Hi Ken,

The excess noise from the environment should override any internal noise
generated by any of the current amateur rigs. If there would be any
advantage, it would be when listening to weak signals that are very close to
strong signals.
Generally, you probably wouldn't see any difference. Now, about those
S-Meter readings on noise level..........the most likely reason for the
difference is probably S-Meter calibration.
To verify this, you would need to have a signal generator with an accurately
calibrated output attenuator. With this piece of equipment, you can inject a
50uV signal into the antenna input. Typically, S9 equals 50uV at 14MHz.
It is hard to tell if this is the reason or if you really do live in a
noisier area.
As far as specs, just about every rig I have tested has an MDS in the 0.1uV
region. When receiver specs are given, there are at least two methods that
can be used. One of them is the soft measurement technique, whereby the
output of the signal generator is directly connected to the antenna input,
while the hard measurement technique has a 50 ohm thru-load connected
between the signal generator and the receiver that is being tested.
The soft measurement technique yields better sensitivity figures, and that
is what most of the manufacturers use.
I hope this helps.

Pete

"Ken Bessler" wrote in message
news:6JJse.15621$6o4.10423@fed1read04...
I know, I know - "RFI *on* an HF rig" & not "RFI
*from* an HF rig"?

Thats it. In trying to match the capabilities of a friend's
HF performance (rx only), I built what seemed to be a
better radio (K2). His rig is no lamer, either - its
a Yaesu FT-920. I can now equal him on signals heard.
We live close enough and have similar antennas so according
to the numbers, I should be able to copy signals he has
trouble copying more often than not.

Still, I rarely hear better than him. We are usually just
equal. According to the specs, I should hear a bit better
and I'm not.

I went over to his place and listened - his noise floor was
lower by 2 S units. He dosen't own a computer and I do
so I figured it was my PC. Came home and shut it down
with maybe 1/2 a S unit drop in my noise floor. Even un-
plugged the power strip going to the PC.

Then it came to me - I live closer to the city and am on
a hill while he lives in a depression. He had noticed another
ham who has much more trouble hearing and we both realised
that the other ham lives much closer to downtown than we do.

Could my noise floor problem be due to the fact that I have
a line of sight path to downtown 3 miles away? My friend
is 2 miles out farther and like I said, in a depression that puts
him 50 feet below downtown's grade. I'm 50' above downtown.

What can I do to lower the RFI from downtown? I've fought
intermod before but on VHF/UHF and that was a long time
ago.

I have very little experience with RFI from a city on HF .

Moving is out.

Help? Ideas? I'm not looking for much - I figure if I lower my
noise floor 3 db I will have gotten 98% of the noise. I have a
RX only port on the K2 and have a 10m inverted V hooked
up there but that just kills the whole spectrum except 10m.

BTW the main band of concern here is 40m. Maybe I could
build a BPF? Anyone know where I could find plans for one?

--
Just my 2¢... 73 es gd dx de Ken KGØWX
Grid EM17ip, Flying Pigs #-1055
Proud builder & owner of Elecraft K2 #4913