Quote:
Originally Posted by WM6
Max, agree, but Iam not speaking about devices as EMFAD based on far away LW transmiters which signal evenly cover the terrain. Here is transmiter by rule far away and receiver close to the target. At the same time we need antena with very directive characteristic.
I am speaking about configuration from picture in which strong near transmitter signal suppres weak and by soil dumped reflective signal on diferent way.
In this case transmitter are to close and at the same time receiver too far from small target. So it is practically unusable. Transmitter have to be reasonably far away and receiver close to the target. Can only be usable if one know where the target is burried.
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Hi,
yes sure, a too close transmitter is a problem...but don't take Esteban's pictures for what they aren't. What's in pictures is from Fisher things/experiments and some old magazines he likes much.
The concept behind the scene is the same of "direction finding", of a very far transmitter, the picture have just informative purposes... it's kind of diagram but it's not real, e.g. transmitter and receiver are not at the distance we see... it's just the "concept" that means something, the drawing itself has no value if seen as something related to actual construction of device.
The trick with south american guys like Esteban is ignoring what he wanna you notice and read in the middle of the textlines...
The EMFAD is exactly the same stuff of you can spot in their stupid PD thing... but the PD stuff have internal transmitter that's the silly thing of whole story... and sure, the transmitter swamps any reflected signal from target , cause is made to trick people more than detecting buried stuff.
BTW the transmitter is present also in EMFAD thing... just EMFAD things usually get rid of any local transmitter unless special cases (e.g. usual transmitters are down or signal is too low quality cause of e.g. interferences). The german EMFAD I posted link has, as example, a 33KHz running separate TX if needed... but it's made to run on long range broadcast signals... like the DCF timing signal at Frankfurt (Main) running on 77.5 Khz.
Kind regards,
Max