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Re: LF: Pre amp *after* BPF??

To: LineOne <[email protected]>
Subject: Re: LF: Pre amp *after* BPF??
From: Rik Strobbe <[email protected]>
Date: Fri, 16 Mar 2018 12:31:03 +0000
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Cc: Chris Wilson <[email protected]>
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Thread-topic: LF: Pre amp *after* BPF??

Keep in mind that you only need a pre amp if the "antenna noise" is below the receiver noise.

Most receivers have reduced sensitivity at LF / MF, but the noiselevels at these frequencies is high compared to HF.

Easy to check: Listen (with connected antenna) on a quiet frequency (only noise, no signal). Next disconnect the antenna. If the noise level decreases you do not need a pre amp (in fact a pre amp will only deteriorate the IMD behavior and thus create more ghost signals).


73, Rik  ON7YD - OR7T



Van: [email protected] <[email protected]> namens Andy Talbot <[email protected]>
Verzonden: vrijdag 16 maart 2018 12:54
Aan: LineOne
CC: Chris Wilson
Onderwerp: Re: LF: Pre amp *after* BPF??
 
After, definitely

Before is applicable to VHF and up where equipment noise figure dominates sensitivity and a filter in the antenna side wold add loss and degrade overall NF

At HF and certainly LF, atmos noise dominates to noise figure is unimportant.   That way you get the benefit of rejecting strong OOB signals that may stress even the preamplifier

'jnt


On 16 March 2018 at 11:36, Chris Wilson <[email protected]> wrote:


Hello  LF'ers,

Been  Googling and see a mixed response to should a receive pre-amp go
before  or after a BPF. I have mine before the pre-amp, does the panel
concur with this being correct? Thanks!

Aerial,  isolation  transformer  for  ground  loops, BPF, pre-amp, Red
Pitaya as the LF receiver.

--
Best regards,
 Chris                          mailto:[email protected]



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