The spectrum scans below show a
comparison of IBOC mode signals received using antennas with different
amounts of gain. The rapid drop off of the sideband, digital
signals, compared to the central, analog signal, suggests the ability
to
receive and decode a usable High Definition radio signal may be
considerably less than the usable range of the analog signal. These
spectrum scans were created using a Ten-Tec RX320D receiver.
A sample MP3 file is included below as an audible
reference for those
who have not heard the effect of the digital sidebands on adjacent
channel audio.
The Status page of this web site
depicts the latest status of IBOC mode broadcasting by the southeast
Florida AM stations equipped to do so.
Composite
Spectrum Scans
WWNN 1470 Pompano Beach
WQAM 560 Miami
[See the Status Log for distance and
signal strength information on these stations.]
There are three antennas presented in these composite spectrum
scans. In the IBOC digital sidebands, the three signal levels are
obvious. In the central analog signal the two higher performing
antennas coincide, while the third no gain antenna is apparent as the
weakest signal.
In all three configurations, with both stations, in analog mode the
signals are received strong and clear. There was no IBOC capable
receiver available with which to judge HD radio reception performance.
Antennas Compared in Spectrum Scans
Antenna
Model
Type
Relative
Gain
High gain
LF Engineering M-601
AM BCB active
vertical
E Field Sensitivity:
-12 dB
Medium gain
LF Engineering H-800
LW/MW/SW active
vertical
E Field Sensitivity:
-24 dB
No gain
RX-320D Rod
Vertical telescoping
rod: 21.5"
Zero
To recognize IBOC when you hear it, this WSBR
740 IBOC sample MP3 file (155 kB) steps through the following
sequence:
740 AM - USB - LSB - 740
AM
730 AM - USB - LSB - USB - LSB - 730 AM
740AM
750 AM - USB - LSB - USB - LSB- 750 AM
740 AM
On 740 in sideband mode, a churning sound can be heard under the
audio. The rushing hiss is easily evident -- dominant in fact --
in AM and U/LSB modes on the adjacent channels.
