FM DX Antenna & Tuner

I decided to try a bit of FM DX after a break of more than 20 years and
needed a new antenna.

First I tried a 7 element log periodic yagi, similar to this example but found the local FMers about 3km away swamped the whole band pretty much. So then I re-built the antenna into one of these combo yagis  which is a hybrid log periodic yagi and standard yagi, sometimes called a “logyag”.

It handles the signals from the locals much better than the straight LPY
and seems to be more directional. Mine is made from old low-band TV
antennas so only cost me some hardware and time.

For those who wish to build one, I’ve metricated the measurements. Note
that all element measurements are taken from the centre of the boom,
even for the 3 driven elements which are insulated from the boom. The
boom itself is 2500mm long.

Refl: 846mm (1692 tip-to-tip) spacing

1st driven: 787 (1574) spacing 533

2nd driven: 673 (1346) spacing 927

3rd driven 643 (1286) spacing 1196

1st director: 635 (1270) spacing 1280

2nd director: 610 (1220) spacing 1702

3rd director: 533 (1066) spacing 2413

Spacings are taken from the centre line of the reflector. The short stub
is a hairpin match and should give a reasonably constant impedance
across the whole 88-108MHz, the very close proximity of the first
director to the 3rd driven is designed to pull the impedance down
towards 75 Ohms.

In testing with an antenna analyser, 3 dips were noted across the band
with the impedance ranging between 47 and 87 Ohms, very acceptable for a
wide-band antenna such as this.

Photo attached. The aerial is not very high at present and will
eventually be moved to a mast on a rotator higher up the roof.

A good antenna is half of what you need, the other essential item is a good tuner.

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 FM as follows:

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

Denon: TU1500

Yamaha: T85

Sansui: TU-X1

Carver: TX11

Harmon Kardon: TU920

Technics: ST9030 (analog)

Pioneer: F-90

I found positive reviews from a DX point of view for all of the above. Hope that helps someone else find a good FM DX tuner.

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.

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