Saturday, December 19, 2015

40 Meter QRSS Beacon II

After monitoring the QRSS beacon for almost a week I noticed something interesting. I had been using Spectran by I2PHD to capture the beacon but have now switched to QRSS VD by AJ4VD which allows me to easily review many hours of collected traces. It seems just after sunrise when the building where the beacon is housed gets heated by the sun the beacon frequency raises by 10-20 Hz and stays there all day and then cools down at night. Click the image below for the details. This is about a one hour segment and starting at 8:40 AM this morning it starts to go up and stabilizes at 9:05 AM.

Monday, December 14, 2015

40 Meter QRSS Beacon

I have activated a 40 meter QRSS beacon at grid DM24.

This beacon is a retired kit I built a few years ago by Hans Summers G0UPL. It is setup to run off 12 volts and tapped directly to a battery array on solar installation in the Arizona desert. The antenna is a DX80 off center fed dipole with its vertex at 15 feet. The screen shot is the signal at my home QTH (DM03) approximately 300 miles from the beacon. So far it seems to appear about 15 minutes after sunrise and disappear about 45 after sunset.

Sunday, December 6, 2015

Double Side Band (DSB) Generation III

I have now built the Si5351 clock generator, attenuators, and Arduino Uno in one metal box and the NE612 mixer in another. This shielding was required because the clock generator was so powerful it was getting into the measurement receiver by radiating it! Here are the tin boxes I used:

Here they are open:

The below image is a screen shot from the 817 Commander tool that has a scanner function which plots the s-meter values over the scanned frequencies. I was feeding the balanced modulator with the carrier and a 4 kHz audio tone. You can see the two side bands and the center carrier. The carrier is in fact below the side bands as I expected. Using my FT-817 as the measurement receiver and using the s-meter measurement method, I was able to confirm the suppressed carrier.
Based on the FT-817 S-meter calibration data I found  HERE this is ~ 27 db below the side bands and probably at least 30 db since the s-meter on the 817 is not linear. Next step is the RF amplifier stages to bring the level up to a couple of watts.