[hpsdr] New HPSDR card for VHF/UHF ?

[David McQuate]

  Unless a filter is specifically designed (an absorptive filter) it 
becomes highly reflective outside the pass-band.
Even in the pass-band, the reflection may be high enough at some 
frequencies that it's a poor mixer termination,
especially if you're hoping for really good intermod performance.

Dave
wa8ywq

On 9/10/2010 9:10 AM, Anthony Taylor wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
>
>
> Shel,
>
> The diode mixer is already looking at 50 ohms across the entire IF 
> range as it's terminated into a suitable LPF, adding a BPF may have 
> some merit, however, if you provide an additional MMIC after the mixer 
> (12db-3dB for the BPF loss) you are looking at adding about 9dB this 
> would cause the ADC to overload, trying to do gain optimisation at the 
> second IF after this will not help.
>
> BTW the RLP-50+ loss across it's passband is less than 2dB, the LTC 
> 6400-20 provides over 20dB of gain so you are looking at atleast 18dB 
> of gain before the ADC.
>
> 73s,
>
> Tony
>
>
>
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