If the manufacturer 'advises' grounding the negative terminal, do they ship
current production that way?
...Dave
----- Original Message -----
From: "Mike Hyder -N4NT-" <n4nt_m_o_hyder@charter.net>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Tuesday, November 29, 2005 4:07 PM
Subject: Re: [TenTec] Comments on "Repairs"
> Can you be a little more vague, Stuart?
>
> Our club lost an Astron supply every time there was lightning in the
> county.
> After grounding the negative post, they never lost another. Be darned
> careful when you advise people to take action contrary to what the
> manufacturer advises. You hurt people in your attempt to sound erudite.
>
> Mike N4NT
>
> ----- Original Message -----
> From: "Stuart Rohre" <rohre@arlut.utexas.edu>
> To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
> Sent: Tuesday, November 29, 2005 1:55 PM
> Subject: Re: [TenTec] Comments on "Repairs"
>
>
> Some comments on the summary of comments and suggestions on the Omni VI
> problems.
>
> 1. Everyone needs a dummy load! I held out for years, but then you have
> a
> bad coax jumper cable or antenna cable and the dummy load and known good
> jumper coax to it and the SWR meter and its coax jumper become "ground
> truth". If you have RF feedback problems in a dummy load set up with
> known
> good cables and SWR meter, then you have a rig problem. If NOT, then the
> problem lies in the coax switches, jumpers to them, jumpers thru the
> system
> and the antenna coax and connectors themselves.
>
> Several times I have had RF feedback to a rig causing audio distortion of
> lack of ease of getting contacts, and it was traced to loose coax plugs,
> or
> bad shield connection on a coax cable, or one side of the feedpoint broke
> connection on a doublet, etc.
>
> Corrosion, water in the coax, and similar problems can be isolated by
> having
> a known good dummy load.
> When everything works on the dummy, then you know to look to the
> downstream
> connections toward the antenna.
>
> It is well known that the floating negative of the Astron 35 Amp power
> supply causes RF to get back into the regulator causing problems. Many
> ground the negative lead right to the chassis of the power supply without
> exploring why they have a critical RF condition, which also depends on how
> your at the rig grounding is done.
>
> This can be because of the total length to earth of any intervening
> chassis
> grounds, bus bars, and final earth rod lead length. I well remember
> having
> my first external ground rod rendered totally useless for RF by having the
> down lead 8 feet long, a perfect 10m quarter wave high impedance at the
> rig
> chassis!
>
> Grounding the Astron negative post can have a downside. In our club
> station, that was done, then lightning surge used that path to get back to
> AC ground as the preferred path, after burning out the RF ground
> conductor!
> So it is not a universal solution and might be a bad "fix". Study and
> diagram out your whole RF grounding scheme to look for sneak loops and
> paths
> back to AC ground, telephone ground, etc. any ground in addition to your
> driven shack ground you installed. Find out how the rest of the building
> is
> grounded and bond all outside to meet the newest electrical code.
>
> Stuart
> K5KVH
>
>
>
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