Looking for a HAM person that knows about DSP'ing..
deno
Posts: 242
DSP = Digital Signal Processing.· I am a boater, that uses a marine Single Side Band, which is a HF radio with marine and HAM frequencies for receive and transmit. This is a no frills type of HF transceiver, with very little control of the output audio other then volume control.
When boating in the Bahamas, receiving weather information is one of the most important duties on board....next to keeping the beer stocked in the refrigerator.
Due to the proximity of other boats anchored or docked running various pumps, airconditioners, etc., there can and often is alot of interferance (QRM) thru my radio, making the weather information very hard to understand.· That is the problem, and the solution I am looking for, if it exsists, is some sort of software for the laptop computer that will process the incoming analog signal, digitize it, allowing me to manipulate it ( making the signal understandable) , then convert it back for playout of the computer speaker. Sort of a real time interference remover.
I have 'googled' around the internet, but haven't really found anything of interest...so I thought I would put out a 'feeler' on this Sandbox forum.· If no software knowledge is available, does anyone know of a good homebrew DSP, and if that is not available, how about a store bought device that you are happy with.
Deno
When boating in the Bahamas, receiving weather information is one of the most important duties on board....next to keeping the beer stocked in the refrigerator.
Due to the proximity of other boats anchored or docked running various pumps, airconditioners, etc., there can and often is alot of interferance (QRM) thru my radio, making the weather information very hard to understand.· That is the problem, and the solution I am looking for, if it exsists, is some sort of software for the laptop computer that will process the incoming analog signal, digitize it, allowing me to manipulate it ( making the signal understandable) , then convert it back for playout of the computer speaker. Sort of a real time interference remover.
I have 'googled' around the internet, but haven't really found anything of interest...so I thought I would put out a 'feeler' on this Sandbox forum.· If no software knowledge is available, does anyone know of a good homebrew DSP, and if that is not available, how about a store bought device that you are happy with.
Deno
Comments
Might I suggest that you start out by using Linux software, which is free. If you have a Windows laptop that you don't want to convert to Linux, you can use a Live CD to operate Linux while keeping the Windows installed. If you stay with Windows, you will immediately have to buy software to edit the digital audio files. It would be better to at least learn what you want.
Google around and I think you will be quite please with what Linux has to offer to filter and sample audio. You really have nothing to loose. Once you really get an idea of what you want, you can construct a Linux system on a USB memory stick and have the computer boot from the memory stick as a way to avoid interfering with the Windows laptop. I suspect that either Ubuntu or Fedora Core Linux will be a good start. Ubuntu may even be better as it has more free multimedia support.
The book "Running Linux" has a good chapter on multimedia that covers tools for any distribution. You can download just that chapter from OReily as a PDF. You may have to pay for the chapter and you might just consider buy the whole book as a PDF download if your are serious. It does a very nice job of explaining digital sampling and you can save your samples to CD if you really have big files.. Try Wikipedia again for "Linux Audio Editing' and I am sure you will be pleased.
I do see one item called 'Sox' - the Swiss Army Knife of Audio and it appears to be free in Linux AND Windows. But, whatever you do, Linux discussions will explain the generic facts of computing more clearly.
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PLEASE CONSIDER the following:
Do you want a quickly operational black box solution or the knowledge included therein?······
Post Edited (Kramer) : 7/12/2008 3:43:00 PM GMT
http://tech.groups.yahoo.com/group/radio_dspic/
I had a small batch of PCBs made, which have all gone. You could get your own made from my files.
Leon
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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle
I was able, using Google to locate info/data on the Si3000, but I would like to be able to see your design.
Thanks...Deno
Leon
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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle
how far from the coasts do you have to be before you can pick up a NOAA weather station? I think they are around 160 - 165 mHz.
- Howard
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Buzz Whirr Click Repeat
stations and has little to do with how "far from the coast" you are. 162-MHz transmissions are
basically line of sight, similar to commercial FM broadcast (88-108 MHz). So, if you're close
enough to one of their transmitters (without an obstructions such as hills, mountains, large cluster
of tall buildings) you should be able to receive NWS. Here in North Texas I can picked up two or
more NWS stations and, when conditions are right, I can pick up the closest transmitters on all
seven NWS frequencies.
At this link, nws.noaa.gov/nwr/, near the bottom of the page is a list of the specific
frequencies currently used by the National Weather Service (162.400-162.550 MHz).
