Hi Barry:
On 15 meters here I notice RF sometimes (not all the time!) gets into my 961
which I use for my Omni-V. I use open-wire feeders for my extended doublet
and also for my Lazy-H wire beam.
One thing I added that's missing from the power supply design is RF bypass
capacitors at the AC line. Why doesn't TT follow "standard practice" and
have bypassing built-in? The schematic is conspicuously bare!
I added a pair of 0.001 uF @ 1500 volts from each side of the line to
ground. I haven't done it yet (ran outta HV caps) but there should be one
across the line as well. You can easily do this where the 4-conductor ribbon
enters the supply by putting a ground lug under a nearby screw.
I also added a 0.001 uF cap from the red DC output line to ground, putting a
lug under the phono plug strip for the ground connection.
I also noticed that the fuse holder (yes, the fuse holder)on the circuit
board in the emitter-output section of the pass transistor-follower board
seemed flakey. There may have been a tad of surface corrosion on the snap
contacts. I cleaned those and added some Stabilant-22 conductive polymer
solution to it and replaced the 20-A fuse. That seemed to help keep the
supply from occasionally shutting down.
Perhaps there was some low level rectification going on at the "diode"
formed by the corrosion. Don't know. But I'm keeping my eye on that.
BTW: I worked for many years as a bench technician at a Heathkit store
during its heyday, and I've seen a lot of weird things happen. Luckily, most
can be fixed. Be patient--and keep smiling while you struggle. I know these
comments may not be perfectly applicable for you, but I thought I'd pass 'em
along anyway.
Vy 73, AI2Q, Alex in Kennebunk, Maine .-.-.
> -----Original Message-----
> From: owner-tentec@contesting.com [mailto:owner-tentec@contesting.com]On
> Behalf Of N1EU
> Sent: Thursday, May 27, 1999 8:12 AM
> To: tentec@contesting.com
> Subject: [TenTec] Still Plagued by RF - Omni/Centurion
>
>
>
> About two weeks ago I solicited help with distorted
> audio being caused by RF getting into my Omni 6. I
> added gobs of ferrite and shored up the ground
> connections, grounded the 961 & disconnected its
> speaker, grounded the dummy load, etc., etc. Thought
> I had it licked, but I checked yesterday on a second
> received and I'm still plagued by the distortion on 17
> and 10 meters when I run over a few hundred watts,
> even into only a dummy load. Plugging a serial data
> cable into the Omni seems to make it worse, even
> without the cable connected to anything else & loaded
> with ferrite. This makes me think the cable is acting
> like an antenna picking up RF that's rampant in the
> shack and exacerbating the problem. The main ground
> connection in the shack is about a 10 foot run of 1
> inch braid to an 8 foot ground rod.
>
> I had a glimmer of suspicion about the Centurion's
> power cable, which essentially runs the length of the
> house unimpeded. Any thoughts on whether that might
> be the culprit & is it worth loading the amp's power
> cable up with ferrite or ???
>
> All help appreciated.
> 73,
> Barry N1EU
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