Hi, George-
On 12 Feb 2002 at 17:28, George & Marijke Guerin wrote:
> The K3KY website shows the loop fed with 450 ohm ladderline. The
> original article is much more detailed. I urge anyone who has
> questions to get the September 1995 issue of QST Magazine and read it
> all.
I make precisely that point in my text, and that comment has
always been there. It takes a lot of carefull re-reading of the two
articles to gain a full grasp of the antennas properties and
possibilities.
The transformer and two band matching become very clear.
> There is reference to a loop with approximately 50 foot sides for
> only
> 160 meters. Can anyone tell me how the turns ratio and tuning
> capacitor configured for the single band RX loop?
I have not tried a 50ft loop myself. If anyone has, I would also
appreciate hearing any design notes about the transformer and
the value of the resonating capacitance. I bet you could take the
reactance values from the transformer design of the original 25ft
loop on 80 meters and scale them to 160 and you would be pretty
close for a 50ft loop. K6STI advised against doubling the sides to
50ft unless the antenna was intended as a monobander for 160m.
> Also note the loop is about omni-directional, so it is not going
> to
> reject a noise source as would beverages or vertically oriented
> directional or phased loops.
Again, I make precisely that point on my web page, but it is not
quite that simple, as you will see if you read the articles and
actually try building one. Results are highly dependent on what
sort of noise predominates. If it is lightning crashes, this antenna
will help little if any. On the other hand, if it is predominately
man-made, vertically-polarized noise, this antenna can
potentially help a great deal- and the use of a preamp is highly
advisable, as it is a fairly low-output antenna, most of the time.
(Moreso than a Beverage, which occasionally needs 10db or so
itself- here the deficit can be more like 20-30dB down from
your transmit vertical). And if the man-made noise source is
very close by, as Tom has pointed out, who knows what its
polarization will be? All bets are off.
In general, the directional receive antenna types like the Beverage
are better, and if you have the space, they are well worth trying.
This loop might just outhear a Beverage *if* the predominant
noise source is man-made and vertically-polarized, and if the
Beverage is boresighted on it, and if it is in the antennas
*far field* and not its near field. Again, variety is the spice of
life, and when it comes to low noise receive antennas for 80 and
160m, what works best from day to day occasionally surprises.
It is always good to have a variety to choose from. 73, David K3KY
> 73 George K8GG
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