[ARC5] DC-DC: Need a Receiver Bias Supply?

[Bill Cromwell]

On 12/23/2013 06:56 AM, David Stinson wrote:
> Another use for these little DC-DC converter bricks:
> If you get one that's isolated (the output does not share a common
> negative or ground with the input), you can use it to "flip"
> your A+ voltage of 6, 12, or 24 volts and zener it to a nice little 
> bias supply.
> There are many little low-current converters available for cheap with 
> various inputs and outputs.
> For example- if your A+ is 12 Volts and you need -7.5 bias,
> get one that does 10-16 Volts in, 9 or 12 Volts out. Resistor and a 
> zener and away you go.
>
> The RFI situation may vary, but I've built a couple of supplies using 
> DC-DC converters with ferrites and a metal box to encase them. It's 
> worked for me with the residual "birdies" not
> being any problem (hey... whadda ya want for a $10 supply??).
>
> To see what's available, search the Bay with this string:
>
> -non dc-dc converter isolated
>
> "-non" because otherwise it will list "non-isolated" and that
> won't work for a bias supply.
>
> 73 DE Dave AB5S

Hi Dave,

I haven't used zener diodes in a grid circuit as they are reported to be 
excellent noise generators. I'm reluctant to put a noise generator on a 
grid and degrade the receiver's noise performance. Since I haven't used 
a zener diode in a grid circuit I can't attest to a noise problem. I AM 
building a noise-impedance bridge and I have confidence the zener diode 
in that will do it's job.

Are there some people who have used a zener diode in a grid circuit 
(bias supply regulator) without noise problems? Maybe with a filter cap?

73,

Bill  KU8H