Friday, March 30, 2012



29 March 2012, SUNSET in Annapolis Maryland:
2330z: LIFTOFF!. heading 150 deg. Temp 19C!
2345z: Heading 145 deg. Temp 10C. lost visual
0000z: Heading 143 deg. Temp 5C. Deadreckoning on APRS moving SE at 6 MPH
0019z: Temp transition to freezing. I value is a garbled "I7". Outside temp now at 0. This is important, since our ballast is a block of Ice. So it has been melting for 50 minutes and losing more mass than planned. Now that we are at freezing, the ice should remain frozen for the rest of the mission and release mass via sublimation, about 3 grams a day.
0045z: Inside temp "I2" (meaningless). Outside 00C. Volts 8.4. Anomolous readings around the transition from +C to -C is expected. We scaled from +70 to -70 using two different biased thermisters and there are some transition anomolies as we go from + to - values. We designed this mission to go to -40C at cruise altitude of 40,000' but when we discovered these balloons will top out at about 17,000 we did not have time to go back and optimize our A/D converters for better resolution around 0C.
0100z: Temp formats now OK. Both temps showing -5C or about 5000', volts 8.4. Luminosity indicates NIGHT so not being transmitted
0154z: Temps are -13C. Maybe at about 16,000' Battery is 8.3
0200z: Cruising Altitude, 15,000'. temps at -15C
0300z: Lost in noise. Temps at -20c. Over my horizon from Annapolis at 180 miles distance. Faded out.
0330z: Estimated position 37.6N and 73.7W and CSE/SPD posted on APRS-IS as W3ADO-11 Balloon object.
0400z: Pictures posted and I'm going home. HOpe to be listening before sunrise...
Wind Predictions anyone? I have no experience with this and no one here is doing a wind/balloon prediction, so if anyone wants to take this last posit and do some formal estimates as to where it should be by morning, then we can all take a listen. I assume we may get some skip over the horison around sun up? BINGO, RObert Rochte KC8UCH to the rescue. Here is his 48 hour prediction:

BEAM HEADING WARNING: My HORIZONTAL beam is weak when pointed at the balloon yet reports strong signals + and - 90 degrees from actual heading. This makes sense. The Balloon is Vertical, and the Beam is horizontal. So I get weakest signal when pointed right at the balloon due to cross polarization. When broadside, then there is a vertical component to the beam and the signal is stronger... at least while it was close and there was some elevation angle to the incoming wave.
At about 0200z I tilted beam about 45 degrees from Horizontal: Now I can peak on the signal. I'm getting about a 135 AZ and so I now posted a DF bearing on APRS. See APRS.FI.
THEREFORE, I am going to ignore all beamheadings reports unless they can prove a VERTICAL beam, or that they have swung either side of the bearing and gotten peaks on either side and then split the difference. Reporting bad beam headings is worse than no beam heading.
Nearby QRM: We notice another beacon with CW on nearly the same freq. Our dial freq is 28.223 USB dial, but we hear another CW signal (Italian) down at 28.222 USB dial.
March 29, 2012: The mission is to give us insight into constant-pressure balloons and especially the use of common mylar party balloons as a fixed volume envelope. Unfortunately, these balloons have a high mass and so the theoretical maximum altitude no matter how many balloons are used is only about 26,000 feet and that is with no payload other than the fixed balloon mass.
Our payload is shown below. It is about 50 grams. We are targeting 6 party balloons 3' in diameter which should give us a float altitude around 16,000 feet. The Telemetry will be in CW on 28.223 MHz (USB DIAL) and will contain Battery voltage, inside and outside temperatures, and surface luminosity of the ocean/clouds. It has no GPS. We will rely entirely on DF bearings and signal reports. At 16,000 feet the radio range will only be about 175 miles or less, not like the 400 miles for high altitude balloons. Though on 10m we may get some good DX? Transmitter power is 100 milliwatts. or less...
EMAIL DF reports to Be sure to include:
  • Your LAT/LONG

  • Time of observation

  • Quality of heading (subjective 1 to 10)

