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HF Emergency broadcast frequencies


Are there many recognized broadcast frequencies in the US or worldwide?

I know there are marine ones, was thinking across a greater range of services.




  • Thanks Jim,

    I found a Wikipedia page of distress frequencies as well so got a few now. We have become so used to the internet and mobiles going back to printed frequency lists for a few days would trip a few up. Like keeping some bottle drinking water, small, low cost step but great if ever needed.

    I collected a few ip addresses too, good for if the DNS system was turned off for a while but the net still up. Might find a way to scrape a bunch to text once a month. I suppose SIP addresses, Mumble servers etc. might be good too.

  • You would be better off keeping IP addresses of alternate DNS servers than keeping a local offline copy of DNS. The likelihood of global DNS failing will be more remote than large swathes of IP inaccessibility.

    Ones I have memorised: - Satlynx german satellite ISP DNS server, I used type this in so often it's in muscle memory at this point. - Google's alternate DNS - Google's main DNS - Ireland's university ISP dns server and - the OpenDNS servers.

  • Satlynx and Ireland are new to me, thanks for that.

    DNS disruption would be a simple way to drop large swathes of people off the social networks and messaging platforms, it makes sense for that to be a real possibility in the event of some conflict. I do run a simple local DNS server so would have a cache for a while but once a "name" does not work the internet can be left up for other traffic but the average user goes away. I need to get into more ham digital stuff send some email over it.

    Think if "Facebook, Youtube, Twitter, News sites etc." failed to resolve most people would simply be lost.

  • edited January 2021

    The Ireland ISP is HEANet who had the interesting note of being the only Irish ISP that was not forced to filter the Piratebay when that court order came through, as it's an academic supplier and not a home supplier. One SSH port forward later from a machine I had access to on an academic network and I once again had unfettered net access via a proxy. That was very useful when I was abroad and using Irish websites that were geo-locked.

    Agreed re: DNS as one of the easy ways to block/lose portions of the net. The other interesting way is BGP poisoning - and that's really interesting to see who trusts who!

  • The HFCC (which coordinates HF broadcast assignments) tries to keep one frequency in each HF broadcast band in reserve for emergency use, which they call International Radio for Disaster Relief (IRDR). More here:

  • @G4DYA Very helpful resource thanks.

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