HF Comms during sunrise & sunset?
Thread Starter
Join Date: Aug 2002
Location: Strategic hamlet
Posts: 115
Likes: 0
Received 0 Likes
on
0 Posts
HF Comms during sunrise & sunset?
Are there any 'rules of thumb' when selecting a HF comms frequency in eastbound and westbound flights during sunrise and sunset? I know it's related to the reduced MUF during the night but how do you choose which frequencies to use to communicate ahead and behind?
e.g. An a/c is flying westbound during sunset, which HF frequencies would be most suitable for communicating ahead and behind?
13261,8867,5643,3467
Thanks in advance!
e.g. An a/c is flying westbound during sunset, which HF frequencies would be most suitable for communicating ahead and behind?
13261,8867,5643,3467
Thanks in advance!
Join Date: May 2000
Location: Seattle
Posts: 3,196
Likes: 0
Received 0 Likes
on
0 Posts
How far ahead/behind? I usually try a freq suitable to the time of day at the ground station...
If I'm over the pacific, talking with San Francisco behind and Tokyo ahead, and it is local sunset where I am (and will be so for quite a while...), I'd try San Francisco on 56 and Tokyo on 88 if I didn't have any other guidance.
If I'm over the pacific, talking with San Francisco behind and Tokyo ahead, and it is local sunset where I am (and will be so for quite a while...), I'd try San Francisco on 56 and Tokyo on 88 if I didn't have any other guidance.
Join Date: May 2000
Location: Seattle
Posts: 3,196
Likes: 0
Received 0 Likes
on
0 Posts
OzExpat:
Actually, your rule of thumb should be that the high/low freqs match the height of the sun in the sky: highest freqs at noon, lowest freqs at midnight (based on local time at the ground station).
Massie:
On what 1000 mi route do you use HF? On the NATracks HF freqs are normally assigned, so no guesswork is required.
Actually, your rule of thumb should be that the high/low freqs match the height of the sun in the sky: highest freqs at noon, lowest freqs at midnight (based on local time at the ground station).
Massie:
On what 1000 mi route do you use HF? On the NATracks HF freqs are normally assigned, so no guesswork is required.
Originally Posted by OzExpat
My general "rule of thumb" for HF comms is :-
Low frequencies for low hours of the day.
High frequencies for high hours of the day.
Works for me.
Low frequencies for low hours of the day.
High frequencies for high hours of the day.
Works for me.
.Massey1Bravo,
The only HF airspace I fly in, the preferred frequency is stipulated by ATC. So you try that first, and if you have no luck getting through, you try one of the other ones.
None but a blockhead
Join Date: Nov 1999
Location: London, UK
Posts: 535
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by OzExpat
Thanks Intruder, I did word my post rather poorly didn't I! 
S2A... even simpler, ta!
Get UP by day.
Go DOWN by night!
Too easy!
S2A... even simpler, ta!
Get UP by day.
Go DOWN by night!
Too easy!
R
Join Date: Nov 2004
Location: Toulouse
Posts: 92
Likes: 0
Received 0 Likes
on
0 Posts
For those interested, there is a site offering more or less real-time MUF charts.
http://solar.spacew.com/www/realtime.php
http://solar.spacew.com/www/realtime.php
More bang for your buck
Join Date: Nov 2005
Location: land of the clanger
Age: 82
Posts: 3,512
Likes: 0
Received 0 Likes
on
0 Posts
A more indepth article on the subject
Cycles that Affect Propagation
Propagation is affected by cyclical environmental conditions. The shortest of these conditions is the day/night cycle. In general, the transmitting and receiving conditions are by far the best in the nighttime hours. During the daytime, the MUF and LUF both rise -- in order to talk across great distances, less reliable (because of the very long skip) higher frequencies must be used. The season of the year also affects propagation The winter/summer cycles are somewhat like the day/night cycles, except having a lesser influence. In general, the MUF and LUF will both be higher in the summer and lower in the winter. Also, the noise from thunder storms and other natural phenomena is much higher during the summer. In fact, except for local transmissions, communications in the 1700- to 3000 kHz range during the summertime are of limited regular use.
The longest environmental cycle that affects propagation is the sunspot cycle. Before the age of radio, it was noticed that the number of solar storms (sun spots) varies from year to year. Also, the number of sunspots per year was not entirely random. The number of solar storms during a good propagational month exceeds 150 and the number during a weak month is often fewer than 30. The sunspot cycle reaches its peak approximately every 11 years, cycles that have a great impact on radio propagation.
