Asymod BT-HPSA V2 User manual
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Table of Contents
Section Introduction
…………………………………………………………………………………………….................3
Making the Most of your Hi-Fi Station…………………………………………………3
A Word about the AM Transmitter and Antenna…………………………..…….4
A Word about Audio Processing…………………………………………………………..5
Controllable and Adjustable………………………………………………………..……….6
Versatile Installation…………………………………………………………………………….7
Section Installation
………………………………………………………………………………………………………………8
Installing the Asymod BT-HPSA V2…………………………………………………………8
Front Panel…………………………………………………………………………………………….8
Rear Panel……………………………………………………………………………………………..9
Transceiver Connector Pin Assignment………………………………………………….9
Unpack and Inspect………………………………………………………………………………10
Check the line voltage, fuse and power cord………………………………………...10
Set the HPSA V2 in Place...........................................................................10
Power Ground.……………………………………………………………………………….…….10
Earth Ground…..……………………………………………………………………………...……10
Connect to Transceiver………………………………………………………………………….11
Connect to Audio Process Chain…………………………………………………………….11
Connect the Recording Device …………..………………………………………………….11
Connect the Headphones…………..………………………………………………………….12
Connect the Playback Device…………..…………………………………………………….12
Connect the PTT (push to talk) …………..………………………………………………….12
Connect AMP KEY…………..………………………………………………………………..…...12
Connect the AC Line Cord…………..………………………………………………………….12
Section Operation
………………………………………………………………………………………………………..………8
Set Up the Audio Process Chain……………………………………………………..………13
Set Up the Transceiver…………..……………………………………………………………….13
Set up The Asymod HPSAV2 for TX…………..…………………………………………….14
Set up the Recording Device…………..……………………………………………………...15
Set up the Asymod HPSAV2 for RX…………..……………………….…………………….15
Set up the Asymod HPSAV2 for Playback……………..…………………………………15
SSB Operation…………..…………………………………………………………………………….16
FM operation…………..……………………………………………………………………………..16
Contact and Information…………..…………………………………………………………….16
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Introduction
The Asymod BT-HPSA V2 Hi-Fi Asymmetrical AM
Modulator and Station Monitor
BLUthunder Technologies’ High Power Standalone (HPSA) V2 was designed to provide the radio
operator with important functionalities required for a Hi Fi radio station. The high power
standalone Asymod Hi-Fi Asymmetrical AM Modulator and Station Monitor provides the power,
controls and useful functions necessary, all in one compact unit. It simplifies your radio station
by reducing the amount of external wiring and components.
The Asymod HPSA V2 can help you achieve the highest possible quality in AM transmissions
comparable to AM shortwave, medium wave and long wave broadcast sound. It delivers louder,
cleaner, brighter, FM-like audio that attracts listeners.
The HPSA V2 delivers high-quality FM-like sound by transparently passing your processed audio
with no limitation. Preset roll off points can be set on board or can be user defined via the
audio process chain. Processing your audio is necessary to make up for the limitations of the
average receiver because such processing can make audible many defects ordinarily lost in the
AM noise, it is very important that the source audio be as clean as possible.
Making the Most of your Hi-Fi Station
The HPSA V2 is suitable for HF operation an all high and low level modulation solid state
transceivers. The installation procedure for low level modulation transceivers do require
more intricate details.
The HPSA V2 increases the spectral density and loudness of the transmitted signal by
providing for amplitudes in excess of +300% modulation while not exceeding the
negative peaks at -100% without the use of negative peak limiting or clipping methods
which produce squaring of the modulation envelope.
The HPSA V2 allows the operator to precisely control the peak levels to prevent
overmodulation. The Asymmetry is adjustable from 100% to 300%+ positive peak
modulation. The available headroom allows for 10 W of carrier at 250% positive peaks
(110 W PEP).
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The HPSA V2 allows the operator to compensate for the high and low frequency rolloffs
of typical AM receivers when using an equalizer to provide high and low frequency
boost to produce the required pre-emphasis that is appropriate for very narrow-band
receivers. Using a parametric low and mid frequency equalizer allow you to tailor your
air sound and rolloff to your precise requirements and desires. On board passive and
active selectable low pass filters provide preset rolloff points that can adjusted by
changing the filters’ capacitor values.
The HPSA V2 can deliver up to 300W of audio modulator power sufficient to drive a
100W+ PA. The modulator stage provides 12 volts to the transceiver RF final stage when
in other modes other than AM thus allowing the transceiver to be typically operated
from a ~1 amp supply.
The HPSA V2 is a station monitor that provides the operator functional simplicity by
providing the operator the ability to monitor, mix, record and playback the transmit and
receive audio.
LED indicators show power on, mode selected, audio peaks and TX.
