A few weeks ago when I started researching HD Radio, I found that there are few high-quality receivers. I asked Jessica Crotty of C. Crane, a high-end radio retailer, which radio they recommended. The answer was none of them. They tested many of them, and they couldn't find any that had good AM performance. The only one they liked was Sony XDR-F1HD, which is discontinued.
I had not planned to revisit HD radio again, but someone lent me a Sony XDR-F1HD, so I decided to test it to see how good HD can get. I compared it to the Insignia NS-HDRAD and an ICF-2010.
XDR-F1HD is a receiver only with line-level audio output. I does not have an amplified output for headphones or a loudspeaker. It comes with a dipole antenna for FM and a loop for AM.
Reception using the provided antennas was excellent. The FM dipole pulled in signals about as well as the whip on the Insignia NS-HDRAD. The AM loop pulled in many weak stations that I could not hear on other radios.
Connecting the XDR-F1HD to an outdoor vertical antenna did not lead to any intermodulation. Connecting this same antenna to the Sony ICF-2010 results in so much intermodulation that it’s unusable on the FM band. (Sony ICF-2010 is a great radio for HF but not so good for FM broadcast reception.)
The digital portion of broadcast signals is 20dB down from the analog carrier, so you only can expect to listen to the digital portion of strong signals. XDR-F1HD did a good job recovering digital signals. There is a lot of hysteresis in XDR-F1HD's signal strength threshold for HD reception. A strong signal is required for it to start decoding HD. From there I can drop the signal quite a bit before it switches back to analog. I never had any problem of it needlessly switching back and forth.
There is a blinking HD indicator to indicate the presence of an HD signal. On many distant AM stations at night, this indicator blinked without the radio ever switching over the HD signal. The indicator lets you know the signal is there even if it's too weak to listen to.
Some stations have multiple HD digital sub-channels with different audio fidelity. For example, my public radio station has two sub-channels with high-fidelity music and a third sub-channel for talk programing with much lower fidelity. The Insignia NS-HDRAD has the annoying problem of the volume being proportional to fidelity. So when you switch from a low-fidelity sub-channel to a high-fidelity one, you must turn the volume down or it will get very loud. The XDR-RF1HD does not exhibit this problem at all.
Under the Hood
The heatsink on the right is connected to a 3.3V linear regulator. The linear drives 1.8V linear regulators that supply power to the tuner and the baseband digital module, the two modules in cans. I would love to know if they used two linears in series to filter noise or for some other reason.
The board on the top of the enclosure (on the left side of the picture above) has no parts on it. It appears to be a stiffener.
The boards have mask and copper etch on one side only. They use jumpers for “solder-side” connections. This cannot have saved that much money. You’d think the added cost of the jumpers would outweigh savings from omitting copper and mask from one side.
If HD radio had been adopted before Internet streaming audio was popular, it might have caught on. It also would have helped if the digital subcarrier were not 20dB below the analog carrier. When I started reviewing HD Radio a few weeks ago, I thought the world needed someone to make a radio with good enough performance to be used for DXing but that also supports HD. The lower power, though, makes HD incompatible with DXing. People willing to adopt a new technology and wanting more audio programming can more easily listen to radio with an app on their phones.
If AM/FM radio is used primarily by people who are not adopting new technology, the service may disappear in the next few decades. Twenty-five years ago there were stations on shortwave packed in 5kHz intervals, and now there are only a few stations on each band. Is this the future of AM/FM radio?
- Brian Beezley does an amazing teardown and review of Sony XDR-F1HD with high-quality pictures.
- The Sony XDR-F1HD Service Manual
- A nice discussion of how adjacent channel interference from HD subcarriers is a problem for DXers