[Elecraft] Seperate Receive Antenna

[David Cutter]

Thanks, Jim, that's opened out the discussion very well for me.  I am not 
able to determine how bad this makes the performance, since the output is 
floating and I think hardly susceptible to common mode problems.  I'm in the 
market for such antennas but most are outside my budget.  I would like to 
have 2 loops (could be large loops)  a half wavelength apart for diversity 
reception on 160 and this system with its delay line might do that 
economically.  2  amplified receive aerials (eg from CCW here in UK) with a 
phasing box would also be economical.  The next on my list is the shared 
apex.

thanks again for the link

73

David
G3UNA

Subject: RE: [Elecraft] Seperate Receive Antenna


Dave,

Here is the quote from W8JI


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10-29-2011, 05:36 PM #8

W8JI


Quote Originally Posted by WV6U View Post

Here is one broadband RX loop design that I found very interesting and 
something worth trying out. Once I am done with my TX loop for 40-15m, maybe 
I will start with this

http://lz1aq.signacor.com/docs/wsml/...op-antenna.htm

 I would not use that system in the link.

 While a good analysis, the amplifier is ground referenced. It is not a 
ground independent differential input. An ideal amplifier should have ZERO 
output if one loop terminal was open circuited. Otherwise, it has less than 
perfect common mode rejection.

 Bandwidth of the loop vs. noise is a myth. The only reasons a narrow loop 
bandwidth, or any antenna or amplifier bandwidth, would ever reduce noise or 
interference are when at least one of two conditions are met:

 1.) The receiver IF filter is wider than bandwidth of the pre-receiver 
system. This helps because overall bandwidth is reduced. 1/2 bandwidth= 3dB 
less noise if the signal is still narrower than the narrowest bandwidth

 2.) Something in a stage in front of the receiver narrow filter is 
overloading, and the system in front of the receiver is narrow enough to 
reduce the unwanted signal and stop or reduce the overload

 73 Tom


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The link to the above quote is

http://forums.qrz.com/showthread.php?318414-Magnetic-Loop-RX-Antennas


Jim