Re: [IRCA] Cascaded loop antenna

[Rick Kunath <k9ao@xxxxxxxxxxx>]

On Friday 24 April 2009 11:09:48 pm satya@xxxxxxxxxxxx wrote:
> I have been reading it, and while I am not looking to set up a diversity
> arrangement necessarily, I am trying to figure out what a cascaded loop
> would do for me.  I sounds like it will "attenuate the strong
> on-great-circle incident signal component (or its diffracted component
> indoors) relative to scattered fields of nearby origin.  To reject
> skywaves, such an antenna must be able to attenuate great-circle modes
> arriving at various elevation angles."
>
> So, it sounds like a CLA will reject sky-waves, perhaps high-elevation
> skywaves from strong semi-locals, and instead preferentially receive
> low-angle signals that might be coming from overseas?  That's what I would
> LIKE it to say, but not sure what all his terminilogy means.

Yes, that's how it reads to me too.

I know that in all of my experimentation and refining of big and small 
air-core MW loops, when you have mixed signals arriving, some at high angle 
or from reflections off of wiring in the proximity and some at low angles, 
nulling gets difficult to impossible. If oyu tilt the loop to null, you never 
can completely reach null because there is always still some signals arriving 
at other angles.

So if the nulling is easier with the high angle rejected, we might be able to 
dig a little deeper, as well as closer to the IBOC hash.

Not sure about his feed though. The spot he shows clipped across the tuning 
cap should be a high impedance. Might be OK on a whip, but I would still 
think it would load the loop too much and lower the Q, thus the gain, too.

I might try using my balanced loop preamp. I built one that eliminates the 
loop secondary coupling winding because it is a high impedance input and can 
be connected directly across the loop main winding, and then connect this 
across the cap as shown. No reason that shouldn't work.

The SW aspects are interesting too. With the sunspots so low, there is a lot 
more interference now with adjacent channels and co-channel interference.

RIck
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