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Re: [Yaesu] FT890 strange behavior

To: <Yaesu@contesting.com>
Subject: Re: [Yaesu] FT890 strange behavior
From: "Tom Osborne" <w7why@frontier.com>
Reply-to: Tom Osborne <w7why@frontier.com>
Date: Thu, 11 Jul 2013 18:41:51 -0700
List-post: <yaesu@contesting.com">mailto:yaesu@contesting.com>
Hi Earl

Or - you could hook the radio to a battery and see if it still folds.  73

Rather than pile $25 worth of ferrite and filters on it why not take a
divide and conquer systematic approach to resolving the problem.

Start with the supply.  Can you draw 20-30 Amps out of it with just a plain
resistive load?  If not, the supply may be defective without even adding the
RF part into the equation.

Next add the radio without all the microphones, CAT interfaces, external
speakers, etc connected.  Transmit into a dummy load at a low power level.
Do you notice the issue?  Check all bands.  If the issue is still non
existent increase power and repeat checking all bands.  Check CW and
Modulated modes.

If the issue is still not recurring start adding the microphones, head
phones, speakers etc back into the equation and recheck functionality to see
what it takes to make that power supply fold up.

The final stage will be adding the antenna and transmitting full power with
everything hooked up.

Once you know exactly what it takes to make the supply fold up it is going
to be much easier to determine the exact fix.  Adding a ferrite bead (what
mix??) to attenuate common mode currents when you are uncertain about which
frequencies or which cables are even causing the issue (1.8-30 MHz is a big
chunk of spectrum)is more of an exercize in how lucky you are rather than
how good you are.

Good luck with the process.  Let us know how it comes out.


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