NCS-3240
Multi-Switcher
& Alpha Delta
PathMINDER
Digital Coax Switch Modification
(By Frank LaFranco - W6NEK)
This modification will allow the Multi-Switcher Unit to command the PathMINDER to allow automatic switching of your antenna from one radio to another. As you press “Radio Select 1, 2, 3, or 4” on the Multi-Switcher the PathMINDER will automatically change to antenna position 1, 2, 3, or 4.
CAUTION, this modification will require drilling a hole in the back chassis of each unit as well as soldering to the wiring in each unit. As a result, your product warrantees will be VOID! If you do not feel comfortable drilling holes in commercial hardware and are not proficient wiring components breadboard style, on vector board, then DO NOT proceed with this mod.
While the instructions and circuits presented here perform the function as described, neither New Communications Solutions LLC, or Alpha Delta Communications Inc., or this author are responsible for damage to your equipment as a result of implementing this modification.
Why Do This Mod?
The NCS-3240 Multi-Switcher is designed to make interfacing multiple HF and/or VHF/UHF radios very easy. The Multi-Switcher was designed to switch multiple microphones, headsets, speaker audio outputs, CW key (or keyer) and foot (or hand-switch) PTT to as many as four radios! In addition to switching these functions between radios, you can also select up to 4 microphone/audio sources at the push of a button. Anyone running multiple radios cannot afford to be without the NCS-3240 Multi-Switcher!
So why do this
mod? No product is ever perfect for every user. As comprehensive as
the NCS-3240 Multi-Switcher is, I found myself wanting the unit to do one more
thing. In addition to switching everything above, I also wanted to
automatically switch my antenna from radio to radio. At the present time,
the Multi-Switcher does not incorporate a coax switch. However, as luck
would have it, Alpha Delta just introduced a new microprocessor controlled coax
switch called the PathMINDER Digital Coax Switch. This is a fine product
that will switch up to six coax connections. Coax selection is as simple
as pushing one of six front panel push-buttons. The PathMINDER is
intelligent in its operation. If your transmitting with a power level
greater then 50 watts and try to select another coax position (while
transmitting), the processor controlled coax switch will ignore your selection
until transmit power is removed. In addition, all non-selected coax
connections are grounded. The PathMINDER Digital Coax Switch is well
built in the tradition of Alpha Delta.
How Do We Make This Modification?
The goal is to get the PathMINDER to switch coax positions (1 through 4) whenever the operator presses one of the Multi-Switcher "Radio Select" buttons (1 through 4). To do this we will add four buffered outputs to the Multi-Switcher unit. These outputs will be driven by the control voltage used to illuminate the LED annunciators in the "Radio Select" switches. That voltage will be used to bias on a transistor switch which will provide a low impedance path to chassis ground via its collector. This switched ground will be used as a trigger signal to drive one of four NE555 mono-stable timers added to the PathMINDER. The output of these timers will simulate a 1/2 second key-press of the PathMINDER front panel selection push-buttons. This will achieve the desired result. Select a radio (1 through 4) on the Multi-Switcher and the PathMINDER will automatically switch its coax selection (1 through 4).
Below is a combined schematic/parts list of the modification. Following the schematic are photos of the mod. They are meant to act as a general guide but are not meant to be definitive. I.E. you may use different in-line connectors, prototyping vector board, mounting options, etc. Your modification need not duplicate my example photos exactly for your mod to work correctly. Just ensure that you study and follow the schematic and interface instructions. Good Luck!
Schematic
These photos are best viewed with your screen resolution set to 1024 X 768. They are formatted to fit that size screen.
NOTE: THESE PHOTOS MAY TAKE A WHILE TO LOAD. PLEASE BE PATIENT
Overview of Completed Modification
Below is a photo of the completed modification. The two units are shown with their top covers removed. You will build and install, per the schematic, a “Trigger Buffer” vector board and interface cable. Then you will build and install the “NE555 Timer” vector board and interface cable. Both units are wired together using 4 conductor + shield cable and suitable in-line male/female connectors.
Building the Trigger Buffer
Here is a closer look at the completed trigger buffer installed in the Multi-Switcher. At this point, review the details in the schematic and assemble the trigger buffer using 4 ea 2N2222A transistors on a 1" X 2" vector board. Be sure to provide pin connections for chassis ground, and four trigger outputs. The 4 conductors + shield cable will be connected to these pins. When the vector board is complete, proceed to the next photo view.
