scanning issue

[Mark Tomlinson]

Was just wondering if anyone could provide insight as to why when I
scan the posted Seattle Center ATC approach and departure frequencies
on any of my mobile or base scanners I can only pick up transmissions
from the aircraft and not ATC?

Thanks!

MT

[zatatime]

On 26 Jun 2004 14:13:44 -0700, (Mark
Tomlinson) wrote:

>Was just wondering if anyone could provide insight as to why when I
>scan the posted Seattle Center ATC approach and departure frequencies
>on any of my mobile or base scanners I can only pick up transmissions
>from the aircraft and not ATC?
>
>Thanks!
>
>MT


Because FM band is a "Line of Sight" communications band.
If you're close to wherever the ATC facility is (you can see it) you
should get all transmissions.

HTH.
z

[Bob Moore]

zatatime > wrote
> Because FM band is a "Line of Sight" communications band.

That's true, but aviation band transmissions are Amplitude
Modulation (AM). Aviation transmissions are line-of-sight
because of the frequency, not the modulation type.

Bob Moore

[Mark Tomlinson]

zatatime > wrote in message >...
>
> Because FM band is a "Line of Sight" communications band.
> If you're close to wherever the ATC facility is (you can see it) you
> should get all transmissions.
>
> HTH.
> z


Thank you. Found this answer in another group after my posting here.


MT

"United WILL Stand"

[zatatime]

On Sun, 27 Jun 2004 00:30:12 GMT, Bob Moore
> wrote:

>zatatime > wrote
>> Because FM band is a "Line of Sight" communications band.
>
>That's true, but aviation band transmissions are Amplitude
>Modulation (AM). Aviation transmissions are line-of-sight
>because of the frequency, not the modulation type.
>
>Bob Moore


Can you explain? 122.6 (for example) is an FM frequency, how does ATC
transmit on the AM band?

z

[Stevenatherton]

why do you say 122.6 is a fm freq

122.6 is a vhf freqency,it can also be either am or fm modulation , fm or am
means the way the signal is transmitted not the frequency
steve

[Dave Stadt]

"zatatime" > wrote in message
...
> On Sun, 27 Jun 2004 00:30:12 GMT, Bob Moore
> > wrote:
>
> >zatatime > wrote
> >> Because FM band is a "Line of Sight" communications band.
> >
> >That's true, but aviation band transmissions are Amplitude
> >Modulation (AM). Aviation transmissions are line-of-sight
> >because of the frequency, not the modulation type.
> >
> >Bob Moore
>
>
> Can you explain? 122.6 (for example) is an FM frequency, how does ATC
> transmit on the AM band?
>
> z

Frequency and modulation type are totally unrelated. There is no such thing
as "an FM frequency." VHF aviation transceivers transmit and receive
Amplitude Modulated (AM) signals. VHF communication is typically but not
always line of sight. Signal propagation is frequency dependent not
modulation type dependent (with exceptions here and there).

[zatatime]

On 27 Jun 2004 16:24:57 GMT,
(Stevenatherton) wrote:

>why do you say 122.6 is a fm freq
>
>122.6 is a vhf freqency,it can also be either am or fm modulation , fm or am
>means the way the signal is transmitted not the frequency
>steve


Thank you. I understand.

[zatatime]

On Sun, 27 Jun 2004 16:30:11 GMT, "Dave Stadt"
> wrote:

>
>"zatatime" > wrote in message
...
>> On Sun, 27 Jun 2004 00:30:12 GMT, Bob Moore
>> > wrote:
>>
>> >zatatime > wrote
>> >> Because FM band is a "Line of Sight" communications band.
>> >
>> >That's true, but aviation band transmissions are Amplitude
>> >Modulation (AM). Aviation transmissions are line-of-sight
>> >because of the frequency, not the modulation type.
>> >
>> >Bob Moore
>>
>>
>> Can you explain? 122.6 (for example) is an FM frequency, how does ATC
>> transmit on the AM band?
>>
>> z
>
>Frequency and modulation type are totally unrelated. There is no such thing
>as "an FM frequency." VHF aviation transceivers transmit and receive
>Amplitude Modulated (AM) signals. VHF communication is typically but not
>always line of sight. Signal propagation is frequency dependent not
>modulation type dependent (with exceptions here and there).
>
>
Thanks. I always thought VORs/Comm were FM and NDBs were AM. Need to
learn more about the VHF band. Appreciate the post, what you say
makes sense (mostly, but because of my need to learn, not because I
think you aren't right).

z