Frequency Signal Strength Mapping
William Abbott
Got kind of a strange question here... I'm wanting to learn a little more
about radio interferences and how to locate them, etc...
In particular I have a newly found FM radio transmitter that I LOVE
listening to (like them since they created this radio station, years ago,
but only recently have we gotten a retransmitter) however it appears we have
some major intereference issues... the transmitter is listed as being in my
city, however in parts of town the station is totaly un-listenable.. in fact
in one area all sound is lost, and other noise is heard, (sounds as if a
carrier is drowning out the actual station)
I figure this might be a good chance to do some learning... I've emailed the
station to let them know of possible problems, from my 2M beam pointing
north (no idea which direction the transmitter is, just where my beam was
already pointing) I found that stations 1 and 2 channels above were comming
clear down into the frequency in question (guessing they have way to high of
deviation on the FM transmitter on said interfering stations?, is this sound
right?)
Anyways, what I thought might be fun/interesting is to go mobile and build
some sort of coverage map... I have radio mobile and have used it for
predicting coverage of my home station, etc... is there something like this
that can be done by interfacing on my my radios (say my 857 that I already
use the CAT connection with) which could also interface with GPS, and could
build a signal strength map of the area as I drive... where it could plot
out the S meter strength of the station, and I could notate areas which may
have high signal but no audio?
This is silly I suppose, but I just thought it could be interesting to be
able to build a real life coverage map of said station... is there some
inexpensive or preferably free software that can do this task? Is there
anything I should/could do to help this radio station locate the problem and
hopefully fix it... as I said I have a feeling other stations are
interfering, which means complaints need to be filed against them by the
station.
I have other interference issues with 2m and HF from my house so I figgure
this might be a good way to learn how to track interference and learn about
the different interferences, as well as neat things one can do with radio
gear.
I don't have a LOT of equipment, but I'm figguring I have gear that should
be able to track simple problems such as this... now if I could only find
the high noise level I get on HF, I think it's the the North/North East as I
hear it on my 6M beam when pointed that direction, and don't hear it locally
on AM hand held radios, etc. Probably a transformer or something a few
blocks away thats messed up.
----------------------------------------
William Abbott
Web Master/Network Administrator
wi...@oregonfirearmsacademy.com
Oregon Firearms Academy LLC
http://oregonfirearmsacademy.com
jfra...@gmail.com
with hamlib, gpsd, and about twenty lines of C code to log signal
strength to a file as you drive (read lat/lon from gpsd and S-meter
reading from hamlib every ten seconds, write data to a file). You can
then easily postprocess the output file and, for example, output a KML
file to display in Google Earth to see your coverage map.
GPSD: http://gpsd.berlios.de
hamlib: http://hamlib.sourceforge.net/
KML: http://earth.google.com/kml/
-=Jeff N0GQ=-
On Jan 30, 10:20 am, "William Abbott" <s...@oregonfirearmsacademy.com>
wrote:
> w...@oregonfirearmsacademy.com
> Oregon Firearms Academy LLChttp://oregonfirearmsacademy.com
William Abbott
Sounds easy enough if I knew C, I used to be ok in VB.Net but I haven't done
it in years, I can't hardly remember it.
Was hoping for something off the shelf as opposed to do it yourself... I did
see theres some commercial software similar to radio mobile which can do
real life strength as well as predictive, but it only costs about $12000 or
something like that.
----------------------------------------
William Abbott
KE7ERQ
KE7...@gmail.com
Lebanon, OR CN84nm
William Abbott
problem without doing field strength
The station I want to hear which is supposed to be local (here in Lebanon)
is on 88.1 Mhz. As I was going through town today I noticed the
interference actually had some signal to it today, I could hear talking
going on through part of town... I tuned it in on my 857D at home, and swung
my beam around till I could hear the interfering station the most (figuring
not only correct direction, but ability to tune it in and figure out what
station it is)
I actually found myself pointing South or SSW... I looked up 88.1 Stations
in Oregon and found a couple, went to their webpages and listened to the
online feed, hmm neither of the 2 listed... both were to the south or south
west of me... so I tuned around to find the best signal on the offending
station, and found it closer to 88.3Mhz, however it's coming in EXTREMELY
clear and strong on 88.1 (can you say TOO wide of a frequency deviation?)
Me thinks they have a messed up transmitter... so I did a new search for
88.3 and found a station in Portland (wrong way for the beam, but we all
know propagation does strange things, could be bouncing off a hill to the
south of me) and Bingo, found my offending station, with the delay of
internet feeds I heard things I was hearing over the air...
Now I don't know what to do? I've sent an email to my station telling them
were having some interference issues... perhaps I should send some mail to
the now identified station, or send a new message to my station and let them
notify the offender.... I'm sure now that we know it's another radio station
and not stray RF or something, and that it's a station deviating one whole
frequency away something can be done... I'm sure the FCC would have a nice
letter to write the other station about fixing it if it were to go that
far... but I'm guessing the offending station would try and fix it if they
knew... it's one thing to be hearing a Portland station down here period,
but to have it blasting out a local station one channel bellow, and 200khz
away in spectrum.
Which brings me to another point... I drove long haul truck for the last 2
years (now unemployed) and heard a few illegal transmissions on the CB band
in that time (some that I could locate easily), and I know it's become an
issue, but it got me wondering, how does one report bad stations not only on
the CB band but on the amateur bands and such? Is there an email address or
form to fill out? I know some of it can't be regulated very well due to
various reasons, but interference someone is having but can't locate and
makes there life terrible might not bug me, but I might be closer and be
able to locate it... I know I'm not the radio police, but I feel as an
amateur I should do more to protect the air waves by helping the FCC out...
and report what I can... I've heard commercial advertising on CB (along with
jamming and other goodies that we know occur there, many times I knew
exactly who was doing it, and could have given an address to the FCC), I've
heard stations nearby using GMRS for what sounded like commercial use (no
callsigns heard) and other things... I always fear that if someone doesn't
help report this stuff (though I don't WANT to get people in trouble)
eventually things will get much worst then they are and we will end up
suffering as more of our frequencies get handed out for new things such as
FRS/GMRS/CB and it will continue to degrade and everyone will lose
Sorry just my rant...
William Abbott
1-541-913-0453
www.NWDIR.Net
http://scuba.oregonfirearmsacademy.com
sc...@oregonfirearmsacademy.com
Tierra del Mar Labs
task easily with your analog detector output. Big dynamic range on the
input too, millivolt to 10 volt stand alone! Makes stuff directly to MS
Excel thru USB port for graphs and plots, mapping...Incidentally, you
can do the polling math, does not work to well with spectrum analyzer
for filter graphs, but does work well for field strength plotting with a
ton of inputting. Cheap too!
Jeremy w7eme
-----Original Message-----
From: PNW...@googlegroups.com [mailto:PNW...@googlegroups.com] On
Behalf Of jfra...@gmail.com
Sent: Tuesday, January 30, 2007 11:52 PM
To: PNWVHFS
Subject: [PNWVHFS] Re: Frequency Signal Strength Mapping