Dual Antennas for LR


Převzato ze stránek www.lrsatx.com

Autor programu Gerry, WB5TXA San Antonio, Texas



If you have a LR station this is something that can increase your world coverage.  By a simple circuit modification you can add a second LR tuned antenna to your system.  This is accomplished by converting the regular preamp into a summing preamp by the addition of a capacitor and resister of the same values as the original.  A summing amp simply adds the two antenna signals into a larger combined one.    Shown below is the modification to Frank Kooimans original circuit I based my home made amp on.  Adding the ANT 2 section  to any other preamp should work fine.  Make sure you use the same values as the ANT 1 of your preamp. 

Very important!  The two antennas must be aligned so that the like coils are on the exact same axis.  This can be done by viewing down the coils so they are in a straight line with each other.   My antennas are spaced about 8 meters apart, how ever this is not at all critical at these audio frequencies.  The antennas being level and in alignment is critical.

This antenna that is added, is only microseconds delay away from the other antenna.  At 10 kHz wave lengths, its so long, you can forget about the usual wavelength phasing and delay problems.  On a scope you will see one combined pulse, that's now larger.  Your now sampling a larger signal area than with one antenna.   Forget VHF problems... this is audio!


SCHEMATIC EXAMPLE FOR A PREAMP MOD.

(Note: A LT1028 amp can be directly substituted for the LF355N for a ultra low noise amp.)

 

 

Combined antenna signal, froze in time.

Read about a summing amp here.  >>  

 


The World side one and side two at the same time.

Samples of dual antennas in action.  Triangulation with Europe and Australia gave these simultaneous storm plots.  (Texas-Europe-Australia)