[AF] Re: NDB antennas, transmitters, etc

[Jeff Welton]

First the preamble... before you get wound up about being corrected, =
it's best you know who is doing the correcting.  Dave has been an FAA =
maintenance engineer for a whole bunch of years - he's also done a pile =
of contract engineering for AM broadcast and has been working on Nautel =
equipment for about as long as I've been here (17 years now).  When it =
comes to being able to say what FAA sanctioned equipment (including our =
units) will and will not do and how they are or are not configured, he's =
an authority that I frequently use as a reference.  Have a cup of tea, =
or something, chill out - anybody can be mistaken about something - and =
accept that it is possible for anybody, including yourself (or me for =
that matter) to be wrong.

>  > The NDBs usually transmit a CW signal on one frequency, and a =
separate
> carrier, 1020 Hz above it that is > keyed with the identification =
code.
>=20
> I think I've read of this system in Canadian NDB usage (I'm not =
certain),
> but the US systems all are AM, modulated with a 1020hz ID tone.
>=20
No. the word ALL is wrong. In fact MOST low power NDBs, the ones used as
"compass locators," co-located with the 75 MHz outer-marker transmitters
are offset carrier devices.

No, the word ALL is correct.  Every NDB we have in use in the USA is AM =
modulated with a 1020 tone, at either 60 or 90-95%, depending on whether =
voice is used or not.  The modulated carrier is then keyed on and off =
according to ICAO Annex 10 standards, which are in use worldwide.

A few Canadian systems use SSB modulation as opposed to DSB, but none =
use offset carriers.  In most instances in Canada the modulating tone is =
400 Hz as opposed to 1020, but the systems are basically identical =
otherwise.

> all use AM for both ID and voice (if it's configured for voice).
>=20

Most NDB transmitters do NOT have voice capability. In fact, I have been =
flying since 1971 and the only voice I ever heard on a NDB receiver was =
from AM radio stations. See what ICAO has to say about that. =
http://www.icao.int/anb/panels/acp/wg/f/WGF9/WP/WGF915.doc

Just because you haven't heard it doesn't mean the option doesn't exist. =
 Every NDB we've built for the past 20+ years, with the exception of one =
model traditionally only sold offshore, has the option for voice.  This =
is being used in some cases, but I certainly can't tell how widely, =
except that I recall taking calls on voice vs tone mod depths from the =
FAA in Oransas Co., TX, among other places.

I'll let Dave state his position on all other points, but having field =
service and tech support on Nautel broadcast and NDB product since 1990, =
I'm pretty sure I know what our boxes will do and I've got some pretty =
good information on how they are being used in the field.

Best,

Jeff Welton
Technical Sales Representative
Nautel=20
Toll-free Tel:    1 877 662 8835 Ext. 127
International: +1 902 823 3900 Ext. 127
Mobile:  +1 902 489 1635
Fax:      +1 902 823 3183
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