Cellphone FM radio chips

[w9wi]

I know I've expressed considerable doubt about the utility of radio chips in cellphones; so have other writers.

I hereby apologize...

We were issued new company cellphones (HTC Evo) a couple of weeks ago. They contain radio chips. I feared they would be uselessly insensitive -- they aren't.

Listening in a suburb 15 miles northwest of Milwaukee, I receive all the local stations. Plus, a variety of Western Michigan signals, including Class A 92.7. (meaning selectivity is pretty good too, as there's a local on 92.5!) Michigan is about 100 miles away, across the lake.

Just turned it on here in Athens, Alabama -- and am receiving 106.9 from Jackson, Tenn., at least 100 miles away.

A few interesting characteristics:
- You MUST plug in earphones. The FM radio app will refuse to launch without them. (the earphone cord is the antenna -- and the app will tell you that) You can however route the audio to the speaker.
- It supports RDS. Kinda. The RDS decoder doesn't seem very sensitive. (stations known to run RDS may be coming in full quieting, but the RDS doesn't display.) Also, it only displays one word of scrolling PS displays. So I see entries like "Milwauke" (apparently the other e didn't fit) (95.7 WRIT), "I'm" (107.3, presumably the West Michigan ESPN station), and "The". (93.3 WLDB)
- You can scan for stations and store the results in a list of presets. Stations can be manually added to the list. Manually added stations can be manually named -- automatically added stations are named by RDS. (which again means you can get rather useless names) I don't see a way to *remove* stations from the list.
- You can switch to mono. This is an audio mix, not a disabling of the stereo decoder -- switching to mono does NOT improve a noisy signal.
- Audio quality is decent. It seems a bit low on bass -- but that seems to be characteristic of the phone itself (or my earphones) as a MP3 of known quality has the same problem.
- You can't directly input a frequency. You can, however, tune manually in 100KHz steps, or scan for the next signal. It stops on weak signals.
- No, it doesn't do AM. Nor HD.
- Haven't run it long enough to evaluate its effect on battery life.
- Unfortunately there's no way to record radio to the SD card.

All said, this is a pretty decent receiver. I won't be bothering to take a "real" radio on vacation for bandscans & DXing anymore...

 

[fugazi]

Used some of them too!

But for reporters with 3 Watt VHF transmitters on their back it's a pain in the *ss. Mobile FM radio phone receivers have big problems in strong RF fields.
They are pretty straight forward and in most cases very insensitive -80dBm for 0dB SNR ( Nokia, HTC ).
Solved it by enclosing the receiver and using a low pass filter on the receiver side. ( ps. the phone was not enclosed, but an old sony walkman with fm receiver ).

BR

 

[w9wi]

But for reporters with 3 Watt VHF transmitters on their back it's a pain in the *ss. Mobile FM radio phone receivers have big problems in strong RF fields.
They are pretty straight forward and in most cases very insensitive -80dBm for 0dB SNR ( Nokia, HTC ).
Solved it by enclosing the receiver and using a low pass filter on the receiver side. ( ps. the phone was not enclosed, but an old sony walkman with fm receiver ).

Interesting. Haven't tried it in a strong field. Would not be surprised.

My impression is this thing is plenty sensitive. Both in Wisconsin & in Alabama it was rivaling my car radio for "pulling power".

BTW I received a PM noting that mixing the audio to mono is indistinguishable from disabling the stereo decoder, in terms of eliminating noise from a weak signal. Mixing to mono would cause any noise brought in on the L-R channel to cancel out. So I can't explain why switching to mono doesn't reduce noise.

 

[Doctor_Technical]

Is it possible that "mono" is just single-channel L or R routed to both channels?

 

[Kmagrill]

BTW I received a PM noting that mixing the audio to mono is indistinguishable from disabling the stereo decoder, in terms of eliminating noise from a weak signal. Mixing to mono would cause any noise brought in on the L-R channel to cancel out. So I can't explain why switching to mono doesn't reduce noise.

The Sony XDR-F1HD table radio has the same SNR in analog mono as it does in stereo, too. These new software defined tuners are really amazing. I put the Sony up against my trusty Pioneer and the Sony blew the Pioneer out of the water, mono or stereo. From what I have read, the trick is in the DSP processing. Basically, because the DSP is able to subtract the noise componant out of the stereo signal thus rendering the same SNR for mono and stereo. Possibly, yours is doing the same thing.