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. 

  

7z benchmark without hyperthreading on i5-1240P

Conclusion

SMT Off (12 Threads)    SMT On (16 Threads)    The Delta
Total Score (Tot)    27,967 MIPS    40,205 MIPS    +43.7% with SMT On
Avg Compression    35,226 MIPS    51,059 MIPS    +44.9% with SMT On
Avg Decompression    20,708 MIPS    29,351 MIPS    +41.7% with SMT On
Max 1T Freq (Single Core)    ~4354 MHz    ~4379 MHz    Virtually identical

Benchmark without hyperthread 

7-Zip 26.01 (x64) : Copyright (c) 1999-2026 Igor Pavlov : 2026-04-27

 64-bit locale=en_US.UTF-8 Threads:16 OPEN_MAX:4096


Compiler:  ver:16.1.1 20260515 (Red Hat 16.1.1-2) GCC 16.1.1 : SSE2

Linux : 7.0.12-201.fc44.x86_64 : #1 SMP PREEMPT_DYNAMIC Thu Jun 11 01:30:16 UTC 2026 : x86_64

PageSize:4KB HPS:2MB THPS:2MB THP:madvise hwcap:2 hwcap2:2

12th Gen Intel(R) Core(TM) i5-1240P

(906A3)  (LP)


1T CPU Freq (MHz):  3093  3992  3707  4310  4347  4325  4354

6T CPU Freq (MHz): 578% 3288   574% 3285  

12T CPU Freq (MHz): 973% 2594   838% 2248  


RAM size:   15676 MB (LP),  # CPU hardware threads:  12 / 16 : FF55

RAM usage:   2669 MB (LP),  # Benchmark threads:     12


                       Compressing  |                  Decompressing

Dict     Speed Usage    R/U Rating  |      Speed Usage    R/U Rating

         KiB/s     %   MIPS   MIPS  |      KiB/s     %   MIPS   MIPS


22:      59717   976   5951  58093  |     304017  1133   2288  25923

23:      29297   934   3196  29851  |     247248  1138   1880  21388

24:      27530   927   3192  29601  |     208846  1104   1659  18325

25:      20460   933   2504  23361  |     193263  1125   1528  17195

----------------------------------  | ------------------------------

Avr:     34251   943   3711  35226  |     238344  1125   1839  20708

Tot:            1034   2775  27967  



With hyperthreading

1T CPU Freq (MHz):  3305  4204  4333  4347  4367  4379  4378

8T CPU Freq (MHz): 769% 3238   761% 3162  

16T CPU Freq (MHz): 1041% 2098   1558% 3073  


RAM size:   15676 MB (LP),  # CPU hardware threads:  16

RAM usage:   3559 MB (LP),  # Benchmark threads:     16


                       Compressing  |                  Decompressing

Dict     Speed Usage    R/U Rating  |      Speed Usage    R/U Rating

         KiB/s     %   MIPS   MIPS  |      KiB/s     %   MIPS   MIPS


22:      70657  1369   5022  68735  |     432269  1452   2538  36860

23:      49188  1285   3901  50117  |     404803  1444   2425  35018

24:      40186  1344   3215  43208  |     320151  1466   1916  28091

25:      36937  1366   3087  42174  |     195977  1550   1125  17436

----------------------------------  | ------------------------------

Avr:     49242  1341   3806  51059  |     338300  1478   2001  29351

Tot:            1409   2904  40205 

 

 

 

Allow sudo to use fingerprint auth when laptop lid is open on Fedora 44

I want to achieve the following on Fedora 44 on Thinkpad x1c gen 10,

• fingerprint auth is allowed in sudo
• fingerprint auth not allowed anywhere else
• fingerprint auth is skipped when laptop lid is closed.

I did the following

check current authselect config

authselect current

If the result contains  with-fingerprint, disable it

sudo authselect disable-feature with-fingerprint

cat /etc/pam.d/system-auth to verify that fprintd is not listed

This disables fingerprint auth for everything

Then add these two lines in /etc/pam.d/sudo, immediately below the #%PAM-1.0 line

auth [success=ok default=1] pam_exec.so quiet quiet_log /bin/grep -q open /proc/acpi/button/lid/LID/state
auth   sufficient   pam_fprintd.so

This two lines enables fingerprint auth only when the laptop lid is open.

Lastly, run fprintd-enroll to enroll fingerprints.

 

References

https://www.man7.org/linux/man-pages/man8/pam_exec.8.html

https://www.man7.org/linux/man-pages/man5/pam.conf.5.html 

 

 

 

 

 

Block guest WiFi clients from reaching other hosts on LAN

On Openwrt 25.12, I set up a guest wifi bridge onto LAN,

config wifi-iface 'wifinet2'
    option device 'radio1'
    option mode 'ap'
    option ssid 'xxxx'
    option encryption 'sae-mixed'
    option key 'xxxxxxx'
    option ocv '0'
    option ieee80211w '2'
    option ifname 'wifi-guest'
    option network 'lan'

However, I want to block hosts on the guest wifi from reaching other hosts on br-lan except the router.

I used the following config.

in  /root/guest_isolate.nft 

table bridge guest_isolation
delete table bridge guest_isolation

table bridge guest_isolation {
  chain forward {
    type filter hook forward priority 0; policy accept
    iifname "wifi-guest" counter drop
  }
}

in /etc/config/firewall

config include
        option type 'nftables'
        option path '/root/guest_isolate.nft'
        option position 'ruleset-post'

kmod-nft-bridge package must be installed.

Tecsun M-801 media player review

I acquired a used Tecsun M-801 music player.

The good,

• Built-in FM antenna with decent reception.
• User replaceable 18650 battery.
• USB-C port supports changing and acting as a USB speakerphone.
• It can record audio into a TF card.
• The built-in mic can be used for answering phone calls via bluetooth.
• It exposes its battery level to phones through bluetooth.
• The audio player can resume from previous location within a file. 

The bad,

• The recorded audio is in MP2 format at 160 kbps instead of MP3.
• Does not play AAC audio files. 
• The only knob has two functions. I prefer a dedicated volume knob.
• The USB-C port is not implemented properly to work with USB-C adapters. 
• No AM reception. 
• The speaker has a noticeable noise floor.
• Volume is not synced to phone in bluetooth mode. 

 

Ricoh GRIV camera review

 I used a GRIV for three days. Here is my take.

The good,

• Very sharp lens
• Lightweight and compact body
• 50GB internal storage
• The RAW format is DNG.
• Crisp display
• UI is clean and intuitive.
• Built-in ND filter
• Superb image stabilization

The bad,

• Video recording is limited to 1080p at 60fps.
• Does not support HEIF.
• Display is fixed. It does not flip or articulate.
• Only supports UHS-I microSD card.

The ugly,

The camera freezes after taking dozens of pictures on a moving vehicle. I ruled out SD card incompatibility because I did not insert one. I had to pull out the battery to reboot the camera. This is why I only kept it for three days.

 

 

 

Making UEFI bootable Win 11 USB drive on Linux

I searched for making bootable win 11 drive on Linux. Many results point to WoeUSB. I read WoeUSB's code and found out I can do it manually.

Steps,

1. Format the USB drive with MBR.
2. Create two partitions, one 10MB, the other bigger than Windows installer ISO.
3. Write this image into the first partition. 
4. Format the second partition in NTFS/exFAT.
5. Copy everything inside the ISO into the second partition.
6. Umount the second partition.
7. Remove USB drive.