I would go along with Rik in principle, but beware of high static
levels giving a misleading high figure of "antenna noise". This test
only works on low static days. I would, in any case, suggest a
"threshold" of several dB to ensure you are really looking at the
band noise rather than static peaks. Perhaps ensure the "antenna
noise" is at least 3dB more than the receiver noise. I have seen
posts in the past suggesting that this figure should be as much as
10dB.
Mike, G3XDV
===========
> 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]<mailto:[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]<mailto:[email protected]>
>
>
>
>
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