Sunday, December 28, 2014

HF with a cheap SDR Dongle

Using an Arduino controlled Si5351 PLL Clock Module, Mixer, and a cheap RTL-SDR Dongle I tuned in on the 40 meter ham band today using the SDR # software

I came across a Mini-Circuit ZAD-1 double balanced mixer (DBM) at the TRW swap meet this weekend in good condition for 7 bucks so I grabbed it. This DBM with BNC connectors turned out to be a standard Level 7 mixer.

I connected my RTL-SDR dongle to the IF port with several adapters and fed the output of the Si5351 directly into the LO port. The antenna is connect to the RF port.

Using NT7S Arduino Library and a Mega 2560 board I set the clock0 to 125 Mhz to feed the LO. Below is the basic setup.

This set-up worked great for the Medium Wave (MW) AM broadcast band too. On 40 Meters I listen to several SSB stations just fine. Using the NT7S library for 125 Mhz may be a bit out of range since I do seem to hear a warble to the clock when I listen to the 125 Mhz signal directly on another receiver. I need to experiment with the original Adafruit library and see if there is a difference. All and all a cool experiment. If I can get the warble out of the clock and maybe add some band-pass filters this could be a very usable SDR receiver for HF.

Sunday, December 21, 2014

Computer Build

I am building a custom game PC based on the Gigabyte GA-Z97X-UD3H motherboard. It needs to be ready by Christmas Day, and I still have a lot to do before it is finished.

Tuesday, December 16, 2014

Desert Farm

This weekend I was back in Arizona at my buddies farm. We had a great time playing with all his farm machines and seeing what new things he is working on, like this pump system. He calls it "FrankinPump". This is 4 gas powered pumps connected in parallel that can empty his 50000 gallon water tank in 2 hours.

We enjoyed the trip and his solar system worked perfectly with plenty of power even with the short winter days.

Sunday, December 7, 2014

Fix or Replace?

I have a 4 to 5 year old Samsung LCD Monitor that developed an issue where after a 20 minute warm up the monitor would go black. If you cycled the power switch it would come back for two seconds then go black again. I did some quick research and found that a frequent issue is with the capacitors in the switching power supply.

I felt that the effort would be worth my time, so I replaced all the capacitors after a fairly lengthy dis-assembly process and then reconnected everything without fully assembling it and re-tested it. Unfortunately the problem remained. I continued the research now after spending nearly a full day on the project and determined after some lengthy tests that the fault is in the back lighting system. The back lights on this monitor are compact florescent (CFL) units. To replace the CFL is not as simple however. These units are attached to the panel assembly on each end and there are two tubes in each. I think many hams and electronic tinkers hate to throw away hardware if it can be repaired and I have gone to great lengths on other items in the past to get it done, but sometimes you just need to call it quits, or it will consume all your time. I wish things were made to be repaired however many are not or the parts costs exceed its value.

So in this case I will be parting it out to the junk box. There are many good parts and who knows they may live again.