Programming or other issue?


May 24, 2010
Springville, PA
Ok all,

What i have:

I have a motorola PM400 45watt VHF. Have a Maxrad antenna,(like 36inch whip style), with a lip mount base.

The problem/issue:

Had it installed then removed, then re-installed. Orignal antenna mount was a right angle bracket not exactly properly mounted, but worked. Then mounted with the lip mount base. When mounted with the angel bracket no issue. With the lip mount, i have static on select few of my channels that i didnt have before.

How to fix/resolve issue

Any ideas? Like is this a grounding issue with the antenna mount? Or is this like a squelch issuse that i need to take to a programming location to reset that? It happens onoccasion, not all the time. But its more often than not. Its just annoing when trying to listen to all the freq. when scanning and it hangs on those few freq.

Let me know what you think

Thanx BJ


Jun 23, 2010
Northville NY
The rf to trigger the squelch bursts may be coming from elsewhere. You might want to use a scanner or other radio to see if that is the case. All the re-mounting and reprogramming won't help if the signal is coming from elsewhere. You may also find it helpful to verify which channels are getting the bursts. If it is the same channel all the time, I'd look elsewhere for the cause.

The antenna needs to be properly grounded at both ends. You might check the radio itself to make sure the connector is tight as a loose ground there will cause problems. Same for the antenna end. If using a trunk lip mount, the mount needs a solid ground to the trunk, and the trunk needs a solid ground to the chassis. This needs to be verified with a VOM meter. No ground at the antenna end causes all kinds of troubles.

If you are getting static instead of rf signals, then check all of the 12vdc connections and grounds. If there is a loose or dirty connection, it may be the culprit. Another device in the car may be causing issues. Sometimes re-routing power wires will solve this. If there is any correlation to engine rpm's, emergency warning equipment useage, etc. those are all places to check for troubles.

I would also trace every wire and cable associated with the radio to check integrity. If there is a rub point, that can cause what you describe. Also proximity to other wire bundles in the car can trigger these things.

In this age of programmable everything in radios, I would not look at that first as a cause of intermittent static or changes in squelch thresholds. But if your other efforts don't solve the problem, then a trip to the shop may be in order.

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