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Re: [TowerTalk] More possible RCS8V problems

To: "Kelly Johnson" <>,
Subject: Re: [TowerTalk] More possible RCS8V problems
From: Jim Lux <>
Date: Mon, 04 Dec 2006 17:46:59 -0800
List-post: <>
At 04:38 PM 12/4/2006, Kelly Johnson wrote:
>I think I resolved my issue of a few weeks ago whereby the signal
>would just start dropping out and a tap on the CW key would bring it
>back to life.  It was either a relay problem OR a bad PL-259 solder
>joint.  I replaced the PL-259 and moved to another output port on my
>RCS-8V and the antenna is working again.  Now, I have a new problem.
>After sitting for an hour or two I start getting S7 or S8 noise.  This
>is similar to the signal dropping out, but this time instead of having
>the signal drop out I get S7 or S8 broadband noise.  The strange part
>is that it affects ALL the antennas this time.  I can switch from
>antenna to antenna and I see the same S7 or S8 noise, even on antenna
>inputs that have no antenna connected to them.

Interestingly, I happen to have an RCS-8V  opened up in front of me 
as I type this.

On the RCS-8V, there's a separate relay for each switch port, so 
there's really no "common" relay.

Are any of your relays strapped for grounding? (not that it would 
cause what you're describing, but it might be useful for diagnosis).

Have you looked inside your relay box?  The open frame relays MFJ 
uses can have their armature bounce out of alignment, and it will 
still work, sort of, but the contacts don't line up right.  This is a 
notorious source of a DOA RCS-8V from what I hear (one of my 4 
switches had one armature out of the socket when I got the boxes from 
UPS), but maybe if it's up on a tower and gets vibrated in the wind 
or something?

The armature is held on by the spring on top. There's two little tabs 
from the frame that hold the armature (serving as a locator), and 
what keeps it from coming off is that the NC contact set keeps it 
from moving too far.

You might look at the alignment of the armature with the fixed 
contacts.  The frame could be "carefully" bent to change the 
alignment of the armature and fixed contacts.

Is there a possibility of the coil/core getting slightly 
polarized?  The power supply/controller is nothing special: a 
mechanical switch and a half wave rectified supply.

>  A tap on the CW key
>once again fixes the problem.  This time I'm thinking it is some relay
>that is common to all of the antennas (ie. connected to the input) OR
>it is yet another bad connection but this time on the feedline that
>goes from the shack to the remote switch.  I don't understand what
>would cause this noise.  Anyone have any thoughts on this?

What size wire and how long is the run to the relay box?  Does the 
problem occur more when it's cold or warm? (warm = higher resistance 
in cable and coil, so less current to pull in the armature).  They're 
120 ohm coils, so they need a good healthy 100 mA to pull in 
reliably.  Can you put an ammeter in series with the common line to 
the remote unit, and see if all the relays have the same current?

Yes, the manual says the cable resistance can be as much as 80 ohms, 
but I'd be a bit skeptical of that.

Do you have any DC in the RF path?

>I'm just about ready to junk this remote switch.  This is the second
>one I've owned and it seems unreliable.
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