Hi Tim and Ross,

Let me copy what I answered to Cris and Willi few hours ago:
--
Willi,

Thanks for remembering! Linear power supply/voltage regulator is
always a good solution for low noise applications. Unfortunately,
sometimes we cannot use them.

Actually, now I'm using the original "chopper" with better filtering.
You may add 47uF capacitor parallel to C7 and double the values of L2,
L3, C8 and C9. Be careful though, the chopper DC1 (NMA1215S) is very
sensitive to all kind of overloads - even to the higher inrush current
of the output filter capacitors! That's why higher inductance values
will be needed. My suggestions are beyond the recommendations of the
manufacturer and naturally, you violate the guarantee rules of
FlexRadio, too. Anything you modify is totally at your own risk and
responsibility.

It may be my good luck only, that this modification has worked three
years in my oldest SDR-1000 and about two years in the two other sets.
For anybody else I suggest  buying (or building) a quiet power supply
with well filtered output voltages +13.8V and ±15V (±12V).

73, Ahti OH2RZ



On 25/09/06, Willi Reppel <[EMAIL PROTECTED]> wrote:
> Chris,
>
> This subject has already been a topic  three years ago on the Forum and so
> far I remember >
--


On 25/09/06, Tim Ellison <[EMAIL PROTECTED]> wrote:
> I think it is more prevalent than not.  The noise is real easy to find
> when the rig hasn't warmed up and you have it on a dummy load.  In the
> Panadapter you can watch the "little hump" wander you the band until the
> radio starts coming to temperature and then back down.  As the radio
> warms up, its rate of travel slows down to almost a crawl.  Eventually
> it settles in a frequency range and wanders around in it.
>
> I see this behavior all the time on 20 meters, and have observed it on
> other bands as well.
>
> -Tim
> ---
> Tim Ellison
> Integrated Technical Services
>
>
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] On Behalf Of Ross Stenberg
> Sent: Monday, September 25, 2006 10:56 AM
> To: flexradio@flex-radio.biz
> Subject: [Flexradio] DC/DC Converter (DC1)
>
> I have noticed this being discussed as an issue several times. It
> appears
> that not everyone is affected by the meandering signals. Some are worse
> than
> others or not even noticed. Is this a known issue or are they just
> isolated
> occurrences?
>
>        73 Ross K9COX
>
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