[TenTec] Omni VI selectivity

[Chuck Guenther]

Here's at least a crude data point for those interested in performance of the Ten Tec Omni VI with new INRAD roofing filter: Perhaps this "real-world" data will be of interest to those who have inquired about the roofing filter. 

I have two neighbors who are active DX'ers that live within about 1000 ft of me.  One of them (KT0NY) was chasing C21DJ on 30 meters this morning.  I made a few s-meter readings with my NAR switch on and off, as he moved around in the pileup.  The NAR switch on my Omni VI, Opt. 1 engages the INRAD 600 Hz CW roofing filter as well as a downstream 9 MHz IF  filter, which is the INRAD 753 (400 Hz BW).  The 6.3 MHz filter was the INRAD 750 (also 400 Hz BW).  The ATTEN on the Omni VI was "off."

When I zero beat KT0NY, he pegged the s-meter, of course.  
When he was up 1.0 KHz, he was approx. s9 + 20 dB with NAR "off," and down to s-8 with NAR "on."  
When he was up 1.4 KHz, he was approx. s-9 + 20 db with NAR "off," and down to s-6 with NAR "on."
When he was up 2.0 KHz, he was approx. s-9 + 20 dB with NAR "off," and down to s-4 with NAR "on."

It should be emphasized that the figures with NAR "on" represent the combined effects of the roofing filter and the 753; I have no way rigged up to engage the filters separately.   I do know from experience without the roofing filter, that it is contributing a significant amount of the reduction in these spurious responses due to overloading the receiver.  Next time I try this, I'll remember to obtain measurements with and without the attenuator on.

73,
Chuck  NI0C