If you look back at my post about the MFJ unun that I am using to help match my Hamsticks, you might see that I got a couple different bits of feedback. The basic question I had asked is this: When matching an antenna is it better to start at lowest SWR or Resonance? The method I ended up using that I described in that post was starting from Resonance - mainly because that seems to be the suggestion from K0BG on his website - plus it had some other advantages that made me lean towards that method.
Like many things, there is a lot of back forth when questions like these come up. There are things like questions about how much it really matters when you consider how compromised a mobile antenna is, where is the matching device located, how long is the coax, etc. With that in mind, I'm considering a small experiment:
Like many things, there is a lot of back forth when questions like these come up. There are things like questions about how much it really matters when you consider how compromised a mobile antenna is, where is the matching device located, how long is the coax, etc. With that in mind, I'm considering a small experiment:
Because the Hamsticks use the whip at the top for tuning, the matching I did, starting from resonance, is a combination of the setting on the matching unit, and the length of the whip. I could unscrew the whip part, and set it aside, and screw in a separate whip, and do the whole matching process again, but starting from low SWR. Doing this would give me a way to compare the two methods because I could quickly swap the Antenna back and forth between one matched starting from resonance, and one matched starting from low SWR. I have an inexpensive meter that I can use to measure field strength - it doesn't give absolute values, but I could set it based on the first antenna arrangement, and then compare the second antenna. The process would go like this:
- Put in the whip matched from resonance, and set the MFJ matching unit to the appropriate setting.
- Put the field strength meter some set distance from the antenna (15 feet?)
- Transmit a carrier on low power - maybe 5 or 10 watts
- Calibrate the field strength meter to mid-scale
- Switch to the second whip, matched from low SWR, and set the MFJ matching unit to the appropriate setting.
- Transmit a carrier on the same low power setting as step 3
- Compare the reading on the field strength meter
Does this sound like it would be a reasonable comparative test, or am I missing anything important? I think by following these steps I'll have a "controlled" experiment, and I'll have a fairly objective way to measure the results, other than just asking someone "how do I sound now?" Thoughts? Comments? Should I go for it?
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