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.

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.

Double Side Band (DSB) Generation II

I made some progress with my NE612 DSB Generator. I built it up in a shielded box and I have observed at least a reduced carrier of 20 db below the side bands now. My problem was with my measurement receiver, it was receiving the radiated carrier! I also have attenuated the Si5351 oscillator separately and not in the same box and then injected it into the NE612. Note the 10 db pad. Next I will try a balancing pot across pins 1 and 2 with the wiper to ground. I should be able to get 30 db of reduced carrier with the NE612. The audio fidelity is very good and I believe this will be able to produce eDSB (Extended Double Side Band).

Double Side Band (DSB) Generation

In my quest for a simple QRP phone rig, I have been experimenting with Double Side Band (DSB) Generation. Using the Si5351 as a local oscillator I have tried both a high level mixer (passive) and a NE612 (active). Both of these produced DSB but with a carrier higher than expected. This was all done on a open breadboard so I believe I am getting carrier leakage. As you can see in in the HDSDR image below I have a very broad DSB signal.

The other test involved here is the fact that I was using my simple Direct Conversion (DC) receiver from my Prototype Radio experiments. A DC receiver normally can not receive a DSB single because of its wide bandwidth causing it to hear both side bands at once. However in the case above, I am feeding the audio from the DC receiver to  HDSDR on my PC. Using the left channel only since the DC receiver does not have a I/Q stereo output (see below the feature in HDSDR).

This method allows the use of a low frequency Intermediate Frequency (IF), in this case 10 kHz allowing the DC receiver with HDSDR to demodulate DSB by receiving either USB or LSB and even ECSS (the DSB feature in HDSDR).

There are other problems with this method like multiple images, however it allows very simple hardware to be used for rigs and I believe two simple DSB transceiver would be able to communicate with each other using this method.

Enhanced Single Side Band (SSB)

I was interested in enhanced SSB so I used two instances of PowerSDR SR40 across two computers with one in transmit mode and the other in receive. I was able to increase the transmit bandwidth to 6 kHz and the audio was amazing. The connection is just line out stereo to line in stereo. This contains the I/Q data. I experimented with USB, LSB, and AM.





The following is a Design to try

Tacoma Compass/Temp Gauge

My new truck had a few minor issues. One was that the Electronic Compass/Temp gauge was dead. A quick check on the Internet forums found known issues with this device particularly with a part that lifts off the board due to heat. I disassembled mine and found exactly that issue.






The surface mount resistor had in fact lifted off the board.






I re-soldered the resistor and powered it up and it is working again. Awesome!

Maker Faire

I attended the San Diego Maker Faire this weekend.



So many great things, from the Ultrascope to Robotics to awesome art pieces like this:





This walker was electric, powered by two large batteries.

Great show.