[TowerTalk] 5 db required to see?

[Pete Smith]

At 06:10 AM 5/28/00 -0600, n4kg@juno.com wrote:
>ABSOLUTELY !  Hearing the little guys with horrible
>locations and/or antennas is what makes the difference.
>
>It never ceases to amaze me to see the difference in
>signal strength between the DX stations you hear CQing
>and the guys who answer YOUR CQ's.  Sometimes it's
>as much as 40 dB, even on the high bands.  This goes 
>WAY beyond power differentials which might be 10 to 
>12 dB.  The QRP'ers with modest antennas are louder
>than the bottom layers of 100 W guys and poor antennas
>and/or locations.

It would be really interesting, sometime, to measure just how far below 0
dBi some of these weak stations must be, at least for a given arrival
angle.  Yesterday afternoon, just before European sunset, I was running
stations on 10 meters, and found signal strengths ranging from S9 + 20 to
not moving the s-meter on my TS-930.  Conservatively, that must be 60 db.
Even allowing 20 db for power and 15 dbi for antenna variations that still
leaves what... maybe 25 dB... for location, antenna height, etc.
 
>	
>No one has even mentioned local and/or atmospheric noise
>considerations so far in this discussion.  That can be even
>more important than a dB or two of antenna gain.  This may
>also explain why many of the East Coast guys prefer 
>antennas with high F/B ratios.  It helps them hear the
>weaker stations on crowded bands.

Not just F/B but also F/S.  You guys to our South and Southwest keep
sending us thunderstorms!
>
>For hunt and call operation, I prefer low F/B ratio antennas
>to pick up the occassional multiplier to the South or West.


>
>On 40M, hearing those incredibly weak Europeans through
>the QRM and QRN is the biggest limitation.  My Beverages
>are quieter than my beam or former 2L Delta Loop but often
>the signals are then too weak to copy.  No wonder W3LPL
>and W4AN (among others) use Phased Beverages with
>additional gain for receiving on the low bands (including 40M).

If gain, per se was the story, counldn't you just jack up the preamp?  I
think a more likely explanation for that design choice is the narrower
pattern, which yields a higher SNR.  For most of the big stations, I'm sure
that SNR, rather than sheer gain, is the limitring factor on the low bands.
  


73, Pete Smith N4ZR
n4zr@contesting.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.htm