[TenTec] Orion Noise Reduction Ability

[Pfizenmayer]

>From TT website.

QUOTE ""All-new suite of ORION II-specific roofing filters is arranged in 
one,
single bank to allow user to select the absolute ideal roofing filter for
mode, band conditions, and personal preference. The narrow (600 and 300 Hz)
filters are now located in the same initial bank with all the rest. This new
arrangement yields subtle improvement in dynamic range and the new filters
have less passband ripple than any we've ever offered.UNQUOTE""


The statement about using the narrow filters with additional loss is  true
about the 565 Orion - The filter descriptions on pages 44 and 45 in the
Orion 566 OII manual are in error having been copied word for word from the
565 manual and not updated. The new Orion 566 roofing filters have
essentially the same loss at any bandwidth and the extra amplifiers are no
longer needed as was for the 250 cycle filter.

If you look at the OII schematic of the 9 mhz IF  A4 81999 you will see the
extra gain amp that was in the 565 has been removed and there is no apparent
resistive padding or reactive matching (mismatching) to equalize filter path
losses.

It is conceivable that there are resistive pads inside the new filters to
equalize losses but there is nothing external to them . I agree GENERALLY
narrow filters will have more loss than wide filters even with the same
number of poles.

I had an O 565 with the 250 cycle filter and can agree - it had no apparent
use at all - always used the Inrad 600 hz filter in the non amplified 1 khz
slot.

The O II 566 300 hz filter on the other hand I use virtually 100 percent of 
the
time (I work virtually nothing but CW and have a very noisy location). I
will admit I was pleasantly surprised by this  - I bought the 300 cycle
filter mainly to prove to myself it made no difference in S/N but it 
certainly
does.(as well as improving close in dynamic range)

One other difference I note is that I have drifted to using the DSP
filtering around 250 cycles in the OII . Going down to 100 - 150  cycles 
even with
reducing taps to soften the 100 hz DSP filter slopes does not seem to be
quite as good for weak signals at least so far.

Conversely , in the 565  with the Inrad at 600 hz I tended to run DSP
filtering with taps at 199 and 100 - 150 cycle DSP BW for best S/N.

One of these days I will buy the new 600 hz filter just for grins - but
don't really expect to go away from the 300 hz filter based on what I have
seen on about 3 months of use. The 600 hz filter will be useful in contests
where people have a hard time hitting freq within 150 hz or so.

 Rgds-- Hank K7HP

----- Original Message ----- 
From: "yahoo email" <barbiekenw at yahoo.com>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Thursday, March 22, 2007 7:55 AM
Subject: Re: [TenTec] Orion Noise Reduction Ability


> It is written up in the manual in the section about weak signal.
> No point in having a narrow roof if there are no signals pumping the AGC.
> Very narrow roofing filters have loss.
> Ken
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