Direct conversion receivers are prone to pick up AC 60 hertz hum as the
result of modulation of the VFO carrier (which is at the operating frequency
in a direct conversion receiver) with the 60 hertz AC in the power supply.
The fix is to put .01 uf caps across the power supply electrolytic caps.
Electrolytic caps are great at 60 hertz but offer no filtering at all at RF.
The .01 uf caps will filter out the RF from the VFO and prevent it from
being modulated by the 60 hertz AC. I used to have an HW8 and this fix
worked well for the HW8 direct conversion receiver.
Carl Moreschi N4PY
121 Little Bell Drive
Bell Mountain
Hays, NC 28635
----- Original Message -----
From: "Ken - N9VV" <n9vv@sbcglobal.net>
To: "Ten-Tec mailing list" <tentec@contesting.com>
Sent: Tuesday, October 10, 2006 9:20 PM
Subject: [TenTec] Mod for Century-21 hum?
> Dear TTers,
> does anyone know of a MOD or fix for hum in a Century-21? is it common
> because of the design? or could it indicate a problem with the P/S?
> TU de ken n9vv
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