Hi Alan!
Thanks for the flowers. Yes, I grounded the Delta 44 breakout box direct to the SDR gnd, the computer direct to the SDR gnd. I use an Astron 25 amp switching supply which is velcroed to the side of the Dell. I have DX Engineering RF clamp toroids on each lead of the pwr supply just before the terminals on the SDR. The SDR is velcroed to the top of the Dell just behind the face panel line. The Delta 44 is velcroed on the top left rear and the HOSA cable leads cut back to just reach the SDR black box. The entire system is then grounded from the SDR to my station gnd. When I turned it on it was "clean".
I use a PR40 mic to a Presonus Digitube mic preamp/3 band parametric. I run the balanced line out (pins 2 and 3 on the XLR) to each of the sound card inputs, pin 1 common to each. I boosted the 2k and 3k fairly brightly as Alan said with the Digitube and use the SDR equalizer just for touch up(especially to get rid of Mr. Nasty 160.
I am getting nothing but great reports on the audio! Thanks, Flex Radio for a great break-through product!
Ryk
N6DQ
Alan Davis <[EMAIL PROTECTED]> wrote:
Alan Davis <[EMAIL PROTECTED]> wrote:
I worked Rick, N6DQ on 14.178 SSB last nite in a group. He was running
his SDR into an amplifier at 500 watts and his HiFi SSB was very clean
without a trace of RFI ! Rick sounded exceptional, but a little "bright" for
my taste. But the high frequencies show up the RFI 1st in my experience,
and there was none on Rick's signal! How did he do it? He grounded
together the Dell computer chassis to the SDR box and tied that to the
station ground. He cut the Hosa cables down to 6" and velcroed the grounded
breakout box to the SDR box. Also he used a separate Astron PS with short
power leads.
My SDR is still having occational RFI issues, the inline isolators, beads
and toroids did not solve the problem completely. If the gain is up just a
little - back comes the RFI shadow! I'm starting to think one of those mini
cpu cards in a shielded box bolted to the SDR cabinet might be better then
ripping apart my computer desk and all the rest. Will it ever end?
IMHO, this demonstrates the flaw with using a soundcard in a near RF
field! If the RF is getting in some other way then the audio cables - even
optical coupling may not guarantee freedom from RFI! The A/D & D/A must be
RF shielded and a computer is not the ideal location for that!
The 870 is back online and the SDR offline, until I can come up with a
solution to this MESS.
BTW, no RFI is evident using the TS-870 driving a 1kw amplifier.
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