Collins made crystal filters for the 9 MHz range for the old KWM-380, but I
think getting up to that frequency with mechanical resonance may be a
stretch.
Ron Castro
Chief Technical Officer
Results Radio, LLC
----- Original Message -----
From: "Carl Moreschi" <n4py@arrl.net>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Saturday, August 05, 2006 2:03 PM
Subject: Re: [TenTec] Omni VII - More IF scheme speculation
> Here's my wild speculation:
>
> Use 9 mhz as the first IF when in the ham bands, and 45 mhz when outside
> the
> hambands. This would give you the Orion main receiver scheme inside the
> ham
> bands and the Orion sub-receiver scheme outside the hambands. Are there
> any
> Collins mechainical filters for 9 mhz?
>
> Carl Moreschi N4PY
> 121 Little Bell Drive
> Bell Mountain
> Hays, NC 28635
> ----- Original Message -----
> From: "Duane - N9DG" <n9dg@yahoo.com>
> To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
> Sent: Saturday, August 05, 2006 4:32 PM
> Subject: Re: [TenTec] Omni VII - More IF scheme speculation
>
>
>> More wild speculation below:
>>
>> --- Bill Tippett <btippett@alum.mit.edu> wrote:
>>
>> > N9DG:
>> > >I'm 98% sure in the 455 kHz IF. The IF scheme from what I
>> > can
>> > tell is very close to the Pegasus/Jupiter with 45 MHz 1st
>> > IF
>> > and ~455 kHz second IF. Putting the improved filtering in
>> > those two spots will improve two areas of weakness in the
>> > RX320/350, Pegasus, Jupiter, Argonaut V and Orion sub rx.
>> >
>> > I agree but am left wondering why this is
>> > not called a Jupiter II rather than an Omni VII? Perhaps
>> > marketing reasons.
>>
>> My guesses are:
>> 1) Because they feel it will equal or exceed the Omni VI in
>> performance.
>>
>> 2) It will be a "step up" from the Jupiter, the Jupiter will
>> remain in the product line for the near term holding down
>> price point just bellow $2K.
>>
>> > Here's my guess about the IF scheme:
>> >
>> > 1st IF: 45 MHz with 20 kHz and (hopefully?) 6 kHz roofing
>>
>> The preliminary info is a bit ambiguous about exactly where
>> the optional filters would go. However my take on it is that
>> there will be both 20 & 6 kHz filters at the 45 Mhz(?) 1st
>> IF. A 6 kHz filter in the 1st IF will make a world difference
>> because my experience with Pegs have been that it is the
>> stuff that gets through the first IF is what actually
>> overloads the 2nd IF and causes the spurs every 12 kHz up and
>> down the band with big signals. It is even more pronounced if
>> you've done the infamous IF gain "full clockwise" tweak.
>>
>> > 2nd IF: 455 kHz with ? standard and optional 2.5k, 500,
>> > 300 Hz
>>
>> My take away from these filter choices at the 2nd IF
>> (assuming that this is where they are) is that the 2.5 Khz
>> 1st LO synthesizer tuning step used in the RX320/350,
>> Pegasus, Jupiter, Argonaut V series radios is history. The
>> 1st LO probably tunes to the actual frequency instead of
>> using the software LO (tunable) in the 3rd IF to compensate
>> for the 2.5 KHz step of the 1st LO in the older series
>> radios.
>>
>> > 3rd IF: XX kHz DSP
>>
>> My guess is it will be either 12 or 14 kHz just like the
>> other TT DSP IF radios. The real question in my mind is
>> whether it uses the same series ADC of the RX320/350,
>> Pegasus, Jupiter, Argonaut V, or the AKM AK4524 of the Orion
>> series. Along with that will it use the same DSP processor as
>> the Orion (ADSP21065L - 32 bit) or is it a ADSP218x series
>> part (16 bit). Inquiring minds want to know.
>>
>> >
>> > I could be wrong about the 6 kHz roofing at 45 MHz...it
>> > could be at 455 kHz instead. If so, it will only have
>> > mediocre front-end performance (similar to Pro 3, etc).
>> > Should the latter turn out to be true, expect Inrad to
>> > offer a 4-5 kHz roofer at 45 MHz in the blink of an eye!
>>
>> I've often pondered the feasibility of modifying the Pegasus
>> (Jupiter, 516 etc.) with a narrower filter at 45 MHz.
>> Couldn't make it any narrower then about 6 kHz because of the
>> 2.5 kHz 1st steps though because the first 2 IF's are
>> actually "nominal" frequencies.
>>
>> The other main that thing I wonder about is image performance
>> on 6M assuming that it is indeed a 45 MHz 1st IF. 45 MHz
>> would only be 5 MHz away from the low end of 6M which would
>> put a some pretty steep requirements on the front end band
>> pass filtering for that band.
>>
>> I have some suspicions about the architecture/implementation
>> of the Ethernet side of the radio but I'll wait for some more
>> official details before publicly speculating on that.
>>
>> In time we will know the answers to all of these questions.
>>
>> Duane
>> N9DG
>>
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