Bob in Colorado has a UHF repeater has been operating on 447.725 MHz here in Monument for a couple of decades now. It started out as a classic “pet repeater” project and has been operating from my basement all this time. Over time it has picked up additional users and has turned into the de facto hangout for our local radio club.
The repeater system has gone through a number of revisions over the years, including the RF transmitter and receiver. I wanted to retire the pair of Motorola Mitrek mobile radios I have been using when they started to exhibit a few lose connections. Really though, I thought it was time for some synthesized, modern RF gear in a compact package.
When Yaesu offered an attractive price on their DR-1X Fusion repeater,
I jumped at the chance. Initially, I put it on the air in mixed analog-digital mode with the repeater automatically switching modes to handle either analog FM or C4FM digital. I used the internal controller of the DR-1X which is quite simple and has limited functionality. (The SCOM 7K controller got put on the shelf for a while.) The DR-1X supports using an external controller but implementing the mixed analog-digital mode is…well…challenging. (Various people have figured out ways to do it with modifications to the DR-1X or using additional hardware.) After 10 months of operation, I decided to reinstall the full-featured SCOM 7K controller, enabling quite a few features including a 2m remote base, synthesized speech, automatic scheduling and weather alerts. This does mean giving up the C4FM mode but usage was minimal anyway.
The SCOM 7K repeater controller has been in service for decades, handling multiple receivers and transmitters, very configurable with programmable macros. SCOM has long since moved on to a newer, improved model but my 7K just keeps on ticking. The 7K has the voice synthesis and autopatch options installed, so, yes the repeater has an auto-patch (not that anyone cares). A Yaesu FT-7800R is used as a 2m remote base and the duplexer is a classic Decibel Products. Not shown in the photo is a Bearcat WX100 weather receiver that is used to transmit weather information when an alert occurs in our area.
I’ve documented the wiring diagram and configuration used here:
Overview of the Repeater:
This is a conventional UHF FM repeater with a few added capabilities:
2m transceiver interfaced to the repeater for use as a remote base.
Telephone autopatch, voice synthesis (controller options)
Weather Radio alert
Output frequency: 447.725 MHz
Input frequency: 442.725 MHz
Yaesu DR-1X Repeater
Decibel Products 4-can Duplexer
SCOM 7K Repeater Controller
Yaesu FT-7800R Transceiver (dualband but only used on 2 meters)
Bearcat WX100 Weather Radio
SCOM 7K Controller
The 7K controller is an awesome design with lots of programming flexibility. SCOM has replaced the 7K
with a newer model but I’ve been using this one for about two decades. Interfacing to the 7K is easy
with the usual inputs and outputs. It is highly configurable and I won’t try to describe the programming
details here. Send me an email if you want to know more.
DR-1X Interfacing and Configuration
The internal controller in the DR-1X is very simple with a limited feature set. Yaesu also provided an
external port (DB-15 connector) for control using an external controller. Unfortunately, they did not
implement a robust design so even this interface is limited. Most notably, there is no easy way to run
mixed analog FM and C4FM digital when using an external controller. Various people have implemented
workarounds to support this but I’ve decided to just implement analog FM.
Most of the connections between the 7K and the DR-1X are pretty obvious, so I will focus on the unique
situations (see Connection Diagram). The DR-1X connects to the TX1/RX1 port on the SCOM 7K. The DR-
1X pin 1 must be connected to ground to enable external control.
The DR-1X is programmed from the front panel for FM mode, input/output frequency, power level, etc.
The manual says to put the DR-1X into “Remote” mode from the front panel but I did not find that it
made a difference. EXT Port 1 and EXT Port 2 (Pins 11 and 12) determine the repeat mode used. FM in
and FM out requires a Low on Port 1 and High on Port 2. The inputs apparently float high, so I just
grounded Port 1 and left Port 2 open.
I normally run CTCSS on both the receiver and transmitter. The DR-1X allows the internal Tone Decoder
to be used with an external controller, so I set the CTCSS tone via the front panel. The DR-1X does NOT
let you use the internal tone encoder for transmit. I supplied an external tone to Pin 6 on the DR-1X. To
accomplish this, I installed a Communication Specialists TS-32 module inside the SCOM 7K. The tone
comes out of the 7K on J2-24.
Note that the handy front panel speaker on the DR-1X is disabled when using an external controller.
Be sure to run the DR-1X at mid power setting (20W) for repeater operation. The full power setting is
not warranted at full duty cycle.
FT-7800R Interfacing and Configuration
The FT-7800R is connected to the TX2/RX2 port on the SCOM 7K. I’ve used the “packet port” on the FT-
7800 for repeater interfacing before and it works pretty well. No hacking into the radio as the required
signals are present on the back panel. The radio is controlled using its front panel. See connection
Bearcat WX100 Interfacing and Configuration
The WX100 is a consumer grade weather radio that has a digital output that triggers when a weather
alert occurs for the designated area. The WX100 is connected to the control receiver port (RX3) on the
SCOM 7K. The digital control line from the WX100 drives the COS input. A few macros in the 7K handle
the routing from RX3 to the repeater transmitter to play the weather radio audio for a specified period
of time (about a minute or so).
SCOM 7K Pin Yaesu DR-1X Pin Comment
RX1 Audio J2-1 AF OUT 9 De-emphasized receiver audio
RX1 COR J2-2 SQL DET 4 Noise squelch (Low = Squelch open)
RX1 CTCSS Decoder J2-5 CTCSS/DCS 3 CTCSS decode (Low = Decoded)
TX1 PTT J2-10 PTT 2 PTT (Low = transmit)
TX1 Audio J2-14 AF IN 7 Transmit audio
CTCSS Output J2-24 Tone In 6 CTCSS input for transmit
Ground J2-21 GND 5 Ground
Ground J2-22 GND 5
Remote 1 Connect to ground
EXT Port 1 11 Set for FM/FM operation – tie to
EXT Port 2 12 Set for FM/FM operation – let float
Power VCC 15 Power connector on 7K
Ground GND 10 Power connector on 7K
Yaesu FT-7800R Pin
RX2 COR J2-3 PKS (SQL) 6 Receiver squelch
RX2 Audio J2-8 RX1200 5 Receiver audio
TX2 PTT J2-11 PTT 3 PTT
TX2 Audio J2-15 PKD (DATA IN) 1 Transmit audio
Ground J2-19 GND 2
Bearcat WX100 Pin
RX3 COR J2-4 Control line
GND J2-22 Ground
RX3 Audio J2-25 Audio output
Communication Specialists TS-32 Tone Encoder was installed inside the SCOM 7K.
Output of encoder is connected to J2-23 (at R68). Encode tone is brought out via J2-24
This was a good opportunity to clean up some of the cabling and physical mounting that had degraded over time. (A kluge here, a kluge there and entropy takes over.) I am happy with the result.
73, Bob K0NR
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