[Hackrf-dev] Amp On or Off

[kd5wdq .]

If your really paranoid, hang a 3 to 6 db pad on the input.
Then you can try the preamp to see what it does to the signal.

 Do this a lot, as I'm always interested in seeing what the preamp
provides - pads are cheap.

--eddie

On Wed, Jul 1, 2015 at 1:34 PM, Paul Connolly <eeipcy at gmail.com> wrote:

> If you look at the bottom right hand corner of the third page (the
> HackRF One front end) of
>
> https://github.com/mossmann/hackrf/blob/master/doc/hardware/hackrf-one-schematic.pdf
>
> The SMA antenna (P4) is followed by a transient-voltage-suppression
> diode to protect the circuit (ESD), which is followed by the Bias-T
> blocking capacitor (C64), then it enters a single-pole triple-throw
> switch (U14 - SKY13317), there are three possibilities:
> The TX  amp (U25) is connected to the Antenna.
> The bypass path is connected to the Antenna.
> The RX amp (U13) connected to the Antenna.
>
> The symptom of a blown amp is that when it is switch into the signal
> path it acts like an attenuator (lower SNR) instead of a providing gain,
> relative to it being bypassed. So you will see a higher SNR with the amp
> bypassed.
>
> On 01/07/2015 16:02, Daniel Bernhardt wrote:
> >> Now the amp is presumed blown it acts more like an attenuator, i.e.
> signals are weaker with it switched on.
> > Not regarding your specific case:
> > Is there a definitive way to determine if ones preamp is blown or not?
> For all we know it could be a faulty antenna setup or a cabling issue. Is
> the amp completely bypassed if turned off or just not amplifying? What are
> the symptomps of a "blown" amp? Does it short or are there signals coming
> through much weaker due to some cuppling effects?
> > Forgive my ignorance on the matter. Just beeing curious.
> >
> > Daniel
> > _______________________________________________
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> > HackRF-dev at greatscottgadgets.com
> > https://pairlist9.pair.net/mailman/listinfo/hackrf-dev
>
>
>
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>
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