平面环天线_图文

1、Spiral Loop Antenna As an experiment I decided 揳fter reading several article on spiral coils to build a full wave loop on 40 meters in the configuration of a compact spiral loop to see just how well it would work. As a form I went with treated 1扻 2攕 that I cut notches in 綌 spacing 搕his took abo

2、ut 2 hours Next I measured the wire using the standard formula for a full wave loop 1005/f then proceeded to wind the coil on the form and attached the feed point. Then after checking resonance with the analyzer I found the first issue. I had calculated the frequency for 7.050 Mhz but the analyzer s

3、howed the resonant frequency above the band so I started adding wire to bring the frequency until I got the resonant frequency down to around 7.070. What I suspect is this configuration becomes capacitive and raises the frequency so instead of 1005/f the formula was closer to 1090/f .   &#

4、160;  Performance of the loop. The loop was mounted on a roof tripod at aproxamitly 25 ft up. The first thing about this antenna is it seamed to be noticeably nosier this I attributed to the vertical polarization. Next I found as one would expect that the signals were around two or three S

5、 units below my main antenna (150 ft double extended zepp with the apex at 35 ft. The band width of the antenna was very narrow 2:1 B.W. was some were around 20 KHz this may have been better if I had used larger wire what was used was #24 gage wire. As you can see from the far field plots there is s

6、ome degree of directivity    So in conclusion I think this antenna may work out ok as compact portable antenna more experamenting and testing would be needed.Loop logDate Time Call RST sent RST rcevd. Freq. Mode Pwr Name QTH07-25-08 05:45z KC2GKU 599 579 7 CW 30 James Wharton NJ08-09-08 01:27z VO2A 599 599 10 CW 30 DXpedition Labrador08-10-08 00:59z CO8LY 599 599 10 CW 30 Ed Santiago de Cuba08-14-08 01