The HPSA V2 is a self-powered standalone unit and operates on 100-240VAC.
A Word about the AM Transmitter and Antenna
The performance of an AM station is highly dependent upon the high-power RF sections of the
transmitter, and upon the behavior of the antenna system. The high average power and the
pre-emphasized high-frequency component of processed audio puts great demands upon the
performance of the transmitter and antenna system. While improved results can be expected
from most configuration and settings of a less sophisticated audio process chain, outstanding
results can only be achieved by a properly tuned audio process chain with the minimal
components necessary such as multiband compressor, limiter, gates, and equalizer comparable
to that of a AM broadcast audio processor.
If the antenna system, whether directional or omni-directional exhibits inadequate bandwidth
or a mismatch, often, the system will exhibit both problems simultaneously, the system will
couple RF energy into space with progressively less efficiency at higher sideband frequencies
(corresponding to higher modulation frequencies). It reflects these higher-frequency sideband
components back into the transmitter or dissipates them in the tuning networks. This not only
causes dull sound on the air which defeats the Asymod’s principal advantage which its ability to
pass a highly pre-emphasized audio signal without undesirable side effects but it also wastes
energy, causes distortion, and can shorten the life of transmitter components.
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A Word about Audio Processing
Loudness and coverage are increased by reducing the peak-to-average ratio of the audio. If
peaks are reduced, the average level can be increased within the permitted modulation limits.
The effectiveness with which this can be accomplished without introducing objectionable side
effects (like clipping distortion) is the single best measure of audio processing effectiveness.
Density is the extent to which the short-term RMS amplitude of audio envelope peaks is made
uniform (at the expense of dynamic range). Programs with large amounts of short-term
dynamic range have low density; highly compressed programs have high density. Reducing the
peak-to-average ratio of the audio increases loudness. If peaks are reduced, the average level
can be increased within the permitted modulation limits. The effectiveness with which this can
be accomplished without introducing objectionable side effects (such as pumping or
intermodulation distortion) is the single best measure of audio processing effectiveness.
Compression reduces the difference in level between the soft and loud sounds to make more
efficient use of permitted peak level limits, resulting in a subjective increase in the loudness of
soft sounds. It cannot make loud sounds seem louder. Compression reduces dynamic range
relatively slowly in a manner similar to riding the gain: Limiting and clipping, on the other hand,
reduce the short-term peak-to average ratio of the audio.
Limiting increases audio density. Increasing density can make loud sounds seem louder, but can
also result in an unattractive busier, flatter, or denser sound. It is important to be aware of the
many negative subjective side effects of excessive density when setting controls that affect the
density of the processed sound.
Clipping sharp peaks does not produce any audible side effects when done moderately.
Excessive clipping will be perceived as audible distortion.
Look-ahead limiting is limiting that prevents overshoots by examining a few milliseconds of the
unprocessed sound before it is limited. This way the limiter can anticipate peaks that are
coming up.
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Controllable and Adjustable
Gain control allows for proper audio drive from the microphone and line level input.
Modulation Level control allows for final audio control and is set in combination with
the Carrier and Asymmetry controls to achieve the level on modulation desired.
Carrier control sets the reference carrier level (dead key) to set the modulation and
asymmetry levels.
The Asymmetry control maintains the negative peaks at -100% modulation while
allowing for positive peaks of excess of 300% without pinching or clipping.
The REC MIX control allows for selecting and balancing RX and TX audio signals to the
desired levels. This provides level equalization of TX and RX audio signal for recording
and monitoring via headphones.
The TX MON switch allows to select between TX line level audio (LINE) or TX
demodulated audio (DEMOD). The audio from the LINE is a sample of the audio from
the audio chain while the audio from the DEMOD is audio sampled from the TX RF stage
of the transceiver via an AM detector/demodulator.
NOTE: The output of the AM detector / demodulator typically sounds high pitched, shrill
and strident because, unlike virtually all real AM radios, the detector / demodulator has
a flat response. Rolloff filtering can be used to adjust this audio so that it more closely
resembles that heard over a typical AM receiver.
REC LEVEL control allows to set the record output level for external recorder / playback
device.
The Phones control sets the desired level for the monitoring headphones.
The transceiver automatically controls the mode set; AM / SSB-FM
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Versatile Installation
The audio LINE IN is a transformerless unbalanced 600Ω input and accepts signals up to
+4 dBu, 1.74 VPK or 1.23 VRMS.
The PLAYBACK input accepts line level input from a playback device.
The REC output provides line level output to a recording device.
The PTT connector provides connectivity for a foot pedal or mouse push-to-talk device.
The AMP KEY connector provides keying for an amplifier and is rated at 10A 250VAC /
10A 30VDC.
