[Elecraft] OT: Aircraft radio FM

[Tim Hague]

More interesting in the permanent  self congratulation you see on here when someone buys a rig!

Best regards, Tim Hague
Skype m0afj.Tim
Sent on my iPad


On 16 Jul 2013, at 23:11, "Rich" <r.bro84 at googlemail.com> wrote:

> Am I the only one wondering what has any of this got to do with Elecraft??
> 
> Can the moderators put an end to all of these OT posts and return it to a reflector for its purpose please?? Yes I know where the delete button is but the threads get longer and longer.
> 
> Nothing personal Mike, just picked your post to reply to.
> Sent from my BlackBerry® wireless device
> 
> -----Original Message-----
> From: Mike Morrow <kk5f at earthlink.net>
> Sender: elecraft-bounces at mailman.qth.net
> Date: Tue, 16 Jul 2013 18:02:36 
> To: <elecraft at mailman.qth.net>; <KX3 at yahoogroups.com>
> Reply-To: Mike Morrow <kk5f at arrl.net>
> Subject: Re: [Elecraft] OT: Aircraft radio FM
> 
> Ken wrote:
> 
>> AM aircraft radio has been around since the end of spark and
>> steadily growing world-wide since that time.  It was solidly in
>> place -long- before FM was a gleam in Armstrong's eye.
> 
> Er...I'm not sure how that supports an argument that transition
> to FM was *at any point and time* considered *by any responsible
> party* to have characteristics that were more desirable than AM
> for aircraft communications.
> 
> The characterization that AM was "solidly in place -long- before FM
> was a gleam in Armstrong's eye" refers accurately only to the era
> when aircraft communications were only on medium and high frequencies...
> an era when long-range aircraft communications often still made use
> of Morse CW (hence the FCC Element 7 exam for Aircraft Radiotelegraph
> Endorsement, now discontinued).
> 
> The transition from MF/HF to VHF for aircraft communications received
> its greatest push with the UK's pioneering use after 1940 of aircraft
> AM command sets operating in the range of 100 to 156 MHz.  This sparked
> the allied US military's transition from MF/HF command sets to VHF
> command sets, one of the earliest being the Western Electric 233A set.
> At this point, VHF FM could have been *very easily* adopted, had it not
> been for its undesirable capture effect.
> 
> Aircraft VHF-AM was chosen long after FM had been developed.  The
> decision to use AM was purposely made.  The adoption of aircraft VHF-AM
> was NOT the result of constraints from earlier legacy technology.
> All civil aviation eventually adopted the military standard of VHF-AM,
> although up to the mid-1950s many private aircraft continued to use
> MF/HF sets with receivers in the 200 to 400 kHz range and a transmitter
> on 3105 (later 3023.5) kHz...still far from a universal commitment
> to VHF-AM at that late date, had VHF-FM been a better choice.
> 
> Further, by 1945, the US military began exploring UHF for aircraft
> comms.  These new sets had no reason to stick with AM, if FM were
> superior.  But FM was not superior...or as good.  AM was chosen for
> use in the military UHF aircraft band as well.
> 
>> It remains that the staggering cost of conversion to FM is the
>> real reason it continues today.
> 
> That is a gratuitous assertion for which my decades of study in this
> area finds no substantiation.
> 
> 73,
> Mike / KK5F
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