Spyverter R2 with USRP B210 #shortwave


erik@...
 

Hi,

I purchased a Spyverter R2, and connected it to my USRP B210.

I note from Airspy, "that moves the entire HF spectrum to the VHF band between 120 MHz and 180 MHz".

I am connected to a 30m 'long-wire', via a balun to FM bandstop, and then to the usrp.

Now, I'm not expecting any signals <120MHz... but I have LOTS of stations to listen to, and clearly right from the start of the band, you need only expand the screen to see them individually:



Then, where I'm expecting signals from 120MHz through 160MHz, I find discernible stations below 100MHz:



Not what I was expecting at all.

Furthermore, if DC to 60MHz, is shifted to 120 through 180MHz, then do I assume 121.350MHz should equal 1350kHz? and 140MHz should equal 20MHz in reality? Nothing is aligned with the global list of stations I have.

Spyverter is powered from USB port on laptop.

Would anybody be so kind as to offer some thoughts here?

Thanks and regards,

Erik.




prog
 
Edited

On Sun, Feb 17, 2019 at 08:00 PM, <erik@...> wrote:
Now, I'm not expecting any signals <120MHz.
Not sure if you fully understand how converters (or any RF mixers) work, but that's perfectly expected. The signals are mixed with a 120 MHz LO. The positive image falls between 120 and 180 MHz, and the negative (inverted) image falls between 60 and 120 MHz. OTOH, the BPF at the output is optimized to attenuate the harmonics, not the negative image.


erik@...
 

Hi, and thanks for the response.

I do understand somewhat, but I tried to describe what I thought was unexpected activity:

1. DC to about 22MHz has lots of stations tunable.
2. And since the Airspy site for the Spyverter described only a positive image, I didn't expect any signals below 120MHz, i.e. I expected filtering of some sort, which you allude to, but I still have lots of stations.
3. Nothing is aligned to expected frequencies. Its nigh on impossible to tell what frequency I am tuned to, even if I were to configure an offset (120MHz?)

As an aside, I read about Ettus trying to charge you money to support their products - I'd have bailed on that idea too. I think they up to their necks in government money, and need little support from the hobbyist community, it would seem. But thanks for trying..

Erik.


erik@...
 

Ahh, I looked again at the picture I posted, and I DO see the symmetry either side of 120MHz.... I'll set that as the offset, but as I said earlier, it didn't match to expected stations freqs.

I'll give it another go.

Thanks again.


jdow
 

For what it is worth DC->60 MHz is shifted to BOTH 120-180 MHz and 120-60 MHz. It's called imaging. 1MHs appears at both 121 MHz and 119 MHz on the output of a mixer. Filtering on the mixer output can remove the image if it becomes bothersome. Done wrong it will also remove the spectrum near DC, probably up to over 2MHz with reasonable circuit element Qs. This is clearly shown in the second picture. The first picture may be not showing the broadcast band due to filters and possibly a very small antenna.

{^_^}

On 20190217 09:10:44, erik@... wrote:
Hi,
I purchased a Spyverter R2, and connected it to my USRP B210.
I note from Airspy, "that moves the entire HF spectrum to the VHF band between 120 MHz and 180 MHz".
I am connected to a 30m 'long-wire', via a balun to FM bandstop, and then to the usrp.
Now, I'm not expecting any signals <120MHz... but I have LOTS of stations to listen to, and clearly right from the start of the band, you need only expand the screen to see them individually:
Then, where I'm expecting signals from 120MHz through 160MHz, I find discernible stations below 100MHz:
Not what I was expecting at all.
Furthermore, if DC to 60MHz, is shifted to 120 through 180MHz, then do I assume 121.350MHz should equal 1350kHz? and 140MHz should equal 20MHz in reality? *Nothing* is aligned with the global list of stations I have.
Spyverter is powered from USB port on laptop.
Would anybody be so kind as to offer some thoughts here?
Thanks and regards,
Erik.


jdow
 

Youssef tried to explain item 2 to you. If you get to this message without understanding then just consider it to be a side effect of the sufficiently advanced technology aka magic.
{^_^}

On 20190217 20:05:15, erik@... wrote:
Hi, and thanks for the response.
I do understand somewhat, but I tried to describe what I thought was unexpected activity:
1. DC to about 22MHz has lots of stations tunable.
2. And since the Airspy site for the Spyverter described only a positive image, I didn't expect any signals below 120MHz, i.e. I expected filtering of some sort, which you allude to, but I still have lots of stations.
3. Nothing is aligned to expected frequencies. Its nigh on impossible to tell what frequency I am tuned to, even if I were to configure an offset (120MHz?)
As an aside, I read about Ettus trying to charge you money to support their products - I'd have bailed on that idea too. I think they up to their necks in government money, and need little support from the hobbyist community, it would seem. But thanks for trying..
Erik.


erik@...
 

Hi jdow,

Yes, as I tired to say, I got it now, I see the symmetry above / below 120MHz. My confusion was from the online literature about the Spyverter r2 that mentioned only a positive image, and therefore I was expecting the negative image (for whatever reason) may have been suppressed / attenuated.

I've just landed in Singapore, so I'm nowhere near my long-wire at the moment, so I can't 'play' just now, but am looking forward to spending some more time tinkering with the Spyverter R2.

As an aside - I'm half way through the book "The Hobbyist's Guide to the RTL-SDR: Really Cheap Software Defined Radio", and so far it seems a crying shame there is no Ettus support for SDR#, which is the primary s/w the book is based on. I found the pirates using the FLTSTAT sats especially amusing...

The Hobbyist's Guide to the RTL-SDR: Really Cheap Software Defined Radio