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Is the HF Band a Noise Wasteland?

J

John O'Flaherty

Jan 1, 1970
0
Thank god for noise blanker circuits....

Speaking of spectrum wastelands.... the petition to reallocate TV
Channel-6 to the FM band is back on the horizon. This time to include
TV-5 as well. (USA)

It would add substantially to the FM broadcast band, which is
congested in most urban areas.
And very few TV stations have elected 5/6 as their terrestrial DTV
channel.
Perhaps the time has finally come?

Now that there is digital broadcast on FM, they sometimes put multiple
channels on a single carrier.
 
D

Don Bowey

Jan 1, 1970
0
Now that there is digital broadcast on FM, they sometimes put multiple
channels on a single carrier.

Many FM analog broadcasts have multiple sub-channels. It's not a digital
phenomenon.
 
J

Jan Panteltje

Jan 1, 1970
0
More than that?
I'm thinkn if the HF band is not used for emergencies, it can be
buzzed with radiated smps noise.

A much bigger problem is internet over power lines.
In Austria the levels were orders of magnitude too high.
It blocked not only radio amateurs, but also some important civillian
emergency services.
And it seems you will get more of that.

The advantage may be that if conditions are good you can perhaps get
free internet from Europe ;-)
 
J

Jan Panteltje

Jan 1, 1970
0
Amateur radio...psshhht :p
'Can you hear me .zzshhhht..Can you hear
me...zsshhhtt..what?.zsszzhhhst..Repeat that ,,,,zssshhhts'
Bad enough I get that sort of frustration from my cellphone.

Sure I have worked South America from Europe on CB wth only 4 watts.
Loud and clear.
Once was member of a DX club (mm still am, actually).
 
J

Jan Panteltje

Jan 1, 1970
0
Then one fine day there is a major power outage, the cell tower backups
runs dry and everyone in the area finds zero bars on their cell phone.
That is where point to point communication can save the day, and has
many times.

Yep, that is why I have this big sealed lead acid that allows me
to transmit 12 hours if we ever flood, or 1 hour world wide at max power.
Interesting this lead-acid now has had about 875 charge-discharge cycles,
and still 100%?
 
B

Baron

Jan 1, 1970
0
D said:
More than that?
I'm thinkn if the HF band is not used for emergencies, it can be
buzzed with radiated smps noise.


D from BC
British Columbia
Canada.

FWIW I have a cell station 3/4 mile away that makes two meters totally
unusable for me. Turns out that its IF is on 144Mhz. 432Mhz is almost
as bad.
 
D

D from BC

Jan 1, 1970
0
A much bigger problem is internet over power lines.
In Austria the levels were orders of magnitude too high.
It blocked not only radio amateurs, but also some important civillian
emergency services.
And it seems you will get more of that.

The advantage may be that if conditions are good you can perhaps get
free internet from Europe ;-)

Wouldn't internet over power lines violate some conducted EMI reg.s in
other countries?
IIRC..
FCC conducted EMI limit is ~54dBuV* for 140khz to 30Mhz.
(HF band 3Mhz to 30Mhz).
This reg probably makes the HF band users happy.


D from BC
British Columbia
Canada.
 
B

Baron

Jan 1, 1970
0
Jan said:
Sure I have worked South America from Europe on CB wth only 4 watts.
Loud and clear.
Once was member of a DX club (mm still am, actually).

I've got a confirmed UK - Sicily on two meters, and a good number of
1000 mile + European confirmations.
 
J

Joerg

Jan 1, 1970
0
D said:
I think if anyone is serious about communication during a disaster,
they would have a satellite phone (ex:Iridium Motorola 9505) and a
solar charging system.
Unfortunately that's >>$1000.00

Not to mention subscription fees ...
 
J

Jamie

Jan 1, 1970
0
Baron said:
Jan Panteltje wrote:




I've got a confirmed UK - Sicily on two meters, and a good number of
1000 mile + European confirmations.
Sure, I hear Japan in the evenings on 20 meters at times but can't get
to the next town! :)


--
"I'd rather have a bottle in front of me than a frontal lobotomy"

"Daily Thought:

SOME PEOPLE ARE LIKE SLINKIES. NOT REALLY GOOD FOR ANYTHING BUT
THEY BRING A SMILE TO YOUR FACE WHEN PUSHED DOWN THE STAIRS.
http://webpages.charter.net/jamie_5"
 
B

Baron

Jan 1, 1970
0
Jamie said:
Sure, I hear Japan in the evenings on 20 meters at times but can't get
to the next town! :)

I could never generate enough interest in the HF bands to want to play
down there, though oddly enough 80mts on my parents radiogram when I
was nine, was fascinating to me. Then discovering that I could
sometimes hear New York taxi cabs around 10mts was wondrous. So I do
understand what you mean.
 
D said:
Wouldn't internet over power lines violate some conducted EMI reg.s in
other countries?
IIRC..
FCC conducted EMI limit is ~54dBuV* for 140khz to 30Mhz.
(HF band 3Mhz to 30Mhz).
This reg probably makes the HF band users happy.

From what I understand, they just declare that these systems are
exempt from the conducted EMC rules, and the politicians suddenly get
to be popular in the newspapers because they are "bringing high speed
internet to your town".

I believe that some of the systems make the transmitters put notches
at the amateur radio frequencies, and in isolation I expect that the
transmitters really do have these notches on those frequencies. After
you connect some fluorescent tubes and switched-mode power supply
rectifiers in parallel with the transmitter, I guess that the notches
will all fill up with intermodulation products (like when two
broadcast transmitters share a tower, anything nonlinear like corroded
galvanised wire ropes can generate frequencies (like 2*f2-f1) that
were never present at the output sockets of the transmitters).

