[hpsdr] New HPSDR card for VHF/UHF ?

[ct1izu]

> My belief is that biggest problem with I/Q is probably the LO.  It would 
> be
> almost trivial to modify the uWSDR 2.3GHz PLL with the addition of a 
> divide by
> 16 prescaler to give 144MHz with fairly low phase noise - if -120dBc/Hz @
> 10kHz is not low enough then I might be able to do some work on an even 
> lower
> noise version.

Looks to be about what a modded FT225 is, see some plots here 
http://www.sm5bsz.com/txmod/ft225eng.htm

>
> Downconvert to HF

> But in order to get the best out of the mixer it is necessary to terminate 
> the
> IF port in a good, broadband 50 ohm load - this is done either with a 
> diplexer
> or an attenuator (or both). Then a filter is required to remove the image
> response at 266MHz - this might not be too difficult, the filter has to 
> pass
> 21-25MHz so a simple low-pass arrangement may suffice.

Active mixer termination also works well. My multiband h/b VHF tcvr uses the 
level 17 TUF1H with a
 MAV11 terminator followed by 2 pole Butterworth filter. I have used the 
dixplexer only, I modded my
 IC202 to use the G3SEK FT221 front end which was the forerunner of the
MUTEK board with the level 7 MD108 mixer.

Shel CT1IZU





 1284064093.0