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
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)
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
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
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
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
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!
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
Another great trip to another great Hamfest. Not sure if we’ll be back next year but we’ll see.
With a pair of needle nose pliers and some very gentle pressure, I was able to bend the plates of the variable capacitor back to where I thought they should be. Both plates are parallel to each other now and don’t hit each other when rotated.
Now I just need to put everything back together, add power and test it out.
Spent some time going over the innards of the MFJ-207 antenna analyzer I picked up and doing some research to figure out what kind of rotary switch I’ll need to replace the existing messed up one with. I think I’ve found the correct replacement switch (a Lorlin CK1025 rotary switch).
Everything else inside looks in decent shape as far as I can tell. I haven’t tried to test all the individual components yet. No leaky/bulgy capacitors or burn marks and all the soldered connections seem solid. Aside from the rotary switch I’m not seeing anything else wrong with it.
Now to go over the MFJ-208. I don’t know if I’ll be able to find a variable plate capacitor to replace the existing one, but I might be able to fix it up so that it works the way it should.
