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Antenna analyzer vs feedline type Sep 21st 2012, 14:37 1 1,149 on 21/9/12
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Latest Posts

Topic Author Posted On
High SWR Inverted L KC7QHE 4 days, 12 hours ago

One would expect a 3rd harmonic resonance around 4MHz. The resistance should be a bit lower, around 100 ohms.

The most likely issue is pickup from local broadcast stations. The MFJ 259 uses broadband diode detectors--they have no way of telling these signals from the low level test signal generated by the analyzer.
MFJ does sell a filter to improve the accuracy of the measurements.

I would use an ordinary SWR meter and higher power to tune up the inverted-L. Interference can be minimized by tuning when the bands are closed.

Zack Lau W1VT
ARRL Senior Lab Engineer
6 meter homebuilt dipole KC2HCY 1 week, 1 day ago

Yes, that should work. Not as strong as aluminum tubing, but not necessary for an antenna that size. You could also use insulated wire--THHN house wire may be cheaper than bare wire. The resonant frequency will be lower, but you can shorten the antenna a few percent to compensate.

Zack Lau W1VT
ARRL Senior Lab Engineer
Dipole Question KD5IUS 2 weeks, 1 day ago

That is likely to draw too much attention.

At present, the best way of dealing with antenna restrictions is to display the American Flag on a metal flagpole and use the flagpole as an antenna. George Bush signed into law the Freedom to Display the American Flag Act of 2006--this law takes precedence over covenants and HOAs.

Zack Lau W1VT
ARRL Senior Lab Engineer
dBmicrowatts? KO0Y 2 weeks, 2 days ago
To convert dBuV to dBm subtract 107 dB: dBm = dBuV - 107 dB
two db-224A's on a repeater tower question N0MZR 2 weeks, 4 days ago

No, you can't get a higher gain antenna and still have a nice omni pattern by doing that. If you orient them so that you get an omni pattern, the gain goes back down to where you started. If you orient them for more gain in one direction, you no longer have an omni pattern. No way to get both, assuming that the net height, from the lowest antenna, to the top one, remains the same.

The only practical way of getting more omni gain is to stack the two vertically, doubling the net height of the antenna. This gives you more gain at the horizon, at the expense of a compressed vertical pattern. Usually this isn't a problem.

That arrangement may allow two different repeaters, run by different owners, on the same tower.

Zack Lau W1VT
ARRL Senior Lab Engineer.

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