Custom Products from Masters Communications
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Custom Products from Masters Communications |
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Looking for radio adapters for digital applications? See our DRA Series.
Why reinvent the wheel, you might ask? Well, here's why.
The RA Series USB Radio Adapters have several advantages over other radio adapter offerings, so I'll explain
the things which are different.
Quartz Crystal Stability:
All RA Series radio adapters include a 12 MHz quartz crystal for optimum temperature and operating stability.
Genuine C-Media CM119A:
All RA Series radio adapters include a geniune CM119A chipset for best AllStar Link performance.
Audio Input (from receiver):
Some radio adapters have audio inputs that have fixed attenuation values and may require additional
components (coupling capacitors and attenuation resistors) to properly connect them to your radio.
All RA Series radio adapters include large quality coupling capacitors, eliminating the need to install any externally. They all have a potentiometer audio input attenuator, allowing for the finest adjustment of input audio level. As such, the RA Series provides for the widest range of receiver levels. The goal was to be compatible with just about any radio or situation out there, where the amount of audio feeding the CM119A 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 receive audio 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.
Transmitter Audio Outputs:
The RA-25, RA-30, and RA-33 are like most radio adapters on the market today; they have
no additional amplification of the TX audio paths. These adapters are fine for
installations where audio is fed into the MIC input, DATA input, or where lower
level audio is sufficient.
Transmitter Audio Amplification :
The RA-35, RA-40, RA-42, and RA-DR1X come standard with two audio amplifiers on board. This
provides two increased 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 12V 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, or any load - even a speaker.
We wanted to eliminate the need of building and installing external
audio amplification between the radio adapter and transmitter.
Manual Transmitter Audio Level Control :
The AllStar Link software allows control of the transmit audio level by settings in the software.
Additionally, all RA Series radio adapters (except the RA-25 and RA-35) have trimmer potentiometers
for fine adjustment. The controls are not totally necessary, but were included on
the rest of the models as a matter of convenience, or for use with applications that don't include
software alignment.
Audio Coupling (to transmitter):
All RA series radio adapters have large coupling
capacitors providing plenty of audio with the ability to drive a low impedance. In the case of the
RA-35, RA-40, RA-42, and RA-DR1X - 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, RA-40, RA-42, and RA-DR1X are all directly compatible with the
Yaesu System Fusion repeaters.
Audio Output Filtering:
If you are feeding the MIC input of your radio, this optional filter is not required.
All RA Series radio adapters (except the RA-25 and RA-38) incorporate two 4-pin headers (H1 and H2)
which are simply jumpered to allow unfiltered audio to go to each of the buffer amplifiers.
As an option, the jumper can be removed allowing
for the installation of optional low pass filtering. 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, To 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 and excessive group delay inside
the desired audio band-pass couldn't happen. High-performance operational 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.
The FL-10 is available in a 4 kHz version for analog voice (or data) applications.
These filters are only required for certain applications where it may not already exist in your
transmitter.
Logic Inputs:
All RA Series radio adapters use the CM119A IC. It 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 CM119A 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 or detector audio.
General Purpose Inputs and Outputs (GPIO):
All RA Series radio adapters include GPIO support. 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.
TX CTCSS support of the RA-30, RA-33 and RA-42 enables a external CTCSS encoder. This hardware function makes it possible to "gate" or "toggle" CTCSS encode from a NPN open collector logic output on the DB9. This output can also be used generically to control anything by toggling GPIO4 or, by default - GPIO8 in the software. TX CTCSS is a feature of HamVoIP and more about this feature can be seen from the RA-42 page. The RA-42 has a fourth yellow LED for indicating the status of this function. The RA-30 and RA-33 only have the added transistor logic - no yellow LED.
Receiver COS Status is indicated by illuminating the Yellow LED on a RA-38 or RA-42. COS is an indication of when the receiver is hearing a valid signal. On the RA-42 - this function is mutually exclusive with the TXCTCSS function above. Only one of these functions can be utilized at a time. Which one is selected by the exact configuration. This option will work on the RA-30 and RA-33 by adding a LED or other indicator externally.
Heartbeat Monitor:
All RA Series radio adapters include a Heartbeat Monitor. When the CM119A is happy, and Asterisk is
running, you will see the HeartBeat status LED (HB) flashing. If everything
is okay, (HB LED is flashing) a Blue LED called "COMM OK" illuminates. If the HB LED stops
flashing because the radio adapter or the computer/appliance has failed, or Asterisk has stopped
or crashed, the Blue COMM OK LED goes out. The Blue LED indicates the health status
of the system, and illuminates when everything is okay.
This health status is used for two purposes:
First and most important, the PTT line is interrupted with this health
status. This function will kill the PTT line if someting has gone wrong.
No more inconvenient trips to the repeater site to kill a stuck transmitter.
This circuitry was designed to operate correctly no matter if the Heartbeat
has stuck in the on or off state.
Second, 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. All radio adapters except the RA-25 can feed such a control line directly - enabling internal controls if there's a problem.
Status LEDs:
There are three differently colored LEDs for status:
Board Dimensions:
All RA Series radio adapters have simple rectangular circuit board dimensions of 1.8 X 3.8 inches (1-13/16" X 3-13/16").
Note this is just the dimensions of the board only. The tallest components are the large output coupling
capacitors which stand a little less than .625 inches (5/8") tall including the thickness of the board. The dimensions
for the finished product, including the additional length of the connectors, are 1.8 X 4.5 inches
(1-13/16" X 4-1/2"), and the height remains unchanged. The mounting holes are separated by 1.56 inches
(1-9/16") on the short sides and 3.56 inches (3-9/16") on the long sides, and are a simple rectangle.
Other Options:
The FL-10 low-pass filter can be added optionally to the
RA-30, RA-33, RA-35, RA-40, RA-42, and RA-DR1X to allow connection directly to a FM modulator.
Metal and Plastic Cases for the RA Series:
Metal-SC Case Extruded blue or black
anodized aluminum case for Standard and Custom RA's.
All Metal - Secure Construction - Totally Shielded. Very nice looking - Now available
in Electric Blue! and Midnight Black.
Plastic RA/DRA-Case A nice plastic case for the
RA or DRA Series radio adapters. Available in several colors.
Click here for detailed features list and adapter comparison.
Custom cables available from URI Cables. They can build a custom cable for the RA Series radio adapters for many radios.
Third Party Compatible Projects:
MABEL is an interface and software that allows analog control of the Yaesu DR-1X repeater and access
to the AllStar VOIP network with the Raspberry Pi3 and AllStar Asterisk. (Offsite Link)
Email Kevin Custer for ordering information, ordering by check, and/or support of these exciting products.
Products of Masters Communications, all rights reserved.
Specifications may change without notice.
Images are property of Kevin Custer - W3KKC
Board layouts by Kevin Custer - W3KKC
HTML June, 1, 2018, W3KKC All Rights Reserved!