Just above that list is '985 Transmitters' -- click on that link for the locations of the NWS
transmitters in the US. You should be able to find one close to you. There's only a few areas
where reception poor or non-existant.
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-Rusty-
--
Rusty Haddock <=> AE5AE
**Out yonder in the Van Alstyne (TX) Metropolitan Area**
Microsoft is to software what McDonalds is to gourmet cooking
Post Edited (Fe2o3Fish) : 7/14/2008 4:39:25 AM GMT
Rusty, does that mean not over the horizon? I'm recalling the little I remember about HAM radio frequencies... would it be correct that Deno's HF receiver's signals are so much lower that they bend or bound off the ionosphere?
Deno, if you're still watching this thread, see if you can get a hold of one of the last versions of a program called Cool Edit Pro (for windows - now it's part of Adobe's expensive 'suite' stuff and is called something else). Cool Edit's last incarnation was multi-track recording software, but it has a ton of DSP filters. You could also try the various Wave editors that have DSP plug ins ... there are several freebees out there. google for sound recording or synthesizer software.
Basically, I'm suggesting the obvious:·capture the radio's audio output via your laptop's sound card, saving it as a .wav file (which could be large depending on how long you record). Then open that .wav file in the editor, run it through filters until you get close to what you want. Then save and/or replay.
Pretty simple idea, but finding what filters and parameters work would take some experimenting. I've used Cool edit to pull out specific musical instruments from a recording - some recordings that are pretty poor for that matter. Of course, I didn't get the pure instrument ....
You'd have to figure out the approx. audio frequencies of the noise and notch them out with a parametric equalizer or a comb filter. However, if the noise is so badly mixed into the audio information, this may be impossible... and then you're back to some serious DSP which would have to have some grasp of the original voice information!
> there can and often is alot of interferance (QRM) thru my radio.
Does it come in through the RF, or is it local noise via power, etc?
- Howard in Florida
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Buzz Whirr Click Repeat
Post Edited (CounterRotatingProps) : 7/27/2008 11:18:14 PM GMT
Deno
the radio folks here can tell you this better than I, but there must be some way to reduce the interference before it gets into your receiver in the first place... I guess HF·antennas are too big to be·movable, so·you could aim it better at the source?
I do recall from my (now ancient) radio days that there were many kinds of RF filters to stop the kind of spurious EM noise you mentioned - brush motors are basically spark-gap transmitters, that is, broadband with lots of harmonics... right just the thing you need from your neighbors as you're trying to figure out where the storms are!
cheers
- Howard
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Buzz Whirr Click Repeat
Under normal circumstances it means 'not over the horizon'. On the other hand, the higher the antenna the
further the horizon! Still, in the VHF, UHF, and microwave bands we can get some tropospheric ducting and
get ranges of 100's to 1000's of miles. NOAA NWS is in the VHF band.
And so far as Deno's HF signals -- yes, since they are lower in frequency they can usually bounce off the ionosphere
depending on time of day and sunspot activity. FWIW, the frequency can get so low (300-KHz to 3-MHz, roughly)
that the signals just generally follow the ground. That's called ground wave propogation.
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-Rusty-
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Rusty Haddock <=> AE5AE
**Out yonder in the Van Alstyne (TX) Metropolitan Area**
Microsoft is to software what McDonalds is to gourmet cooking
thanks for the detailed and informative replies.
The 2007 version of the ARRL handbook doesn't seem to say much about the kinds of interference Deno's experiencing. Do you have any suggestions where to look further ?
thanks,
- H
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Buzz Whirr Click Repeat
A filter on the antenna may help. A bandpass filter specific for the
VHF band can help. A TVI filter could work, depending upon the
source of the interference.
Keep in mind that noise on the radio can come through the power supply
as well, especially when motors, compressors, and florescent lights are nearby.
Deno might try putting an automotive filter on the radio's power supply lines if
the radio is running off 12-14 VDC (and not 120-VAC).
Ferrite beads or snap-on ferrit cores around the power supply lines might be
useful too.
Deno may also want to try contacting a local HAM radio group and talk with
their local RFI guru.
RFI (Radio Frequency Interference) can be such a PIA!
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-Rusty-
--
Rusty Haddock <=> AE5AE
**Out yonder in the Van Alstyne (TX) Metropolitan Area**
Microsoft is to software what McDonalds is to gourmet cooking
Post Edited (Fe2o3Fish) : 8/3/2008 8:56:28 PM GMT
www.sgcworld.com/ADSPProductPage.html