Question on Antenna design - will mismatch alone change antenna radiation pattern ?


I have a fundamental question - may be Glenn or other experts can answer:

I have a nice antenna in mind to build up for reception only (Wsprdaemon)
However this design is only well matched at a single band. Neglecting any radiating feedline or common-mode effects, the NEC2 model tells me however, that even with high mismatch  on other bands the radiation pattern would be different but also very beneficial.

Now for the practical construction, I wonder:
- if I would put a buffer pre-amplifier directly at the feedpoint (where the source in the NEC2 model is) and therefore do not introduce a feedline at all between antenna and pre-amp, would the radiation pattern will be any different than what the NEC2 models tells me, because of the heavy mismatch between the antenna impedance and the input impedance of the amplifier ? Would it require any special pre-amp to keep the radiation pattern unchanged to the NEC2 model ?

From theory I would say that there is no change in radiation pattern, rather than most likely a heavy drop in antenna efficiency (losses)... however from practical builds, my experience is completely different! Heavily mismatched antennas never really worked, even with a pre-amp...
(The design is for the high bands 10Mhz and higher)

As it would be some significant work to build it up - what do you think..?
Just go for it, even though it is a single band design and even though Wsprdaemon requires broadband performance ?
(but for reception with active feed)

What do I need to pay attention for, if I want to feed it with a pre-amp for wideband use, although the wire construction shows a narrowband characteristic at 75Ohm feedline (RG6)

Ulli, ON5KQ

Join to automatically receive all group messages.