DRM is unlikely to replace analog AM broadcast on HF band

I learned a bit about DRM broadcasting on HF band recently. I don't think it will succeed in replacing AM shortwave broadcast.

DRM is a digital broadcast scheme. It features 16/64QAM, OFDM, xHE-AAC. A DRM station usually takes up 10kHz bandwidth in HF band. It may carrier one audio program and some auxiliary data (text, program guide, emergency warning, etc).

Analog AM is good enough for voice. DRM can provide FM radio like audio quality on shortwave band. However, most shortwave stations are operated by governments (e.g. BBC, VOA, CRI) or religious groups (e.g. FEBC). They usually have voice programs. AM's ~4kHz audio bandwidth is good enough for this use case. Another use case for shortwave radio is emergency. Analog modulation also works well for this purpose.

Complexity and cost. An analog AM receiver simply need LO, mixer, filters, envelop detector, audio amplifier. A DRM receiver must have a DSP that can demodulate OFDM, a xHE-AAC decoder, and a micro-controller. All these adds to the cost and power consumption of DRM receivers. I could not find any DRM receiver for less than 1000 CNY in China. I tried listening to DRM on SDR, the effort is not trivial. I also experimented with the CML DRM1000 module, which I do not recommend.

Lastly, mass media broadcasting itself is going downhill IMO. The mobile Internet is capable of carrying high quality audio and video streams from independent "creators". I have not subscribed to cable TV for years. 

  

Thoughts on EU USB-C mandates

EU and some other countries will mandate USB-C on cellphones, tablets, and even laptops in a couple of years. I am ambivalent towards such mandates.

Firstly, USB-C is a physical connector specification. It does not guarantee charging interoperability. I encountered several devices with USB-C connectors but only charge with USB-A power adapters. However, I expect that manufactures will learn to implement USB-C correctly eventually.

Secondly, the mandates seem to target Apple only because other phone manufactures have converged USB-C. Apple debuted the reversible lightning connector in 2012. Two years before USB-C came into being. However, Apple holds patents on the connector and tightly controls who may use it. Apple even embeds a small chip into the connector so that phones can refuse to work with unauthorized cables. As a result, lightning connector accessories are more expensive than USB-C counterparts. It seems that complaints to Apple's money grab caught attention from EU legislators and they passed a law to essentially "ban" the lightning connector. However, I don't think such a ban is necessary to force Apple to embrace USB-C. Apple already use USB-C on iPads, probably due to lightning's speed and current limitations. I expect Apple to encounter the same problems on iPhones and thus switch to USB-C voluntarily. In addition, Apple's main patent on lightning will expire in 2032.

Thirdly, I don't think governments should regulate low voltage charging ports. However, governments are justified to mandate certain mains sockets and fuel pumps because they could cause safety issues.

The biggest concern I have on USB-C mandates is the suppression on innovations. Mandating USB-C would disincentive innovators to work on better technologies. The EU lawmakers seem to be aware of this problem. Since the mandate 1)  applies to devices with physical charging ports only and 2) allows manufactures to include other ports in addition to USB-C.

My Ideal Car

Exterior

• Amber turn signal
• LED steering responsive headlights with good IIHS rating.
  
• Small front grill
• Auto-dimming side mirrors
  
• Rain sensing wipers

Interior

• Seats at least 4 people
• Auto-dimming rear view mirror
• 6 way powered driver seat or better
  
• Cloth seats or leather seats with heating and ventilation
• Heated steering wheel
• Sunglasses storage in the headliner.
• Black headliner.
• No sunroof.
  

Mechanical

• Automatic transmission (CVT or AT, but not DCT)
  
• Electronic parking brake with shift interlock
  
• Auto brake hold
• Full speed range adaptive cruise control with lane centering
  
• 0-60 mph in less than 8 seconds
• Combined fuel economy better than 30 mpg
• Independent front and rear suspensions
• Disc brakes
  

Misc

• Wireless smart phone projection
  
• Steering wheel control must have physical buttons
• Automatic HVAC
  
• AC temperature control must have physical buttons
• Has a spare tire.
  

Reasons to avoid cable modem router combos

I recently upgraded my Comcast Internet connection to 600Mbps. But my old cable modem only supports 160Mbps. So I bought a used Netgear C7000v2 router modem combo to replace both my old modem and router. I hoped that it would make my room more tidy.

The router combo's specs is not bad. It supports DOCSIS 3.0 and WiFi 5. The setup was very smooth. And a speed test yielded more than 300Mbps.

However, I found many limitations of the modem router combo in the first two weeks with it.

• Only the ISP may upgrade the firmware. And ISP can push new firmwares without user consent. This implies that ISP might have full control over the router. A friend's Netgear CAX80 got bricked overnight likely due to an ISP initiated firmware update.
  
• The guest WiFi does not hand out IPv6 addresses.
• Does not support DNS over TLS or HTTPS.
• No support for WPA3.
  
• The management web page is sluggish and lacks many options (intentionally?). I was not able to
• Disable WiFi Protected Setup completely
  
• Change WiFi channel bandwidth (it always uses 80MHz on the 5G band)
  
• Turn off 2.4G band radio

Fortunately, the router combo has a bridge mode, which makes it a standalone cable modem. So I turned on the bridge mode and reconnected my old router.

So my conclusion is, if you are a tech-savvy person, you are not likely to be happy with a router modem combo. But if you do not know WPA3, IPv6, DNS, or wireless channel bandwidth, a router modem may be a good choice.

Using iPhone without iCloud

I found my iPhone has been more sluggish after upgrading to iOS 14. So I factory reset it last week. Here is my experience.

Firstly I had to sign in my Apple ID to use the phone. So Apple assumes all customers can access Internet and its servers are always up. Can I use my iPhone if Apple goes out of business like Nokia did? I can still use my Nokia X2-00 today.

iCloud was enabled in full by default. There was no option to disable iCloud during phone activation. Apple assumes all customers want to use iCloud. However, iCloud does not have E2E encryption for backups, photos, etc.

I turned off iCloud immediately after activation. Then I found I had to sign in separately for AppStore, iMessage, and Facetime. In addition, ApplePay (wallet) and Sign in with Apple, Find my phone, were no longer available. Airpods Pro won't switch sources automatically. My reasoning is that Apple does not care about users who do not use iCloud because they are the minority.

Since iOS 13 I notice a trend of declining software quality. iOS have gained more and more features. But so did the number of bugs. However, Android is still less polished. Maybe one day I will switch back to Android.