Q about lighting & AM...

[pianoplayer88key]

(I almost put this in DX, but I don't consider the close distance to a TX I'll mention to be DX'ing (unless you can hear the station in your brain...)

Ok, you're standing about 1/32nd of a wavelength from KOMO's active tower during daytime operation. (I picked that frequency because my dad, a senior RF engineer, said lighting is strongest at approximately 1 MHz.) You have a portable radio tuned to 1000 and pointed at the station's transmitting antenna (most likely it's probably overloading your radio.)
While you're listening to the station, there's a lighting strike off to one side, in the direction of your receiving antenna's deepest null. During the strike, KOMO is COMPLETELY blanked out - no sign of a station on 1000 at all!

How far away do you think the lighting might be in that case?

 

[BlitzK]

> During the strike, KOMO is
> COMPLETELY blanked out - no sign of a station on 1000 at
> all!
>
> How far away do you think the lighting might be in that
> case?
>

It's really hard to say how far it was... but the basic way a
lightning detector works is an am radio with multiple antennas.
(ok, so it's not THAT simple... but you get my point).

Boltek.com might be a good start to finding out your answer.

 

[taylorengineer]

> (I almost put this in DX, but I don't consider the close
> distance to a TX I'll mention to be DX'ing (unless you can
> hear the station in your brain...)
>
> Ok, you're standing about 1/32nd of a wavelength from KOMO's
> active tower during daytime operation. (I picked that
> frequency because my dad, a senior RF engineer, said
> lighting is strongest at approximately 1 MHz.) You have a
> portable radio tuned to 1000 and pointed at the station's
> transmitting antenna (most likely it's probably overloading
> your radio.)
> While you're listening to the station, there's a lighting
> strike off to one side, in the direction of your receiving
> antenna's deepest null. During the strike, KOMO is
> COMPLETELY blanked out - no sign of a station on 1000 at
> all!
>
> How far away do you think the lighting might be in that
> case?
>
The lightning caused the DX50's VSWR protection to dump the carrier.....
What made you think of this.....do you stand 1/32 wavelength from 50 Kw radiators very often?

 

[SamBuca]

> How far away do you think the lighting might be in that
> case?

It would have been easier to just count the time between the flash and the thunder.

I would assume that EMF from lightning within several hundred miles would even be enough to overpower a transmitter....AM = ground conductivity and lightning = ground conductivity. 50,000 watts vs 40,000,000,000 watts.

As previously suggested, tranny may have cut off to prevent damage. Everything near a strike gets a surge from inductance, regardless of whether it takes a direct hit or not.<P ID="signature">______________
</P>

 

[SML]

> How far away do you think the lighting might be in that
> case?

Too darn close. Time to get the heck out of there!

 

[awj223]

> I would assume that EMF from lightning within several
> hundred miles would even be enough to overpower a
> transmitter....AM = ground conductivity and lightning =
> ground conductivity. 50,000 watts vs 40,000,000,000 watts.

Isn't it more dependent on spectral power than total power? Like watts/Hz in the relevant channel rather than just watts. The 40,000,000,000 watts probably spreads over a lot of spectrum, all the way up to visible.

 

[EncSpy]

> > During the strike, KOMO is
> > COMPLETELY blanked out - no sign of a station on 1000 at
> > all!
> >
> > How far away do you think the lighting might be in that
> > case?
> >
>
> It's really hard to say how far it was... but the basic way
> a
> lightning detector works is an am radio with multiple
> antennas.
> (ok, so it's not THAT simple... but you get my point).
>
> Boltek.com might be a good start to finding out your
> answer.
>

back when I worked in radio.....during thunderstorms we would have lighting in our lobby radio, which is about 300 feet from the tower and about 25 feet from the transmitter (1kw near 1Mhz)