Just a question for Alex (or anyone)

[AA0OI]

HI All:

     Still haven't had much luck with rtl-sdr  and gqrx on the HF bands when I use rtl=0,direct_samp-2 input switches to "Other",, with that being said I can hear something down in there-  way down. still trying to pull it out..

Alex (way off topic) do you have any experience with EaxGear Desk top, and emulator for x86 on the pi's?

Would it be able to run HDSDR or SDR#  or any of the other radio programs with little problem? Not that I have given up on gqrx and HF but a way around it for the time being. Pse let me know if any ideas,, Tnx! Garrett

[Alexandru Csete]

Like I have said in a previous message, it is normal that the text in
the input selector changes to other when you modify the device string.
Please do not concern yourself with it, It just means that you have
modified the device string.

I have an rtl-sdr blog V3 dongle on the way. When I receive it I will
test direct sampling to see what works and what doesn't.

I have no experience with any emulators or simulators, sorry.

Alex

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[AA0OI]

OK Tnx You Alex

Garrett / AA0OI

On ‎Saturday‎, ‎May‎ ‎12‎, ‎2018‎ ‎06‎:‎53‎:‎40‎ ‎AM, Alexandru Csete <oz9...@gmail.com> wrote:

Like I have said in a previous message, it is normal that the text in
the input selector changes to other when you modify the device string.
Please do not concern yourself with it, It just means that you have
modified the device string.

I have an rtl-sdr blog V3 dongle on the way. When I receive it I will
test direct sampling to see what works and what doesn't.

I have no experience with any emulators or simulators, sorry.

Alex

On Sat, May 12, 2018 at 3:17 AM, 'AA0OI' via Gqrx SDR
<gq...@googlegroups.com> wrote:
> HI All:
>      Still haven't had much luck with rtl-sdr  and gqrx on the HF bands when
> I use rtl=0,direct_samp-2 input switches to "Other",, with that being said I
> can hear something down in there-  way down. still trying to pull it out..
> Alex (way off topic) do you have any experience with EaxGear Desk top, and
> emulator for x86 on the pi's?
> Would it be able to run HDSDR or SDR#  or any of the other radio programs
> with little problem? Not that I have given up on gqrx and HF but a way
> around it for the time being. Pse let me know if any ideas,, Tnx! Garrett

>
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[Robin Gape]

Garrett,

there's a review of the ExaGear desktop in the June 2018 Linux Format. The long and the short of it is that ExaGear is not fast enough for mainstream SDR use.

In regards to HF, one suspects that the direct sampling mode is not very sensitive. Other people have reported better results with an upconverter. Beware, though, the cost of an RTL-SDR plus an upconverter is rapidly approaching—or may be more than—the cost of an HF capable 12 or 14-bit dongle such as an SDRplay RSP1A which is inherently capable of much better results.

With an SDR dongle, of any form, one needs a good antenna and, particularly if the aerial is an unbalanced just-a-length-of-wire, a good RF ground. The dongle needs to be well away from the host computer, and will benefit from (= is probably essential) a good screened USB cable, with ferrite chokes to suppress EMI from the computer.

HTH, 73,

Robin, G8DQX

[AA0OI]

Hi Robin:

  (hope I'm not becoming to familiar !) ha  ha.  Not the antenna's 20 meter, 40 meter, and 80 meter. all tuned correctly. besides can hear CB , 11 meter and then 10 meters is just gone.  Have tried everything that Alex suggested , with no results.   what I can hear is something way down in the noise but can not make out and shows nothing on the graph (yes gain is all the way up.).No other HF at all, ordered up-converter, which the Post office has lost,, now to wait 3 more week to get another one. (39.95) ..  You maybe right,, quit fooling around with this cheap stuff and buy a good one (dongle),, only  problem is the V3 (cheap stuff works just great on the windows platform)  copy all over the world on all bands and SW, HDSDR, SDR# etc. problem is dropping down to the Pi's, and GQRX (Alex said to forget GQRX on window, performance will not be and different. (or different- I may just give it a kick anyway.

         ExaGear desktop has free test run for free for a few weeks,, I'm going to try on the 3B+ its a little faster. I'll try to load HDSDR and maybe SDR# an see what happens,, if for some reason it works its only 29.95 for two machines for life. (at least till Alex gets to look at gqrx with V3 dongle) getting sorry I sold the FT 990AT.

ALEX, if your reading  "HF capable 12 or 14-bit dongle such as an SDRplay RSP1A which is inherently capable of much better results"  is this true and work better on the GQRX and Pi's???

Got to ask ,, what does  "HTH" mean, have never heard it before.

TNX -thanks

CUL - See you later

Garrett / AA0OI

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[Alexandru Csete]

Hi Garrett,

Today I have received the RTL-SDR blog V3 dongle. This dongle supports
direct sampling as is and it even includes a small preamp for HF.

