Imax with a Transformer to match at the Feed Point
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Base My Imax model with secret capacitor on the rasiators middle section.
- Thread starter Marconi
- Start date
Eddie
you have all currents in phase on a 5/8wave radiator,
i have seen this idea of using a capacitor to shift current phase on a 5/8wave element before,
https://rudys.typepad.com/ant/files/antenna_colinear_zepp.pdf
you have all currents in phase on a 5/8wave radiator,
i have seen this idea of using a capacitor to shift current phase on a 5/8wave element before,
https://rudys.typepad.com/ant/files/antenna_colinear_zepp.pdf
Bob, that Imax is an older model that DB and I both worked on when we were informed that the Imax has a 43 pF capacitor near the middle section of the 3 part radiator. It does seem to do away with the out-of-phase bottom wavelength of the conventional old Imax I made before.
Use PDF Zoom feature ( + - ) for close-up image at top of page.
I remember modeling the Imax with the capacitor for the first time. The model worked well with the capacitor right where it is on the Imax, and the capacitance as measured from an actual Imax capacitor.
As I recall, position was very important, as moving it to far in either direction on the model would drastically reduce the phase shift effect of the capacitor. I presume that much like coils, which are current devices, have far more of an effect when near a current node, the capacitor, a voltage device, seems to need to be near a voltage node for best effect.
Another thing I noticed with said models is the feed point impedance was very close to a half wavelength antenna, and so I figured that part of the goal was to use the same matching system as they used on the a99.
The phase change effect, and the feed point impedance are why I have, on multiple occasions, called the Imax an extended electrical half wavelength antenna in the past.
Like in the .pdf bob posted, I have modeled EDZ antennas with this setup, and said model had more gain than a standard EDZ antenna, and didn't have the two minor lobes near the main lobe.
The DB
As I recall, position was very important, as moving it to far in either direction on the model would drastically reduce the phase shift effect of the capacitor. I presume that much like coils, which are current devices, have far more of an effect when near a current node, the capacitor, a voltage device, seems to need to be near a voltage node for best effect.
Another thing I noticed with said models is the feed point impedance was very close to a half wavelength antenna, and so I figured that part of the goal was to use the same matching system as they used on the a99.
The phase change effect, and the feed point impedance are why I have, on multiple occasions, called the Imax an extended electrical half wavelength antenna in the past.
Like in the .pdf bob posted, I have modeled EDZ antennas with this setup, and said model had more gain than a standard EDZ antenna, and didn't have the two minor lobes near the main lobe.
The DB
DB, I tweaked the Capacitor location when you suggested the cap did not go at the middle of the middle section. This is an old model from those discussions and I have not gone back since.
The middle of the antenna lines up with the wire #2 notation, in the antenna image. The cap, a 2 part insertion object, is located between segments #33 and #34 of wire #2, which has 90 segments.
The model could stand another look in case I missed something with this location.
The middle of the antenna lines up with the wire #2 notation, in the antenna image. The cap, a 2 part insertion object, is located between segments #33 and #34 of wire #2, which has 90 segments.
The model could stand another look in case I missed something with this location.
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