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Antenna suggestion
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) |
Antenna suggestion
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 |
Antenna suggestion
Is it possible that your radio power level is 1,000 m.w. rather than 1000
m.a.? It most certainly is 1000 m.A.! I must have been quite exhausted when I wrote that. I think this 'antenna' problem can be easily/inexpensively solved. if the location of the balloon is known. The location of the balloon is not 'known'. I was hoping that you would not have to point the antenna in the general direction. Can you get an omnidirectional antenna? Thanks, Brett |
Antenna suggestion
I must be cursed:
Yes, the power output is 1000 milliwatts. |
Antenna suggestion
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 -- |
Antenna suggestion
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 |
Antenna suggestion
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 -- |
Antenna suggestion
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 |
Antenna suggestion
wrote:
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. REDACTED YEP! Three hundred miles away IF ... IF the balloon is at 100,000 feet altitude!! The specs read "line of sight". At an altitude of 10,000 feet the radio line of sight horizon is about 120 miles. A typical UHF [900 MHz] receiver should be able to receive a signal as weak as 0.0000000000002 [2E-14] watts [1 uV] using a simple vertical antenna. Three hundred miles line of sight from 100,000 feet altitude is approximately 1.4E6 wavelengths. The power density at 300 miles from a 100,000 feet high balloon is approximately 8E-14 watts/wavelength^2 [2 uV]. The signal should be heard, but the noise margin is low for reliable digital data transmission. A gain antenna at the receiver will improve the signal to noise ratio significantly. The forces at work here are simply the receiving sensitivity of your earth bound receiver. Ham receivers have sensitivities less than 1 uV. The power divergence from the transmitter was assumed spherical for 1.4E6 wavelengths, and the receiver was assumed to have 1 uV sensitivity. 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. Above is for the balloon. Below is for the chase vehicle. 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 REDACTED Either antenna should do the job. The hg908Y would let you eyeball sight along the axis in the general direction of the balloon. Both are gain antennas. |
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