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Read the latest Stereophile Magazine review.
Overview. The
Signature Upgrade is designed to breathe new life into every
DaySequerra FM Reference by addressing head-on the two major challenges
facing the 25 year-old high performance analog design:
- Limited life expectancy of its cathode-ray tube (CRT) display used for tuning and audio displays.
- Reduced signal-to-noise performance caused by HD RadioTM OFDM sideband interference, commonly called HD Radio “self-noise”.
Other
electronic components typically affected by old age, such as power
supply electrolytic capacitors and incandescent bulbs, are also replaced
with more modern solutions to extend the FM Reference’s useful life.
Click here for Owners' Comments on the FMR 25 Upgrade.
TFT to the Rescue.
To replace the decades-old CRT display, DaySequerra engineers developed
a synthesized VHDL file to configure a Xilinx Spartan 6TM Field
Programmable Gate Array (FPGA). The analog IF and audio signals are
digitized using a 64X oversampling TI Burr-Brown 24-bit, 96 KHz A-D
converter; the FPGA then processes each respectively to provide the
Tuning and Audio Vector displays. The user-selected display is output to
high contrast 480 by 272 pixel ruggedized TFT display with a fast 20 mS
response time.
The
resultant front panel display has more contrast than the original CRT
and its blue trace compliments the DaySequerra timeless industrial
design.
Another
benefit to eliminating the CRT is a substantial reduction in internal
heat and electrical noise on the ground plane caused by the original
high-voltage CRT drive circuitry.
HD Radio – Analog Radio Interference.
HD Radio was approved by the Federal Communications Commission in
October, 2002, as the only system for digital AM and FM broadcasting in
the United States. HD Radio In-Band On-Channel (IBOC) technology is
developed and licensed by iBiquity Digital Corporation, and HD Radio
broadcasts are available subscription free but require specially
designed HD Radio enabled receivers.
One
negative side-effect of HD Radio IBOC broadcasting is an increase in the
analog FM stereo noise floor caused by IBOC Orthogonal Frequency
Division Multiplex (OFDM) sidebands; this is known in the industry as HD
Radio “self-noise.” HD Radio self-noise negatively affects the
performance of almost all analog radios in the U.S.
Stop. Here’s a message from our Legal Department.
1]. The
term “HD” in HD Radio does not stand for “high definition” rather it
relates to “hybrid digital” technology used in HD Radio.
2].
DaySequerra is the leading provider of modulation monitors and
confidence monitors to AM and FM HD Radio broadcasters in the U.S.
3].
DaySequerra’s founder, David Day, speaking most recently at the National
Association of Broadcasters Show, said, “Taken as a
whole, HD Radio delivers incredible dynamic range with a vanishingly-low
noise floor. The HD Radio lossy-codec is quite good; and while not as
transparent as the best closed-circuit analog FM broadcasts, its
real-world performance and feature-rich user experience outweighs its
shortcomings, and moves broadcast radio into the internet age.”
HD Radio… continued. HD
Radio IBOC “hybrid digital” technology used today provides the analog
FM stream on the same center frequency as before but with IBOC OFDM
digital sidebands on either side of the analog broadcast.
Here is screen capture of a real-world HD Radio FM broadcast:
HD
Radio unique features include: Additional digital-only local FM
multicast channels e.g. HD2/HD3 Channels; PSD - Program Service Data,
which displays song title and artist name on the radio screen; iTunes
Tagging which allows listeners to store song information with the touch
of a button for later purchase and download through iTunes; Artist
Experience which enables images that match the audio content to be
displayed on the radio screen; and subscription-free traffic and data
information sent directly to your car’s display radio or navigation
system.
As
of April 2013, there were over 2,200 AM and FM stations broadcasting HD
Radio in the U.S, meaning there are HD Radio stations on-the-air in
every major U.S. market.
HD Radio Self-noise. As stated earlier, HD Radio self-noise and increased IBOC power provide for a lively dialog in the industry; read more here and here.
Simply put, HD Radio self-noise substantially increases the FM analog
stereo noise floor; this is caused primarily by the linear sum and
intermodulation of the FM analog FM L+R (sum) L-R (difference) signals
and IBOC OFDM sidebands. In most high-quality FM receivers, this means
more than a 40 dB increase in stereo noise floor.
In
the DaySequerra FM Reference in Wide IF Bandwidth mode this means a
substantially decreased SNR: from -75 dB to -25 dB, meaning continuous
hiss and white noise on every HD Radio FM station and on most analog FM
stations adjacent to an FM HD Radio station.
Back to Basics.
Luckily for DaySequerra, the solution to HD Radio self-noise in the
25-year old FM Reference design was fairly straightforward and has
almost no side effects: a post-FM demodulation filter designed to remove
noise energy starting at 53 KHz and above.
As
illustrated below, if the post demodulation filter removes most noise
energy above 99 KHz, there will not be any noise energy to translate
into the audio band by the FM Reference’s stereo decoder. The challenge
here, however, was to preserve the L-R response so that stereo
separation was not negatively affected while eliminating the noise above
99 KHz. DaySequerra’s engineers employed a 7th order elliptical filter to maximize the attenuation of noise outside the pass band while minimizing group delay variation.
Recently
upgraded FM Reference units have measured SNR of better than -78 dB (3
dB improvement over 25 years ago) and stereo separation of better than
50 dB – equal to pre-upgrade performance.
Other Improvements.
The FM Reference Signature Upgrade includes a few other improvements as
well: new hand-matched JFETs are installed in the IF filter amplifiers
and in the input buffer for the Class-A biased audio outputs. Also, key
electronic components typically affected by old age such as power supply
electrolytic capacitors, are replaced. All incandescent bulbs are
replaced with LED indicators.
Call 856-719-9900 or email sales@daysequerra.com to
schedule your FM Reference for the FMR 25 Signature Upgrade. Older FM
Studio units can be updated to FMR 25 Signature Upgrade.
Unfortunately, FM Reference Panalyzer and original Sequerra Model One units cannot be upgraded.
There is a one year limited warranty on each FMR 25 Signature Upgrade unit, even covering the parts that are 25-years old.
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