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Happy Independance Day!

God Bless America!

No radio today…just enjoying our Freedom and Liberty.

40m Magnetic Loop Antenna with Modifications 

Here is the final version of my 40m magnetic loop antenna using my homebrew hi-voltage variable capacitor. As I mentioned yesterday, I fixed an issue with the variable capacitor feed screw. Today I set it up outside handing from a tree as before. The difference is that the capacitor is now at the 3 o’clock position to facilitate tuning without a ladder. This moves the feed point to the 9 o’clock position. No changes were made to the pvc supports as I merely change the position. I read a 1.31 SWR at 7.039 MHz with am fully engaged. I am running 1W WSPR on it now and will report results tomorrow. Here is what it looks like in operation:

Planning a 20m WSPR station Using Raspberry Pi

I have a Raspberry Pi that has been sitting around the shack for years looking for an application. I have decided to implement a 20m WSPR station with it. I have ordered a 20m WSPR shield from TAPR that has the necessary LP and BP filtering needed to make it work cleanly.Expected output will be 20dBm (100mW). I will likely be using a long wire antenna with this to get started. I have also come across a 20dB amplifier development board that may come in handy if I need to run additional power. It is made by TI for their THS3202 amplifier chip.

In preparation for the board’s arrival I have been setting up the Raspberry Pi. I loaded up the operating system onto a 16GB SD card. I am running the board “headless” i.e., without a monitor, keyboard or mouse attached. A micro USB plug provides +5V power and the connection to the outside world is via an Ethernet connection. Using the application puTTY, I can open an SSH session to the Pi and interact with it. I have since installed a USB WiFi Dongle and have now eliminated the need for the wired Ethernet connection.

I would ultimately like to run this mounted outside the shack running on solar power. With this in mind I have ordered a small USB dongle that will measure the current drawn by the Pi in this circuit so I can size the panel and battery for 24 hr operation.


UPDATE: Installed the software on the Raspberry Pi with no issues today. The software is called WsprryPi and can be downloaded at GitHub through the Pi’s headless interface. Just follow the build instructions. Inital power consumption tests are showing about 400mA @ 5V.

Portable Solar Battery Pack Wiring

Here is the wiring diagram for the portable solar battery pack:

Photo Aug 30, 8 37 48 AM

The solar charge controller is a 20A unit.

Portable Solar Battery Pack

A while back, I mentioned that I had been gifted four new 12V, 6Ahr batteries. I have been working on mounting them in a large plastic ammo box along with the connections and charge controllers to use with the solar panels and the radios.Last night I drilled out the holes for the outside connections and installed braces to hold the batteries in position. Here is what it looks like thus far:

Photo Aug 30, 8 19 28 AMPhoto Aug 30, 8 20 03 AM

The front has a power switch, a Voltage meter to monitor the battery state and an output for a single pair of Anderson power poles for the load. A 12V cigarette jack is located on the side in case I want to use a small AC inverter or some other 12V load.On the side not shown is another Power Pole connection for the solar panel input and a 12V cigarette jack. The second 12V jack is direct emergency access to the batteries either as load or for mains charging. I intend to keep this on disconnected internally and will only use in an emergency. Next steps are to mount the charge controller and two watt-meters inside the box and wire the whole thing up.



Email over HF Revisited

I setup the ICOM 7100 to run with Winlink Express (formerly RMS Express) software to send email over HF. The software allows direct use of the ICOM 7100 through it’s on-board digital mode interface. Overall, this was fairly simple to setup and surprisingly I was able to send some test emails in the morning hours on 40m to a server in Houston. Be sure to select USB digital mode in the software. I set my power out to 50% and connected fairly easily. I am going to play with the settings a bit and see if I can improve connection reliability. At some point I’d like to try this using the FT-817ND as well.

Anybody who would like to exchange some test email with me can send their messages to

Update 4/20/2017: Per request I am attaching screenshots of my RMS Express configuration. Note that you will likely need to adjust your port settings. First up is the winmor settings:

winmor settings

Here are the Radio Settings

radio settings

Using WSPR to Compare HF Antennas

Playing with WSPR over the last few months has got me thinking about how this data can be used to compare the performance of different HF antennas. My thought is to setup two WSPR stations at the same QTH running the same band and power output over a 12 to 24 hour period. I have done this with my homebrew magnetic loop antenna and my end fed Dxtreme antenna on 40m and 20m. The data is then downloaded and reporter data is compared over time. Attached are the results as well as the raw data for this initial test.

Using WSPR to Evaluate Antennas

20m WSPR Data

40m WSPR Antenna Test Data RevA Temp

My apologies for the rough data files but I am still working on how to crunch the numbers efficiently. The methodology appears sound and opens the door to quite a bit of additional potential experimentation.



Homebrew, High Voltage Variable Capacitor for Magnetic Loop Antenna

I built a prototype today of a high voltage variable capacitor for the 40m Magnetic Loop antenna I am building. My original plan was to make it a fixed capacitor out of a length of coax for a single 40m frequency. I played with cutting the coax to the right length and finally decided against this method.Instead I started looking at a “trombone” style of cylindrical capacitor made from copper pipe. After making some calculations, I settled on the following for the prototype:

  1. Inner cylinder made from 6″ of 1/2″ copper pipe: O.D. = .0.625 in
  2. Outer cylinder made from 6″ of 3/4″ copper pipe: I.D. = 0.811 in
  3. Dielectric made from 4mil Polyethylene clear plastic sheeting from Home Depot. You will need a strip about 7 inches wide and 6 feet long.
  4. A couple of sheet metal screws and some scotch tape

The nice thing about this capacitor is that PE sheet has a dielectric strength of 3kV per mil. This will easily allow operation at the 4.2kV generated in a magnetic loop when operated at 100W.

Here is what it looks like now:


So as a prototype definitely a success!

I have a scheme in mind to make this precision adjustable using a threaded rod so I will likely do that in the final version. On the 40m loop antenna, I expect to use this almost fully engaged and only need to tune about an 1″ of play to cover the whole band.

TYT MD-380 DMR Radio Arrives!

My TYT MD-380 arrived yesterday for DMR use. First impression is positive as looks like a solidly build radio and comes complete with charger, two UHF antennas and a USB programming cable. I downloaded the TYT software and drivers from their website and these installed without issue. I did not have the Talkgroup info available oto program this myself, but Joe, N5JLR, met with me this morning and downloaded the code block needed to setup the radio for use on the local repeater.

Amazingly crisp audio during a QSO is the result! I am looking forward to playing with this and many thanks to Joe and the local digital club for getting DMR on the air for this area.

DMR HT Radio on the Way

I ordered a TYT MD-380 DMR radio today on Amazon. It should arrive by end of next week. In preparation to setting this up, I have registered my call-sign. The local digital group has setup a local repeater that is linked to one in the upper valley as well. Should be fun to play with digital voice on UHF.