[Hackrf-dev] Amp On or Off

[Tom]

Just curious to what people do with the amp, do you run it most of the time
and not worry about frying it due to nearby transmitters? I'm in two minds
as in I would like to use it as much as I can because it makes a huge
difference, especially when driving and monitoring the ISM bands but at the
same time I worry that a strong transmitter nearby might damage it, I mean
is this really the case even though It might me few hundred mhz away from a
strong transmitting station.



I read one story where someone has destroyed the amp but that was because it
was connected to a satellite dish or something like that (can't remember the
full story) are there any other cases where someone has destroyed the amp?



Thanks

Tom

[Chris Kuethe]

I leave it off unless I know I need it. And if I do need it, I put in a
filter - either a bandpass for the interesting stuff, or at least an
bandstop to squish the commercial FM band.

Post by Tom
Just curious to what people do with the amp, do you run it most of the
time and not worry about frying it due to nearby transmitters? I’m in two
minds as in I would like to use it as much as I can because it makes a huge
difference, especially when driving and monitoring the ISM bands but at the
same time I worry that a strong transmitter nearby might damage it, I mean
is this really the case even though It might me few hundred mhz away from a
strong transmitting station.
I read one story where someone has destroyed the amp but that was because
it was connected to a satellite dish or something like that (can’t remember
the full story) are there any other cases where someone has destroyed the
amp?
Thanks
Tom
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[Tom]

Thanks Chris





From: Chris Kuethe [mailto:***@gmail.com]
Sent: Wednesday, 1 July 2015 12:43 PM
To: Tom
Cc: hackrf-***@greatscottgadgets.com
Subject: Re: [Hackrf-dev] Amp On or Off



I leave it off unless I know I need it. And if I do need it, I put in a filter - either a bandpass for the interesting stuff, or at least an bandstop to squish the commercial FM band.



On Tue, Jun 30, 2015 at 7:03 PM, Tom <***@hotmail.com <mailto:***@hotmail.com> > wrote:

Just curious to what people do with the amp, do you run it most of the time and not worry about frying it due to nearby transmitters? I’m in two minds as in I would like to use it as much as I can because it makes a huge difference, especially when driving and monitoring the ISM bands but at the same time I worry that a strong transmitter nearby might damage it, I mean is this really the case even though It might me few hundred mhz away from a strong transmitting station.



I read one story where someone has destroyed the amp but that was because it was connected to a satellite dish or something like that (can’t remember the full story) are there any other cases where someone has destroyed the amp?



Thanks

Tom






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[Michael Ossmann]

Post by Tom
I mean is this really the case even though It might me few hundred mhz
away from a strong transmitting station.

The important thing to realize about safety of the RF amplifier is that
frequency is irrelevant. The amplifier sees 6+ GHz of bandwidth
regardless of what frequency the HackRF One is tuned to. If you are
sitting right next to a powerful transmitter at 100 MHz, it doesn't
matter if you tune to 100 MHz or 1 MHz or 6 GHz; the RF amplifier is
affected the same way in all cases.

I tried to make this clear in this video:

http://greatscottgadgets.com/sdr/5

Mike

[Tom]

Thanks Mike,

Have you experienced any blown RF amps due to overloading ? if so do you
know what the specifics were that caused the failure?


-----Original Message-----
From: Michael Ossmann [mailto:***@ossmann.com]
Sent: Wednesday, 1 July 2015 2:24 PM
To: Tom
Cc: hackrf-***@greatscottgadgets.com
Subject: Re: [Hackrf-dev] Amp On or Off

Post by Tom
I mean is this really the case even though It might me few hundred mhz
away from a strong transmitting station.

The important thing to realize about safety of the RF amplifier is that
frequency is irrelevant. The amplifier sees 6+ GHz of bandwidth regardless
of what frequency the HackRF One is tuned to. If you are sitting right next
to a powerful transmitter at 100 MHz, it doesn't matter if you tune to 100
MHz or 1 MHz or 6 GHz; the RF amplifier is affected the same way in all
cases.

I tried to make this clear in this video:

http://greatscottgadgets.com/sdr/5

Mike

[Simon Kennedy]

Sadly, I am in a position to comment on this.
I have been meticulous in unplugging my HackRF One (& Blue) but at the
weekend I forgot and keyed up my HF transmitted for a second with about 50W
of RF at 18MHz. That blew the RF amp in the HackRF One.

The HackRF was next to the transmitter and the antennas plugged into each
are quite close.

