[TenTec] OMNI - C Noise blanker modification

[Marinos Markomanolakis M.D.]

Hi to All,
I have just uploaded a new article at eham, regarding the above title. It may be accessed at https://www.eham.net/article/51274

The utube videos should be available within the next 12 hours.
Updated info on the Omni NB modification.
During the night when the extremely strong broadcast stations filled the 40m band above 7200Mhz in Europe, significant intermodulation products appeared in the 40m band only, when activating the modified NB.
Further testing showed that increasing the new resistance value installed between R5 – R9 to 3M3, instead of 2M, led to improvement of the IMD products while maintaining a similar effectiveness of the NB.. Based on the above observations, my revised recommendation is to install a 3M3 resistor. This will decrease the potential at the base of Q1 to 0.25V.
Apparently the IMD products are produced from the IC1 acting as a "mixer" when huge signals are present within the near by frequencies.
Any ideas or suggestions on improving the IMD performance when the NB is activated are welcome.

73,
Marinos, sv9dru / ki4gin