Channel Width

[thejim]

This question relates to VOR.
I read that when VORs where increasing continuously in number in the
beginning of their "career" there was a lack of available frequencies.

So they increased the frequencies by increasing the number of chanels
and they did that by decreasing the chanel width e.x from 100kH width
to 50kH width.

Can you explain me please how this(meaning increase of channels by
reducing their width) will increase the number of available frequencies
for the increasing number of VOR stations.

[Jose[_1_]]

> Can you explain me please how this(meaning increase of channels by
> reducing their width) will increase the number of available frequencies
> for the increasing number of VOR stations.

It means you can put channels in between existing channels. If done
right, there is no interference. It requires that existing transmitters
be modified (if they are not already "narrow" enough) so that there in
fact is no interference.

Jose
--
The monkey turns the crank and thinks he's making the music.
for Email, make the obvious change in the address.

[Jim Macklin]

VOR is line of sight so the same frequency can be used over
and over as long as there stations are located far enough
apart and the "service volume" is protected. If you look at
the useable distance for a VOR signal, you will see that
very high altitudes are shorter range than lower and middle
altitudes because the interference is greater at high
altitudes.

Better quality radio receivers can reject interference,
radio band width can't be increased because all the
available frequencies have been assigned. But by making a
channel narrower, you can double the number of possible
channels each time you narrow the channel. Going from 100
KHz to 25 KHz quadrupled the number of channels. Forty
years ago, 90 comm. channels and 50 VOR was common and now,
Comm. channels are in the thousands. VOR is less suited to
adding more and more channels because of the location
issues.

If you have 108 to 117 for channels and you can only tune
whole numbers, you get ten channels. If you can tune 108.5,
you get 20 channels. If you tune 108.1 you get 100 channels
and 108.010 gets a 1,000. But if the power is high, it is
harder to reject the nearby station.

The FAA flight tests naviads and one of the issues is clear
radio reception.


--
James H. Macklin
ATP,CFI,A&P

"thejim" > wrote in message
ups.com...
| This question relates to VOR.
| I read that when VORs where increasing continuously in
number in the
| beginning of their "career" there was a lack of available
frequencies.
|
| So they increased the frequencies by increasing the
number of chanels
| and they did that by decreasing the chanel width e.x from
100kH width
| to 50kH width.
|
| Can you explain me please how this(meaning increase of
channels by
| reducing their width) will increase the number of
available frequencies
| for the increasing number of VOR stations.
|

[Peter Duniho]

"Jose" > wrote in message
. net...
>> Can you explain me please how this(meaning increase of channels by
>> reducing their width) will increase the number of available frequencies
>> for the increasing number of VOR stations.
>
> It means you can put channels in between existing channels. If done
> right, there is no interference. It requires that existing transmitters
> be modified (if they are not already "narrow" enough) so that there in
> fact is no interference.

And that the receivers also be updated to ensure that they can select within
the narrow enough frequency range (and of course, be tuned to the
intermediate frequencies as well).

Pete

[Dave S]

thejim wrote:
> This question relates to VOR.
> I read that when VORs where increasing continuously in number in the
> beginning of their "career" there was a lack of available frequencies.
>
> So they increased the frequencies by increasing the number of chanels
> and they did that by decreasing the chanel width e.x from 100kH width
> to 50kH width.
>
> Can you explain me please how this(meaning increase of channels by
> reducing their width) will increase the number of available frequencies
> for the increasing number of VOR stations.
>

Older radios, with older technology, were capable of transmitting on
their tuned frequency, but the signal spilled over onto neighboring
frequencies.. this dictated fairly wide channel spacing... to prevent
interference...

Newer radios with newer innards are capable of much more precise
transmission, with much less "width" to the spillover. By mandating
everyone use the newer radios to transmit, you in effect open up more
"channels" in between the existing ones that you can use.

Right now we have (on com frequencies) 25 khz spacing between designated
frequencies.. Many of the new radios being sold are already capable of
operating at the NEXT spacing designation, somewhere on the order of 8.3
khz, which will triple the existing amount of aviation band com freqs
(from 760 to over 2000).

By simply halving the nav frequency spacing, you can double the number
of nav frequencies available. Navs are currently at 50 khz spacing, if I
remember correctly.

Dave

[Roy Smith]

"Jim Macklin" > wrote:
> Going from 100 KHz to 25 KHz quadrupled the number of channels. Forty
> years ago, 90 comm. channels and 50 VOR was common and now, Comm.
> channels are in the thousands.

So why are we still stuck with almost every uncontrolled field in existence
having their CTAFs crammed into just 2 or 3 freqs? How many years is it
since you could even buy a radio that didn't have 25 khz spacing?

