Good one.
----- Original Message -----
From: "Adam Farson" <farson@shaw.ca>
To: <tentec@contesting.com>
Sent: Wednesday, November 19, 2003 00:34
Subject: RE: [TenTec] 7800 purchases (was Orion in contests)
> Hi Ron,
>
> I used the term "by definition" for a reason. Popular legend to the
> contrary, the Orion is not an SDR. (Neither are the IC-756Pro II or
> IC-746Pro, for that matter - except for their DSP engine.) It is a
> software-controlled radio. No software known to man or beast will alter
one
> whit of the IF frequency, local oscillator range and RF bandpass-filter
> parameters which determine its frequency coverage. These are all
> "hard-wired" in RF hardware. The same remark applies to the PA low-pass
> filter bank.
>
> By definition, the Orion's TX/main RX 9 MHz first IF (as opposed to a
first
> IF above the highest operating frequency) will in and of itself preclude
> continuous transmit and receive coverage, which are prerequisites in HF
> equipment intended for the mil/gov radio services. There is a "forbidden
> band" around the 9 MHz IF which cannot be incorporated into the radio's
> coverage whilst maintaining acceptable image and spurious suppression.
Even
> if the more RF bandpass filters and PA LPF's are added to provide
contiguous
> passbands, this limitation imposed by the low first IF will still apply.
>
> The only solution is to place the first IF above the highest
> transmit/receive frequency, e.g. at 64 or 70 MHz, and down-convert (RX)
and
> up-convert (TX) to the final (DSP) IF. This will call for a complete
> redesign of the radio's RF/IF chains.
>
> I hope this adequately addresses your question.
>
> Cheers for now, 73,
> Adam VA7OJ/AB4OJ
>
>
>
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