Topband: pre-amp placement

[Chris Maness]

Yes, after asking the question I tried the experiment and found no
difference.  My concern was common mode pick up before the pre-amp not
so much insertion loss.  If noise was going to be inserted in the
path, it would be much better for this to happen after the LNA for
obvious reasons.

Chris KQ6UP

On Wed, Jan 19, 2022 at 10:12 AM ko7i <ko7i at comcast.net> wrote:
>
> I manage a EMC test lab in the Seattle area. Typically we place a LNA pre-amp at the DRG Horn we use for Radiated RF Emissions measurements above 1GHz. Below 1Ghz, we place a pre-amp at our measurement receiver - not the antenna. Assuming a ham is using properly terminated double shielded CATV 75 ohm coax for the RX antenna, the insertion loss of the coax should be less than 2db for a 200 ft run. I find it hard to believe a ham would be able to "hear" the difference between pre-amp locations during real live operating conditions. If a ham wants to further improve the noise figure of their LNA, they would be well served by placing a bandpass filter, for the band of interest, at the front end of the pre-amp. Vy 73 de KO7I Sent from my Galaxy
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