I purchased an apartment antenna and a manual antenna tuner at HRO in Sunnyvale and Oakland on April 2007. |
Apartment antenna is an AP-10B from B&W corp, and rated 300W, work from 40m to 2m band including WARC band. It has a bottom loading coil and change tap to change band. Element is collapsible and extend to 1.5m. |
Manual tuner is an MFJ-945E, rated 300W also. It can work with either coax feed or random wire antenna from 1.8MHz to 60MHz. |
First I tried tap positions specified in manual provided with the antenna but didn't work. May be too low in height or too close to a wall or trees. |
Can not tune coax feed antenna therefore I tried to tune using antenna analyzer RF-1 from Autek that I bought before. First, adjust frequency dial so that minimum SWR will be obtained and check the frequency. Thereafter move tap position and measure again. It is not difficult at all. I could obtain proper tap position pretty quickly. |
Result? I used this system at 2007 CQWXP CW contest and worked with 13 counties. Not a great result but a good enough for the antenna with only 2m high. |
Only 2m high antenna. Need a counterpoise to operate.
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Can change frequency by changing tap position. Photo shows
the tap of 20m. I could not tune to 40m band as is. At 40m, use all coil
(no tap at all) but went down as low as 7400KHz. I added 2 more turns
coil but only down to 7200KHz. Therefore, in the case of 40m, antenna
tuner is a must.
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Adjusting antenna with using RF-1. First find minimum SWR position. I changed bigger dial for easy adjustment. |
Next, show the frequency. When frequency is out of the
band, move tap position and try again.
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I changed to alligator clip for easier band change. Original design need screw driver to change (see center top). |
Front view of MFJ-945E tuner. |
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Variable capacitors were fixed on front panel directly
but sensitive for human body. Therefore I moved back for stable operation.
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The tuner stop tuning after a while. I opened the case
and found that capacitor blades are touching each other. Finally and fortunately,
I could manage fixed it.
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