[TenTec] SSB and CW filters wanted

[Barry N1EU]

Although I would agree that the narrow xtal filters are generally
unnecessary for general Orion 565 use, I wouldn't agree that they are never
needed if you're a semi-serious cw contester or low band dx'er.

The xtal filters have one main purpose - prevent the hardware AGC from
kicking in to prevent ADC overload on strong s9+ signals in the passband.
It's not the end of the world if the hardware AGC kicks in, but you'll
suffer gain compression and possible audible artifacts.

So if you operate cw in a crowded contest or chase dx on a crowded band,
there's a reasonable chance that you'll encounter an adjacent s9+ signal
inside the 1000hz filter passband that could be tamed with a narrow cw
roofing filter.

And for reasons explained here, http://users.vnet.net/btippett/inrad_.htm ,
go with the Inrad 600hz filter NOT the Ten-Tec narrow filters on the Orion
565.

Due to the inherent broadness of ssb signals, I don't think there's an
advantage to installing the 1.8KHz roofing filter.

Barry N1EU


On Sat, Oct 10, 2015 at 6:52 AM, Rick - DJ0IP / NJ0IP <Rick at dj0ip.de> wrote:

> Allen, Carl is correct.
>
> You don't need really steep skirts and deep attenuation with the roofing
> filter.
> The roofing filter's job is to add just enough selectivity to prevent
> overloading of the down-stream circuits.  The DSP filters on their own do
> the job of providing the main selectivity and they do it quite well - far
> better than the XTAL filters we were previously using for this job;
> assuming
> their circuitry is not overloaded
>
> In the old designs, the roofing filter had to assist with the overall
> selectivity because the single XTAL filter in the downstream IF did not
> have
> steep enough skirts nor enough ultimate attenuation.
>
> Although good XTAL filters measured in the lab can show attenuation of up
> to
> 100dB, when inserted into a radio their ultimate attenuation typically
> falls
> off to just 80 dB, due to blow-by.  Cascading XTAL filters (i.e., roofing +
> IF) raises the ultimate attenuation to about 100 dB.
>
> When the Orion came out, I discussed this with Jack Burchfield and he
> assured me that adding more XTALS to the roofing filter did not bring any
> additional benefit.  It just brings additional size, cost, attenuation and
> points of possible failure.
>
> 73 - Rick, DJ0IP
> (Nr. Frankfurt am Main)
>
>
> -----Original Message-----
> From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of A R
> Sent: Saturday, October 10, 2015 6:26 AM
> To: n4py3 at earthlink.net; Discussion of Ten-Tec Equipment
> Subject: Re: [TenTec] SSB and CW filters wanted
>
>
> Carl,
>
>
>
> Is that really true? Aren't the 218 and 219 employed as roofing filters in
> the 1st IF, and isn't the DSP BW control in the 3rd IF? If strong adjacent
> (and/or dirty) signal conditions warrant tighter/narrower BW roofing
> filters
> than the narrowest 2.4KHz and 1.0KHz roofing filters supplied as "standard"
> in the ORION, then wouldn't the option roofing filters at the 1st IF be
> more
> effective in dealing with the consequences of strong adjacent/dirty signal
> conditions than at the 3rd IF?
>
>
>
> Allen--W7GIF
>
>
> ----- Original Message -----
>
> From: Carl Moreschi<mailto:n4py3 at earthlink.net>
>
> To: Discussion of Ten-Tec Equipment<mailto:tentec at contesting.com>
>
> Sent: Friday, October 09, 2015 7:33 PM
>
> Subject: Re: [TenTec] SSB and CW filters wanted
>
>
>
> You don't need them.  The skirts on the Orion DSP filters are very sharp
> making those filters not really needed.
>
> Carl Moreschi N4PY
> 58 Hogwood Rd
> Louisburg, NC 27549
> www.n4py.com<http://www.n4py.com/>
>
> On 10/9/2015 9:14 PM, Tim Wininger wrote:
> > Looking for # 218 (1.8Khz) and #219 (250Hz) filters for a newly
> > acquired Orion.
> >
> > Anyone got these filter excess to their needs?
> >
> > Thanks for the response,
> >
> > Tim, AB4B
> > Rogersville,AL
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