Using gqrx on HF

[Randy Berry]

I have one of those mass produced RTL-SDR's I purchased on ebay. It's an HF-VHF/UHF model. Supposedly good for 300 KHz to 1.7GHz. I'm wondering how to use it on HF. Is anyone using this device for HF with gqrx? Thanks..

[neutr...@gmail.com]

Sorry I had misread you post initially. Since you have a SDR that will receive below 24Mhz (the normal range of the dongles), you don't need an upconvertered like I had previously suggested. You should be able to attach a long wire antenna or build an "Active mini whip antenna" that will receive on the lower freqs. Just for reference, here is my setup with GQRX, RTLSDR, Hamitup upconverter and mini whip antenna:  https://www.youtube.com/watch?v=BID-IT9LiHo

[Alexandru Csete]

Can you provide a link to "this device"? There are by now a million of
different variations over rtl-sdr devices.

I think you mean it is one those where a standard rtl-sdr device is
built together with an upconverter and has separate antenna inputs for
HF and VHF/UHF, right? If so, you need to tuine to a VHF freuquency
depending on the LO value. For example, if the LO is 125 MHz and you
want to receive 10 MHz you tune to 135 MHz.

This offset can be entered into gqrx as "LO offset" and the frequency
shown will then correspond to the HF frequency.

Alex

[Randy Berry]

This is exactly what I bought... http://tinyurl.com/qbxc7rj There was no docs with it and no specific LO frequencies that I've found yet. It's a generic enough name so the a billion hits come up on google, and none of them that I really want. 

[AndreaVi]

Judging from this picture:

http://www.hellocq.net/forum/attachment/Mon_1310/8_120_1cb65a23519ca11.jpg

it seems there is no upconverter inside your board. I think the smart guy :( who built this stuff decided to go with direct sampling, but it's only a guess; have a look at http://www.rtl-sdr.com/rtl-sdr-direct-sampling-mode. Anyway, I do not know if there's a way of enabling direct sampling in gqrx. Maybe I'm wrong and there's an upconverter on the other side of the board. Can you open the box and see what's on both sides? I'm also asking myself what would be the use of that jumper with A-P markings...

[AndreaVi]

My mistake, you can enable direct sampling in gqrx (from https://github.com/csete/gqrx/wiki/Device-strings ) :

Direct sample mode

To enable direct sampling mode (i.e. reception of 0-28 MHz) on RTL2832U-based devices add the following to the device string:

direct_samp=1

Give it a try ... 




[Alexandru Csete]

Indeed.
Note that you will have to disable direct sampling to tune back to VHF and UHF.

Alex

[Randy Berry]

Great, thanks guys, I'll give it a go later today.

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[Randy Berry]

OK, stupid question, where does said string go?

On Sun, Jan 11, 2015 at 5:41 AM, Alexandru Csete <oz9...@gmail.com> wrote:

[AndreaVi]

From menu File->I/O Devices

[Randy Berry]

Ah, I see.. I was expecting a [Device] section in the config.. Thanks..

On Sun, Jan 11, 2015 at 8:11 AM, AndreaVi <naf...@iperbole.bologna.it> wrote:

From menu File->I/O Devices

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[Randy Berry]

I tried it and all it did is peg the panadapter and no audio in any mode. Also, I have no clue what the jumper is for.

On Sun, Jan 11, 2015 at 8:11 AM, AndreaVi <naf...@iperbole.bologna.it> wrote:

From menu File->I/O Devices

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[grege...@gmail.com]

Depending on your budget and needs, you might look at the Funcube Dongle Pro Plus.  Works great with GQRX and has built in prefiltering.  For some reason when I install GQRX from PPA in Linux Mint 17 or 17.1, it fails to include gr-fcdproplus.  I install that with synaptic, and then all is good.

[Alexandru Csete]

On Sun, Jan 11, 2015 at 3:43 PM, Randy Berry <randy...@gmail.com> wrote:
>
> I tried it and all it did is peg the panadapter and no audio in any mode. Also, I have no clue what the jumper is for.
>

You can try the rtl_test application to see if the driver can talk to
the device and please, give us some details about your setup. Which
operating system, how was gqrx installed and which version?

Alex

[Randy Berry]

I'm using Fedora 20 and gqrx 2.2 (yes, I know it's out of date, but it's whats in the repo.) The application was installed via yum. The system is a P4 3 GHz 4gb of ram.

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[AndreaVi]

I have fedora 21 with the same gqrx version as you, plus a 2.3 experimental-unstable opengl version; in both cases adding direct_samp to device string works, but sometimes I have to quit and restart the program to apply the changes (possibly due to the mess I did with configuration files, my fault.....), so theoretically it should work with you. Does your device operate in vhf and stop working when you add direct_samp, or does it not work at all?  To be on the safe side, open a terminal console and type "rtl_test", see what happens... By the way, there is also an option direct_samp=2 to use both q channels instead of both i channels, depending where that ferrite xmfr has been connected. See also https://github.com/csete/gqrx/issues/64