I am interested to know when it is possible to blow the amp, for example is
it possible:
- when the HackRF is unplugged from power;
- when it is connected to an antenna but not powered up;
- when conected to an antenna and powered up but the RF amp switched off?

How paranoid do I need to be regarding unplugging?!

Simon.

Post by Tom
Thanks Mike,
Have you experienced any blown RF amps due to overloading ? if so do you
know what the specifics were that caused the failure?

[Tom]

Sorry to hear that Simon,



Was the hackrf receiving anything when you keyed up the HF and if so was the RF Amp enabled on the hackrf?



From: HackRF-dev [mailto:hackrf-dev-***@greatscottgadgets.com] On Behalf Of Simon Kennedy
Sent: Wednesday, 1 July 2015 5:39 PM
To: hackrf-***@greatscottgadgets.com
Subject: Re: [Hackrf-dev] Amp On or Off



Sadly, I am in a position to comment on this.

I have been meticulous in unplugging my HackRF One (& Blue) but at the weekend I forgot and keyed up my HF transmitted for a second with about 50W of RF at 18MHz. That blew the RF amp in the HackRF One.



The HackRF was next to the transmitter and the antennas plugged into each are quite close.



I am interested to know when it is possible to blow the amp, for example is it possible:

- when the HackRF is unplugged from power;

- when it is connected to an antenna but not powered up;

- when conected to an antenna and powered up but the RF amp switched off?



How paranoid do I need to be regarding unplugging?!



Simon.



On 1 July 2015 at 07:08, Tom <***@hotmail.com <mailto:***@hotmail.com> > wrote:

Thanks Mike,

Have you experienced any blown RF amps due to overloading ? if so do you
know what the specifics were that caused the failure?

[Simon Kennedy]

Tom,

The HackRF was connected to USB so was powered up and therefore was
receiving. I had received a Meteor M-N2 weather satellite pass not long
before this unfortunate incident so the RF amp would have been enabled. To
receive Meteor at 137MHz I also use a masthead pre-amp which was also
enabled.

Simon.

Post by Tom
Sorry to hear that Simon,
Was the hackrf receiving anything when you keyed up the HF and if so was
the RF Amp enabled on the hackrf?

[Tom]

Hmm wouldn’t the RF amp be disabled if you’re not actually receiving and have selected the amp to be enabled?

What symptoms do you have now that the RF Amp is blown ?

Are you going to try fix the thing yourself ?



From: ***@gmail.com [mailto:***@gmail.com] On Behalf Of Simon Kennedy
Sent: Wednesday, 1 July 2015 6:17 PM
To: Tom
Cc: hackrf-***@greatscottgadgets.com
Subject: Re: [Hackrf-dev] Amp On or Off



Tom,



The HackRF was connected to USB so was powered up and therefore was receiving. I had received a Meteor M-N2 weather satellite pass not long before this unfortunate incident so the RF amp would have been enabled. To receive Meteor at 137MHz I also use a masthead pre-amp which was also enabled.



Simon.



On 1 July 2015 at 09:02, Tom <***@hotmail.com <mailto:***@hotmail.com> > wrote:

Sorry to hear that Simon,



Was the hackrf receiving anything when you keyed up the HF and if so was the RF Amp enabled on the hackrf?

[Simon Kennedy]

The thing is that if the HackRF is powered up then it is receiving, running
a program on your computer to collect all those I and Q bits that come from
the USB port doesn't change the RF part of the device (someone correct me
if I'm wrong).

Now the amp is presumed blown it acts more like an attenuator, i.e. signals
are weaker with it switched on.

I doubt I can fix it myself, I present a challenge to my optician and
soldering SMD parts is not something I have tried out yet.

Post by Tom
Hmm wouldn’t the RF amp be disabled if you’re not actually receiving and
have selected the amp to be enabled?
What symptoms do you have now that the RF Amp is blown ?
Are you going to try fix the thing yourself ?

[Daniel Bernhardt]

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

[Paul Connolly]

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.

Post by Daniel Bernhardt

Now the amp is presumed blown it acts more like an attenuator, i.e. signals are weaker with it switched on.

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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[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

Post by Paul Connolly
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
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.

Post by Daniel Bernhardt

Post by Simon Kennedy
Now the amp is presumed blown it acts more like an attenuator, i.e.

signals are weaker with it switched on.

Post by Daniel Bernhardt
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?

Post by Daniel Bernhardt
Forgive my ignorance on the matter. Just beeing curious.
Daniel
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[王康]

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.

