[hpsdr] hardware question ( Mercury HPSDR)

[Graham / KE9H]

Gedas:

It is much more likely to be the relay that runs the 20 dB attenuator
than a defective A->D converter.  I would change the relay, first.

--- Graham / KE9H

==

Gediminas Kasparaitis wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> Hi,
>
> so many people responded, thank you my friends. Pdf  is so nice.
>
> No, I do not have RF source with known level, but I got good advice 
> from where to get one
> not too big , not too expensive ( Elecraft).
>
> Today I did some aditional testing, now I have no doubt,  my board has 
> that instability,
> sometimes everything is OK, sometimes a bit bigger noise
> ( very hard to understand if it is bigger than it should be)
> , sometimes terrible noise increase.
>
> When it works good, sensitivity is close to that of my radio, when it has
> problems, then  base line just goes up  ( 10-30 db) and weakest 
> signals dissapear,
> strongest became weak... It takes time to duplicate this.
>
> The idea to put heatsing on top of the chip ( on my board at least) 
> turned to be totally wrong.
> On the opposite side it doesn't hurt at least and helps somewhat with 
> cooling.
> It seems to me, that  the best thing is keep everything away from that 
> A/D, then it ( or front end ) is the most stable.
> Strange, but it becomes apparent only after few hours of warm up......
>
> In CW skimmer  problem is  very visual..., but I misplaced somewhere 
> cable from camera, so can't share
> screen shots.
>
> For a while I will play with extra fan, mightbe I still can get it 
> more reliable ....If that won't help,
> I don't know...will try to look for the best A/D  ( -40 - 85 C) and 
> try to replace with it.....
>
> 73, Gedas, nx2px
>
>
> ----- Original Message -----
> Subject: Re: [hpsdr] hardware question ( Mercury HPSDR)
>
>
>> Hi,
>>
>> The basic shape of the noise looks OK but the base line is high - 
>> have you calibrated PowerSDR against a known signal level?
>>
>> 73's Phil...VK6APH
>>
>
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