Now that I have an operational lowfer transmitter, I need to make an antenna that is able to receive low frequency stations. A simple and proven antenna for low frequency reception is the loop antenna. I chose to make the loop with a 6 foot diameter.
I used 3/4 inch plastic conduit from lowes to hold the wires together. The wire is home 14 AWG solid wire. I fit as many turns as I could in to the conduit. I was trying to get as high of an inductance as I could so I would have as large of a tuning range with the adjustable capacitor as possible.
I managed to get 13 loops of wire into the conduit before I got tired of fighting it. The next order of business was to make a way to tune the loop. I did not have an adjustable capacitor and they are pretty expensive online. I also thouhgt it would be better if I was able to tune the loop remotely. I came across a few pre-amp designs online that used varactors to remotely tune loops.
The design I decided to go with was Lyle Koehler's High Gain Preamp. Go to http://www.lowfer.us/k0lr/preamp/preamp.htm and look at the last design that is specifically for a remotely tuned loop. Once again I used the toner transfer method to make the board.
Next I assembled everything into the electrical box on the loop. I mounted a 10k pot to the box so I can tune the antenna locally until I come up with a perminent location. With the 13 turns, I was able to tune from around 150khz to 185khz. I added a switch to bring in more capacitance to get me from 185khz to over 200khz. I also built a temporary wooden stand out of a 2X4.
Unfortunately, I finished this project just in time for all the lowfers to shutdown their transmitters for the season. I was able to hear some European radio stations with my ICOM-R71A.
UPDATES!
7/25/2016
TH lowfer in Chapin, SC has been testing on 189.360khz. This is about 100 miles from my house. The antenna worked great once it was tuned properly. Remote tuning will certainly save some time. You can see the captures, as well as an audio clip filtered through spectrum analyzer, in my archives section under 7/24/2016.