[Hackrf-dev] Low TX power

[Mark Jessop]

Roger, will give the hackrf_transfer command a go when I have access to a
spec-an next.

Cheers,
Mark

On Sun, Feb 1, 2015 at 10:48 AM, Paul Connolly <eeipcy at gmail.com> wrote:

>  It could be acting like a short circuit, and you would see no difference
> switching the TX amp on or off. I'm sure it depends on the mode of failure.
>
> IC's U13 & U25 are part number MGA-81563-TR1G one is for RX and the other
> is TX. I think U13 is RX and U25 is TX, you should to load up the schematic
> in KiCAD and check.
> (source:
> https://github.com/mossmann/hackrf/blob/master/doc/hardware/hackrf-one-bom.csv
> )
>
> Probably best to verify with the hackrf_transfer command as well before
> masking the board with aluminium foil, kapton tape and blasting with hot
> air.
>
>
> On 31/01/2015 23:24, Mark Jessop wrote:
>
> I was using GNURadio Companion, not hackrf_transfer for my tests.
> I experimented with varying all of those parameters, and could not get an
> output any higher than -30dBm.
>
> If the TX amplifier was broken, i would have expected to see a noticeable
> difference when i switched the amp on and off (i.e. RX LNA gain between 0
> and 14dB), as from what I could tell in the schematic doing so would switch
> the amp in and out.
>
> Cheers,
> Mark
>
> On Sun, Feb 1, 2015 at 2:33 AM, Paul Connolly <eeipcy at gmail.com> <eeipcy at gmail.com> wrote:
>
>
>   Are using -c 127 as an argument for your testing. And -x goes from 0 to
> 47dB, why stop at 14dB ?
> $ hackrf_transfer
> receive -r and receive_wav -w options are mutually exclusive
> Usage:
> ... snip ...
>         [-l gain_db] # RX LNA (IF) gain, 0-40dB, 8dB steps
>         [-g gain_db] # RX VGA (baseband) gain, 0-62dB, 2dB steps
> *        [-x gain_db] # TX VGA (IF) gain, 0-47dB, 1dB steps*
> ... snip ...
>         [-c amplitude] # CW signal source mode, amplitude 0-127 (DC value
> to DAC).
> ... snip ...
> $
>
> From https://github.com/mossmann/hackrf/wiki/HackRF-One#transmit-power
> you should be seeing about 15dBm that close to 10MHz
>
> It could be that you have damaged the TX amplifier, did you have -a 0 in
> your tests. Because if it is broken then it would probably act like an
> attenuator.
>
> Paul
>
>
> On 31/01/2015 12:43, Mark Jessop wrote:
>
> Hi all,
>
> Bought a HackRF a few months back, never properly measured the output power
> on it when I got it unfortunately, but it has certainly dropped at some
> point in the last few months.
>
> I finally got the chance to put it on a spectrum analyzer the other day.
> Transmitting a single carrier, I'm seeing a maximum of -30dBm output power
> at 14MHz. Only a few dB difference noticed when turning the RF Gain setting
> from 0 to 14dBm (This does actually do something, doesn't it?)
>
> Any thoughts? I have the facilities to replace QFN components if required...
>
> Cheers,
> Mark VK5QI
>
>
>
>
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