Chris
 
J

John O'Flaherty

Jan 1, 1970
0
Many FM analog broadcasts have multiple sub-channels. It's not a digital
phenomenon.

I was aware of SCA channels that carried muzak, but I wonder if this
is different. A friend of mine bought an HD car radio, and it can
actually play several different channels of music from a single
station, stepping from one to the next at a button push.
I thought I'd get a digital receiver for the house, but they seem to
go for about $200, so I guess I'll wait.
 
J

Jan Panteltje

Jan 1, 1970
0
Wouldn't internet over power lines violate some conducted EMI reg.s in
other countries?
IIRC..
FCC conducted EMI limit is ~54dBuV* for 140khz to 30Mhz.
(HF band 3Mhz to 30Mhz).
This reg probably makes the HF band users happy.

Sure, same here, but none of that stuff meets specs.
I dunno how? Lobbying? They got it installed.

I could look up the article if it is still there, IIRC
they lowered the RF level a bit, but you have still problems
close to those lines.
http://www.arrl.org/tis/info/HTML/plc/aud-vid.html
 
Baron said:
FWIW I have a cell station 3/4 mile away that makes two meters totally
unusable for me. Turns out that its IF is on 144Mhz. 432Mhz is almost
as bad.

That really shouldn't be the case - the specs with which cellular
basestations have to comply are fairly strict, and they do test them
for compliance, and they usually overdesign them anyway. For GSM and
UMTS you can actually download the specs for the basestations and the
handsets from the 3gpp website (free of charge).
Here is a list of the specifications:
http://www.3gpp.org/ftp/Specs/html-info/SpecReleaseMatrix.htm

And here is the RF specification for 3G basestations:
http://www.3gpp.org/ftp/Specs/latest/Rel-6/25_series/25104-6g0.zip
It shows they are allowed to emit -36dBm in any given 100kHz channel
over the frequency range 30MHz to 1GHz, but I would be surprised if
they came anywhere close to breaking that spec.

Have you verified with a spectrum analyser or a careful experiment
with your receiver and some fixed attenuators to make sure that it is
not intermodulation or cross modulation distortion in your LNA? If
the interference drops by more dBs than the wanted signal drops when
you insert say a 6dB attenuator inline between your antenna and your
Rx LNA input, then that points to problems with the receiver linearity
that could be solved with a band pass filter for 2m. If everything
drops by the same number of dB - interference and wanted signal alike
- then it points to genuine spurious emissions.

Chris
 
J

John Larkin

Jan 1, 1970
0
FWIW I have a cell station 3/4 mile away that makes two meters totally
unusable for me. Turns out that its IF is on 144Mhz. 432Mhz is almost
as bad.


We look up at this out of our rear window.

http://www.jimprice.com/sutro/

I can get a few lines around -20 dBm by hanging a banana lead off the
input of our spectrum analyzer. I bet a modest antenna and some
schottky diodes could light an LED.

Oh, Jim also posts this:

http://www.nullmodem.com/


John
 
B

Baron

Jan 1, 1970
0
That really shouldn't be the case - the specs with which cellular
basestations have to comply are fairly strict, and they do test them
for compliance, and they usually overdesign them anyway. For GSM and
UMTS you can actually download the specs for the basestations and the
handsets from the 3gpp website (free of charge).
Here is a list of the specifications:
http://www.3gpp.org/ftp/Specs/html-info/SpecReleaseMatrix.htm

And here is the RF specification for 3G basestations:
http://www.3gpp.org/ftp/Specs/latest/Rel-6/25_series/25104-6g0.zip
It shows they are allowed to emit -36dBm in any given 100kHz channel
over the frequency range 30MHz to 1GHz, but I would be surprised if
they came anywhere close to breaking that spec.

Have you verified with a spectrum analyser or a careful experiment
with your receiver and some fixed attenuators to make sure that it is
not intermodulation or cross modulation distortion in your LNA? If
the interference drops by more dBs than the wanted signal drops when
you insert say a 6dB attenuator inline between your antenna and your
Rx LNA input, then that points to problems with the receiver linearity
that could be solved with a band pass filter for 2m. If everything
drops by the same number of dB - interference and wanted signal alike
- then it points to genuine spurious emissions.

Chris

Yes I agree, you are right, I shouldn't have a problem. I did complain
at the time and even had words with the local planning department, but
it was so hard to actually get at anybody that was the slightest bit
bothered. Then other things got in the way, so pursuing it got
waylaid.

I can/could stick a dipole on the receiver and still hear the chatter
from the cell IF, even through a 3db pad, Ok it doesn't move the S
meter, but its still quite audible. Its also a vertically polarised
signal. Its most prominent in the lower part of the band dropping off
as you move up to 146Mhz. I suspect that the signal peaks about
143Mhz, just outside the bottom of the band.

I must confess that I no longer have any antenna on the tower now and
the internet has taken over my communication needs so its not something
that I am leaping up and down about.

I will go and have a look at those links though, just out of interest.

Thanks.
 
T

T

Jan 1, 1970
0
A much bigger problem is internet over power lines.
In Austria the levels were orders of magnitude too high.
It blocked not only radio amateurs, but also some important civillian
emergency services.
And it seems you will get more of that.

The advantage may be that if conditions are good you can perhaps get
free internet from Europe ;-)

In the U.S. it was known as BPL (Broadband over Power Line). It died a
spectacular death when they realized that we U.S. amateurs are allowed
to run up to 1.5kW on the HF bands. That would do stuttering wonders for
a broadband connection.
 
T

T

Jan 1, 1970
0
I've got a confirmed UK - Sicily on two meters, and a good number of
1000 mile + European confirmations.

Furthest I've gotten on 2m is about 600 miles, from RI to North
Carolina.
 
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