Post by Daniel Bernhardt

Now the amp is presumed blown it acts more like an attenuator, i.e. signals are weaker with it switched on.

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 mailing list
https://pairlist9.pair.net/mailman/listinfo/hackrf-dev

[Scott Davis]

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

Post by 王康
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.

Post by Daniel Bernhardt

Now the amp is presumed blown it acts more like an attenuator, i.e. signals are weaker with it switched on.

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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[Tom]

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-***@greatscottgadgets.com] On Behalf Of Scott Davis
Sent: Thursday, 2 July 2015 1:15 PM
To: hackrf-***@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

Post by 王康
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.

Post by Daniel Bernhardt

Now the amp is presumed blown it acts more like an attenuator, i.e. signals are weaker with it switched on.

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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[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.

Post by Tom
Unless I am reading it wrong but doesn't the MGA-81563 have an absolute max Pin of +13dbm?
-----Original Message-----
Sent: Thursday, 2 July 2015 1:15 PM
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

Post by 王康
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.

Post by Daniel Bernhardt

Now the amp is presumed blown it acts more like an attenuator, i.e. signals are weaker with it switched on.

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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[Paul Connolly]

If you set the sample rate to 20MSPS and decimate in your flowgraph down
to a bandwidth of 1.25MHz (20000000/(2^4)) you will have increased the
observed signal level by 12dB (3dB*4) with no possible damage to
hardware. Provided at least one bit in the ADC sample is being tickled
by the signal of interest, every time you decimate the bandwidth in half
you will gain an extra 3dB of signal level. 12dB of extra signal, with
no risk of damaging any hardware, provided what you are doing can
function with 1.25MHz (or less) of bandwidth.

I leave the amp off at all times. The only time i would consider
enabling it is if I was in a RF desert and I had scanned from DC to 6GHz
and found no signals above -5dBm (see:
https://github.com/mossmann/hackrf/wiki/HackRF-One#receive-power ).

Post by Tom
Just curious to what people do with the amp, do you run it most of the time
and not worry about frying it due to nearby transmitters? I'm in two minds
as in I would like to use it as much as I can because it makes a huge
difference, especially when driving and monitoring the ISM bands but at the
same time I worry that a strong transmitter nearby might damage it, I mean
is this really the case even though It might me few hundred mhz away from a
strong transmitting station.
I read one story where someone has destroyed the amp but that was because it
was connected to a satellite dish or something like that (can't remember the
full story) are there any other cases where someone has destroyed the amp?
Thanks
Tom
_______________________________________________
HackRF-dev mailing list
https://pairlist9.pair.net/mailman/listinfo/hackrf-dev

[Paul Jones]

In a future revision of Harkrf would it be possible to add an overload indicator for the rf frontend? Like a clipping indicator in audio equipment. That would be quite handy. I guess a quick utility that scans the entire usable frequency range, finds the peaks and gives a suggested max gain setting would be just as good.

Paul.

From: HackRF-dev [mailto:hackrf-dev-***@greatscottgadgets.com] On Behalf Of Paul Connolly
Sent: Wednesday, 1 July 2015 3:29 PM
To: hackrf-***@greatscottgadgets.com
Subject: Re: [Hackrf-dev] Amp On or Off

If you set the sample rate to 20MSPS and decimate in your flowgraph down to a bandwidth of 1.25MHz (20000000/(2^4)) you will have increased the observed signal level by 12dB (3dB*4) with no possible damage to hardware. Provided at least one bit in the ADC sample is being tickled by the signal of interest, every time you decimate the bandwidth in half you will gain an extra 3dB of signal level. 12dB of extra signal, with no risk of damaging any hardware, provided what you are doing can function with 1.25MHz (or less) of bandwidth.

I leave the amp off at all times. The only time i would consider enabling it is if I was in a RF desert and I had scanned from DC to 6GHz and found no signals above -5dBm (see: https://github.com/mossmann/hackrf/wiki/HackRF-One#receive-power ).
On 01/07/2015 03:03, Tom wrote:

Just curious to what people do with the amp, do you run it most of the time

and not worry about frying it due to nearby transmitters? I'm in two minds

as in I would like to use it as much as I can because it makes a huge

difference, especially when driving and monitoring the ISM bands but at the

same time I worry that a strong transmitter nearby might damage it, I mean

is this really the case even though It might me few hundred mhz away from a

strong transmitting station.







I read one story where someone has destroyed the amp but that was because it

was connected to a satellite dish or something like that (can't remember the

full story) are there any other cases where someone has destroyed the amp?







Thanks



Tom
















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