[Boatanchors] Johnson Matchbox 275W

[Al Parker]

Hi Larry,
	The manual I have on the 275w Matchbox makes sense to me.  Looks like 
maybe whoever put that coax connector on yours didn't know what was 
going on.  Looks to me that if you put your 300:75 ohm balun in the line 
to the rcvr antenna terminals you'd be OK, and you could substitute the 
coax connector for the terminals.
	There was no provision for switching the tuner out of the ckt, but 
maybe I don't follow your meaning there.  The transmitter should be 
disconnected by the relay when in receive.  They could make things 
clearer by showing the relay "normally", with the receive contacts 
closed when at rest.
	I don't know if my rambling helps or not, I don't remember any 
particular mods for the unit.
73,

Al, W8UT
www.boatanchors.org
www.hammarlund.info

"There is nothing -- absolutely nothing -- half so much
worth doing as simply messing about in boats"
Ratty, to Mole

On 7/27/2011 2:34 PM, telegrapher at q.com wrote:
>
> In hooking my 275W matchbox to the Viking II and back to the R-388 i'll be using with it i noticed that i could not get any signal thru it in the receive direction.  Well one thing is that the receive side is 300 ohm out to the receiver.  Hmmmm, a TV 300/75 ohm balun fixed that.  Still no signal.  Why does it have the extra coax connector on the back side.  What was it put there for?  Better pull it apart and see what is going on.

  Back to the topic at hand.  When i finally got the cover off the 
problem became pretty apparent.  On the screw terminals for the antenna 
lead to the receiver, nothing was attached to the supposed hot side. 
The coax connector that was added, apparently part of a mod goes to the 
common leaf on one side of a 3 pole relay.  Both cont
>   acts whether operated or released runs the center contact of the coax connector to ground.  Wonder what was accomplished there?

The RF input connector which goes to another side of the relay was 
totally bypassed so the tuner was in the line all the time and could not 
be switched out.  Simple jumper removal and addition here will fix this.
>
> Why or what was the purpose of the mod to add the coax connector and were there other changes included?  I've got the documentation off of Edebris or the Bama site but there is no mention of any mods.  I think i've heard from other sources that the 275W matchbox did have a coax mod done to it and i think it is for the receiver side but not sure.  Any clues from other users that have one of these?  Otherwise it appears to be a very nice clean unit.
>
> Larry
> W0OGH
> _________