The DEMOD input accepts signals up to 4 VPP from an Am demodulator / Detector RF
sampler.
The SPK input accepts speaker level signals and connects to the transceiver speaker
output.
The TX IN input accepts line level inputs from the transceiver’s microphone audio and
control stage.
The TX OUT output provides line level audio to the balanced modulator.
The Transceiver connector provides the mode selection, high power modulation signal
to the RF stage, and PTT signals to and from the transceiver.
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INSTALLATION
Installing the Asymod BT-HPSA V2
Front Panel
①POWER switch
②POWER ON indicator
③GAIN (line in) control
④MODULATION control
⑤CARRIER control
⑥ASYMMETRY control
⑦REC MIX control
⑧TX MON switch
⑨REC LEV control
⑩PHONES control
⑪PHONES jack
⑫AM mode indicator
⑬SSB/PK indicator
⑭TX indicator
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Rear Panel
①GND (ground) terminal
②PTT jack
③PLAYBACK jack
④AMP KEY jack
⑤REC jack
⑥TX IN jack
⑦DEMOD jack
⑧SPK jack
⑨TX OUT jack
⑩LINE IN jack
⑪TRANSCEIVER connector
⑫AC power connector
⑬Mains switch
⑭Fuse Holder
PIN ASSINGMENT
1. GND
2. PTT
3. 8V AM
4. GND
5. GND
6. GND
7. N.C.
8. High level modulation
9. High level modulation
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DO NOT connect power to the unit yet!
1. Unpack and Inspect.
If you note obvious physical damage, contact the carrier immediately to make a damage
claim.
2. Check the line voltage, fuse and power cord.
Install the proper 4-A-250V Slow-Blow for 115V, or 2-A-250V for 230V in the fuse holder.
3. Set the HPSA V2 in place.
Do not mount the unit over large heat-producing devices (such as a vacuum-tube power
amplifier) may shorten component life and is not recommended. Ambient temperature
should not exceed 45C/113F when equipment is powered. Equipment life will be
extended if the unit is mounted away from sources of vibration, such as large blowers
and is operated as cool as possible.
4. Power Ground
Make sure the HPSA V2 chassis is well grounded through the third wire in the
power cord. Proper grounding techniques never leave equipment chassis
unconnected to power / earth ground. A proper power ground is essential for
safe operation.
5. Earth Ground
Connect the GND (ground) terminal to a solid earth ground by a wide copper strap wire
which is ineffective at RF frequencies because of the wire’s self-inductance. There
should be a good ground connection between the GND terminal and earth ground.
Check this with an ohmmeter to verify that the resistance is less than 0.5Ωbetween the
HPSA V2 chassis and the ground source.
All equipment circuit grounds must be connected to each other; all equipment
chassis grounds must be connected together.
In a low RF field, cable shields should be connected at one end only —preferably
the source (output) end.
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In a high RF field, audio cable shields should be connected to a solid earth
ground at both ends to achieve best shielding against RFI.
6. Connect to Transceiver
Connect the DEMOD, SPK, TX IN and TX OUT (color to color except blue to yellow) RCA
connectors from the transceiver.
Connect the TRANSCEIVER 9 pin connector.
7. Connect to Audio Process Chain
Connect one end of a ¼” TS balanced connector to the LINE IN connector and the other
end to the output of the audio process chain.
8. Connect the Recording Device
Connect an RCA jumper cable from the REC jack to the audio input of the recording
device.
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9. Connect the Headphones
Connect a set of good quality headphones to the PHONES jack.
10. Connect the Playback Device
Connect an RCA jumper cable from the PLAYBACK jack to the audio output of the
recording device (playback device).
11. Connect the PTT (push to talk)
Connect a foot or mouse switch wired to an RCA connector to the PTT jack.
12. Connect AMP KEY
Connect one side of an RCA jumper cable to the AMP KEY jack (center tip +) and the
other to the RF amplifier’s TX / key jack.
13. Connect the AC Line Cord
Connect the AC line cord to the AC connector.
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Operation
Set Up the Audio Process Chain
Set up the audio process chain - whether computer based or rack gear. These
instructions are for a setup where a studio microphone and an audio process chain are
being used. Audio may be fed via the transceiver’s front panel microphone connector as
a last resort. For FM operation a hand microphone connected to the transceiver’s front
panel microphone connector must be used.
Set Up the Transceiver
Connect power to the transceiver.
Turn on the Asymod HPSA V2. Switch the Mains switch on the rear panel to the
ON position and turn the POWER switch on the front panel to the ON position.
Set mode to AM, the AM indicator should come on solid. Turn the TALKBACK off
and tune to the desired frequency.
Connect the dummy speaker 1/8” TS connector to the EXTERNAL SPEAKER jack.