Between these peaks are several years with very low sunspot activity. During years with high sunspot activity, the MUF dramatically increases and long-distance communications across much of the HF band is possible. During the peak of the last sunspot cycle, in 1989, the MUF was often above 30 MHz! When the cycle is at its low point, the MUF decreases and much less of the HF band is usable for long-range communications. Generally, the frequencies above 10,000 kHz dramatically improve during the peak years of the sunspot cycle, and the frequencies below 10,000 kHz are much less affected
@ dawn and dusk there is also a phenomina called GREY LINE propagation which enhances the north / south line range significantly
hope this helps
Cycles that Affect Propagation
Propagation is affected by cyclical environmental conditions. The shortest of these conditions is the day/night cycle. In general, the transmitting and receiving conditions are by far the best in the nighttime hours. During the daytime, the MUF and LUF both rise -- in order to talk across great distances, less reliable (because of the very long skip) higher frequencies must be used. The season of the year also affects propagation The winter/summer cycles are somewhat like the day/night cycles, except having a lesser influence. In general, the MUF and LUF will both be higher in the summer and lower in the winter. Also, the noise from thunder storms and other natural phenomena is much higher during the summer. In fact, except for local transmissions, communications in the 1700- to 3000 kHz range during the summertime are of limited regular use.
The longest environmental cycle that affects propagation is the sunspot cycle. Before the age of radio, it was noticed that the number of solar storms (sun spots) varies from year to year. Also, the number of sunspots per year was not entirely random. The number of solar storms during a good propagational month exceeds 150 and the number during a weak month is often fewer than 30. The sunspot cycle reaches its peak approximately every 11 years, cycles that have a great impact on radio propagation.
Between these peaks are several years with very low sunspot activity. During years with high sunspot activity, the MUF dramatically increases and long-distance communications across much of the HF band is possible. During the peak of the last sunspot cycle, in 1989, the MUF was often above 30 MHz! When the cycle is at its low point, the MUF decreases and much less of the HF band is usable for long-range communications. Generally, the frequencies above 10,000 kHz dramatically improve during the peak years of the sunspot cycle, and the frequencies below 10,000 kHz are much less affected
@ dawn and dusk there is also a phenomina called GREY LINE propagation which enhances the north / south line range significantly
hope this helps
Join Date: Jun 2001
Location: UK
Posts: 146
Likes: 0
Received 0 Likes
on
0 Posts
After a few years of diligent study,here's the method I've had the most success with on the nattracs.
Try 5598,then 8906,then 13336.If you are still feeling keen choose another frequency completely at random from the chart(forget all that "nat A,B,C,," stuff,prop forcasts etc,just stick a pin in).If it's a line check and you've still had no joy try a for a relay.If that fails,do the crossword and repeat the cycle at the next waypoint.
Try 5598,then 8906,then 13336.If you are still feeling keen choose another frequency completely at random from the chart(forget all that "nat A,B,C,," stuff,prop forcasts etc,just stick a pin in).If it's a line check and you've still had no joy try a for a relay.If that fails,do the crossword and repeat the cycle at the next waypoint.
Join Date: Sep 2000
Location: Darraweit Guim, Victoria
Age: 64
Posts: 508
Likes: 0
Received 0 Likes
on
0 Posts
"the high/low freqs match the height of the sun in the sky: highest freqs at noon, lowest freqs at midnight"
HF works by bouncing signals (refracting anyhow) off the ozone layer, activity within which is driven by the sun. It lags the actual position of the sun though, MUF's are at their max mid afternoon, at a min before dawn. It is the activity between you and the station you need to consider, not just overhead the ground station.
I used to do International HF many moons ago in Perth, West Australia. Our transmitters were in Perth, but our recievers were miles away near Pearce. If you transmitted while disabling the reciever mute you got a nice squeal to tell you the radio worked. Near the end of a long winter night the higher freq recievers couldn't 'hear' their transmitters! On the other hand an aircraft checking the radio on 3 MHz on the ground at Perth in the afternoon could sometimes not be heard.
HF works by bouncing signals (refracting anyhow) off the ozone layer, activity within which is driven by the sun. It lags the actual position of the sun though, MUF's are at their max mid afternoon, at a min before dawn. It is the activity between you and the station you need to consider, not just overhead the ground station.
I used to do International HF many moons ago in Perth, West Australia. Our transmitters were in Perth, but our recievers were miles away near Pearce. If you transmitted while disabling the reciever mute you got a nice squeal to tell you the radio worked. Near the end of a long winter night the higher freq recievers couldn't 'hear' their transmitters! On the other hand an aircraft checking the radio on 3 MHz on the ground at Perth in the afternoon could sometimes not be heard.
Join Date: Sep 1998
Location: wherever
Age: 55
Posts: 1,616
Likes: 0
Received 0 Likes
on
0 Posts
"around the world on eights"
Having spent far too many hours flogging up and down the atlantic north and south. Having taken part in many equipment tests at all times of year, month and day I can honestly say that the best option is eights regardles of local/station time of day.
Often it's as much use not keying the mike and shouting at the windshield.
Having spent far too many hours flogging up and down the atlantic north and south. Having taken part in many equipment tests at all times of year, month and day I can honestly say that the best option is eights regardles of local/station time of day.
Often it's as much use not keying the mike and shouting at the windshield.
Join Date: Nov 2004
Location: Toulouse
Posts: 92
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by FE Hoppy
I can honestly say that the best option is eights regardles of local/station time of day.
This is supported by the maritime HF service where distress alerts from ships have a default selection of the 8MHz band. Experience has shown that it usually works.
