[TowerTalk] GAIN - TX VS. RX

[Tom Rauch]

> Date:          Thu, 30 Apr 1998 12:06:45 -0400
> From:          DOUG WALLER <nx4d@gate.net>
> Subject:       [TowerTalk] GAIN - TX VS. RX
> To:            TOWERTALK <towertalk@contesting.com>

>     IN HIS BOOK "HF ANTS FOR ALL LOCS", MOXON STATES ".....INCREASING
> THE NUMBER OF ELEMENTS FROM TWO, TO THREE OR FOUR WITH CLOSE SPACING HAS
> COMPARATIVELY LITTLE EFFECT ON TRANSMITTING GAIN."  AND ".....IN TERMS
> OF TRANSMITTING GAIN, THE LARGER (3&4 ELE) BEAM IS SLIGHTLY DOWN EVEN
> COMPARED WITH THE BEST THAT CAN BE ACHIEVED WITH TWO ELEMENTS,......".
> FINALLY  ".....FOUR-ELEMENT DESIGN IS QUITE POOR IN THIS RESPECT(XMIT
> GAIN) SO THAT THERE SEEMS TO BE HERE A PARTICULARLY STRONG CASE FOR THE
> USE OF SEPARATE TUNING UNITS FOR TRANSMISSION AND RECEPTION."

When receiving HF signals directivity is important and gain is not. 
When transmitting, gain is important and directivity often is 
not (unless you want to protect someone from your QRM).

Gain includes efficiency along with directivity, directivity excludes 
efficiency. The close spaced array can have a quite good pattern, 
focusing in on the signal and not the noise from other directions. 
You care less if the thing is -2 dBd gain or 20 dBd gain on receive, 
but you sure want a narrow clean pattern.

That's why Beverages work for receive, and stink on transmit. They 
have negative gain, but offer decent directivity.

   
73, Tom W8JI
w8ji.tom@MCIONE.com

--
FAQ on WWW:               http://www.contesting.com/towertalkfaq.html
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com
Search:                   http://www.contesting.com/km9p/search