[op25-dev] HackRF options ? More than this needed like the Airspys???

op25 at zellners.com op25 at zellners.com
Mon Sep 7 15:19:22 UTC 2020

Quoting iain macdonnell - N6ML <ar at dseven.org>:

> I just started playing with a HackRF One ("clone"). This seems to
> basically work:
> --args 'hackrf' -N RF:0,IF:24,BB:28 -S 4000000 -o 100e3 -q 0 -d 0 ....

I've got 2 clones to play with... as I felt they may solve another problem.

But I think there are 2 issues there, one devices, and two signal.

The devices that have 8bit ADC are basically akin to the old double IF  
conversion scanners, plagued with issues especially in dynamic range.  
Even more so in the 700MHz PS LMR area. With FirstNets RFI butting  
right up to that band, even with the 1MHz guard band the RTL's with  
8bit ADC are plagued with RFI junk from the FirstNet RFI. in the D  
Block...I can watch the RFI disappear as you shove the tuning further  
up the band. Unfortunately my systems operate over the entire band...

The 12bit Airspys, and the MSI's aka RDSDR, are they even supported?  
Are more like triple conversion IF radios. I don't see the RFI  
splurges all over the band, 700MHz NB PS LMR that I see with the RTL's  
be it V3 or the other asian junk. I don't see this as much at the  
850MHz NSPAC band, but my prime system is well below the 862 ESMR and  
the A/B Cell blocks at 870Mhz.

> I think 4M SMPS is around the limit for the processor in my RPi3 -
> beyond that, regular traffic sounds like it's encrypted :)
> Not sure if '-g' does anything in this context?

Not sure either thats why I am asking before I bang my head playing  
with options that don't do anything like I did with the Airspy

> I included the '-o' since there's a pretty hefty DC center spike.

Another plus to the airspy line, can't say if the MSI/RDSDR ones have  
this as far as I know none of them are supported by a real OS and  
software. Other software has it on its list for the future but seems  
to be getting shoved down the priority level.

> Still need to figure out if I can make op25 park on a fixed center
> frequency and find the channels with the sampled space, but I need
> something better than the RPi3 to cover the system that I want to
> monitor (channels span about 5MHz).

OP25 doesn't work that way , and with out a major rewrite to do that  
you are better to just set a smaller bandwidth/sample rate as the rest  
is wasted processing.

I set my op25 setups to be about 1MSPS or so as thats more than enough  
for things.

> You probably know already, but in case not; the gains are:
> RF: preamp - either 0 (off) or 14 (on)
> IF: aka LNA - from 0 to 40 in 8dB steps
> BB: "baseband" (a.k.a. VGA) - from 0 to 62 in 2dB steps

Well I know what the HRFO have, I didn't know the conventions to match  
up to OP25/rx.py, thats why I am asking. I found some rx.py  
examples.... which gave those and can translate them to it, but the  
Airspy's needed some other options in the args options to actually  
make it work, and I'd like to have these all ready to go so as to not  
waste lab time..Thanks for the info... save some headaches right there.

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