Topband: Some experiments with a short beverage, not succeeding very well

Jim Brown jim at
Wed Jul 1 01:28:11 EDT 2020

On 6/30/2020 6:27 PM, Mail 10 wrote:
> I read somewhere that one test for a receiving antenna is to compare the 
> received noise floor against no antenna, during the day with little 
> atmospheric noise. There should be a *slight* lift in the noise when the 
> receive antenna is connected. This is as little as 2-3 dB at my QTH, a 
> rural area.

Not quite right. A good number to remember is that in order to hear the 
weakest signals, noise picked up on the antenna should be at least 10 dB 
stronger than circuit noise by the time it reaches the first gain stage, 
whether that first gain stage is an outboard preamp or the receiver’s 
input stage. At this level, signal to noise ratio will be degraded by 
only 0.4 dB. Increasing the ratio to 13 dB makes it 0.2 dB.

73, Jim K9YC

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