You mentioned that the site's noise floor is "pretty low". Could you be more specific about that and how it was measured?
The usual method of determination of the site noise floor is to measure the receiver's "effective sensitivity" using an RF coupler such as the Microlab FXR or Bird devices that have been mentioned recently [or one you have constructed] along with a signal generator and a dummy load. The signal generator is connected to the isolated port , a reference level is established for 20 dBq or 12 dBs with the antenna replaced by a 50 ohm load, and then the antenna is connected in place of the load. It is often [especially at VHF] necessary to increase the generator level by several dB to re-establish the same quieting level that was measured with the load in place. This number of dB is the degradation of your receiver due to site noise. Along with the receiver's basic [static] sensitivity measurement [made by connecting the generator directly rather than through the coupler] - you have sufficient information to state the receiver's effective sensitivity and also to compute the potential improvement that a pre-amp may be able to offer. ---------------------------------------------------------- --- In [email protected], "ldgelectronics" <[EMAIL PROTECTED]> wrote: "... The sensitivity without the pre is about 0.35 uV. The noise floor is pretty low, but the ARR pre was picking up a bunch of garbage without the attenuator...."
