[Antennas] Studies of propagation and signal strength of aviation antennas

[Dave Holford]

Almost all of my operations were below 5,000 feet, usually much lower, and 
with 100W to inefficient antennas transatlantic comm was normally not a 
problem. If you listen to the MWARA (Major World Air Route Area) comms they 
are very much ruled by propagation. Typically each route has 4 or 5 
frequencies - i.e. 3/6/8/11/13 and 17Mhz assigned and they choose 
frequencies as propagation changes. I have never heard anyone assign a 
frequency on the basis of aircraft altitude, it is invariably on the basis 
of geographical location. Google MWARA for a list of global HF frequencies. 
Military operations have similar sets of frequencies and operate in a 
similar manner.

For example go to www.ips.gov.au (Australian Government Radio and Space 
Services) and take a look at the hourly HAP charts  - select HF systems, 
Global HF, HAP Charts, Hourly HAP Charts and pick a global location. Gander 
is a good choice since they have separate hourly charts for each frequency 
family A,B,C,D,E,F. New York is similar but they have a much smaller area of 
responsibility and less options.
The frequency selections are strictly geographical with no consideration 
given to altitude.

Dave



----- Original Message ----- 
From: "Henry Mei'l's" <meils at get2net.dk>
To: "Dave Holford" <holford at cogeco.ca>
Sent: Saturday, June 26, 2010 4:47 PM
Subject: Re: [Antennas] Studies of propagation and signal strength of 
aviation antennas

> Thanks for thedetailled info Dave.
> But how good/effective was airborne to land HF contact compared to land to 
> land operations ?
> I assume the great height usually enhanced reliability. Or were prop. 
> condx, QRN etc
> just as decisive?
>
> vy 73 Henry, OZ1UF
>
> ----- Original Message ----- 
> From: "Dave Holford" <holford at cogeco.ca>
> To: "rbethman" <rbethman at comcast.net>; <antennas at mailman.qth.net>
> Cc: "Henry Mei'l's" <meils at get2net.dk>
> Sent: Saturday, June 26, 2010 9:34 PM
> Subject: Re: [Antennas] Studies of propagation and signal strength of 
> aviation antennas
>
>
>> It has been a long time, but I have operated with trailing wires, fixed
>> wires and sections of the airframe on HF. My recollection is that the
>> trailing wire, when extended out to its full 200 ft length was the best 
>> when
>> the navigator wanted an antenna for LORAN-A; which operated on 1750, 
>> 1850,
>> 1900 and 1950 kHz (those were the days when sections of the 160m band 
>> were
>> prohibited to avoid interference with LORAN). Otherwise the only real
>> difference I recall between fixed wire and trailing wire was that 200ft 
>> of
>> trailing wire could pick up one heck of a static charge, especially in 
>> snow.
>> It was amazing how far those purple arcs could jump sometimes.
>>
>> One aircraft used the top half of the vertical stabilizer - fin and 
>> rudder -
>> as an HF antenna. There was an insulating band between it and the rest of
>> the airframe and it was fed with a remote antenna tuner. In my 
>> recollection
>> it was almost always superior to the fixed wire.  Since that aircraft did
>> not have a trailing wire I cannot make that comparison.
>>
>> Operations were conducted in CW, AM and SSB; with some specialized data
>> systems, over the range 2 to 28MHz; but mostly beteen 3 and 18MHz.
>>
>> Incidentally there is still a lot of HF aviation traffic. Most, if not 
>> all,
>> operations beyond VHF range still involve some HF comm, even if only for 
>> a
>> communications and SELCAL check as a standby for loss of SATCOM. Also 
>> there
>> is a lot of HF Data Link in both civil and military aviation use.
>>
>>
>> 73
>> Dave
>> VE3HLU
>>
>
>
> --------------------------------------------------------------------------------
>
>
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 9.0.830 / Virus Database: 271.1.1/2964 - Release Date: 06/26/10 
> 08:35:00
>