On Sat, 11 Sep 2004 18:23:12 +0000 "Rob Atkinson, K5UJ"
<k5uj@hotmail.com> writes:
> I have a pair of computer speakers in the shack that are unusable when
I transmit because they are in cheap plastic unshielded enclosures and
one cabinet contains a 10 w. ss amp to boost the sound card audio and
drive the speakers. This thing rectifies RF and goes crazy when I
transmit. I have thought about buying a small all tube guitar amp to use
in its place on the theory
> that the diode rectification prob. would go away. Does this seem like
a good idea? I've tried ferrite cores and shielding--all no gud.
> tnx
> rob/k5uj
Dear Rob,
Have you tried to deal with the RF in your shack? My station used to
"howl" when transmitting. LED's would light up, the computer would lock
up, every speaker in my house would make noises, the mike and the key
base would give me shocks and even the dummy load pilot lights would DIM
as I tuned up.
The solution:
0.01uF/1KV disks on every wire in every box.
Single-point grounding with a short run of 4/0 AWG to the surge-arrestor
ground bar outside the house.
All ground rods and the ground ring bonded together.
The neutral bare messenger going from the utility pole through the
outside meter box bonded to a 4/0 cable and
then to its own ground rod, that ground rod bonded to all the others.
HF-rated ferrite cores on many, many leads with more than one turn.
Radio Works Line Isolators on the coax in four places.
And finally,
Reducing the length of 600 ohm balanced feedline running in the shack
from 20 feet to 1 foot.
Seem like overkill?
You should have been there when I operated from a hotel room on the fifth
floor in Secaucus,
with an un-neutralized tetrode amplifier that was squirrely
(oscillations) and the night clerk
started quoting $88,888.88 for a room, and all the tv's in the hotel
started changing channels.
(Toilets flushed, the vending machines gave away soda, the washing
machines went immediately
to spin-dry, every WiFi hook up on every lap top connected to the "XXX
Fun Site," but the hotel
manager, who was another NAVY radioman, knew all, and said nothing...)
(( Years ago, in the Bronx, there was a torch-light parade when the
peasants stormed out into the streets
after a certain 6 meter, 500 watt A-M ham station wiped out TV
reception even tough the antennae had
line-of-site to the Empire State Building.))
It's only money.
Fondly,
Hal Mandel
W4HBM
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