Antenna SWR curves

Spent some time yesterday using the MFJ-259B to collect SWR values for the antenna in the different ham bands from 160m to 6m (I skipped 60m). The end result looked like this (vertical scale on all the graphs is from 0 to 10 SWR).

Antenna SWR curves
Antenna SWR curves

So I have an antenna that’s pretty good on 6 bands: 40m, 20m, 17m, 12m, 10m and 6m. Interestingly, even with the high SWR on 15m, the radio will tune the antenna there too. Not bad for a dipole that’s straight on one side and kind of L-shaped on the other one (darn tree branches)

Playing with the antenna analyzer

Finally got around to playing with the antenna analyzer I picked up at the Atlanta Hamfest. Came with batteries installed and a wall wart so it was ready to go out of the box. First thing I tried out were the inductance and capacitance measurements. Grabbed random wire wound inductor out of the junk box and put it against the antenna connector.

Random inductor on the MFJ 259B
Random inductor on the MFJ 259B

13 μH at 7.06 MHz. A pretty decent amount of inductance. It’s got a lot of windings and came out of a dead laptop power supply I think. Next I put a random capacitor on it. Capacitance meter told me it was around 216 pF. At 7.06 MHz, the analyzer measured 177 pF. Not too far off and something that I might expect at high frequencies.

Random capacitor on the MFJ259B
Random capacitor on the MFJ259B

The analyzer will also measure the amount of coax loss at different frequencies. Put a 75′ length of RG-8X to see what I’d get. At 7.06 MHz, a respectable 0.3 dB loss. At 146 MHz, though, 2.8 dB. Will have to make sure to keep the coax relatively short for whatever VHF/UHF antenna I decide to build.

Coax loss with the MFJ256B
Coax loss with the MFJ256B
Measuring coax loss at VHF with the MFJ256B
Measuring coax loss at VHF with the MFJ256B

Time to bring it in and try it out on the antenna. I know the antenna works really well on the 40m band, and the analyzer confirms it. SWR of 1.1 and 50Ω impedance at around 7.2 MHz, pretty much smack dab in the middle of the band. SWR ranges from 2.1 to 1.5 across the band.

Measuring the antenna with the MFJ259B
Measuring the antenna with the MFJ259B

Next I want to go through and record some more detailed measurements about the frequency performance of the antenna and maybe graph some things out. I’m sure that will look interesting.

I wonder what the analyzer will tell me about my HT antennas…Analyze ALL THE THINGS!

Barcamp session idea

There’s an idea for a BarcampCHS session brewing in my head. Something along the lines of open source software and amateur radio. There’s a fair bit of it out there, most of which is something I’m interested in learning more about (like GNURadio). What better way to make yourself learn about something than to try to give a presentation on it, right?

The idea isn’t very well formed yet and may or may not happen, but it’s there. I’ve got until November to figure it out. Plenty of time, right?

Field Day!

Another ARRL Field Day is upon us!

ARRL Field Day 2013 logo
ARRL Field Day 2013 logo

Like last year, I’ll be helping out with the CARS Field Day activities over on the Yorktown. Now that I’ve got a little bit more radio experience under my belt, I’ll be able to help out more with the preparations and will enjoy playing with the radios more than last time.

In preparation for Field Day, I’ve been given the task of getting the club laptops ready: installing updates and performing maintenance, updating the logging software (N3FJP), and getting them networked together so that operators at each station can see what’s going on.

TARC will be having their Field Day activities up in Goose Creek at the Marguerite H. Brown Municipal Center.

If you’re in the vicinity of either one of these Field Day locations, stop by and check out the amateur radio operations!

Atlanta Hamfest fun

This year’s trip to Atlanta Hamfest marks a bit of an anniversary for me. Last year at Hamfest, I got to meet up with Connie, and got my General class ham radio license.

Had a great time at this year’s Hamfest again. We met up with Jim (N4BFR) and Newt (N4EWT) again, who I met at Hamfest last year. Had dinner with Jim and his wife Tammy, got a tour of their new house and the new shack. Connie and I both served as VEs at the testing session (my first time as a VE). I helped proctor the test and even got to sign off on some CSCEs for people who passed their test. Attended an early morning forum titled Linux in the Shack. Learned about the Shackbox linux distro which I might have to check out.

Both the outside swap area/boneyard and the inside vendor area were pretty well populated again this year, although it seemed like there weren’t quite as many people selling in the boneyard this year as last year. The Hamfest crowd also seemed a bit smaller this year too. A big chunk of my Hamfest time was spent in the test session though, so I might have missed seeing the bulk of the crowd.

Out in the boneyard I managed to score a pretty sweet deal on an MFJ 259B antenna analyzer in excellent condition. Picked it up for $150 with far less haggling than I expected. Used up all of my Hamfest spending money, plus two months worth of our ham radio budget, but it was too good of a deal to pass up. I’ll just have to wait until later to pick up the connectors, adapters and other antenna stuff I was originally planning on getting.

MFJ259B antenna analyzer
MFJ259B antenna analyzer

Another great trip to another great Hamfest. Not sure if we’ll be back next year but we’ll see.