K6TU's blog

As of 00Z February 1st 2015, I am stepping down as one of the administrators for WSPRnet.

If you have questions or need help with WSPRnet such as updating your email address, site issues etc, please contact Bruce W1BW.

I finally bit the bullet and applied for a new callsign - N6TTO, my call for more than 20 years, was a handful on CW and voice - takes awhile to say! So I opted for a shorter call - both in CW and phonetics!

N6TTO is now K6TU.

I've generated a short video of using VOAAREA to predict received signal levels for my 200 mW WSPR transmissions. Comparing spots from the WSPR database to the predictions has been very interesting and show a pretty good correlation.

You can find a writeup of my results and a link to the video on my personal blog at:

WSPR & Propagation Predictions

Feedback appreciated!

UPDATE Feb 26, 2009

I've added a couple of additional features to the QRP WSPR transmitter.

1. Completed the switched attenuator so that I can send at 23 dBM, 17 dBm and 10 dBm under control of the PIC.
2. Added GPS support (see below)

I use the GPS to get time of day information and also an accurate 1 pulse per second clock. This is used to update the time of day and to calibrate the symbol clock for WSPR (generated from the internal soft clock generated from the 32.768 Khz (nominal) crystal.

Being paranoid, I also added a thermal fuse to my "oven" so that power to the heater is removed (permanently!!) if the temperature inside the enclosure gets to 72C.

I got the TX on the air just after sunset local time today so missed the bulk of the day's propagation - that said, my first spot was from WA2YUN!

Look forward to getting spots - especially at the lower power levels!


With thanks to Gene W3PM and indirectly to Johan SM6LKM, I am now on the air with a homebrew WSPR transmitter running 0.5 watts (antenna = 160m inverted L with remote tuner) on 30m.

Completed the installation of a remote antenna tuner at the base of my 160m inverted L this afternoon - just before the heavier rain started.

Can already see a significant improvement on receive having copied HG8LMQ and IK1RKU for the first time on 30m. Judging the transmit improvement will take a little longer but also appears to be better.

I've attached a picture of the temporary center loaded vertical I've been using on 30m for the last week.

Motivated by the QRPp day on 30m (and stuck without a ready to hand attenuator to knock down the output power of the TS-2000 further... I decided to grab a manual antenna tuner, put it at the base of my 160m inverted L and load it up on 30m.

This is a second "temporary" antenna for 30m - I've been using a short home-brew vertical that I use when portable - its about 12 feet high, center loaded with 4 short (non-resonant) radials.

I will usually leave WSPR running in receive mode during the night here on the West Coast on either 80m or 160m.

I've done this for the last couple of nights on both 160 and 80 - there seems to be a pretty stable path on both 160 and 80 between VK7 and W6. Also a path exists in the hours before dawn to Wake Island on 80m. Despite WSPR not decoding or logging any spots, I also leave WSJT7 running in WSPR receive mode - WSJT decoded the signals from WA2YUN on Wake this morning at sign levels between -10 and -14 dB. Very impressive as all of these were with 5 watts on the sending end!