A New Antenna!

As some may remember, my only antenna used to be a Radiowavz DX40. Unfortunately that came down last month. It was a great antenna and I wanted to put it back up, but the antenna hasn't fared too well with the bizarre weather in Massachusetts over the past year. The balun was rusting and the wire was snapped. It was time for something new. After researching some different designs to save money with a homebrew antenna, I found that a loop antenna could be made very inexpensively. I wanted to put up the biggest one possible in order to take advantage of the available space in the yard. I found that a 40m full-wave loop would fit well. I also found it to be incredibly simple to make and put up. Here's a quick list of what you'll need:

•  About 150 feet of wire. I used 17 gauge aluminum electric fence wire. If you go with that, DO NOT use steel wire, the impedance is 4x that of the aluminum. This stuff is really inexpensive. I purchased 250 feet for about $5. 
• Support rope. 200-300 feet, depending on your setup would be enough. I use UV-resistant high strength parachute cord. You can also use Dacron. 
• 4 dogbone insulators. These are pretty cheap, about $1-2 each at any ham supplier. 
• 4:1 balun 
• 1:1 isolation transformer.

You can also do this with ladder line and eliminate the transformer and the balun, but most new hams have coax, so I'll cater to that. The formula for wire length is 1005/frequency (in MHz). I used 7.2 MHz as a target. That comes out to about 139.5 feet. You don't need to be exact with this. Loops are very broad-banded and you'll be using a tuner anyways. With loops, you can tune the antenna using a tuner from 10m all the way up to the target frequency. So in reality, if you had a 160m target, you'd have an all-band antenna. Here's a sketch of my antenna and how it's configured.

   

The yellow square is the antenna, the green is the support rigging, the blue is the insulators, the white square is the balun, and the star is where the coax enters the shack. The isolation transformer is just outside the shack window. Here are a few helpful hints as you move through your project:

•  Symmetry is not critical.
• The isolation transformer will help because it keeps rf off the shield of the coax. Loops are more susceptible to this than a dipole as there is so much more area to collect static. 
• Height is not critical, but higher is better. Mine is about 20 feet up. 
• The balun can be placed ANYWHERE on the loop. 
• You don't necessarily have to hook it up to a meter or analyzer and tune it. Just do the measurements correctly and you'll be ok.

You'll be surprised by the performance of a loop. If you're used to a dipole, you'll be amazed when you can break pileups and get that far-off DX contact! If you have any questions, send me an email at kc1ajt@kc1ajt.com


Update 12/28/15: The loop came down last week as a result from sharing a support with a new antenna and putting too much weight on the 17 gauge wire. I made the decision to put the antenna back up in the same configuration, but with 14 gauge wire. This time, I planned ahead and purchased 1/4 mile of wire for any future projects. The thicker wire is a little harder to work with because it doesn't bend or stretch as much, but in the end it will be better in the end.

Project Update

A couple of months ago, I posted some projects I wanted to get done. Well things haven't gone EXACTLY as planned. Moving the ADS-B and scanner feeds to Raspberry Pis hasn't happened, nor do I think it will ever happen. The current setup works and really isn't using a ton of power. Right now my desktop, 2 scanners, a monitor, and an LED lamp pulls about 110 watts. The APRS iGate project was scrapped and redone a few times. The final conclusions: the Argent Data radio shield is just not sensitive enough for this application and the crystal scanner I intended to use just had too wide of a receive on it and was catching interference too easily. I went with a cheap Whistler scanner instead. I did put a new antenna in the attic that now feeds both the scanner feed and the iGate. It seems to be working well. I have also scrapped the idea of putting up a digipeater. There are about 4 or 5 that cover most of eastern MA. Putting another on the air would just clutter the frequency even more. I also reorganized the shack this week and added battery backup. The computer and feeds can remain online for about 40 minutes without power. If my HF rig is on, it will take that down to about 18. I think this will greatly benefit the police/fire/ems scanner feeds in the event of an outage. Still a few more small tasks to go, but I am happy overall, as we rarely have a power outage here.

Getting My Feet Wet With PSK

I had my first experience with PSK back in March of this year during a quick QSO with AB9VJ. It wasn't great. PSK takes a little more setup than most would expect. I had just received a new Signalink USB interface and that was all setup, luckily. Unfortunately, I had not considered setting up all the macros in Ham Radio Deluxe. It was all new to me and I just wanted to try it out.

A waterfall display depicting several PSK31 transmissions.

After that first QSO, it would be another 8 months before I would try digital again. Just last month, when I was home for Thanksgiving, I decided to give it another shot. I familiarized myself with the program again and I was on my way. I made over 50 contacts that weekend on PSK31. That would include close to 20 different DXCCs. I think once that an operator has PSK setup and configured, it is a very satisfying mode. It's very fast-paced and you can have a number of contacts in just a few minutes. This will probably be the mode that takes me to DXCC and WAS.

Current and Future Projects

Don't worry readers, I haven't abandoned the blog! I am undertaking a few new projects, but they may take some time. Here are some things I am currently planning or already working on:

• Move ADS-B feed to Raspberry Pi to save power
• Move scanner feed to Raspberry Pi to save power
• Create an APRS iGate for my local area where there is currently no coverage.
  This is currently a work in progress. I wanted a system that could run on minimal power and be as stable as possible. I will be completely eliminating the need for a server or computer by building the iGate itself out of an Arduino board. The receiver is going to be a Realistic Pro-48 crystal scanner from the 70s. I picked one up used and figured there can't be anything more solid for this install. No frequency programming needed! I already have a crystal being made especially for this, so we will see how a crystal iGate works!
• APRS Digipeater
• Move scanner and future iGate to one discone antenna in attic.