NO Ground 27 MHz antenna

I have read on other forums that this doesn't work very well.

 

I believe coax length is important to the tuning of this design as this coax type serves as the ground plane / counterpoise / second half of the antenna / whateveryawannacallit.

I've been told that this design achieves about 70% of the range of a standard ground-based antennas of the same length

 

Well a few thoughts


First is there is no such thing as counterpoise in mobile applications

Sorry it is true, because it is applied to fixed station antenna systems only.

Second these antennas are common mode current antennas. They tuned the coax to act as part of the unbalanced system and gives a false swr.

Does it work?

Sort of but very ineffective antenna.

 

It's been awhile since I've studied this stuff...

But, I believe the counterpoise is simply the reflective element. Whether it's a ground plane, earth gtound, or ground half of a dipole... the counterpoise is what the driven element reflects against. In order for the antenna waveform to generate and develop a field it needs something to act like the phantom half, or negative image...

Antenna efficiency is dependent on the conductivity of both the driven element and ground image element, as well as the radiation resistance of the feedpoint and how closely the impedances match between the antenna, feedline, and signal source, I think.

SWR is nothing more than the ratio between the impedance of the radio, and the load, the load being the antenna....

If the coax shield is used as the counterpoise then it's length is critical because it's acting as half of the antenna. It's undesirable to do this because the RF traveling on the ground braid is coming back to the radio.

Where am I going wrong?

 

Yeah, ole Ridgeline is a stickler for using the precise definition of such terms as "counterpoise." Such terms and their definitions probably originated for base station operations, and they don't transfer exactly as conceptualized to mobile applications, although they are quite functionally similar in how the antenna works.

It's kind of like those folks who go nuts when somebody spells "Cummins" with an extra "g" at the end. It's not important in the grand scheme of things, but it ain't perfect in application.

 

Yes I like proper terms.

trees, please learn how balanced systems work, it will explain how the rf signal is transmitted.

 

I believe a balanced system is one where the driven element and the reflective element are the same physical length. A balanced system is symmetrical at the feed point.