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Lectrosonics Block 470 / Block 19 overlap explained

While on a recent job using a Lectrosonics Venue receiver (narrow band) and some LT and HHa transmitters (same thing could happen with HMa, LMb, SSM transmitters) I came across a situation that stumped me for a while. I performed an RF scan using the receiver and then tuned the transmitters to the suggested frequencies. Afterwards, I couldn’t get the receiver to sync up with some of the transmitters even though I had tuned the transmitters to the correct frequencies. What would explain this?
On page 8 of the HHa manual this explanation is given:

On page 13 of the LT manual, this explanation is given:

Notice that this is a very specific situation where you need the combination of a narrow band device (470 or 19 block) with a wideband device in the A1 band (covers 470 / 19 / 20) to discover it. Even with the right (or wrong) combination of gear, you may avoid this issue randomly but at ssome day you might get caught. I did and so did one of my fellow engineers. This post isn’t directly related to measurement per se but you could run into the issue described below if you are using Lectrosonics gear for measurement purposes.

Here is a PDF chart showing how Lectrosonics frequency blocks are assigned. Note how Block 470 and Block 19 overlap.
lectrosonics.com – TV Channels Frequency Blocks PDF

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