Hd concerns

Kelleher, Daniel DanKelleher@clearchannel.com
Wed Mar 23 11:32:37 EDT 2011


FM HD uses digital carriers surrounding the analog frequency. The power
of the digital signal was limited to -20 dBc or 1% of the analog power.
A 50,000 watt ERP analog FM station only has a HD power of 500 watts.
The FCC approved a FM HD power increase of 10 dB last year and stations
can now use a HD power of 10% of the analog power. But not all have made
this increase. There is some good dope about FM HD on Wikipedia
http://en.wikipedia.org/wiki/HD_Radio#FM .

That said... even with stations running 10% there can still be an issue
of getting enough rf into the HD radio so it can be decoded reliably.
This seems to be the frustration John is experiencing. The solution is
to get more signal into the radio. If possible use an outdoor antenna. A
simple S shaped omnidirectional dipole might work just fine. If not then
a yagi will give more gain but is directional. Sometimes a left over
analog TV antenna on the roof works really well. If an indoor antenna is
the only option I have had best luck with folded dipole style antennas.
Spread the legs apart and experiment with placement for best reception.
I have not had good results with "amplified" antennas. The exception to
that is TERK which makes some amplified antennas that are full size.
About 4 feet long. They are meant to be mounted outdoors and have
amplification. I imagine these would work pretty well inside too.

AM HD works differently than FM HD. But AM HD also needs enough digital
signal to work reliably. I have had poor results using the factory
supplied loop antennas. I have had good results with even a short length
of wire run outside. AM HD can still be disrupted by static or dimmer
emissions so placement of the loop or wire can be critical. AM HD has no
secondary channels, just HD1 which is a duplicate of the analog audio.

The digital nature of FM HD allows features to be added within the data
stream. itunes tagging, data such as traffic reports and extended text,
and other cross media connections are adding some unique value to this

Dan Kelleher

I am having reception problems getting some Hd 2 and 3 stations. Does
anybody have any suggestions on how I can improve fm reception with
getting Hd 2 stations? I  need help setting up the loop antenna. Do you
have any suggestions on what I could tell the person who sets up the
loop antenna.  

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