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Author Topic: Preppers Calling Frequency.  (Read 8794 times)

gil

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Re: Preppers Calling Frequency.
« Reply #45 on: May 01, 2017, 02:38:22 PM »
Thanks Scarr, I need to allocate a couple hours to research this...  :)

Gil.

cockpitbob

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Re: Preppers Calling Frequency.
« Reply #46 on: May 02, 2017, 09:31:22 AM »
Thanks Scarr, I need to allocate a couple hours to research this...  :)

Gil.
Ditto.  Those charts will take some learning to interpret, but I bet there's real valuable info in them.

scarr

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Re: Preppers Calling Frequency.
« Reply #47 on: May 02, 2017, 05:29:54 PM »
foF2 is the Critical frequency in a given location - the highest frequency you can knock straight up and have it come straight back down, vital for deciding on NVIS regional comms. I've kept an eye on it lately and the frequency is rarely going near 7MHz - meaning if you want local HF comms, you've got to decide between 80M or 60M.

From foF2, a rule of thumb is that the Maximum Usable Frequency will be three times foF2 - so if foF2 is hovering around 5MHz and it's daylight in Europe and North America, well - generally - no point trying to cross the pond on 10 Metres, your best bet is likely to be ~20M.

The VOACap page is really useful for calculating likely condx between any two points on various bands. Just feed in the locations and to be honest, for the most accurate prediction - put the sunspots at zero. The (11) sunspots we have at the moment are miniscule and have little if any impact on the solar flux level. SF is at 75 at this moment - from the last solar minimum, I remember that figure dipping into the 60's. In short, that means forget the higher HF bands.

This all goes back to something gil and others have said - if people just expect to fire up a HF rig in a SHTF situation and talk with little or no experience - forget it.

The charts aren't 100% necessary, but they inform operational experience - e.g. if I'm on 40M at 1PM local and I'm hearing no Irish or UK stations, but Germany is booming in, I know foF2 is less than 7MHz.

If we ever have to use HF in a scenario where mains is out, spending time listening first is going to be vital - when you've decided on where you'd like to contact, you've got to figure out what's happening with the bands before keying. No point blasting 100W into the ether on 20M when 5W on 80M will get the desired result. Power could be precious.
« Last Edit: May 02, 2017, 05:51:05 PM by scarr »