Noise Blanker Issues by Tim K3LR


The problem with the NB front panel control is well documented by INRAD in their "MP Filter Selection and Operating Thoughts" It is a 4 page document. The document comes when you purchase INRAD filters.

The IMD is deteriorated when the NB1 and NB2 switches are in the OFF position and the NB pot is in anything but the full CCW position.

I have received many emails telling me that operators do not see any difference when he front panel control is varied with the NB's in the OFF position. Not every receiver will be affected the same. Signal strength and the number off signals on a band have a direct impact on this problem. The only time I can hear the problem is when the bands are full of contest signals...It is then very noticeable,

According to INRAD's excellent info, the third order intercept goes from +14.5 dBm at full CCW to -7.0 dBm at full CW. This test was made on 7 MHz, tuned front end, 500/400 Hz CW filters. The difference is amazing (21 dB!).

The mod I mentioned before takes the NB circuit out of line when the NB's are off and then the control has no affect on the receiver performance. Tim K3LR


This site was last updated 08/27/07