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[Yaesu] RE: FT-1000 60 Hz Hum Problem

To: yaesu@contesting.com
Subject: [Yaesu] RE: FT-1000 60 Hz Hum Problem
From: Marty Rosenzweig <marty@cmn.net>
Date: Mon, 26 Jul 2004 15:24:35 -0600
List-post: <mailto:yaesu@contesting.com>
Well Marinos gets the grand prize today! I tried a pair of Koss phones and no hum. The Koss measured about 240 ohms...I know that's DC resistance, not impedance, but it does indicate a much higher impedance than the Yaesu phones which measure about 34 ohms DC. A couple of 220 ohm resistors in series with each "channel" and the hum is gone with a somewhat higher AF gain control position than without the resistors. Interesting that Yaesu doesn't design phones appropriate for (at least) this radio (or maybe not designing radios for common low impedance phones!), and it also explains why some FT-1000 users don't experience the hum at all.
I expect it's all an exercise in technology and the radio really doesn't perform any better now, with the modification, but the knowledge is worth the effort!
That brings me to the question of what people like in headphones, particularly for the 1000, I guess? I bought the Yaesu phones to optimize voice and, primarily, CW response as opposed to the wide bandwidth of high quality audiophile phones. They're also much lighter than the Koss I used to use.

Any ideas?

Thanks to everyone who responded and ain't the Internet (and this list) a great resource?



Marinos Markomanolakis, M.D. wrote:

Dear Marty,

My 1000D has the same low hum noticeable only when using the headphones and having the AF pot all the way CCW. I have seen this in other rigs too TR7, Tube radios etc and it is related to the use of low impedance headphones.
If you try using headphones with low (16 Ohm) impedance that either have volume control or you can add a variable resistance in series with them before going to the radio, you will see the problem disappearing when you increase the resistance and returning when going back towards the 16 Ohm.
Then you can check the added resistance value with a multimeter and add a small (or 2 one in each channel) resistor within a Radio Shack large stereo plug and then connect your headphones through it to the 1000D.
Of course in doing so you will have some attenuation in your audio but the hum will be gone.

Hope this helps,

Marinos, sv9dru/w4 or KI4GIN

Greetings, I have a 1992 FT-1000 which, with the RF and AF gain CCW (off) and everything disconnected from the radio except a pair of Yaesu headphones, has a very noticeable 60 Hz hum (about 5 mv on the scope, both channels (ie., main and sub in "stereo").

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