4410Re: [linrad] Fwd: [softrock40] Ver 7 28Mhz preamp? Yes
- May 6, 2006--- In firstname.lastname@example.org, KD5NWA <KD5NWA@...> wrote:
> I notice that the amplifier has a attenuation pad on it's output,
> rendering the impedance problem to be moot.
> I have some MMIC's that I'm planning to experiment with for the
> bands and use a SoftRock, since their gain is a little excessive Ithe
> was planning on using a 3dB to 6dB pad, which will help setting
> impedance of the filter at a more stable valueHi Cecil,
Regarding the W7AAZ Post-Mixer amplifier in the CDG2000 has a 50 ohm
output for the very simple reason to permit a testing point. The
4xJ310 output is 200 ohm. This would make an easier matching to the
post amplifier xtal filter Zin = 500 ohm. The amplifier has around
14dB gain and very low noise. The output IP3 is lower than expected,
measured at +27dBm. Probably this is due to the changing input Z of
following xtal filter. Adding an attenuator will reduce this effect
and increase the OIP3 before the filter.
I am sure that in the SoftRock an OIP3 of +27dBm of a preamplifier
will be more than necessary.
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