We expect the local down the block may overload our receiver when he
keys up his kilowatt 40kHz from the frequency we're listening to, but
what are the largest signals received via skip in the HF bands? What
are the chances you'd ever see anything as large, say, as 0dBm into
your receiver via skip? (0dBm = 73dB above s9, given that s9 = 50uV
into 50 ohms.) This could potentially include SW broadcast stations
running fairly high power.

Cheers,
Tom

"K7ITM" wrote:
What are the chances you'd ever see anything as large, say,
as 0dBm into your receiver via skip?
________________

At 14 MHz with a rx antenna gain of 0 dBd and no transmission line loss,
that would call for an incident field strength of about 78.7 mV/m. Maybe
not impossible for some SW broadcast stations and very good propagation
conditions?

The maximum nighttime skywave fields received in the skip zones of a 50 kW,
non-directional, MW AM broadcast station generally are less than 5 mV/m.

RF

In article , "Richard Fry"
wrote:

"K7ITM" wrote:
What are the chances you'd ever see anything as large, say,
as 0dBm into your receiver via skip?
________________

At 14 MHz with a rx antenna gain of 0 dBd and no transmission line loss,
that would call for an incident field strength of about 78.7 mV/m. Maybe
not impossible for some SW broadcast stations and very good propagation
conditions?

The maximum nighttime skywave fields received in the skip zones of a 50 kW,
non-directional, MW AM broadcast station generally are less than 5 mV/m.

RF


Actually if one were to calculate the Free Space Path Loss for any
Frequency, it becomes trivial to come up with the MAXIMUM Possible
Receive Signal Strength for any distance, from any amount of transmitted
power level.

Bruce in alaska
--
add a 2 before @

On Jan 26, 11:11 am, Bruce in Alaska wrote:
In article , "Richard Fry"
wrote:

"K7ITM" wrote:
What are the chances you'd ever see anything as large, say,
as 0dBm into your receiver via skip?
________________

At 14 MHz with a rx antenna gain of 0 dBd and no transmission line loss,
that would call for an incident field strength of about 78.7 mV/m. Maybe
not impossible for some SW broadcast stations and very good propagation
conditions?

The maximum nighttime skywave fields received in the skip zones of a 50 kW,
non-directional, MW AM broadcast station generally are less than 5 mV/m.

RFActually if one were to calculate the Free Space Path Loss for any
Frequency, it becomes trivial to come up with the MAXIMUM Possible
Receive Signal Strength for any distance, from any amount of transmitted
power level.

Bruce in alaska
--
add a 2 before @

Well--yes--assuming no antenna gain and no "gain" effects from
focussing by the ionosphere. Does ionospheric "gain" happen? I'm
pretty ignorant about that. But freespace path loss is
((4*pi*distance)/wavelength)^2, according to my reference. So to
receive 0dBm if 1 megawatt is transmitted, assuming no antenna gain on
either end, wavelenth/distance = .000397. For 40 meters, you only get
about 100km separation. However, I get reports from people I trust
that European broadcast stations on 40m can put a 0dBm signal into a 3
element beam on the US East coast. That's way more than 100km path
length! The 8dB or so gain from the receiving antenna doesn't seem to
fully account for things.

I was just looking for anecdotal input, but some discussion about what
lets signals be as strong as they can be might be interesting too.

Cheers,
Tom

I once measured a 250 mV RMS signal (+1 dBm) at my receiver input when
using a vertical antenna, from KGEI, a religious shortwave broadcasting
station near San Francisco, about 600 miles from here. It was at night,
and KGEI was just above the 40 meter band, 7335 kHz as I recall. They
were broadcasting in Russian, so their pattern was probably pretty much
in my direction.

I'm quite sure the folks in Europe routinely see signals larger than
this from SW broadcast stations.

Roy Lewallen, W7EL

K7ITM wrote:
We expect the local down the block may overload our receiver when he
keys up his kilowatt 40kHz from the frequency we're listening to, but
what are the largest signals received via skip in the HF bands? What
are the chances you'd ever see anything as large, say, as 0dBm into
your receiver via skip? (0dBm = 73dB above s9, given that s9 = 50uV
into 50 ohms.) This could potentially include SW broadcast stations
running fairly high power.

Cheers,
Tom