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Re: [TenTec] Corsair II buzz

To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Subject: Re: [TenTec] Corsair II buzz
From: "Bob McGraw - K4TAX" <RMcGraw@Blomand.net>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Fri, 3 Apr 2009 21:43:11 -0500
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
Do recall that any station ground has length and inductance and impedance. 
It may be a good DC ground as it has low resistance, but is it a good RF 
ground?  In almost any condition, the station is above RF ground.  For 
example, a station ground that is some 16 ft in length puts the station at 
1/4 wave above ground on 20M.  That 1/4 wave ground wire can radiate or 
receive noise just like an antenna.

I've found that station grounds can be more problematic than providing 
solutions.  Some will say that it is necessary for lightning protection.  I 
say "do your want lightning to come in your house to your station before 
being diverted to ground?"  I certainly hope not and therefore strongly 
suggest that all lightning protection must be done outside of the house and 
not inside the house.

To approach this issue methodology, disconnect every cable from the radio, 
power it from a 12V battery and terminate the RX input with 50 ohms and 
listen.   I prefer a 1/2 watt  51 ohm resistor inside a PL-259 connector 
with a 3/8" metal hole plug covering the open end of the connector.  That's 
is about as close to 100% shielding as one can get.   If the noise is there 
it is most likely coming from inside the radio.  If it is not there then it 
is coming from the outside world.  That will give one a solid direction to 
look for a solution.

Bob, K4TAX

----- Original Message ----- 
From: "Jim Brown" <k9yc@audiosystemsgroup.com>
To: <Gary@doctorgary.net>; "Discussion of Ten-Tec Equipment" 
Sent: Friday, April 03, 2009 9:42 AM
Subject: Re: [TenTec] Corsair II buzz

> Gary Smith wrote:
>> Hi again,
>> While truly the idea of three phase noise generation and equipment is
>> reading which I enjoy following, I gotta reiterate that I most
>> recently heard this when running off a deep cycle battery and no
>> antenna (a 6" piece of wire was inserted in the 239 connector for a
>> minimal antenna) or other wires attached.
> Gary,
> Do you have access to any form of audio FFT?  I'm thinking of software
> that could run on your laptop using the sound card. Laptop is important,
> because it can run on battery and independent of the AC line. This might
> yield some clues as to the nature and source of the buzz.
> Note that by talking about the power-related stuff here, I was trying to
> help you eliminate it as a source of the problem before you tear into
> the radio looking for something more complex.  Another point. The
> power-related buzz is IR drop from current flowing on the ground wiring,
> and the source of that current is the power system. You could, for
> example, be running on battery but have connection to ground at two
> points and your radio could be seeing that voltage. The Ten Tec Omni V
> has  multiple "pin 1 problems," so a connector at one of them going to
> some ground, combined with a ground to the chassis, could be injecting
> that power-related buzz. Consider this when you're running off of
> battery for testing. That is, for this test, NOTHING but the battery
> connected to the radio (except headphones to listen to it). Definitely
> not a ground, and nothing plugged into any of the connectors on the back.
> 73,
> Jim K9YC
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