This board is a lower-cost alternative to the DMK URI and RB RIM.
It is built with mostly through-hole components to allow for customization, repair, or modification by the common technician.
It is used with AllStar distributions like ACID, DIAL, XIPAR, etc. for interfacing to a repeater controller, radio, or repeater.
This product uses the C-Media CM119A.
Comes complete with all components - kit, or assembled and tested.
This product is currently only available in the United States.
Why reinvent the wheel, you might ask? Well, here's why.
The RA-35 has several advantages over other radio adapter offerings, so I'll explain the things which are different.
Audio Input (from discriminator or wherever):
Some radio adapters have two audio inputs - one AC-coupled and one DC-coupled. The DC-coupled input isn't very compatible with radio interfacing - I'm not sure why they went to the effort of bringing it to a pin. The AC-coupled input has a fixed attenuation of approximately 85%, and while it's good for radios with lots of audio like the M2 and MICOR, many other radios won't interface well. This may require you to use the DC-coupled input, providing your own coupling capacitor and some amount of attenuation by soldering up a fixed resistor divider.
The RA-35 has only one audio input, and it includes a coupling capacitor, eliminating the need to install one externally. The RA-35 has a potentiometer audio input attenuator, allowing for the finest adjustment of input audio level. There are two software selections for audio input gain (with the RXBOOST setting). As such, the RA-35 provides for the widest range of receiver levels. The goal was to be compatible with just about any instance out there, where the amount of audio feeding the CM119 is concerned. Since audio levels are 'calibrated' when doing a "Radio Tune" the user has the ability to optimize the audio input level assuring the best signal to noise ratio and the lowest distortion. As little as 20 mV P-P can be used with a setting of rxboost=1, and as much as 20 volts P-P with a setting of rxboost=0. If your discriminator level is adjustable or the level can be programmed, we recommend around 2.0 volts P-P and a rxboost=0 setting for very good signal-to-noise ratio and low cabling cross talk.
Audio Outputs (to transmitter):
Some radio adapters have a limited amount of audio available for the transmitter, and only provide one optional amplifier with limited output capability.
The RA-35 has two robust audio outputs - left and right (or main and aux or voice and tone). There are two possible maximum output level selections in hardware, determined by JU2. The low selection provides about 4 V P-P and the high about 12 V P-P, depending on the voltage present at DB9 - pin 9. The objective of this design is to have enough audio to drive an FM modulator directly. We wanted to eliminate the necessity of an audio amplifier after the RA-35 to drive the transmitter. The RA-35 has large coupling capacitors providing plenty of audio with the ability to drive a low impedance - even a speaker. Of course, the amount of audio that is available is also dependent on the software setting of TXBOOST and if pre-emphasis is required or not. This ultimately provides four basic audio output levels, which are fine-tuned by the settings in the "Radio Tune" menu. This allows the user to choose the right amount of audio to feed their transmitter, insuring the best signal-to-noise ratio and the least amount of distortion. The RA-35 is directly compatible with the Yaesu System Fusion repeater**.
Audio Output Filtering:
If you are feeding the MIC input of your radio, this optional filter is not required.
The RA-35 incorporates two 4-pin headers (H1 and H2) which can be simply jumpered to allow unfiltered audio to go to each of the buffer amplifiers. The jumper can be removed allowing for the installation of an optional low pass filter. The FL-10 filter option provides five poles of audio filtering. The filter can be added to one or both audio outputs if desired. These filters serve two purposes:
1, To smooth the waveform.
2, Prevent ultrasonic content from modulating the transmitter.
Two filter cut-off frequency options are available - 4kHz and 15kHz. For digital applications, it was decided to move the filter's corner frequency (cut-off) way out so roll-off inside the desired audio band-pass couldn't happen. High-performance audio amplifiers were selected and absolute flat audio response of the filtering and buffering is from a few cycles to about 5 kHz; it's only 0.5 dB down at 10 kHz and the 3 dB down point is approximately 14 kHz. These filters are only required for certain applications. The FL-10 is also available in a 4 kHz version. This version is for analog voice applications where no filters already exist in your transmitter.
