[TenTec] Sub receiver bandwidth plots (was Roof filters)

[Grant Youngman]

Just an "I should have made that clear" comment, relative to the spectral
displays in the document at the link, lest anyone incorrectly conclude the
Orion II receive audio output is not flat.  These graphs were made on an
RTA, not an FFT display with equal size bins.  On on RTA analyser, white
noise shows a 3dB per octave rise (pink, or 1/f, noise would be flat).

The receive audio output spectrum (viewed on an FFT display) is about as
flat as one can get between the -3dB points.  It's really very good on both
the Main and Sub receivers.

In looking more closely at what seems to be going on in the Sub receiver, it
appears that rather than the BW control just sliding the upper (relative to
audio) side of the bandpass up or down, it is controlling the width of a
bandpass filter centered at about 1500 Hz.  Whether that's exactly what's
happening or not is another question, but that's the effective result.

Grant/NQ5T

> -----Original Message-----
> From: Grant Youngman [mailto:nq5t at comcast.net] 
> Sent: Wednesday, March 15, 2006 4:32 PM
> To: 'Discussion of Ten-Tec Equipment'
> Subject: RE: [TenTec] Roof filters (N4PY and KC9CDT)
> 
> > Have you e-mailed DitsnBits about this SUB RX bandpass issue.
> > Or has anyone else??
> 
> Yes, I have.  I'm going to send them another note, with this 
> file attached.
> 
> http://tinyurl.com/n82l2
> 
> It's hard to miss the fact that something is amiss :-)
> 
> Grant