Topband: Evaluating Rx antennas with Spectran

[Luis Mansutti IV3PRK]

Hi friends,

I wonder if anyone has ever tried to evaluate his receiving antennas with 
the method fully described by W3EEE with a talk given at the RSGB HF 
Convention in November 2003  http://www.hifidelity.com/w3eee/rsgbtalk.html

By means of a FFT audio frequency spectrum analyzer "Spectran" it is 
possible to "see" and separate several BC carriers on  the same channel, and 
identify them after knowing their direction and power.
After normalizing the readings taken on an ominidirectional antenna it 
should be possible to build an azimut plot with the comparative readings 
with the target Rx antenna as shown in the interesting W3EEE work.
It should be possible to see if a 3 dB improvement on an End-fire Pennants 
configuration, calculated with EZNEC, is confirmed "in the real world" !

But could those BC audio frequency carriers, taken during the day on the 
ground wave, be really reliable?
Here is my problem: I am unbable to get stable readings, as they are 
continously moving up and down on Spectran.... where am I wrong?
(Not found enough explanations on the several Spectran settings!).

My Rx antennas are working OK as switching between Pennants, (or the K9AY 
loop or rotating the Flag), I can substitute on the "radio" one AM station 
with another on the same channel and see the S-meter variation, but I can't 
get a meaningful audio frequency variation on Spectran.

I hope to get an help from the wisdom on this Reflector !

Many thanks

73 Luis IV3PRK