[AudioI] Ultra 2 -10dB Input and Mic

[Matt Flax]

Sounds good. SDR is fascinating ! I've added you to the list.
 

 
On 11/11/21 11:10 am, jr52884 at aim.com wrote:
 
 
 
 
 
 
 
Hi Matt,
 

 
 
Thank you for your reply. I’m interested in natural radio emissions in the ULF/VLF band, like sferics, whistlers, and chorus emissions. I’m also interested in amateur radio transmissions in the VLF/ULF band as well. I’m primarily interested in frequencies from 300 Hz to 30 kHz, up to 100 kHz in some cases. A soundcard is an excellent VLF SDR. 
 
 

 
 
Thanks for the information. I removed the M1,M2, and Vbias pins on the mic header and only have G connected. 
 

 
 
PS, I sent an email off list for you to check the status of this email address. Hopefully this email posts to the list. 
 

 
 
Thanks again.
 

 
 
Jonathan
 

 
 

 
 
 
 
 On Monday, November 8, 2021, 3:59:37 PM EST, Matt Flax via People <people at lists.audioinjector.net> wrote: 
 

 
 

 
 
 
 

Hi Jonathan,

 

Is VLF SDR where you do very low radio frequency signalling through the ground ? What types of frequencies do you use ? 

 

Regarding the top level Ultra IO board and the middle level Ultra preamplifier board ...
 

 

The -10 dB header on the board is for the balanced line inputs, like XLR and TRS. The other connector is for RCA inputs and ground connections.

 

If you don't plan to use the onboard microphones, then you don't need to connect the middle header on the front of the preamplifier board. Although having said that one of its pins is a ground connection, so it is another anchor between two board's ground planes.
 

 

Matt

 

p.s. You can only post to the list once you join it !

 On 9/11/21 4:54 am, JONATHAN RIZZO wrote: 
 
 
 
 
 
 
Hi All, Matt,
 

 
 
I purchased an Ultra 2 (for use with a VLF SDR project) and I was just wondering about some of the interconnects.
 

 
 
On the IO board (v1.8), what is the -10dB header used for? I'd like to use the input channels without any attenuation. If so, should I just omit soldering this header?
 

 
 
Also, I need to use the line inputs and don't want to be collecting sound from the onboard microphones, so on the preamp board (v1.13), do I just omit soldering the mic header? For reference, I'm using the Ultrasound v1.24. 
 

 
 
Thanks.
 

 
 
Jonathan 
 
 
 

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