[Towertalk] Tribander anomaly

[W4ZW]

Thanks for the comments, Bill,  (N3RR)


*Be sure you're not overlooking something in the system.
*Are all three antennas pointing in the proper direction?
Yes.

*Is there additional feed line loss in the A4S antennas?
No.  New 9913 coax, but the 402CD is slightly longer since it is higher
and the driven element in at the end of the boom. Lengths to the A4's
are identical.

*
*Also, as I read your posting:
*
*402CD @ 70 ft above ground on roof-tower
Actually at 73'

*A4S @ 58 ft on same roof tower (closer to the roof - too 
*close? how close?)  
At 61' and about 14' above the roof.  The tower is mounted on the edge
of a higher roof deck with  half the antennas hanging over space below.

*A4S @ 52 ft on another mast not on the roof. 
Also on the roof at about 48' on the top of an elevator which opens onto
the roof deck.

*
*Is it possible that the proximity to the roof of A4S #1 and 
*the 18 ft lower position of A4S #2 causes both antennas to be 
*6 dB (1 S-unit) less in signal level from the 402CD?  Again, 
*check the line losses to be sure we're apples-to-apples.


*Is there anything in the system? - antenna relays?  different 
*antenna switches?

No.  I use an ATR-30 tuner to switch antennas and tune the wire
antennas.  I do have a Daiwa coax switch to switch radios, but it is not
presently in the circuit.

Two Reponses pointed out that the defense in height might be just enough
on 15M to put the A4S in a null.  I intend to try several on the air
comparisons between the 402CD and the A4S.

Thanks for all the comments, guys!  Wow, six, Jon Hamlet,  W4ZW
Casey Key Island, FL

"A little bit of Paradise in the Gulf of Mexico"


 just minutes after I posted this!