Dave et al:
I've found things like this
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=2563&item=5905564095&rd=1
on e-Bay for the past few months. Maybe they have the RS-232 controlled
version somewhere on nearby pages.
73 de
Gene Smar AD3F
----- Original Message -----
From: "Dave Bernstein" <aa6yq@ambersoft.com>
To: <towertalk@contesting.com>
Sent: Monday, June 28, 2004 4:15 PM
Subject: RE: [TowerTalk] Actual LP Performance vs Tribanders
> A model helicopter with a GPS receiver, a UHF link for the NMEA data,
> and software for navigation and position/signal-strength recording --
> what a cool idea! Are there off-the-shelf model helicopter controllers
> with RS-232 or USB interfaces?
>
> 73,
>
> Dave, AA6YQ
>
>
>
> -----Original Message-----
> From: towertalk-bounces@contesting.com
> [mailto:towertalk-bounces@contesting.com] On Behalf Of Michael Tope
> Sent: Monday, June 28, 2004 15:43
> To: Larry Phipps; towertalk@contesting.com; Jim Lux
> Subject: Re: [TowerTalk] Actual LP Performance vs Tribanders
>
>
> One of my colleagues at work fly's model Helicopters. Seems like a model
> helicopter with a small beacon transmitter might be the way to make a
> poor man's HF antenna range. Alternatively, a tethered helium balloon
> with a small beacon might be another way to build a cheap HF antenna
> range.
>
> Mike, W4EF........................
>
> ----- Original Message -----
> From: "Jim Lux" <jimlux@earthlink.net>
> To: "Larry Phipps" <larry@telepostinc.com>; <towertalk@contesting.com>
> Sent: Monday, June 28, 2004 11:37 AM
> Subject: Re: [TowerTalk] Actual LP Performance vs Tribanders
>
>
> > At 02:08 AM 6/28/2004 -0400, Larry Phipps wrote:
> >
> > >Jim, I'm not that familiar with the beacons, but since your post I
> > >did a little research. There are a couple of major problems.
> > >
> > >First, the transmissions are very short... there wouldn't be time for
> more
> > >than one sample per beam heading.. and it would take almost 2 hours
> > >just to gather the samples for one rotation (36 samples). The signals
>
> > >are
> going
> > >to be all over the place during that time frame... and that doesn't
> > >take interference into account. Timing would also be critical... your
>
> > >computer clock would have to be dead nuts on. There's also really no
> > >accurate way to correlate the signal strength to anything else
> > >minute-by-minute, so
> the
> > >levels would be more or less meaningless.
> >
> > Yes, I agree that you'd have a problem doing the measurement in one
> > pass through. You'd have to do a statistical approach over many days
> > and
> hours.
> >
> >
> > Timing you can get from the signals themselves, and the PC clock is
> > good enough to sequence it. As long as you're within a few seconds of
> > the
> "real"
> > time, it's fairly straightforward to track (programs like BeaconSee do
>
> > it, for instance).
> >
> > You could correlate the signal strength on the antenna under test to a
> very
> > short monopole antenna or small non-resonant loop (which will be
> > fairly consistent in azimuth and elevation response).
> >
> >
> >
> >
> > >Even with a 20 minute continuous carrier at 100W, I doubt the
> > >received strength of the beacons would be enough to be useful for
> > >plotting the pattern of a beam with 30dB F/B ratio. You would need a
>
> > >stable signal about 50dB above the noise floor... probably something
> > >around S9... and you'd have to listen to make sure there is no
> > >interference while the samples are being taken.
> >
> > Kind of depends on the accuracy you require. If you want tenth dB
> accuracy
> > on something that is 30 dB down, it would be a challenge (I doubt
> > there
> are
> > many antenna ranges or network analyzers that can do that well). If
> > you are willing to tolerate 1dB errors (out of 30), and, say, 0.5 dB
> > out of 10dB, I think you could do it with, maybe, 10-15 dB SNR.
> > Depending on the integration time. If the beacon is sufficiently
> > narrow band (which the NCDXF beacons are, during the test tones), your
>
> > measurement bandwidth (which sets the SNR) can be quite narrow
> > (probably limited by ionospheric doppler spread). Maybe 5-10 Hz?
> >
> > Using the noise level in VOACAP for residential areas (-145 dBW/Hz),
> > you're only going to be seeing something like -105 dBm noise floors.
> > Running a quick VOACAP from a monopole in Tangier to a swwhip Los
> > Angeles, (june SSN=100) it looks like you'll have SNR (in 1 Hz) of
> > above
> 15
> > dB for about 4 hours. That's going to be a bit marginal.
> >
> > However, as you point out, big broadcast stations would be a better
> > bet.
> >
> >
> >
> >
> > >My tests used commercial stations with BIG signals that transmit
> > >continuously, like WWV. I was testing a very broadband beam, so
> > >actual frequencies weren't that important. Testing a LPDA or SteppIR
> > >should also work OK with my software. You could probably make it work
>
> > >with a ham with a strong signal though, who would be willing to make
> > >several 5 minute continuous transmissions while the data was
> > >gathered.
> > >
> > >If you happened to have a neighbor within a few blocks, you could get
>
> > >meaningful results, especially if your antennas are high. You could
> > >use the TRX-Meter utility that comes with TRX-Manager since only one
> > >pass,
> and
> > >one sample per 10 degree heading would be needed. I got the idea for
> > >my program from trying TRX-Meter, but added the ability to integrate
> multiple
> > >samples over time to smooth out the effects of fading on skywave
> > >signals. Further away than about 10 wavelengths would give you a nice
>
> > >pattern, but I doubt that it would correlate into similar skywave
> > >performance.
> > >
> > >Larry N8LP
> >
> > _______________________________________________
> >
> > See: http://www.mscomputer.com for "Self Supporting Towers",
> > "Wireless
> Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with
> any questions and ask for Sherman, W2FLA.
> >
> > _______________________________________________
> > TowerTalk mailing list
> > TowerTalk@contesting.com
> > http://lists.contesting.com/mailman/listinfo/towertalk
> >
>
>
>
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
> Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with
> any questions and ask for Sherman, W2FLA.
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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