On Fri, 28 Jul 2006 22:29:51 GMT, Owen Duffy wrote:


sending an experimental balloon to over 100,000 ft. I have purchased
two 900MHz RF Aerocomm ConnexLink Radios. The radios have a power of
1000 m.a., which states it will transmit and receive up to 20 miles
line of sight. I do realize that this is probably under ideal

I did mean to comment on the temperature spec for the radio. The
temperature in the troposhere can be as low at -50 to -75 deg C, will
the radio get cold enough in transit to fail (eg battery failure,
condensation etc).

Owen
--

Owen Duffy wrote:
On Fri, 28 Jul 2006 22:29:51 GMT, Owen Duffy wrote:



sending an experimental balloon to over 100,000 ft. I have purchased
two 900MHz RF Aerocomm ConnexLink Radios. The radios have a power of
1000 m.a., which states it will transmit and receive up to 20 miles
line of sight. I do realize that this is probably under ideal


I did mean to comment on the temperature spec for the radio. The
temperature in the troposhere can be as low at -50 to -75 deg C, will
the radio get cold enough in transit to fail (eg battery failure,
condensation etc).

Owen
--


YEP!

You have to account for loss of battery power, loss of gain in the
semiconductors, etc. Or, provide a stable thermal environment.

sending an experimental balloon to over 100,000 ft. I have purchased
two 900MHz RF Aerocomm ConnexLink Radios. The radios have a power of
1000 m.a., which states it will transmit and receive up to 20 miles
line of sight. I do realize that this is probably under ideal

I did mean to comment on the temperature spec for the radio. The
temperature in the troposhere can be as low at -50 to -75 deg C, will
the radio get cold enough in transit to fail (eg battery failure,
condensation etc).

You should read Paul Lloyd (Lloyd Paul?) Verhage's long series of
"near space" articles which have been running in Nuts & Volts magazine
for at least a year! He started sending balloons and packages of
scientific experiments (radio telemetry and DF'ing, cameras, once
even included some roaches!) into near space years before that.

FWIW, he is a "ham", and when he started, he was a student here at
Kansas State University. Even better, he launched his balloons
from the "Johnson Near Space Center" about 10 miles south of Manhattan,
Kansas; so-called because Dr. Gary Johnson, K0HGJ, who was working to
duplicate some of Tesla's high-power experiemts, owned a humongous-
big-and-tall metal building with VERY-big sliding doors that was
perfect for inflating balloons inside (out of any wind) and carrying
outside for launching, and the similarity with the name "Johnson Space
Center" was just too good to resist!

I believe Lloyd (the name he used then) is now a high-school teacher
somewhere, and he incorporates his balloon launches into his science
classes.

--
--Myron A. Calhoun.
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
NRA Life Member W0PBV "Barbershop" tenor CDL(PTXS) (785) 539-4448
Certified Instructor (KS Concealed Carry, Rifle, Pistol, Home Firearm Safety)

Yes, I did think of temperature concerns. The radio unit itself should
be kept at above freezing if my calculations are correct. However,
does the antenna need to be kept warm?

Owen Duffy wrote:
On Fri, 28 Jul 2006 22:29:51 GMT, Owen Duffy wrote:


sending an experimental balloon to over 100,000 ft. I have purchased
two 900MHz RF Aerocomm ConnexLink Radios. The radios have a power of
1000 m.a., which states it will transmit and receive up to 20 miles
line of sight. I do realize that this is probably under ideal

I did mean to comment on the temperature spec for the radio. The
temperature in the troposhere can be as low at -50 to -75 deg C, will
the radio get cold enough in transit to fail (eg battery failure,
condensation etc).

Owen
--

If the radio is the CL4790-1000 it is rated to -40C. For short term exposure to
cold, have you considered a small thermal blanket? It is drawing 5 watts from
the battery and power output is one watt. So, you have 4 watts of heat. Possibly
enough for a small thermal blanket.

Antenna should not require any heating element.



wrote:

Yes, I did think of temperature concerns. The radio unit itself should
be kept at above freezing if my calculations are correct. However,
does the antenna need to be kept warm?

Owen Duffy wrote:

On Fri, 28 Jul 2006 22:29:51 GMT, Owen Duffy wrote:



sending an experimental balloon to over 100,000 ft. I have purchased
two 900MHz RF Aerocomm ConnexLink Radios. The radios have a power of
1000 m.a., which states it will transmit and receive up to 20 miles
line of sight. I do realize that this is probably under ideal

I did mean to comment on the temperature spec for the radio. The
temperature in the troposhere can be as low at -50 to -75 deg C, will
the radio get cold enough in transit to fail (eg battery failure,
condensation etc).

Owen
--

wrote:
Yes, I did think of temperature concerns. The radio unit itself should
be kept at above freezing if my calculations are correct. However,
does the antenna need to be kept warm?

Hi Brett

In most cases, the transmitter will be in an enclosure. I'm assuming
that there will be an experiment package. Many who do this sort of thing
will make the enclosure out of Styrofoam. Some actually use styro picnic
coolers. For typical flight durations, the inefficiencies of the
electronics equipment on board the payload (read waste heat) will make
up for the nasty temps outside. I've seen some cases where there has
actually been a temperature rise. The criteria is a well sealed
insulating box.

And no, the antenna itself does not need to be warm. Just seal off the
exit port to keep internal heat from leaking out.

Your watt should be sufficient power. At 100 kilofeet, you will reach
more that you likely want to reach! I've seen propagation maps that show
a single balloon repeater at these heights covering 1/3rd of the US.



- 73 de Mike KB3EIA -

Owen Duffy wrote in
:

On Fri, 28 Jul 2006 21:20:43 GMT, "Ralph Mowery"
wrote:


wrote in message
groups.com...
Sirs:

I am a programmer and electrician, but not a radio person! I am
sending an experimental balloon to over 100,000 ft. I have
purchased two 900MHz RF Aerocomm ConnexLink Radios. The radios have
a power of 1000 m.a., which states it will transmit and receive up
to 20 miles line of sight. I do realize that this is probably under
ideal circumstances and will not likely be the case when I actually
deploy. I would be interested in purchasing some antennas which
would somehow increase the range. What sort of characteristics make
up a good antenna for what I want to do? It is possible that
someone could find me one that would work with my project? Also,
anything you might contribute concerning radio transmission would be
very much appreciated.
Money is no object for this experiment, so any ideas you have are
very much welcome.

Just about any antenna will work . I would look into a 1/4 wave
antenna mounted upside down so it is pointed down for the balloon. I
hope you ment

So that would have its pattern null pointed down at the earth?

Not to imply that the balloon would necessarily be directly above the
observer(s), but if and when it was at the zenith, it would be
relatively hard to hear.

I used to do a lot of radiosonde work. Those balloons would go to
110,000 feet at times. The transmitters were small, probably not more
than a watt, but we tracked them with an automatic system. The instrument
used a 1680mhz transmitter with an upside-down ground plane antenna in
the bottom (I think that was the freq. but it was near there). The
tracking antenna, though, was a parabolic dish with a wobbling feed-point
antenna that automatically tracked the balloon's radio, giving us a
continual readout of azimuth and elevation angles. By combining this
data with the received data from the instrument's aneroid barometer,
temperature and humidity sensors, we could locate the balloon with good
accuracy in three dimensions. Thus the run would provide temperature and
humidity profiles as well as data on winds aloft. Balloons almost never
go straight over you and when they do it is almost always early in the
flight when the signal is close and strong.

The OP hasn't told us the elevation angles of the locations of the
balloon in flight, how fast it is likely to spin, data rate or
equivalent (eg is this intended to send images back?), etc... they are
all relevant to commenting on suitability of the 1000mA??? radio, and
the type of antennas for the balloon and ground station(s).

A lot depends on frequency, too. Tracking a 2.4 or 5.8 ghz transmitter
is different from tracking a 35mhz transmitter.



--
Dave Oldridge+
ICQ 1800667

At an altitude of 100,000 feet 1000 mw [1 watt] should reach to the radio
horizon of about 300 miles assuming a good receiver on the far end of the range.

A vertically polarized 1/2 wavelength antenna should work fine. At least it
would be my starting point. Second option would be an inverted [upside down] 1/4
wavelength ground plane. Either antenna is not expensive.

What information is to be transmitted? If you are looking for moderate speed
telemetry then a path loss versus error rate study needs to be done. If data is
being transmitted a gain antenna may be required at the receiver. Gain antennas
are not expensive and the antenna needs to be pointed at and follow the
balloon's flight path.

/s/ DD

wrote:

Sirs:

I am a programmer and electrician, but not a radio person! I am
sending an experimental balloon to over 100,000 ft. I have purchased
two 900MHz RF Aerocomm ConnexLink Radios. The radios have a power of
1000 m.a., which states it will transmit and receive up to 20 miles
line of sight. I do realize that this is probably under ideal
circumstances and will not likely be the case when I actually deploy.
I would be interested in purchasing some antennas which would somehow
increase the range. What sort of characteristics make up a good
antenna for what I want to do? It is possible that someone could find
me one that would work with my project? Also, anything you might
contribute concerning radio transmission would be very much
appreciated.
Money is no object for this experiment, so any ideas you have are very
much welcome.

Thanks,
Brett

Dave wrote:
At an altitude of 100,000 feet 1000 mw [1 watt] should reach to the radio
horizon of about 300 miles assuming a good receiver on the far end of the range.


Do you mean that I should be able to pick up a signal from 300 miles
away??? I don't believe I understand the forces at work here.


A vertically polarized 1/2 wavelength antenna should work fine. At least it
would be my starting point. Second option would be an inverted [upside down] 1/4
wavelength ground plane. Either antenna is not expensive.


I was hoping to only put an antenna on the vehicle that I chase the
balloon with. It weighs too much to put it on the balloon itself.
However, would it decrease my performance that much??? I asked this
similar question to Aerocomm(who manufactures the radios). They sent
me two possible antennas, but I'm not sure either is really what I
want.
http://www.coronaos.com/hg908y.pdf
http://www.coronaos.com/hg908p.pdf


What information is to be transmitted? If you are looking for moderate speed
telemetry then a path loss versus error rate study needs to be done. If data is
being transmitted a gain antenna may be required at the receiver. Gain antennas
are not expensive and the antenna needs to be pointed at and follow the
balloon's flight path.


I'm not really sure how much data is transmitted. You need to check
out the product description for these devices. From a programmer's
perspective, I don't need to do any initializing of the radio.
Whatever data I transmit out of the serial port is what shows up out of
the other radio's serial port. Pretty basic. I am not planning to
send images back, just little bits of data. But I would like the
reliability of the connection to be such that I could send back a photo
if I needed to.

It would be nice if somebody could give me a link to a website where I
could buy the proper antenna with a proper connector.


Here is the e-mail from Aerocomm:

You can try one of the antennas that I have attached information on.
The panel offers better overall coverage while the yagi is more focused
and covers longer distance. These are not officially approved for use
by the FCC. Remember that the ConnexLink has a reverse polarity SMA
jack for the antenna connector.



Thanks for all the replies!
Brett

On 31 Jul 2006 09:59:54 -0700, wrote:
http://www.coronaos.com/hg908y.pdf
http://www.coronaos.com/hg908p.pdf

Hi Brett,

These are commercial antennas, the first is what you might use in your
chase car. It exhibits gain from the complexity of its design. It
also exhibits a sharp lobe that is inconsistent with use on a balloon
(unless you add tracking servos - yeh, you are not going there).

It would be nice if somebody could give me a link to a website where I
could buy the proper antenna with a proper connector.

If you have such a tight weight budget, you should be doing it
yourself. Packaged products are always heavier. You "could" get away
with a simple piano wire stinger stuck into the transmitter's jack.

73's
Richard Clark, KB7QHC