Testing HD Radio

A few months ago someone asked me where to find an HD radio.  Despite my interest in radio, I had heard of HD but knew almost nothing about it. 

When I researched it, I learned that digital broadcasting (as expected) is much more efficient, but no digital standard has been adopted to replace AM/FM broadcast radio.  “HD radio” is the digital standard the US adopted. 

HD originally stood for hybrid-digital because the signals are transmitted in parallel with the legacy analog transmissions.  HD is now just the brand name for the standard.  It has never stood for high-definition. 

High-performance radio retailer CCrane told me they have plans no to carry an HD radio.  They tried many models and could not find a single receiver that met their standards.  They said, "AM reception is abominable on all of the HD tuners we tested".  When they did carry them the return rate was two to three times the rate for other radios.  This is possibly because the subcarrier that carries HD is 20dB down from the analog carrier, so you need a strong signal to receive HD reliably. 

Testing Insignia NS-HDRAD

I tested the Insignia NS-HDRAD receiver.  It did very well.  There was no noticeable intermodulation from the strong FM stations located near the office.  It detected the HD signal from several stations in my area. 

Most stations with HD provide two channels with similar programming.  The WI Public Radio FM station in my area has three choices of digital programming on the same frequency.  Their third subchannel is dedicated to talk programming and had noticeably limited audio bandwidth.  Stations can have several subchannels, but at least one must be at least the same quality as the analog signal .

One nice feature with the Insignia radio is the AUX IN port.  I used it to listen to audio from my MP3 player.

The biggest downside to this radio is it has no AM coverage.  I looked at other HD radios, and many have no AM or analog-only AM. 

Another issue is the volume.  I had to turn up the volume near maximum to listen to the low-bandwidth digital station with talk programming.  The same was true when listening to my MP3 player (at its max volume) through the AUX port. 

Next Time

Next week I test a JVC KT-HDP1, which does support AM, and tear it down.  It becomes clear that someone needs to design a high-quality AM/FM HD Radio receiver.