  • The CW string copied (examples below)CW Format: The CW format will be something like this. It is assumed that all outside termperatures will be below zero or negative so the minus sign is not transmitted. The inside temperature might get above 0 during sunlight. So assume the I inside temperature is positive and the outside temperature is negative in Degrees C. When the inside temperature goes negative then the I will change to IN to indicate negative temps. The outside Temp is always negative. If it goes positive, then the value will be replaced with an X.
    . . . W3ADO I nn T nn V nn APRS.ORG . . . <== inside temp positive and outside negative and Bat volts(in tenths)
    . . . W3ADO N nn T x V nn APRS.ORG . . . <== inside temp negatve and outside positive(X)
    The CW message takes about 35s and then will sleep for 60 seconds. The WEB page is only sent every 4th beacon to save power. A photo resistor looking down will report the Luminosity of the ocean and clouds. During the day it will send a Daylight or D xx value and at night it will change to a Nighttime number N xx. The luminosity count is inversly proportional to light level. The larger the number, the darker. When it maxes out Nightime at 99, that parameter will not be transmitted to save power.
    . . . W3ADO I 10 T 40 V 85 D 07 APRS.ORG . . . <== inside 10C, outside -40C, Battery 8.5v Daytime Luminosity "07"
    . . . W3ADO IN 20 T 43 V 84 N 75 APRS.ORG . . . <== inside -20, outside -43, Battery 8.4v Night Luminosity "75"

    TRACKING: The balloon has no GPS. All tracking will be done by HF DFing. The luminosity value will give us a time-of-sunset data point. All APRS users are assumed to know how to enter an APRS DF bearing report so that their DF bearing line shows up on global APRS maps. Those without APRS DFing capability, can email their reports to this address [].
    de WB4APR, Bob

    April 1991: The above photos are from our April 1991 launch. Notice our nice tracking antenna in the background.

    June 2000: The photo above is our Sunday 26 March 2000 trial-balloon payload that was launched from the Baltimore Hamfest consisting of two 3v Lithium batteries, a 555 oscillator with thermister and a 10mW 433.92 MHz key chain transmitter inside a tiny plastic bottle. It weighed less than 16g and rose to over 20,000' on a single 18" party balloon (Which we underinflated and ended up using 3 before we got it up in the wind). It was a trial test of our launch and tracking capabilities in preps for our larger 1 April APRS balloon launch (whichi was canceled). The balloon was tracked and chased across the DLMARVA penninsula and out over the Atlantic when we ran out of land on the shoreline near Dover Deleware. The balloon had only a temperature sensor, but when matched to an elevation temperature profile we got this telemetry:

  • 1230 launch

  • 1306 temp was 65 at about 2500 feet

  • 1400 temp was 54 at about 8000 feet

  • 1430 temp was 48 at about 11,000 '

  • 1500 temp was 34 at about 18,000 'See USNA Radio Club's PHOTOS and description of the Launch and chase.
    We are contemplating another launch on a weekend in April to let some other Midshipman clubs participate in the chase and recovery. Sort of simulating a "downed flier" search and resue mission.

    APRS BALLOONS: Balloons make a good test bed for small satellite payloads that are very low cost. Mission duration may last from a few hours to a few days and just about matches the modern student's attention span. The Naval Academy has launched one such payload in 1993 which was detected as far away as South Carolina and Conneticut.
    APRS SETTINGS: One of the most critical aspects of Balloon Mission design is the use of proper APRS settings. This has always been problematic. A 2-hop path is desired once the balloon is on the ground and lost, but was a nightmare for early balloon launches before the New-N paradigm. Now that most of the APRS network is New-N compliant, balloons may safely get the advantages of 2 hops using the same generic WIDE2-2 recommendation of all other mobiles. These 2-hop paths do not cause dupes throughout the network, becuse the New-N paradigm system eliminates all dupes assuring that each digipeater throughout the huge footprint of the balloon will only transmit the packet once and only once.
    Further, since the APRS New-N network has all digis with UIDWAIT set to 0, this means that all digis will digipeat the packet at the same time using up only one time slot, no matter how many digis are involved.
    DO NOT USE WIDE1-1! Notice that WIDE1-1 should NEVER be used on a balloon or any other high altitude aircraft or anything that can hit large areas. This is because most of the WIDE1-1 digipeaters only do callsign substitution and are not part of the WIDEn-N algorithm. When these packets get delayed for whatever reason by a second or so, then other digi's hear them and can end up with multiple dupes from every nearby digipeater.
    PACKET RATES: These balloons will be seen by everyone within hundreds of miles, and although they do not add more than the equivalent of a local mobile traveler, they should adhere to the same gentlemenly rules of channel sharing as everyone else. In that regard, short duration flights should never use a packe period any shorter than once a minute. FOr longer duration flights, a 2 minute rate should be considered.
  • No comments: