[BC] Weekend Drive - HD Radio Observations

[Kirk Harnack]

Group:

After sitting on my workbench for over a year, I finally installed my 
Kenwood Excelon 979 head end and a Kenwood HD Radio receiver into my '99 
Toyota 4Runner.  (I also installed an ICOM 2710 dual-band transceiver 
right under it in the 4Runner's doublie-DIN radio hole.)

Driving from Nashville through Memphis and back this weekend, here are 
some thoughts...

The analog AM reception is actually quite good.  Sensitivity is great.  
Audio bandwidth is no worse than most AM radios. I was hearing analog 
AMs during the day that I didn't hear or notice with the factory radio.  
In Nashville, WLAC(AM) is HD.  The Kenwood locked onto it fairly well, 
although it seems the HD signal has to be rather strong to stay locked.  
Just 30 miles west of Nashville, the radio was switching quite a lot 
from HD to AM on WLAC.  On a subjective listening basis, I'd like for 
WLAC to turn down the high-end a bit on the HD side for two reasons.  
One, the AM/HD/AM transitions would be less abrupt, and two, the codec 
would work better with less HF audio energy.  I *do* wish I could 
program the Kenwood to exhibit more hysteresis in its decision to switch 
back and forth.  In marginal areas it was switching AM/HD/AM quite a 
lot.  One other weirdness - the temporal sync on WLAC was quite good, 
until Sunday late afternoon.  About 4:15pm CST, there became a 3 or 4 
second delay in the HD reception compared to the analog.  Perhaps the 
station's delay switching and the HD shutoff (for night) are operated 
separately and are out of sync?

The other AM HD station I listened to was WREC(AM) in Memphis.  It's 5 
kW DA-N.  I was never close to WREC's transmitter site, but even when I 
was about 7 miles away in open terrain, my Kenwood switched AM/HD/AM 
quite a bit while driving.  If I stopped the car, it would lock onto HD 
just fine.  I thought WREC's HD audio processing was better than WLAC's 
- fewer artifacts in the codec.  (I'd like to try the new Omnia 
Multicast on WLAC soon to analyze the reduction in voice coding artifacts.)

The FM side of things was considerably better.  In Nashville, I listened 
extensively to WPLN-FM (public station) which is now transmitting HD1 
and HD2.  Under typical driving conditions, with road noise and 
multipath in the analog, I think the HD1 and HD2 signals are a great 
improvement.  What slight coding artifacts exist are not noticable under 
typical driving conditions. The lack of multipath and other noise is 
rather disconcerting at first - in a good way.  When switching from HD1 
to HD2, the "station" change is instant (since the date buffer for 
either channel is full).  The Kenwood Excelon allows one to program a 
radio button to recall the HD2 signal; the display says "Linking" for 4 
seconds if you're switching from another station to the HD2 preset.

Another Nashville FM HD is WRNQ-FM.  Their HD1 sounds very, very good.  
It's slightly louder than the analog, too.  Conspicuous by their absense 
on WRNQ's HD1 are pre-emphasis artifacts, noise and multipath 
distortion.  It sounds great.  Fun to crank it up between classic rock 
songs and hear NO NOISE.

In Memphis, WHRK-FM (97.1) is transmitting HD.  This station sounds 
incredibly good in HD, even though the Hip Hop format is difficult for 
me to appreciate.  Temporal sync with the analog is perfect; loudness 
match is perfect; AGC texture is perfect; but when the HD1 comes on, 
those bad FM things that we've come to live with are gone. 

WHAL-FM at 95.7 also appeared to be HD, but my radio swtiched FM/HD/FM 
quite a lot with the car moving.  It's a 6 kW Class A, but I was within 
the city grade coverage contour.

FWIW, the independent car "performance" shop in Nashville that helped 
with my Kenwood installation reported they did 1 other HD installation 
in 2005.  They said the customer was not a broadcast engineer.  This 
shop does not sell Kenwood or any HD radios, but it you want 10 
subwoofers and custom speaker enclosures with 2 kW or more of 
tri-amplification, they appear to be the people to see. While I was 
there, they showed me a Cadillac Escalade with a $15,000 custom 
sound/video installation.  And, yes, they're putting plenty of TV 
screens pointed at the driver.  Sheeesh.


Kirk Harnack
Telos/Omnia/Axia