Jim,
There would be negligible difference by using the inrad filters in the
Orion. 99% of the time, the DSP filters won't even need the a narrow
roofing filter. The difference between the tentec and inrad filters in this
application would be almost immeasurable.
Carl Moreschi N4PY
Franklinton, NC
----- Original Message -----
From: "Jim Reid" <jimr.reid@verizon.net>
To: <tentec@contesting.com>
Sent: Tuesday, April 15, 2003 6:53 PM
Subject: [TenTec] Ten Tec vs. Inrad 9 MHz Filters
> Hi,
>
> I would appreciate a lead as to where I could find performance
> curves for the Ten Tec filters say the 217, 218, and 219 optional
> available for use in the Orion.
>
> I believe the TT filters are "less" steep skirted close in, but are
> actually more narrow further on out from the center frequency;
> thus actually would perform "better" in the roofing filter application
> in the Orion front end than the available Inrad models. Curves
> for the Inrad filters are found at:
>
> http://www.qth.com/inrad/tentec_menu.htm
>
> Couple of examples from the above site:
>
> Inrad 400 Hz BW CW 9Mhz filter, the #759, is down 6 dB at
> a BW of 455 Hz; and at 60 dB down it is 955 Hz wide;
>
> their 250 Hz filter, the #760, is down 6 dB at a BW of
> 315 Hz; and at 60 dB down it is 700 Hz wide.
>
> But, I have been told these actually "come back" up
> and have less attenuation on beyond the close in curves
> shown by Inrad at their site. I do not know if this is true!
>
> Why, well "only" 60 dB down is really not that large
> an attenuation in some ham band situations, and coming
> back up again could really be bad.
>
> But, I don't know how to compare to the "standard" Ten Tec
> filters. I had an Omni VI+ in the past equipped with the Inrad
> filters in all slots, replacing the TT filters. At the time I was
> not apprised of the possible benefit of staying with the standard
> Ten Tec units; that is, perhaps not as steep close in skirts,
> but they "stay down", hi. Frankly, I cannot say that the
> Inrad filters "really" made the Omni a better performer, but
> I did not do a direct A/B comparison, for obvious reasons:
> I only had one Omni, hi.
>
> Any comments, actual data per this topic would really be
> appreciated, should you have any or know of a source.
>
> Would like my new Orion (coming in May?, lot #2 somewhere)
> to have the best roofing filter performance possible, giving
> the narrow IF-DSP filters the greatest opportunity to provide
> super selectivity. BTW, have ordered the TT 1.8 kHz and
> 500 Hz optional roofing filters to be included with my Orion.
>
> So far, have heard of no one replacing Ten Tec filters in
> their Orion with the now available Inrad filters for that
> radio; perhaps that is sacrilege!
>
> 73, Jim KH7M
>
>
> _______________________________________________
> TenTec mailing list
> TenTec@contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
|