Is the HF Band a Noise Wasteland?

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

On a sunny day (Sat, 26 Jan 2008 18:16:40 -0800) it happened D from BC wrote in :

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 ;-)

On a sunny day (Sat, 26 Jan 2008 17:52:38 -0800) it happened D from BC wrote in :

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).

On a sunny day (Sat, 26 Jan 2008 18:02:39 -0800) it happened Joerg wrote in :

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%?

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.

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Best Regards:
                     Baron.

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.

I've got a confirmed UK - Sicily on two meters, and a good number of

1000 mile + European confirmations.

--
Best Regards:
                     Baron.

Not to mention subscription fees ...

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Regards, Joerg

http://www.analogconsultants.com/

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"

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.

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Best Regards:
                     Baron.

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

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.

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John

On a sunny day (Sun, 27 Jan 2008 08:44:29 -0800) it happened D from BC wrote in :

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.

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:

And here is the RF specification for 3G basestations:

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

We look up at this out of our rear window.

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:

John

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.

--
Best Regards:
                     Baron.

Oh wow. Thats nearly as big as Emily !

Useful reference.

--
Best Regards:
                     Baron.

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.

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