Building the Trigger Buffer Cont:
With the trigger buffer built, mount and solder it to the Multi-Switcher at the junction of the transistors and resistors called out in the schematic. To help clarify the soldering of the base leads of Q5, Q6, Q7 and Q8 see the next picture.
Building the Trigger Buffer Cont:
Once the base leads are soldered you can connect the chassis ground as well as the shield of the 4 conductor cable. Then you can connect each of the 4 trigger outputs of the 4 conductor cable. When finished, insert the cable through the hole you drilled in the rear panel of Multi-Switcher using a suitable rubber grommet for your size cable. Finish off the Multi-Switcher mod by adding a small tie wrap to the cable to act as a strain relief.
To test the trigger buffer, power up the Multi-Switcher. Connect a DVM across each of the trigger outputs and chassis ground (one at a time). Press Radio Select button #1. Radio Select #1 LED should light. The DVM should read <20 ohms between trigger #1 output and chassis ground. Press Radio Select button #1 again. Radio Select #1 LED should go off. The DVM should read > 10 Meg ohms. Now repeat the above for Radio Select buttons 2, 3 and 4. If all is correct, move on to assembly of the NE555 Timer board.
Overview of NE555 Timer Board Installed In PathMINDER Unit
Below is a photo of the completed NE555 Timer board installation. Carefully review the schematic of the Timer board. All timer circuits are identical to the schematic for Timer #4. Repeat the layout on a 1" X 5 1/4" vector board. Use the next three photos to show you the detail of component layout, trigger inputs, switched outputs and 4 conductor + shield cable connections. When the board is fully assembled, you should pre-test prior to actual installation. To test, connect the NE555 Timer board to + 13.8VDC, and Ground return. Connect a DVM across output transistor #1 collector and ground return. Connect a clip lead between Ground return and trigger input #1. The LED #1 should turn on for about 1/2 second then turn off. At the same time output transistor #1 DVM should go from OPEN to SHORT and back to OPEN (>10 Meg ohms). Remove the trigger lead and re-attach to Trigger #1. Again LED #1 should turn on for about 1/2 second then turn off. Output transistor #1 DVM should repeat the readings above. The half second conduction of Transistor #1 is what will simulate the half second key press. If everything for Timer #1 is working then repeat the same steps for Timer #2, 3, and 4. When you confirm that all four timers are working your can install the Timer board into the PathMINDER Unit.
NE555 Timer Board Installation Cont:
Position the Timer Board into the PathMINDER Unit as shown below. Connect the inputs and outputs as shown below. Connect +13.8VDC and Ground Return. When fully connected, the wiring will hold the board in position. If you feel you must secure the board to the chassis, I recommend using a small amount of two part epoxy to secure the board standoffs to the chassis. Later you can remove the board by giving the standoffs a light tap to break the epoxy free. This method will result in no additional holes in your PathMINDER Unit.
NE555 Timer Board Installation Cont:
This view is shown to give more detail on how the 4 conductor cable shield is attached to the PathMINDER Ground return. A small terminal lug was used to secure the shield and make termination. After everything is properly connected you are ready for final operational testing. Wire a suitable in-line connector to allow both units to be electrically connected together. Apply 13.8VDC to both units. Turn on the Multi-Switcher Power Switch. The unit should power up and respond normally. Press "Radio Select" switch #1. The PathMINDER should immediately switch to Coax Input #1. Now press "Radio Select" switch #2, #3, and #4. In each case the PathMINDER should switch from Coax #1 to #2, then #3, and #4. Congratulations, your modification is complete and fully operational. Now whenever you select a radio from 1 to 4 you will also select a coax input from 1 to 4. You’re now able to switch from radio to radio with the push of a single button! Thanks to the fine products from New Communications Solutions LLC, and Alpha Delta Communications Inc.
Completed Units Working Together
Modified Units Working Together
This is the radio shack at W6NEK. Changing Radios, Microphone Inputs, PTT Line, Keyer and Digital Audio sources is as easy as pushing a button! Thanks to NCS for making products a HAM operator can really use!
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