Tag Archives: antenna analyzer
I recently had the need to check a transceiver to ensure that it was on-frequency. This is easiest done with a frequency counter, which is included in an MFJ Antenna Analyzer. I use an inductive coupler made from some coil wire around a small (1/2 inch) piece of CPVC, with the coil connected to a BNC connector.
Since I had a few minutes after the XYL went to bad (after a *very* busy Saturday for both of us), I went into the basement and played with the antenna analyzer.
This isn't the most ground-breaking post on my blog, but they don't really teach much about antenna analysis in traffic engineering classes!
The first thing I did was drop the frequency of the analyzer to something low and see how much power the analyzer puts out. 4V peak-peak.
SWR Check - 25 Ohms
SWR is based on the mismatch between the impedance of the source and the load. So a 2:1 SWR could mean that the load is twice or half the source impedance. So I decided to put a few resistor arrangements on the analyzer and see if what happens is what I thought would happen.
SWR Check - 100 Ohms
Since I couldn't figure out a way to make my two BNC terminators in series, I pulled a resistor out of my parts bin. It was really a 98.3 ohm resistor, according to my non-lab-grade Radio Shack meter, so I figure that's close enough!
Other Dummy Load Test
I had a dummy load I built for QRP uses (specifically the Softrock). I built it a while back, which is why the callsign is wrong.
So the MFJ-259B has a capacitance check on it. This is really for the capacitance of an antenna, not for what I did in the pictures below. I basically took a ceramic disk capacitor and clipped one end to the ground and the other I held into the center conductor of the antenna port. This is a 10,000 pF capacitor.
I figured the stuff above was a little more fun than me talking about how I tested every antenna I own... again.
Oh crap, that probably sounds bad. Ah well.
So my first find was a key. It's nice, heavy, and probably has a history, which I added "purchased for $35 by KE8P" to.
I found this. For $165. Like any normal ham that likes to push buttons and turn knobs, I turned it on, just to be greeted with it flashing "LOW VOLTAGE 6.5V". I figured that was a sign that it probably works.
And when I got it home, I found these in it. Ten Energizer rechargeable batteries.
So I removed the batteries and plugged in a wall wart. I was greeted with "VOLTAGE OK 15V" and something like the display in the picture above. I did check my dummy load, it claims it is around 50 ohms at 1-1.3 SWR. Guess it works!
Also included were these. They are coils to use the analyzer as a dip meter. I didn't really need these, as I built one (they're really quite simple). My built version worked quite well for the coax traps on my attic trap dipole.
So I did try it with my HF and 2m antennas...
The third purchase was a case for my SoftRock
The last thing I got was some fiberglass mast. I didn't take a picture of that.