Re: softrock liteV 6.2 spike at 7.056 @ 58dB level
- Hi Joe,
Many people assume that the spike they see at the centre frequency is the LO iteslf.
If you stop and think about it, as this is a direct conversion receiver, so the LO frequency itself would be 0Hz, i.e. DC! The outputs from the SoftRock are AC coupled, plus the sound card would not respond to DC.
What you see is an artifact of the A/D conversion at exactly the centre point, and any hum or noise each side of it.
Generally the better quality sound cards have a far smaller (or even no) spike at the centre point.
If you use PowerSDR, that shifts the LO on receive by a fixed amount to work with a 'pseudo' IF, usually 9kHz, in order to move the point you are listening to away from and spike or hum around the centre frequency.
As Alan said, the poor audio is often the CPU running out of processing power. If you are running at 96kHz sampling, try droppin to 48kHz to see if that improves. Other problems might be the sound card driver you are using.
73, Bob G8VOI
--- In firstname.lastname@example.org, "Joe Holstein, n8ea" <n8ea@...> wrote:
> Recently completed building the 40M version and it plays OK except in two respects. It has a 58dB spike in the spectrum display at the crystal (1/4) frequency of 7.056MHz and the sound is scratchy. Any suggestions on what I should check. I assume the scratchy audio may just come with the sound card in my older computer ? Could the big spike be due to incorrect wiring of the RF transformer ? Or ? Otherwise I am amazed at the performance. (I am using Rocky).
> 73 joe n8ea
- On Tue, 2011-03-01 at 19:56 +0000, g8voip wrote:
> What you see is an artifact of the A/D conversion at exactly theOn my el-cheapo onboard Intel, it's a DC offset. It's unsightly but
> centre point, and any hum or noise each side of it.
> Generally the better quality sound cards have a far smaller (or even
> no) spike at the centre point.
doesn't really do any great harm.
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