Re: [TenTec] INRAD Omni VI roofing filter kit - success

[Charles Greene <w1cg@qsl.net>]

Rick,

That answers one question I had.  Now another.  Why couldn't you install 
both roofing filters, the 2400 Hz in series with the 600 Hz filter, and 
only switch the 600 Hz filter with the N-1 switch.  That way you would have 
two filters in tandom when the N-1 filter was switched in.  Otherwise, you 
would have a 2400 roofing filter for SSB.  Not that I plan to do this, but 
I was curious.

Another question:  Can you replace the stock 2400 Hz 9 MHz filter (Y2 on 
the 9 MHz Mixer / IF Board) with an Inrad 754, 2800 Hz  9 Mhz filter?  At 
my age I have problems understanding SSB on the OMNI-VI because of its 
limited audio bandwidth and the LPF in my ears.  If you had a 2800 Hz 
filter in the 9 MHz position, you could  use the PBT to offset the bandpass 
of the 6.3 MHz IF up in frequency 300 Hz, so that the 9 MHz filter would 
receive 300 to 2800 Hz and the 6.3 MHz 2400 standard filter would receive 
600 to 2800 Hz.  Loss of below 600 Hz hardly affects intelligibility.  On 
transmit, you would have 300 to 2800 Hz audio vice 300 to 2400 Hz audio.

Question 3.  Anyone know when the OMNI-VI roofing filters will hit the 
market?  They are listed on the Inrad web site as sometime in the future.

Tnx,  Chas,  W1CG

At 11:19 AM 1/14/2005, you wrote:
> Ken I think that you may have misunderstood where the roofing filter is in
> the "food chain".  The "stock" Omni V and VI have 2-pole filters at the very
> front end of the 9 MHz IF board.  These filters are 12 to 15 kHz (yes that's
> kHz) wide and hard wired.  Their purpose is a first line of defence for
> nearby signals.
>
> The InRad mod goes in front of this filter and gives the operator the option
> to significantly narrow the front end of the 9 MHz board.  It's location is
> between the RF board and the 9 MHz board.  The mod contains a 4-pole filter
> (either 600 Hz or 2400 Hz).  The NAR switch(s) are used to (a) control the
> roofing filter and/or (b) the NAR filter.  The roofing filter is not located
> at the end of the 9 MHz "food chain" like the NAR filters.  It is actually
> at the opposite end of the 9 MHz schematic.
>
> The roofing filter can be switched in or out so that the operator does not
> lose any functions (e.g. FM or a wider 2,800 Hz IF filter) by installing the
> mod.
>
> I have installed the 2400 Hz version in my Omni V.9 and, other than a small
> glitch with the cabling, found the process relatively painless.
>
> 73,
>
> Rick
> VE7TK
>
> Website:  http://www3.telus.net/ve7tk

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