FT8 setup using KX2/KX3 during SOTA activation

As a frequent SOTA (Summits On The Air) QRP operator, the potential of enhanced weak signal readability offered by the new FT8 digital mode intrigued me. I set out to assemble an ultralight FT8 setup for SOTA operation (I like to keep my total pack weight under 10lbs) so it would not present much extra burden for my summit hikes. This page is a work in progress detailing what has worked and hasn't worked for ultralight portable FT8 operation with my KX2 (or KX3).

Equipment Setup

KX2 or KX3
kx2b.jpg
use DATA A mode (allows you to keep separate settings from SSB mode)
check RX Filter is fully wide (default is narrow)
adjust mic gain carefully (compression is off)
if VOX doesn't function on the KX2, power cycle the rig
run power at 50% maximum to avoid overheating due to 12sec continuous FT8 xmsn
monitor PA temperature using DISP metering selection, avoid running much higher than 50degC to be safe
depending on ambient temperature and number of sequential QSO's, KX2 may overheat at 5 watts in FT8 mode

Nuvision M800W610L Tablet

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runs Windows 10
8-inch 1920 x 1200 screen
only weighs 262g (0.6lb)
runs WSJT-X software


Generally, you want to run in NON Tablet mode (which forces apps to resize to maximum, etc). Go into Settings-System-Tablet mode and change these settings:

  1. "When I sign in" to "Remember what I used last"
  2. "When this device automatically switches tablet mode on or off" to "Always ask me before switching"

This tablet is often heavily discounted on eBay and I highly recommend it at those discount prices

Sound Card

I initially assumed I needed to use an external USB sound card with the Nuvision tablet and I purchased the Syba shown below. However, with subsequent experimentation, I was able to get the internal soundcard working for both rx and tx audio.

Internal Sound Card

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a 3.5mm TRRS splitter is needed to split rx and tx audio from the single 3.5mm tablet jack

External Sound Card

Syba SD-AUD20101 usb soundcard

syba5.jpg

buy on eBay or Amazon for < $15, widely recommended


Micro USB OTG adapter cable

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if needed to supply external power to USB soundcard (I had to do this)

Mogix Li Ion USB battery

mogix2.jpg

needed to supply external power to USB devices, a smaller battery would be fine

Optional

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small bluetooth keyboard


Rubber tipped stylus pen is also nice to have

Time Sync

One issue that needs to be dealt with is establishing sufficient time sync (+/- one second is more than sufficient) on the Windows device so that WSJT-X will decode properly. Here are three options in order of increased accuracy (and complexity):
1. Set the time before you leave the house, using an internet time server and hope the time stays accurate
2. Set the time on the summit using your cell phone as the time source. You can install GPS Test or ClockSync android apps to get accurate time via GPS or Internet respectively. On your cell phone, you will need to observe seconds ticking (either android app mentioned provides that). On the Windows device, open Control Panel - Date and Time Settings and you can set time down to the second when you click "OK."
3. Use external bluetooth or USB GPS receiver to set the system time via free BktTimeSync Windows app (available here) - I tried this method with two different GPS devices (one bluetooth and one USB) that others reported success with but I was unable to get either device working reliably. I cannot recommend using a GPS receiver for time sync based on my experience. Below is info on the GPS receivers, but in the end I switched to manually sync'ing (option #2 above) using my cell phone running GPS Test android app as the time reference.

Bluetooth GPS

  • under Windows Bluetooth devices, pair/connect the GPS receiver and add a virtual COM port (output port) for the GPS device
  • point BktTimeSync to that virtual COM port and set for sync'ing every minute (this can be lengthened once you observe good time sync (DT values under one second) in WSJT-X
  • I experienced reliability issues with the bluetooth/software
tomtom2.jpg

I initially tried using a TomTom GPS receiver, weighing only 68g.

The GPS receiver needs to indicate GPS lock (flashing green). If not, power cycle it.
The GPS receiver needs to show as "connected" (not just paired) under Bluetooth Devices. If not, remove it and re-pair it.
Check the GPS outgoing COM port number under Bluetooth Devices.

USB GPS

ublox.jpg

After my difficulties with the TomTom bluetooth GPS receiver, I tried a USB GPS dongle like this one, available for about $10 on eBay

Unfortunately I was not successful in getting BktTimeSync to retrieve GPS time info from it under Windows 10. It worked fine on my Windows 7 laptop but couldn't get it working on the tablet.

Startup Checklist

  1. Turn on Tablet and cell phone
  2. Turn off Windows Tablet mode (interferes with window re-sizing)
  3. Open GPS Test app on cell phone and check/set Windows time on the tablet
  4. start WSJT-X and set grid square, FT8 mode and correct band (for logging purposes)
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