View Single Post
  #63   Report Post  
Old August 27th 04, 05:16 AM
Roy Lewallen
 
Posts: n/a
Default

Richard Clark wrote:
. . .
However, Beverages are not typically the first choice for
transmission, but rather reception. Does reciprocity hold? As no one
has offered to help the Little Red Hen, would they care to share in
the cake?

For the receive single wire Beverage @ 10° w/600 Ohm load
Total load power = 5.543E-07 watts

For the receive double wire Beverage @ 10° w/600 Ohm load
Total load power = 6.623E-07 watts

Now, if we compare the two receive loads we find they differ by .77dB
which is the same difference for the transmission models. By most
accounts, that means reciprocity prevails. By further accounts, that
means the double wire system is superior - if you want to lay out 1000
meters of wire for less than one dB (that pesky one dB value judgment
again).
. . .


You wouldn't modify a Beverage or any HF receiving antenna to get more
gain. The whole object is directivity. If you need more gain, turn up
the receiver gain control.

Of course reciprocity prevails. But at HF, the important criteria are
different for transmitting and receiving. When transmitting, it's gain;
when receiving, it's directivity. The Beverage is poor in the first
category but good in the second -- it's a good receiving antenna but a
poor transmitting antenna.

Incidentally, Tom W8JI and I worked out a way some time ago to get
directivity information from EZNEC. You can see an example at
http://www.w8ji.com/receiving_basics.htm in the discussion about Beverages.

Roy Lewallen, W7EL