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Author Topic: NEW JOHNSON MATCHBOX NEED HELP!  (Read 1243 times)
KB3DRF
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Posts: 11




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« on: September 01, 2001, 04:54:55 PM »

I HAVE A BRAND NEW NEVER USED(I OPENED THE ORIGINAL BOX) JOHNSON 250 VIKING MATCHBOX.HOW DO I RUN IT WITH AN ICOM 746,I THINK I HAVE TO PUT A JUMPER ON THE RELAY, BUT I DO NOT HOW TO,OR IF I EVEN HAVE TO.ANY HELP WOULD BE APPRECIATED! MATT KB3DRF E-MAIL KB3DRF@ARRL.NET
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KJ5GT
Member

Posts: 1




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« Reply #1 on: September 02, 2001, 02:02:21 AM »

Matt,
I have had two Johnson matchbox tuners (used) and both of them had the Transmit/Receive relay jammed in the transmit positon with a piece of cardboard.You will have to open the case to do this.It sounds like you don't have a manual for this piece of equipment, which seems unusual for an item new in the box, but I don't know what Johnson did in the past.Both of mine were hamfest buys.If you need a manual you can download one for free at http://bama.sbc.edu/  .You can get a nice printed version from W7FG Vintage Manuals, but not free.The manual does not have a lot of information in it, but does have basic instructions  and a schematic.Hope this helps, Al, KJ5GT.
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KA5N
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Posts: 4380




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« Reply #2 on: September 02, 2001, 04:50:44 PM »

The Matchboxes were designed for 40's 50's style radios
and operating.  They have separate connections for
the transmitter and receiver.  The transmitter connector is
low impedance (~50 ohms) and the receiver
terminals is high balanced connection (150-600 ohms).
Receivers used to(typically) have three antenna
terminals two balanced and a ground.  For unbalanced
antennas one of the balanced terminals was connected
to chassis (ground).  With a modern transceiver, you
need only the coax input for both receive and transmit.
You have to open the box and either put a jumper on
the relay or move the wire from the coax to the other
relay termainal.  You can just jam the relay but that
might result in a bad connection and possible arcing.
Arcing could damage your transceiver.
The Matchbox is best used with balanced feed line
on the bands indicated on the bandswitch.  It is
possible to use it with unbalanced, or long wire antennas,
but you will have better luck with open line
or G5RV type dipoles.   WARC bands tuning is less than
optimum.  A balanced dipole with ladder line will
operate well on several bands with easy tuning with
the Matchbox.
Allen KA5N
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KB3DRF
Member

Posts: 11




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« Reply #3 on: September 03, 2001, 06:32:35 AM »

Thank you for the info on the matchbox and manuel,there was one sheet of paper in the box(may have been opened and resealed with the same piece of tape).It says operatingf instructions Johnson Directional Coupler And Directional Coupler Indicator cat. no 250-37 and 250-38.The tuner says 250-23 on the back.it has the meters and coupler.The paper many talks about the coupler and all the measurements that can be done with the coupler,reactance,swr,inductance,radiation resistance of an unbalanced antenna,etc.Also alot of formulas.Pretty technical compared to today standards(manuels of today) 73 matt kb3drf   thank you again!!
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N9AYH
Member

Posts: 21




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« Reply #4 on: September 04, 2001, 12:32:16 PM »

Hey Matt:
Where did you find a "brand new in the box" MatchBox!Man are you fortunate. I've got 2 Kilowatt verisons and 2 250 watters. If I came across one in the box I buy it so fast.LOL. I remove the relay and resolder the link coil tap to the SO239 input connector. Make sure you also remove the 300 ohm receiver tap off the coil. It could cause problems later. Keep the relay. It makes a great open wire antenna switch. Let me know where you found your "new" tuner.
Thanks
73
Blake
N9AYH
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