**These features make the RA-35 usable in DMR, D-STAR, and FreeStar* applications**.
** Are references to features or capabilities which are currently in beta testing.
Since the CM119 IC has logic inputs which are internally pulled up, changing their logic states requires a pull-down to ground. This was originally done by mechanical switches in a FOB, but must now be done with transistors or whatever logic is available from the radio. Protection diodes on these inputs help to complicate the situation because they have a voltage drop. The hardware inputs of the CM119 require the voltage to drop to about 1V or less to become valid. While Schottky diodes keep this to a minimum (because their voltage drop is about 2/3 that of a silicon diode), you still need a solid pull-down to ground logic signal for a valid COS or CTCSS logic state. Logic inputs are only necessary for simple USB setups. Using the full DSP capabilities of the application (USBradio) eliminates the need for COS and CTCSS logic, as the application figures out the noise squelch and CTCSS detection from the receiver's discriminator audio.
General Purpose Inputs and Outputs:
GPIO buffer circuitry takes up a lot of real estate. Since space is limited in a small package like this, there just isn't enough room to buffer everything - especially with all of the additional circuitry for the improvements we've incorporated. Since you cannot really drive anything directly from a GPIO pin, and other interfacing circuitry would be required to use these pins, we decided to skip any additional buffering. The GPIO pins are brought out to small circular solder pads for connection as you see fit.
When the CM119 is happy, and Asterisk is running, you will see the HeartBeat status LED (HB) flashing. The RA-35 has additional circuitry that monitors the heartbeat of the CM119, and in turn this circuitry determines the overall health of the system. If everything is okay, (HB LED is flashing) an LED called "COMM OK" illuminates. If the HB LED stops flashing because the RA-35 or the computer/appliance has failed, or Asterisk has stopped or crashed, the COMM OK LED goes out.
This health status can be used for two purposes:
First, the logic developed (user-selectable, none, high or low - with header jumper JU1) can enable a secondary control method. Some repeaters only require one logic lead change to enable internal controls. Some repeaters already have such a control revert option. The RA-35 can feed such a control line directly - enabling internal controls if there's a problem.
Secondly, and possibly more importantly, the PTT line is interrupted with this health status. This function will kill the PTT line if the RA-35, computer, or application has stopped. No more emergent trips to the repeater site to kill a transmitter which has stuck on. This circuitry has been designed to operate correctly no matter if the heartbeat has stuck in the on or off state.
There are three differently colored LEDs for status:
Push To Talk (PTT - Red)
HeartBeat (HB - Green)
COMMunications OKay (COMM OK - Blue)
About the inputs and outputs:
There are only four necessary connections for input: buffered discriminator audio, TX audio, power, and ground.
The logic inputs for PL and COS are diode protected.
|Compatible with AllStar, DMR**, D-STAR**, and FreeStar** applications.|
|USB "B" computer connection - cable not supplied.|
|No case is provided, nor is one specified for this product.|
|DB9 female radio connection.|
|Easy to set potentiometer for receiver audio calibration.|
|All conventional ICs have sockets for easy replacement.|
|Comes with EEPROM for saving radio tuning configuration.|
|Optional audio filtering available with installation of FL-10 filter boards.|
|Audio amplifiers and optional FL-10 filters can be run from internal 5VDC, or externally if more audio is required.|
|Best radio adapter for the Kenwood TKR-750/850 repeaters. Click for suggested settings and programming example.|
|Three status LEDs that can be remotely mounted.|
|HeartBeat monitoring provides a way to revert to internal control should something fail.|
|HeartBeat monitoring also prevents stuck PTT should something fail.|
|Complete kit comes with all of the required thru-hole components, for easier construction, repair and modification
by the common technician.
The kit is now supplied with the surface-mount 48 pin IC, and the surface-mount 8 pin EEPROM IC preinstalled.
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Custom cables available from URI Cables. They will
build a custom cable for the RA-35 for many radios.
Here's one of Marshall's cables connecting the RA-35 to a Yaesu DR-1X repeater.
Email Kevin Custer for ordering information, ordering by check, and/or quantity pricing of this exciting product.
Product of Masters Communications, all rights reserved.
Specifications may change without notice.
Images are property of Kevin Custer - W3KKC
Board layout by Kevin Custer - W3KKC
HTML November 23, 2016, W3KKC All Rights Reserved!