[TenTec] NB verses NR

[Carl Moreschi]

I am in the country and I have intermittent power line noise.  When it 
is bad, the Noise Blanker in my Flex 6500 will remove it completely, 
dropping the S meter reading by sometimes as much as 10 DB.  Very 
impressive.

Carl Moreschi N4PY
58 Hogwood Rd
Louisburg, NC 27549
www.n4py.com

On 12/15/2014 1:53 PM, Rick - DJ0IP / NJ0IP wrote:
> Peter,
>
> It is as Carl said, if you have a narrow filter before the NB tap, it simply
> won't work.
> In the country, you probably won't need it anyway unless you have an
> electric fence nearby.
>
> I can't recall the filter plan on the original OM6.
> If you series two filters on separate IF frequencies, you get at least 10dB
> more ultimate attenuation than if you series them on the same IF frequency.
> Don't ask me why, I've long sense forgotten.  This was explained by DL1BU in
> about 1979 in a CQDL test of the old Icom 730.  I "think" I still have that
> article saved somewhere.  Not sure if I could find it again.
>
> The problem with placing two filters directly in series is, you will drop
> about 6dB of gain, assuming they are narrow filters.  This needs to be
> compensated for with a low gain, low distortion amp.  I also used two 9 MHz
> filters in series with my old Argonaut 509; I replaced the original 4-pole
> xtal filter with an 8-pole KVG XF-9B, then placed a 6-pole 500 Hz Yaesu
> filter behind it. The signals I could no longer hear due to the additional
> insertion loss were too weak to work anyway with only 5w.
>
> Ten-Tec was already managing stage-gain better than the JA OEMs when they
> developed the OM5.
> In fact it goes back all the way to the original Omni where they had
> different gain depending on the band.
> However they improved it even more when developing the OM7.
>
> At the end of the day, if it is working for you and you are happy with it,
> then it was a good move.
> That's how I judged my dual-filter in the Argonaut, even though I knew it
> was technically no exactly kosher to do it that way.
>
> 73 - Rick, DJ0IP
> (Nr. Frankfurt am Main)
>
>
> -----Original Message-----
> From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Peter
> Bertini
> Sent: Monday, December 15, 2014 6:13 PM
> To: tentec at contesting.com
> Subject: Re: [TenTec] NB verses NR
>
> Rick
>
> I have two of the roofing filters kits from Inrad; they are connected in
> series... since I have the basic Omni VI, I only have one NARROW filter
> selection on the front panel... so I have one of the roofing filters always
> in line. Narrow drops the SSB roofing filter, and selects the board with the
> CW filter. It is in series with the input to the monolithic roofing filter
> on the 9 MHz IF board.  My understanding is that the NB sampling is after
> this filter, but I could be mistaken.
>
> Fortunately, being in a rural area I don't have much need for noise
> blankers.  I've often wondered if just buying better quality IF filters from
> Inrad would reduce the need to cascade additional filters at 9 MHz to
> improve the skirt selectivity.
>
> Peter
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