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

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

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

The noise is arriving in the 40M band. Since a 40M BPF passes 40M, how
wouold it "know" the difference between noise and signal?
As for noise floor- take Pete's suggestion or take your K2 to your friends
house and compare signals there.

It is likely the noise comes from your house- switching power supplies in
consumer electronics, fan speed controls, dimmers, microwave ovens etc.

Put the K2 on battery power and turn offf the main breaker into the house.

Dale W4OP

"Dale Parfitt" wrote in message
news:JdVse.4796$kj5.3590@trnddc03...

As for noise floor- take Pete's suggestion or take your K2 to your friends
house and compare signals there.

It is likely the noise comes from your house- switching power supplies in
consumer electronics, fan speed controls, dimmers, microwave ovens etc.

Put the K2 on battery power and turn offf the main breaker into the house.

Dale W4OP



I did that today - WOW! What a difference! Unplugging my PC and
turning off the SEC 1223 ps (leaving the K2 on SLA cells automatically)
made a HUGE difference! The PC was causing 90% of the noise.

My noise floor went from S7 to S4 and new stations just jumped
out of the air.

My friend still hears less band noise than me but only by 1-1.5db at
the most now.

Now, how do I solve the PC noise problem? I guess I could spend
a small fortune in ferrite snap on chokes but I doubt I would be able
to equal how quiet it is with the PC off. If that's so, I doubt I'll bother
- it's just too easy to turn off the PC during net time......

Would a laptop on batteries work without noise?

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

To cut down on PC noise, use a metal case with no plastic inserts.
Use ferrite beads/chokes on all cables coming out of case, and if
possible, put a metal plate between PC and radios, I have a metal layer
under my desktop/workbench that is grounded, with the radios above, and
Pc's below, with a LCD monitor connected to each pc through a KVM
switch, with very little if no noise from pc!!!

Bob N9LVU

Ken Bessler wrote:
"Dale Parfitt" wrote in message
news:JdVse.4796$kj5.3590@trnddc03...


As for noise floor- take Pete's suggestion or take your K2 to your friends
house and compare signals there.

It is likely the noise comes from your house- switching power supplies in
consumer electronics, fan speed controls, dimmers, microwave ovens etc.

Put the K2 on battery power and turn offf the main breaker into the house.

Dale W4OP




I did that today - WOW! What a difference! Unplugging my PC and
turning off the SEC 1223 ps (leaving the K2 on SLA cells automatically)
made a HUGE difference! The PC was causing 90% of the noise.

My noise floor went from S7 to S4 and new stations just jumped
out of the air.

My friend still hears less band noise than me but only by 1-1.5db at
the most now.

Now, how do I solve the PC noise problem? I guess I could spend
a small fortune in ferrite snap on chokes but I doubt I would be able
to equal how quiet it is with the PC off. If that's so, I doubt I'll bother
- it's just too easy to turn off the PC during net time......

Would a laptop on batteries work without noise?

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

If you have any fluorescent lights in the house, turn them off. Take a
small radio on AM and walk around to find the source.
Much of your noise is probably the PS of the PC. I use to get that when
I used the regular $20 PS's Go to Comp USA and get a good high end
supply, the cabling is shielded and they are designed for low RFI. The
cost is a bit higher, $150-500 but it's worth it if you have computers
near radios. I have 4 computers running in the radio room on 4 UPS's
NO NOISE to the radios at all.
Good Luck!
73 Chris, VE3NGW/W4 Florida

Robert Kubichek wrote:

To cut down on PC noise, use a metal case with no plastic inserts.
Use ferrite beads/chokes on all cables coming out of case, and if
possible, put a metal plate between PC and radios, I have a metal
layer under my desktop/workbench that is grounded, with the radios
above, and Pc's below, with a LCD monitor connected to each pc through
a KVM switch, with very little if no noise from pc!!!

Bob N9LVU

Ken Bessler wrote:

"Dale Parfitt" wrote in message
news:JdVse.4796$kj5.3590@trnddc03...


As for noise floor- take Pete's suggestion or take your K2 to your
friends
house and compare signals there.

It is likely the noise comes from your house- switching power
supplies in
consumer electronics, fan speed controls, dimmers, microwave ovens etc.

Put the K2 on battery power and turn offf the main breaker into the
house.

Dale W4OP




I did that today - WOW! What a difference! Unplugging my PC and
turning off the SEC 1223 ps (leaving the K2 on SLA cells automatically)
made a HUGE difference! The PC was causing 90% of the noise.

My noise floor went from S7 to S4 and new stations just jumped
out of the air.

My friend still hears less band noise than me but only by 1-1.5db at
the most now.

Now, how do I solve the PC noise problem? I guess I could spend
a small fortune in ferrite snap on chokes but I doubt I would be able
to equal how quiet it is with the PC off. If that's so, I doubt I'll
bother
- it's just too easy to turn off the PC during net time......

Would a laptop on batteries work without noise?

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

As for noise floor- take Pete's suggestion or take your K2 to
your friends
house and compare signals there.

It is likely the noise comes from your house- switching power
supplies in
consumer electronics, fan speed controls, dimmers, microwave
ovens etc.

Put the K2 on battery power and turn offf the main breaker into
the house.

Dale W4OP



I did that today - WOW! What a difference! Unplugging my PC and
turning off the SEC 1223 ps (leaving the K2 on SLA cells
automatically)
made a HUGE difference! The PC was causing 90% of the noise.

My noise floor went from S7 to S4 and new stations just jumped
out of the air.

My friend still hears less band noise than me but only by 1-1.5db
at
the most now.

Now, how do I solve the PC noise problem? I guess I could spend
a small fortune in ferrite snap on chokes but I doubt I would be
able
to equal how quiet it is with the PC off. If that's so, I doubt
I'll bother
- it's just too easy to turn off the PC during net time......

Would a laptop on batteries work without noise?


I banished my desktop 3 rooms away and still had to do ferrite
tricks to quiet the monitor. I am using a laptop in the radio room
and find no noise. Laptops that use fluorescent backlighting
for the LCD may cause problems, but I haven't seen any noise
with my old Tosh t2100. I am also using an Astron linear power
supply for the entire station.

Being on a hill is nice for VHF/UHF, but there is no advantage
for HF operation due to the added exposure to line noise and
various other man-made distractions.

ac6tk