First I wanted to test it with a signal generator to measure the MDS
in a lab setup but I never got that far. Even with a 2m/70cm J-pole
antenna I could receive HF in direct sampling mode, see attached
screenshots.

[Alexandru Csete]

(I hit the Send a little too early in my previous mail)

As you can see there are many spurs and the signals are not very
strong, but still more than what I expected when using a VHF/UHF
antenna in the middle of an industrial zone in Copenhagen. I will do
some more tests with a real HF antenna when I get home later tonight.

Device string:
rtl=0,direct_samp=2

Sample rate:
2.4 Msps

Decimation:
8

Hardware AGC:
On

It seems hardware AGC is a good idea here, so I am thinking that
perhaps that is what you are missing in your setup.

Alex

[Alexandru Csete]

Hi Garrett,

I have now tested direct sampling using a real HF antenna it seems to
be working quite well. The only thing I noticed is when changing the
device string to direct sampling and pressing OK, gqrx stops with an
error so you have to restart it. After that it works fine.

Alex

[AA0OI]

Hi Alex:

      I just had a few min tonight to try some of this out.. Only had V-2 dongle set up,, will try others tomorrow.. with the V-3 and your setting I see lots of spikes but no audio at all. Tried AM-80 meters and up thru 20 meters, and 40 (including 15) and not one sound. (but also nothing that looks like your waterfall) , will try agn tomorrow after a little sleep..

CUL

Garrett / AA0OI

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[AA0OI]

Hi Alex:

        Ok here is what I have found out V-2 dongle is junk (for fm and 2-440 only.

The Key is the "Dicimation" if it is set at anything other than 8 thing go to hell pretty quick.. When set at 8 and a V-3 dongle everything is Excellent  ! (and the right antenna). just a little bit scratchy ( not bad).  I'm only trying this out  on the Pi B3 (ver 2.6) tonight an will try on the Pi B3+ (ver 2.11.4)tomorrow.

I am EXTATIC ! , slight drifting (to be expected) .  A little bit miffed with the CPU use of 55% on "No Limit" when I go back to fm and stereo stations usage goes back to 86 to 90%  (??)  (because of stereo??)

Why does waterfall drop off  at the end of some freq's (goes to black) (maybe when I go to the b3+ and 2.11.4 instead of 2.6 and b3 this will improve or go away. 

Only off 1.00 ppm. pretty good.

     I can now hear dam near everything on the bands.  Just wonderful !

over driving the "Gain" solves the scratchy.  fixed

By the way how did the up converter work that you got with the V-3?  is it worth the extra or anything at all??

CUL, I'll keep you up to date as I go.

Garrett / AA0OI

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[Alexandru Csete]

Hi Garrett,

Glad to hear that you got it working. FM stereo consumes more CPU than e.g. AM or SSB because it runs at higher bandwidth and requires more filtering for the separation of the channels. It has not been optimized, so it will use quite a lot of CPU.

I would definitely recommend to try upgrade to 2.11.4 because many bugs and improvements have been done since 2.6.

Alex

[AA0OI]

Tnx Alex

     I have both 2.6 and 2.11.4  .. the 2.6 is on the b3 machine and the 2.11.4 is on the new b3+.   That way I can listen to both at the same time.. T-Mart had 200 watt mini amps on sale for 11.95 including shipping.. runs on 12 volt at 2.5 amps,, works great for the Pi's with a couple of old speakers, only problem is no headphone jack, have to unplug it from the Pi's output,,, and it just sound great!.

     The signals that I receive are great but there is lots of garbage along with it.. sounds like my other computers and electronic in the shack.  Will try to get it cleaned up tonight,, seems I saw something about spread spectrum on the Pi's, turn on will help.  I saw on your picture that it was pretty clean.

Tnx Agn

CUL

Garrett / AA0OI

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[Alexandru Csete]

On Wed, May 16, 2018 at 11:48 PM, 'AA0OI' via Gqrx SDR
<gq...@googlegroups.com> wrote:
>
> The signals that I receive are great but there is lots of garbage along with it.. sounds like my other
> computers and electronic in the shack. Will try to get it cleaned up tonight,, seems I saw something
> about spread spectrum on the Pi's, turn on will help. I saw on your picture that it was pretty clean.

Noise from computer can get out to the antenna on the coax shield,
then come back in to the receiver as if it was received on the air. To
mitigate that, I have grounded the coax shield right outside the house
where I also have a lightning protection that needs to be grounded
anyway. It's not a very good ground, it only goes about 50 cm down,
but it seems to remove a lot of noise from my computers.

Alex

[AA0OI]

Hi , wish that were my problem,, I have 5   8 foot copper rods down 7 and 1/2 feet, three in my leach field ( so they are wet always.. grounds are always 1 1/2" braided copper coming to the window, central entry point.  Everything in my shack is grounded to this including outlets and fans and lights.  I do notice the LED lights tend to add some noise as most diodes do ..  Going to rain tomorrow all day so I'll have some time to work on it !!

CUL TNX

Garrett / AA0OI

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