Tuesday, June 12, 2012

Intermod and Spurious Emissions!

So, as I was scanning the 10m band, I noticed that I was receiving occasional bursts of static on my 2m radio.  These were occurring as I crossed fairly strong carriers, which means that these carriers were interacting with my rig in receive mode, and causing what is called intermodulation, which was resulting in a spurious emission.

Here are some links for more reading on these phenomena: 

I recorded a quick video of it to show folks that just because you are using a receiver, it does NOT mean that you are not also broadcasting a signal!  Something to be mindful of, especially if you are in an area that is sensitive to RF fields (thinking of mining sites that use an RF signal to detonate explosives, among other scenarios).

I should probably point out that the volume on the radio that I am adjusting is completely down, the only radio that has its volume turned up is my Yaesu FT-2200 2m radio.  The sounds that you are hearing are the spurious emissions generated by my TS-440S tuned to ~28.5MHz being received by my FT-2200 on 147.120MHz.  I should also point out that these are extremely localized and can not be picked up beyond my shack.  I tried with an HT in the yard under the dipole and got nothing.  Also, I apologize for the poor quality of the video, I shot it with my iPhone 3GS, which has a pretty lousy camera.


Richard, KK4JDO

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