[Bob Noel]

In article >,
Roy Smith > wrote:

> > Going from 100 KHz to 25 KHz quadrupled the number of channels. Forty
> > years ago, 90 comm. channels and 50 VOR was common and now, Comm.
> > channels are in the thousands.
>
> So why are we still stuck with almost every uncontrolled field in existence
> having their CTAFs crammed into just 2 or 3 freqs? How many years is it
> since you could even buy a radio that didn't have 25 khz spacing?

Isn't it "interesting" that nearly all the new AWOS frequencies require 25 kHz
spacing? Yet they can't change any CTAF frequencies.

--
Bob Noel
Looking for a sig the
lawyers will hate

[Jim Macklin]

government assigns the channels, we are stuck with it.


"Roy Smith" > wrote in message
...
| "Jim Macklin" >
wrote:
| > Going from 100 KHz to 25 KHz quadrupled the number of
channels. Forty
| > years ago, 90 comm. channels and 50 VOR was common and
now, Comm.
| > channels are in the thousands.
|
| So why are we still stuck with almost every uncontrolled
field in existence
| having their CTAFs crammed into just 2 or 3 freqs? How
many years is it
| since you could even buy a radio that didn't have 25 khz
spacing?

[RST Engineering]

You can buy legal 1, 6, 90, and 360 channel radios.

Jim


"Roy Smith" > wrote in message
...
> "Jim Macklin" > wrote:
>> Going from 100 KHz to 25 KHz quadrupled the number of channels. Forty
>> years ago, 90 comm. channels and 50 VOR was common and now, Comm.
>> channels are in the thousands.
>
> So why are we still stuck with almost every uncontrolled field in
> existence
> having their CTAFs crammed into just 2 or 3 freqs? How many years is it
> since you could even buy a radio that didn't have 25 khz spacing?

[Jim Macklin]

But they now must meet the latest standards for bandwidth,
etc. Many of the old Narco, ARC and other radios cannot be
used.



"RST Engineering" > wrote in message
...
| You can buy legal 1, 6, 90, and 360 channel radios.
|
| Jim
|
|
| "Roy Smith" > wrote in message
| ...
| > "Jim Macklin" >
wrote:
| >> Going from 100 KHz to 25 KHz quadrupled the number of
channels. Forty
| >> years ago, 90 comm. channels and 50 VOR was common and
now, Comm.
| >> channels are in the thousands.
| >
| > So why are we still stuck with almost every uncontrolled
field in
| > existence
| > having their CTAFs crammed into just 2 or 3 freqs? How
many years is it
| > since you could even buy a radio that didn't have 25 khz
spacing?
|
|

[kontiki]

Jim Macklin wrote:
> government assigns the channels, we are stuck with it.

An airport may request a different frequency assignment, it is not
that big of a deal... just fill out some forms. Of course FAA must
be in the loop as well.

The bigger possible PIA for the airport is that it must then modify
any equipment involved in pilot controlled runway/VASI/PAPI/approach lighting.

[Mike[_5_]]

"Jose" > wrote in message
. net...
>> Can you explain me please how this(meaning increase of channels by
>> reducing their width) will increase the number of available
>> frequencies
>> for the increasing number of VOR stations.
>
> It means you can put channels in between existing channels. If done
> right, there is no interference. It requires that existing
> transmitters be modified (if they are not already "narrow" enough) so
> that there in fact is no interference.

Actually the biggest limiting factor is the receivers. I'm not sure
what was done during the VOR changeover, but I can say that when the FAA
went from 50Khz to 25Khz spacing for voice channels, the only change to
the ground equipment was to change the bandpass of the receivers. Older
receivers were less sensative and had to have a wider bandpass. As
receiver technology progressed, the bandpass could be made more narrow.

[Dave S]

RST Engineering wrote:
> You can buy legal 1, 6, 90, and 360 channel radios.

Agreed.. But who sells new ones nowadays that are ok to transmit with?
(that are only 1, 6, 90 and 360 channels, respectively)

[RST Engineering]

Didn't see the "new" word in the OP. I s'pose I could round up enough parts
to make a 541 (single channel) and 542 (6 channel) and if I dug deep enough
into the obsolete parts bin I might even be able to do a 571 (360 channel).
The type certificate approval never runs out, just like a pilot certificate.

Jim



"Dave S" > wrote in message
ink.net...
> RST Engineering wrote:
>> You can buy legal 1, 6, 90, and 360 channel radios.
>
> Agreed.. But who sells new ones nowadays that are ok to transmit with?
> (that are only 1, 6, 90 and 360 channels, respectively)