Hi Chris,
There is loads of detailed stuff on the subject of antennas on the internet, but it gets pretty technical very quickly. Without getting too technical, the short answer is ‘No’.
Monopoles (such as transponder or PilotAware external mount antennas - which are 1/4 wavelength long monopoles) require either a ground plane or a counterpoise element* to lower the radiation angle closer to the horizontal and create an effective match to the transmitter (* adding an equal length counterpoise directly opposite a monopole makes the antenna a dipole - like the PAW ‘Internal’ ‘T’ shaped antennas - which don’t need a ground plane.).
The antennas used for the ATOM, on the other hand are NOT monopoles, they are colinears, which comprise a number of tuned length elements, connected together in a linear stack by matching stubs (often short coils tuned to equal a 1/4 wavelength at the appropriate frequency). This has the effect of ‘adding’ the signal from each element together ‘in phase’, which focuses and magnifies the radiation at a relatively low angle all round the antenna and thereby increases the ‘gain’ and therefore the effective range of the antennas. This type of antenna does not require a ground plane. The short ‘ground radials’ on the bottom of your PAW antenna, are more than likely included to improve the match (technically ‘impedance’) between the antenna and the coax feed line, thus ensuring optimal power transfer into (and out of) the antenna.
Hope this helps.
Best Regards
Peter
