Topband: RX epiphany?

[jbwolf at comcast.net]

Tom, 



In your opinion; given a receive antenna with negative gain, at what level does the negative gain start to come into play? -25 dBi, -35 dBI  ? 



Jim 



----- Original Message -----


From: "Tom W8JI" <w8ji at w8ji.com> 
To: "topband" <topband at contesting.com> 
Sent: Thursday, September 13, 2012 11:37:20 AM 
Subject: Re: Topband: RX epiphany? 

>I agree with Tom's assessment.  I wouldn't be too quick to give up on your 
>tx 4 square.  Having  a tx 4 square, a 1/4 wave vertical, and an 8 circle 
>rx array, I find the 4 square really does hear quite well.  My man made 
>ambient noise level is quite low (during daytime hours when the atmospheric 
>noise is quiet, I see virtually no manmade noise).  In my circumstances the 
>4 square tx array will dig down and hear those very weak signals (say -115 
>or -120 dbm, or even less) that the 8 circle array sometimes cannot hear 
>due to the comparatively small size and capture area of the elements (mine 
>are 26'). 


Dave, 

Just curious. Why is your 8 circle array so insensitive? Is the circle 
small, or is there something in the design causing excessive attenuation? 

My array, with passive 20 ft tall elements, comes through 1500 feet or more 
of coax. Much of the run is F11 sized, maybe 500 feet or so is 625 CATV 
hardline. It has plenty of signal level with no amplifier, and always 
out-receives my TX four-square. 

Capture area relates to system gain and operating wavelength, not physical 
element size (unless that size changes gain). Unless something is causing a 
severe sensitivity loss taking some part of the system down very near 
receive system noise floor, it should be external noise limited. 

73 Tom 

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UR RST IS ... ... ..9 QSB QSB - hw? BK