Set the volume to 12 o’clock.
Connect the RF output of the radio to a good quality RF PEP power meter.
Connect the output of the RF PEP power meter to the RF input of an RF sampler.
Connect the output of the RF sampler to a well-tuned antenna or a 50Ω dummy
load.
Connect the SAMPLED output of the RF sampler to the input of a 30 MHz +
Oscilloscope (optional).
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Set up The Asymod HPSAV2 for TX
Turn all controls to minimum - CCW (counterclockwise position).
Key the transceiver using the PTT switch connected to the PTT connector,
whether a mouse, foot pedal or other and raise the CARRIER control while
observing the RF power meter to the desired carrier (dead key) level not to
exceed 10 W unmodulated carrier.
Once the carrier level has been set, adjust the oscilloscope’s volts-per-division /
vertical deflection to cover TWO vertical divisions as a reference to later
measure the modulation envelope.
Set a signal generator to a 1 kHz tone at 1 VPP to the LINE IN input. This can be
easily done if using PC based audio processing with a built in signal generator for
the audio process chain.
Key the transceiver and raise the MODULATION control until the negative peaks
approach -99% and the positive peaks reach +100%. At this point you should see
the peak indicator come on.
At this point the transmission is set for 100% modulation and the modulation
envelope’s vertical deflection will be covering FOUR vertical divisions at the
peaks. TWO divisions above the 0 volt line and TWO divisions below the 0 volt
line at the peaks.
To raise the modulation percentage beyond 100% modulation, slowly raise the
ASYMMETRY control while observing the modulation envelope on oscilloscope.
When the modulation envelope peaks reach THREE divisions above the 0 volt
line and THREE divisions below the 0 volt line at the peaks the modulation will be
at 200%.
To further raise the modulation percentage beyond 200% modulation, slowly
raise the ASYMMETRY control while observing the modulation envelope on
oscilloscope. When the modulation envelope peaks reach FOUR divisions above
the 0 volt line and FOUR divisions below the 0 volt line at the peaks the
modulation will be at 300%.
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Once the carrier and modulation percentage has been set, disable the signal
generator and activate the microphone via the audio process chain and speak
into the microphone at a regular distance and normal tone of voice. Adjust the
audio level output of the audio process chain to where the voice peaks on the
oscilloscope do not go beyond -99% modulation peaks and avoid pinching at the
0 volt line.
Set up the Recording Device
Power up the recording device.
Initially set the input level to mid position (do not start recording yet).
Set up the Asymod HPSAV2 for RX
Put on the headphones and set the PHONES control to 12 o’clock. Adjust as
needed for comfort.
Headphones tone control can be adjusted at the PHONES TONE control located
on the audio board. Cover must be removed.
Initially set the REC MIX control to 12 o’clock.
Set the TX MON to the LINE setting.
Speak into the microphone (do not key up the transceiver at this time) and
adjust the REC MIX control to where both the received audio signals and your
voice are at the same level.
Observe the input level of the recording device while slowly raising the REC LEV
control, continue to raise the REC LEV not to exceed 0 dB on the recording
device input level.
At this point the recording levels settings are properly adjusted.
You can now start recording. The transmit audio and received audio will be
recorded at the same level.
Set up the Asymod HPSAV2 for Playback
To play back the recorded audio, set the playback device audio output level to
minimum.
Key up the transceiver and start the playback device.
While observing the modulation envelope, slowly raise the playback device audio
output level not to go beyond -99% modulation peaks and avoid pinching at the
0 volt line.
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Playback level control should be controlled at the playback device, however, the
playback level can be internally adjusted at the PLAYBACK control located on the
audio board. Cover must be removed for access.
At this point you are ready to transmit and receive and monitor both audio signals via the
headphones. At the same time you may begin recording. To play back key the transceiver and
playback your recording.
SSB Operation
Switch mode to LSB or USB. The SSB/PK indicator should come on solid. Operate
normally as you would in AM. Adjust the audio output level from your process
chain to avoid over modulating the SSB signal. If the transceiver has been set up
for eSSB your rolloff should take place at approximately 5 kHz, otherwise 2.5
kHz. On the Stryker SR-955HPC SSB TX audio input level can be adjusted in the
transceiver at the location shown below.
FM operation
Switch mode to FM. The SSB/PK indicator should come on solid. Connect the
hand microphone to the transceiver’s front panel. Operate normally using the
hand microphone.
Asymod products are available at www.asymod.am and at www.bxc.mobi
Demo Video: https://www.youtube.com/watch?v=KsgQ1eA7fPs&t=3s
Facebook: https://www.facebook.com/asymod
“Asymod” is a registered trademark and may not be reproduced or
used by any means or in any form whatsoever.
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