Atmospheric conditions affecting VOR reception range

[Mike Noel]

Has anyone ever noticed a drop in VOR reception range when flying in smoky
conditions? Last Saturday in southern AZ we had significantly reduced
visibility from the big fire north of LA. I saw a lot of flagging on and
off of the CDI along with back and forth needle drift until within about 30
miles of the VOR station. We usually get much better reception.
--
Best Regards,
Mike

http://photoshow.comcast.net/mikenoel

[kontiki]

Smoke will not affect VOR reception.

Mike Noel wrote:

> Has anyone ever noticed a drop in VOR reception range when flying in smoky
> conditions? Last Saturday in southern AZ we had significantly reduced
> visibility from the big fire north of LA. I saw a lot of flagging on and
> off of the CDI along with back and forth needle drift until within about 30
> miles of the VOR station. We usually get much better reception.

[Denny]

Suspended particles in the air can absorb VHF energy, will affect UHF
signals, and will absolutely swallow gigahertz and light wave energy
(which is why you can't see through haze) - now whether ash
particulates from a forest fire will bother VHF is something I'm not
ready to take a position on... But, if there are boron molecules in
that haze from the firefighting chemicals that raises the probability
that it is affecting VHF, and up in frequency...
If the erratic VOR signals that day were due to the forest fire, what
is also likely is that the rising heat from the fires is causing
temperature layering and air turbulence which definitely bends VHF
signals, the same as it distorts light waves when looking down a
highway on a hot day, or looking through a bonfire...

denny

[kontiki]

Denny wrote:
> Suspended particles in the air can absorb VHF energy, will affect UHF
> signals, and will absolutely swallow gigahertz and light wave energy
> (which is why you can't see through haze) - now whether ash
> particulates from a forest fire will bother VHF is something I'm not
> ready to take a position on... But, if there are boron molecules in
> that haze from the firefighting chemicals that raises the probability
> that it is affecting VHF, and up in frequency...
> If the erratic VOR signals that day were due to the forest fire, what
> is also likely is that the rising heat from the fires is causing
> temperature layering and air turbulence which definitely bends VHF
> signals, the same as it distorts light waves when looking down a
> highway on a hot day, or looking through a bonfire...

The ionized contaminants in the smoke would have to be significant
before it would significantly affect VOR reception... not likely.
The poster did not state the altitude he was at not the class of
VOR in question.

VHR radio signals can be affected by certain tropospheric contitions
such as temperature inversions. As you stated, it is possible that
the heat of the fire could have cause a sort of temperature inversion
layer that affected the signal strength resulting in some CDI fluctuation.

[Mike Noel]

I was also wondering if the large amounts of carbon particulates in the
Arizona dry air could cause a static charge to build up on the airframe and
affect the signal.

--
Best Regards,
Mike

http://photoshow.comcast.net/mikenoel

"kontiki" > wrote in message
...
> Smoke will not affect VOR reception.
>
> Mike Noel wrote:
>
>> Has anyone ever noticed a drop in VOR reception range when flying in
>> smoky conditions? Last Saturday in southern AZ we had significantly
>> reduced visibility from the big fire north of LA. I saw a lot of
>> flagging on and off of the CDI along with back and forth needle drift
>> until within about 30 miles of the VOR station. We usually get much
>> better reception.
>