Question regarding the Voltage Input Range

[df5fh]

Hello dear OMs,

I have a question regarding the input voltage of the Red Pitaya. I assume a Red Pitaya ADC input range of -1V to +1V, in other words 14 Bits for 2V.

16384 = 2000000 uV --> 1 = 122 uV

The antenna is directly connected to the ADC and a RF-Signal with S9 comes in with 50,15 uV ... In my view not enough to set Bit0 to H in the ADC-Output-Value ?
How is it possible to read weak signals in this environment ? Where is my fault ?

Vy73
Henning, DF5FH

[df5fh]

Hello Pavel,

thank you very much for your response. This is near-miracle stuff for me and I have further questions. I heard people say that the Hermes-Board is better than the Red Pitaya because it owns a 16Bit ADC. Hmmm ... this requires that these more bits are really used. If I connect my 80m antenna with the Red Pitaya what could I expect at the digital output seen by the software? What is the maximum adc-output-value your software has to handle ? How many ADC-Bits are really toggling ? In my simple imagination I would expect that the Red-Pitaya works at maximum performance if the complete value range of the ADC is involved. I would expect that this goal can be achieved using a preamplifier ... in best case with an automatic control loop for leveling. But meanwhile I have doubts. I need enlightenment, please !

friendly regards
Henning

[Uli DF5SF]

Hallo Henning,

es gibt grafierende Unterschiede zwischen SDR und Analogempfängern. Umdenken ist erforderlich.

Hierzu findest du sehr viel im Internet, z.B.:
http://www.ab4oj.com/sdr/apdxc16_sdr.pdf
http://mirror.thelifeofkenneth.com/lib/ ... dRadio.pdf

Viel Spass beim Lesen

[df5fh]

Hello Uli,
thank you for the links, I already tried those documents but while reading I feel my limits quickly Think I have to try again ...
Do you have an idea about the number of bits which are used in the RP-ADC under "normal conditions" ? Actually this is of personal interest to me. What is your opinion about using a preamplifier to increase the RP-performance ?

Vy73
Henning

[Uli DF5SF]

Hi Henning,

the RP uses 14 bit. The difference to 16 bit is minimal, see document from AB4OJ page 14.
At beginning I had a 1:9 unun at the input of RP. Infos here. This works fine from 80 to 20m.
Now I have a preamplifier from DC2PD, kit see here.

[df5fh]

Hello Uli,

thank you for your patience. Yesterday we had "OV-Abend" and we discussed this stuff endless. Keeping friendly and patient is very important when different opinions are expressed in a discussion I made some basic faults regarding the size and influence of values.

friendly regards
Henning