impedance help (resistance, reactance, etc.)

[KB1KGA]

Just for a laugh I did some searching and here's a very similar discussion about matching (or not) between an audio amplifier's output impedance and speaker impedance.

http://forum.allaboutcircuits.com/showthread.php?t=2126

[VK2BFQ]

Your 21.5 / j0 means that the radiation resistance of the antenna is 21.5ohms. There is no inductive or capacitive element. The antenna is therefore resonant,and will look like 21.5ohms to any feeder connected to it.
If you were to transmit into this antenna, at the resonant frequency, using a
length of 50ohm cable the VSWR would be 2.3 : 1 ( 50/21.5 ), however you are receiving on this antenna so this isn't relevant. Personally I would use a preamp mounted directly on the antenna,which will give you 15dB to 20dB gain, to overcome any feeder loss etc.

Amateurs nearly always design their antennas for maximum gain,which hardly ever results in the impedance they wish to match. In your case you are on a fixed frequency so bandwidth is not a consideration, F/B ratio is not either, as the back of the antenna will be facing into the ground, so design your antenna for 50ohms, and get extra gain with preamp, which will be far more than you will get from the antenna.

[M0DSZ]

VHF theoretical designs are not usually perfect in practice so, once the SWR is reasonably close, I would always fit 3 or 4 ferrite tubes over any coax as close to the antenna terminals as possible.

My recommended design programs are EZNEC, and it might be worth buying the fully-functioning version, or MMANA-GAL which is easier to use, not so good for complex feeder designs, but free.