[Hackrf-dev] Amp On or Off

[Paul Connolly]

CW power-in exceeding +13dBm could be the cause of killing the MGA-81563.

Or it could be that an external LNA is powered up after the HackRF and
provides a small transient spike that exceeds the maximum allowed Vin
(+0.5V to -1.0V), which is below the +/-15V<->+/-8000V protection
provided by the ESD TVS diode D1.

On 03/07/2015 07:08, Tom wrote:
> Unless I am reading it wrong but doesn't the MGA-81563 have an absolute max Pin of +13dbm?
>
> -----Original Message-----
> From: HackRF-dev [mailto:hackrf-dev-bounces at greatscottgadgets.com] On Behalf Of Scott Davis
> Sent: Thursday, 2 July 2015 1:15 PM
> To: hackrf-dev at greatscottgadgets.com
> Subject: Re: [Hackrf-dev] Amp On or Off
>
> This hypersensitive behavior is a little odd for a device that is meant to be an experimental RF platform.  Is there possibly a more robust front-end component set that could be substituted for the existing one?
>
> FWIW, I routinely transmit 3 to 5-watt signals (usually ~10-15 seconds duration) using resonant antennas within a meter or two of my HackRF, and the preamp still works perfectly.
>
> -Scott
>
> Sent from my iPad
>
>> On Jul 1, 2015, at 7:13 PM, 王康 <scateu at gmail.com> wrote:
>>
>> Actually, you can tune to a FM station nearby, observe the signal 
>> strength with preamp switched on and off, using `osmocom_fft` or 
>> `gqrx`.
>>
>> If your signal peak become *higher* when preamp is *off*, then the 
>> preamp is definitely blown.
>>
>> I made some batches of HackRF a year ago, and found that preamp can be 
>> easily damaged even before shipped.
>> You may buy some preamp components, replace the broken one if needed.
>>
>>> On Wed, Jul 1, 2015 at 11:02 PM, Daniel Bernhardt <daniel at dbernhardt.com> 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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