Topband: XMT and RCV antenna questions

[Jon Zaimes AA1K]

Hi Dave,

That loop should be a killer. I remember K2BU in New Jersey had one a few years ago at a height similar to yours and fed the same way and it equaled or beat my 100-ft shunt fed tower with 200 radials at the time.

There will be a null in the direction of the feedpoint -- so if that is toward Europe and you're trying to work Europe, that could be the problem. 

Or you may have some interaction with the towers or other antennas. See www.w8ji.com   for ideas on detuning towers.

With the height you have available, a half-wave sloper also should be effective. The tower may act as a reflector -- or could be tuned to do so. You could have one to the NE and one to the SW. Or the loop could be used as a reflector with the sloper as the driven element in a 2-el. array (W2GD has done something similar at his contest site in New Jersey, although off a higher tower). You also could hang a wire 4-square off the tower -- see ON4UN's book Low Band DX'ing for several variations of this.

Lengthening the Beverage should be a slight improvement (see w8ji.com for some comparitive numbers). And the Beverages are almost always better than small alternatives, in my experience. Going to phased Beverages offers a significant improvement. I have a pair of 465-foot stagger-phased Beverages (spaced 33 feet) that generally equal performance of a single 880-foot Beverage in the same direction. Other factors such as distance from noise sources (such as power lines and houses) and interaction with the towers may play more of a role in performance than lengthening the wire a couple of hundred feet.

BTW what's your call?

73/Jon AA1K

At 07:16 AM 2/28/04, you wrote:
>Presently, I have a 160m delta loop (apex up) for my transmit antenna.  
>Loop is fed about 30' up one bottom corner and has a 75 ohm coaxial matching transformer.  Station has two 140' towers spaced 150' apart but orientation is directly N-S.  Some ground radials in ground but very extensive enough for exciting the towers without lots of extra work.  
>Loop is at 140' tied under the 40m yagi.  Other antennas on that tower, including an 80m dipole array.  Phillystran guys.  Antenna oriented SE-NW.
>
>Question:  What antenna is most practical and constructable and maintainable at my station considering the physical description?  Right now, the loop works has a nice VSWR but is weak on transmit capability.  
>(It is possible there is length of feed line with high loss underground but in winter this is hard to change.)  The antenna would need to be good for DX.
>
>Question:  How much improvement on 160 would be noted  extending a beverage antenna  from 475 to 700' or so?  In general, I note other stations hear better than I do.  For that matter, is a beverage the gold standard of listening antennas or should I be looking at the short loops with tuneable directions hung off one of the phillystran guys on the towers?  Yes, I know about terminators, feed transformers and the like.
>
>Thanks, Dave.
>
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