Common dipole antenna dimensions for Amateur Radio HF bands

When building your own antennas, you can either look up a design or dimensions online or from book, or you can use a common formula. 468/MHz is commonly used to calculate the total length of a wire dipole in feet. I had a few dimensions jotted down for reference, but it’s easy to stick the formula into a spreadsheet and just enter the freqs you’re interested in. For example, here’s a Google Doc with the common HF bands:

I hope I’ve got these right, but if not, drop me a comment below.

Here’s a link direct to the Google Sheet if you’d like to bookmark it: https://docs.google.com/spreadsheets/d/1d3Mmnyzvj8AG1lFPd59RSMJhE9ihbE2M4w5noDzyedo/edit?usp=sharing

TAPR QRPi: QRP Raspberry Pi WSRP transmitter – 100 mW output on 20m

I finally got my TAPR QRPi shield on a Raspberry Pi 2, setup with WsprryPi software to transmit WSPR (Weak Signal Propagation Reporting) signals, and the results from just 100 mW output on the 20m Amateur Radio band are nothing but amazing. Here’s a screenshot from the WSRPnet.org site this evening over the past couple of hours showing stations that have received my 100 mW signal to a roughly cut dipole wire antenna (zipcord electrical wire split into two) for 20 meters plugged directly into the TAPR QRPi board:

When I got my first spot from VA7MM in Vancouver I was pretty happy with that. 744 miles on 100 mW is pretty good going. But then in the following couple of hours spots from stations even further afield started popping up on the map, including K9AN in Illinois, that’s 1784 miles from here in Davis, California, on just 100 mW. That’s absolutely incredible! (thanks to everyone that spotted my signal!)

This is my second attempt to get this working. My first attempt on a Raspberry Pi 1 Model B didn’t get any spots over a several hours period one weekend, so I wondered if something was not working right on the original Pi model (remembering I’d read somewhere what the WsprryPi software was updated to run on the 2 and 3 recently). This afternoon I installed WsprryPi and the QRPi board on a RPI 2, and the reports started rolling in!

My antenna is just a wire dipole, strung between two bushes in the back yard at roughly 5ft above ground, with the broadside aiming roughly north/south.

Update: it’s 7:30pm local and my signal is being received almost all the way over on the East coast!

Amateur Radio: 2m Packet Radio mobile / go kit

Tried something different today – tried some mobile / go-kit style packet radio on 2m:

  • IMG_20160225_121754Yaesu FT60 connected to a 2m/440cm mag mount antenna on my car
  • Rigblaster interface connected to a HP Mini
  • UZ7HO soundcard packet modem & terminal software

Connected to the local KBERR node on 145.05MHz, and then also AG6QO-1 / WINTBB via BERR37 on 144.37MHz while I was having lunch in Natomas.