[TenTec] INRAD Orion roofing filters?

[Mark Erbaugh]

Bill,

Did you make any comparisions between then 400 Hz roofing filter and the
stock roofing filter?

Mark

----- Original Message ----- 
From: "Bill Tippett" <btippett at alum.mit.edu>
To: <tentec at contesting.com>
Sent: Tuesday, November 11, 2003 6:51 AM
Subject: Re: [TenTec] INRAD Orion roofing filters?


> KE5C wrote:
> has anyone stuck a 2100 Hz and a 400 Hz
> INRAD in an Orion instead of the TT's?
>
>          I'm using the Inrad 400 Hz.  I chose it because it has a slightly
> narrower bandwidth (455 Hz vs 500+ Hz) and was on sale at the time.
> It works fine but is specified for slightly more insertion loss than
> the TenTec 217 (9 dB vs. 7.5 dB).
>
>          The main thing to remember with all roofing filters is that in
the
> Automatic mode, they will not be switched in until about 75% of the
> nominal Ten-Tec filter bandwidth.  This means they will switch in at the
> following points, independent of the actual filter bandwidth:
>
> Filter position Switchpoint
> "1800"          1400-1410
> "500"           370-380
> "250"           190-200
>
> There is slight hysteresis in the switch points, so the roofing filter
> is switched from 2400 to 1800 as you narrow the DSP setting to 1400 Hz
> from higher values, and it switches to 2400 when you widen the DSP to 1410
> Hz from lower values.
>
>          Regarding the 2100 Hz Inrad, it is actually 2200 Hz, so I doubt
you
> would notice much difference with the standard 2400 Hz filter.  If you
> do put it into the "1800" position, just remember it will not switch in
> "Auto" mode until ~1400 Hz as noted above.  When I used my TT218 (which
> is actually 1900+ Hz) in the CQWW SSB, I simply locked the filter in
> the "1800" position for the contest.  By adjusting PBT to +150 and RX
> EQ to -10, I could copy quite well with DSP BW set anywhere from 2000
> to 1600 Hz.  I normally left DSP at 2000 and adjusted it down only if
> necessary.
>
>          As I mentioned before, I was amazed how easy it was to copy weak
> signals with Orion in the CQWW , which I attribute to both excellent
> IMD performance (reduces passband noise due to distortion products) and
> the Digital AGC (which helps with signal QSB at the noise floor).
>
>                                                  73,  Bill  W4ZV
>
> _______________________________________________
> TenTec mailing list
> TenTec at contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
>