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Re: [Amps] SB220 "A" mods

To: Rob Atkinson <>
Subject: Re: [Amps] SB220 "A" mods
From: "Roger (K8RI)" <>
Date: Mon, 31 Mar 2008 14:49:34 -0400
List-post: <">>
Rob Atkinson wrote:
> I'm happy for you that you can afford at least $500 for a pair of computer
> PC speakers but I think I'll handle the RF noise by turning my $10 hamfest
> speakers off when I'm on the air and save around a thousand bucks.
I don't go quite that cheap, but with a pair of active speakers on three 
of the computers in the house,  Two computers are with in 4' of my 
station including the not gold plated, old, used Alpha 76 and manual MFJ 
989C tuner.  There are two more computers in the shop with one being on 
the gigabit network tied to the ones in the house. The second one is 
stand alone.  That computer in the shop also has a TV tuner, FM radio, 
and ties to a Satellite receiver sitting "on top" of my old HT33B 
Hallicrafters  amp and right  beside an Icom 7000, 100 watt 1.8 through 
440  rig driving a  Tokyo Hy-Power HL-1.5Kfx.  The audio out, runs about 
20' to my stereo receiver with about 30' leads to each of the speakers.  
The CAT5e and the 2 RG-6 runs, run within a few feet of the coax from 
the house to the tower and the shop to the  tower.  Actually there are 3 
runs of RG-6 to the house that run IN the conduit with the LMR-600 and 
600. One only goes up the tower 20 feet to the satellite receiver while 
the other two make it all the way to the top along with the feeds to the 
Tri-bander, 7L C3i on 50 MHz, and the 144 and 440 arrays. I run the 
legal limit on 1.8 through 28 MHz from  the house , 1 KW PEP and CW 1.8 
- 144 from the shop.  (Henry 2002A on 144).  BTW the TV antennas are at 
roughly 90 feet (both with remote pre-amps) with 2-meter antennas at 40' 
(top of which is 60') and a stacked pair of vertically polarized 12L 
144's at 130 ' (soon to be 120') I also have another TV antenna on the 
West end of the shop.

I do not have any noticeable interference to any TV, house or shop (off 
the air, satellite, or cable), I do not get into any of the 
"inexpensive" active speaker systems including the stereo in the shop, 
nor do I hear a peep out of the computers or network.  BTW , the modem, 
router, and 5 port switch are within  2-3 feet of the station in the house.
I would add I have one whale of a ground system with single point ground 
near as I can.  The point of contention being the house and shop are on 
different electrical feeds but are tied into the overall ground system.  
That  and the two computers in the ham shack which tie to the station 
via serial and audio cables are on a different circuit than the station.

The only problem I've had would be a pin 1 problem on the 756 Pro.  
There is so much AC floating around in here I used to be able to key the 
rig to full output by picking up the mike. It was not RF feedback, but 
60 cycle pick up.  Merely reaching up and placing a hand on the metal 
mike connector on the rig or the metal on the Alpha would stop the 60 
cycle pickup. The confusing part was the problem was intermittent.  I 
fixed it permanently by tying  the mike cord shield to actual ground. 
Unfortunately I lost a number of functions in the mike, but fortunately 
I never used those functions from the mike anyway. <:-))

So, cheap speakers aside, a lot depends on the layout, cable routing, 
and grounding system.
> I guess with gold plated Alphas, $13,000 transceivers, $1200 watt meters,
> $500 keyer paddles nothing should surprise me anymore.
Hey, I like CW and one of those gold keyers is about my only real 
indulgence to vanity<:-)) Besides, it was only between $20 and $30 more 
than the chrome based one. (and it's easy to clean)


Roger (K8RI)
> 73
> rob / k5uj
>>> I use Studio Quality Active Monitors from Genelec... RF proof, Aluminum
>>> Enclosure, self contained with amplifiers. NOTHING gets into them!
>>> Vy 73, Cliff - W4NJ - From near The House of The Mouse - Disneyworld, 
>>> Florida
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