A good antenna is half of what you need for serious FM DX, the other essential item is a good receiver.
A general purpose receiver with MW, SW and FM can provide a lot of fun when the band is open. The Digitech AR1747, Tecsun PL-380, Panasonic RF-B300 etc may be all that you. Many car stereos will also provide mobile FM DX shacks, especially if they have old-school whip aerials 800mm or longer. Alpine and Kenwood car stereos are renown for having good receivers.
If you need a receiver with better selectivity and sensitivity, then an FM stereo tuner intended to grace a home hi-fi system may be the answer.
There are heaps of tuners available second-hand e.g. on Trademe and for excellent advice of which to buy, particularly for older models, The Tuner Information Center is a great place to look. You’ll find tuner reviews by brand on the left hand side. Best bet is one with a switchable IF bandwidth (usually marked as “Wide/”Narrow”) and with 4 ceramic filters, particularly with the amount of congestion on the bands these days.There is one more factor to keep in mind, i.e. the ability of the tuner to cope with high signal levels and thus prevent overloading and spurious signals flooding the dial. The best tuners at keeping those unwanted byproducts in check are ones with MOSFET front ends, instead of bipolar transistors.
The tuner is connected directly to the line input sound card (light blue collar) on my computer and I use the free and easy to use “Audacity” recording software. Sending an audio clip to a station with an e-mailed reception report is a great idea, many stations these days carry no detailed log of music, news, etc etc.
Here’s a short list on tuners rated for serious FM DX:
Onkyo: T-4970, T-9090 II (very highly favoured), T-9990, T-450 TDS, T-4711, T-488F
Kenwood: L-1000T, KT-6040, L-02T, KT-880D
Sony: ST-SA5ES, XDR-F1HD (probably the best of the lot), XDR-S3HD
NAD: 4300, 4155
Harmon Kardon: TU920
Technics: ST9030 (analog)
Airspy R2 SDR
Apart from TradeMe and Cash Converters, there are a number of retro audiophile resellers like Good Hifi in Dunedin, The Eco Shop, Blenheim Road, The Listening Post & Penny Lane in Chch, Stereoscope and Vintage Audio World in Auckland and no doubt most second-hand record sellers. You may get lucky and pick up a real bargain from a recycling store.