[Hackrf-dev] FM 96.5MHz rx works but 70cm 441.1MHz rx does not?

[Gavin Jacobs]

The hackrf is MUCH less sensitive than a typical handheld. If you are using the vertical antenna that came with the hackrf, then you will have trouble receiving any ham transmissions. I had the same experience as you, so here are some tips that got me going:

- calculate the 1/4 wavelength and set the telescoping antenna to that length

- put the antenna (and the hackrf unless you have some appropriate rf cable) high in the room

- increase the if_gain to 40; use a QT GUI slider to decrease it once you acquire a signal

- set the center frequency to an even multiple of MHz; then set your offset to hit the desired channel

It takes some patience, but eventually you will get the frequency visible on the chart.


Also, be careful not to hit PTT on your handheld, at any time, at any frequency, in the vicinity of the hackrf; any moderately strong rf can damage the front end of the hackrf. So, I suggest starting with the APRS frequency (in North America 144.39 MHz); you get steady traffic, you can hear it on your handheld, but you don't have to transmit anything.


Unfortunately, my flowgraphs are 2000 km away right now, but we can probably help you get going.


Jake





________________________________
From: HackRF-dev <hackrf-dev-bounces at greatscottgadgets.com> on behalf of David Hubbard <david.c.hubbard+hackrf at gmail.com>
Sent: November 9, 2016 7:23:31 AM
To: John Ostrander; hackrf-dev at greatscottgadgets.com
Subject: Re: [Hackrf-dev] FM 96.5MHz rx works but 70cm 441.1MHz rx does not?

On Wed, Nov 9, 2016 at 6:10 AM, John Ostrander <john at crackroot.org<mailto:john at crackroot.org>> wrote:
David,

You're likely receiving it, but 70cm is nbfm not wbfm so you're probably
getting loads of noise around the signal you're trying to get at. Try a
flowgraph like the one attached, but with the osmocom source of course.

regards,


Thanks, John! I ran your flowgraph tuned to 443.000 and looked for a 443.700 signal that was coming in at S9 on my handheld ham radio.

I have attached the flowgraph with my modifications and the screenshot. I believe there's no signal. What do you think?


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