my 
knowledge, it doesn't have the ability to sense RF and preclude 
hot-switching in the presence of RF.

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.  The point of this post is to obtain your input for 
antenna/preamp switching and sequencing requirements.  I'll write the 
microprocessor code based on that feedback. A preliminary description of my 
S-QSK Board is available on my QRZ.com page.  Unlike the programs I've 
recently written, I may find out that there's no real universal algorithm 
that will work and may require each user to customize the switching code.

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

Feedback from you concerning switching requirements, sequencing, etc. is 
much appreciated.   Current feature list is shown below:

Paul, W9AC
-------------------------------------------------

S-QSK Board 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 solid-state 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) RF sample 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) A remote RF Sensor Board has been designed for applications where the
inclusion of a "T'eed" RF connector presents unreasonable line mismatch when
using long lines, or in instances where one desires to sample RF at a
remote location;

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

10) 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);

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

12) 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;

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

14) 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;

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

16) 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;

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

18) 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.