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Re: [Amps] AL1200 weak receive

Subject: Re: [Amps] AL1200 weak receive
From: Aleksandar Petkovic <>
Date: Sat, 30 Jul 2022 07:47:05 +0800
List-post: <>
Don't engage the relay. The relay must not be engaged during receive, no matter which position the operate switch is on.

The only time the relay engages is during transmit. If it is engaged during receive, you'll hear very little.

If you have weak receive, when the relay is not engaged, it is dirty contacts.

Open it up. Lift the armature spring off the relay but don't let it flick away and get lost. You can then take off the armature/lever springs assembly and get to all the contacts and clean them properly. Reassemble but don't let that spring fly away and then close it all up and test.

Dunno what else it can be.

73, Alek, VK6APK

On 30/07/2022 6:57 am, Ed Swiderski, KU4BP wrote:
Okay. I've done it with no power to the amp and just the signal passing through and manually engaging the relay.

On 7/29/2022 5:45 PM, Mark Bitterlich wrote:
Try unplugging the PTT line from the amp and see if the problem goes away.

Sounds like when you are going to "operate" on the front panel, there is a path to ground from the relay coil. Either inside the amp, or the PTT cable going to the radio. To confirm you could unsolder one side of the relay coil, etc.


-------- Original message --------
From: "Ed Swiderski, KU4BP" <>
Date: 7/29/22 12:33 PM (GMT-05:00)
Subject: [Amps] AL1200 weak receive

I have a confusing problem with my AL1200. During operation when the
stdby/oper is on, the received signal is very weak. Switching back to
standby and the signal level is fine. Checked the relay and it was
operating correctly. Engaging with 12v applied to it. With no power to
the amp and a rx signal going through, manually engaging the relay
weakens the signal. Releasing it and it's back to normal. Cleaned the
contacts using the method described by W8JI on his site. Still no go.
Stumped on where to look next to track this down. A tests on another
radio produced the same results.

With no power to the amp, I connected my RigExpert analyzer to the "RF
in" and a dummy load to "RF out". Doing a sweep, the SWR reads around
1:1. Engaging the relay by hand shoots the SWR very high. Goes back down
when released.

That's the best symptoms I can give. Any suggestions would be an immense

Thank you,
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