High Altitude Balloon Project


Actually only antenna changes EIRP. Altitude does wonders for range, but that’s due to lack of obstructions, not an increase in radiated power.



Walter, The Tracksoar utilizes an Radiometrix HX1 module which should already be FCC certified.



Yep, sorry my mistake.



It is my understanding that the FCC doesn’t certify modules, but only systems. Which include antennas. The only transmitting modules I have seen that were certified were complete radios with antennas. Of course I could be wrong

I did a quick google and found some interesting things. First, radiometrix site has a page about UNINTENTIONAL radiators on its certification page. These items are clearly not unintentional radiators.

But I also found this link which says:

" Some transmitters come with an FCC ID on them. Does using these
devices exempt me from further testing to achieve FCC authorization?

Not entirely. While it does lower the bar from the costly 

Certification process, you are still responsible for ensuring that your
product does not emit other radio frequencies. In short, you must test
it as though it were an unintentional radiator."



Alright, will do, always glad to help out other makerspaces.

The thing to remember about APRS is there are probably a lot of other people trying to hit those same repeaters so your signal could easily be drowned out and some packets missed, it’s pretty common in a busy area like dallas. The nice thing about being up high with LOS to lots of repeaters is youre very likely to be able to get into atleast one of them.

I dont have an exact date yet, I am assembling a board this week for a test launch on saturday. If the launch goes smoothly then the kickstarter will likely pop up within the next week or two. Even if you don’t launch in time for the kickstarter some feedback / data / video would be awesome for the tracksoar site.



relevant FCC regulations:
The applicable portions of Part 97 are 97.315 and 97.317

Ҥ97.315 Certification of external RF power amplifiers.
(a) No more than 1 unit of 1 model of an external RF power
amplifier capable of operation below 144 MHz may be
constructed or modified during any calendar year by an
amateur operator for use at a station without a grant of
certification. No amplifier capable of operation below 144
MHz may be constructed or modified by a non-amateur operator
without a grant of certification from the FCC.
(b) Any external RF power amplifier or external RF power
amplifier kit (see §2.815 of the FCC Rules), manufactured,
imported or modified for use in a station or attached at any
station must be certificated for use in the amateur service
in accordance with Subpart J of Part 2 of the FCC Rules.
This requirement does not apply if one or more of the
following conditions are met:
(1) The amplifier is not capable of operation on frequencies
below 144 MHz. For the purpose of this part, an amplifier
will be deemed to be incapable of operation below 144 MHz if
it is not capable of being easily modified to increase its
amplification characteristics below 120 MHz and either:
(i) The mean output power of the amplifier decreases, as
frequency decreases from 144 MHz, to a point where 0 dB or
less gain is exhibited at 120 MHz; or
(ii) The amplifier is not capable of amplifying signals
below 120 MHz even for brief periods without sustaining
permanent damage to its amplification circuitry.
(2) The amplifier was manufactured before April 28, 1978,
and has been issued a marketing waiver by the FCC, or the
amplifier was purchased before April 28, 1978, by an amateur
operator for use at that amateur operator’s station.
(3) The amplifier was:
(i) Constructed by the licensee, not from an external RF
power amplifier kit, for use at the licensee’s station; or
(ii) Modified by the licensee for use at the licensee’s
(4) The amplifier is sold by an amateur operator to another
amateur operator or to a dealer.
(5) The amplifier is purchased in used condition by an
equipment dealer from an amateur operator and the amplifier
is further sold to another amateur operator for use at that
operator’s station.
© Any external RF power amplifier appearing in the
Commission’s database as certificated for use in the amateur
service may be marketed for use in the amateur service.
§97.317 Standards for certification of external RF power
(a) To receive a grant of certification, the amplifier must
satisfy the spurious emission standards of §97.307(d) or (e)
of this Part, as applicable, when the amplifier is:
(1) Operated at its full output power;
(2) Placed in the “standby” or “off” positions, but still
connected to the transmitter; and
(3) Driven with at least 50 W mean RF input power (unless
higher drive level is specified).
(b) To receive a grant of certification, the amplifier must
not be capable of operation on any frequency or frequencies
24 MHz and 35 MHz. The amplifier will be deemed incapable
of such operation if it:
(1) Exhibits no more than 6 dB gain between 24 MHz and 26
MHz and between 28 MHz and 35 MHz. (This gain will be
determined by the ratio of the input RF driving signal (mean
power measurement) to the mean RF output power of the
amplifier); and
(2) Exhibits no amplification (0 dB gain) between 26 MHz and
28 MHz.
© Certification may be denied when denial would prevent
the use of these amplifiers in services other than the
amateur service. The following features will result in
dismissal or denial of an application for certification:
(1) Any accessible wiring which, when altered, would permit
operation of the amplifier in a manner contrary to the FCC
(2) Circuit boards or similar circuitry to facilitate the
addition of components to change the amplifier’s operating
characteristics in a manner contrary to the FCC Rules;
(3) Instructions for operation or modification of the
amplifier in a manner contrary to the FCC Rules;
(4) Any internal or external controls or adjustments to
facilitate operation of the amplifier in a manner contrary
to the FCC Rules;
(5) Any internal RF sensing circuitry or any external
switch, the purpose of which is to place the amplifier in
the transmit mode;
(6) The incorporation of more gain in the amplifier than is
necessary to operate in the amateur service; for purposes of
this paragraph, the amplifier must:
(i) Not be capable of achieving designed output power when
driven with less than 50 W mean RF input power;
(ii) Not be capable of amplifying the input RF driving
signal by more than 15 dB, unless the amplifier has a
designed transmitter power of less than 1.5 kW (in such a
case, gain must be reduced by the same number of dB as the
transmitter power relationship to 1.5 kW; This gain
limitation is determined by the ratio of the input RF
driving signal to the RF output power of the amplifier where
both signals are expressed in peak envelope power or mean
(iii) Not exhibit more gain than permitted by paragraph
©(6)(ii) of this Section when driven by an RF input signal
of less than 50 W mean power; and
(iv) Be capable of sustained operation at its designed power
(7) Any attenuation in the input of the amplifier which,
when removed or modified, would permit the amplifier to
function at its designed transmitter power when driven by an
RF frequency input signal of less than 50 W mean power; or
(8) Any other features designed to facilitate operation in a
telecommunication service other than the Amateur Radio
Services, such as the Citizens Band (CB) Radio Service.”



It is not clear to me if you believe (or how it applies) that the citation supports the idea that these components are certified by the FCC and do not require any additional testing by the licensed HAM who uses them.

When you build your own HAM transmitter you are expected to test its output to ensure that its spurious transmissions meet the standards expected. You don’t need to get a formal FCC certification for it, nor would I expect for a DIY radio on the balloon. However, I would expect that the FCC would expect such a DIY radio would have the appropriate testing conducted by the amateur responsible for it.

Anyway, best of luck with the launch and other aspects of the project.

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Ah, sorry I misunderstood your previous post.

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Your Tracksoar board just came out of the solder oven and is now being programmed. There is one minor error on the board, the FTDI TX and RX are flipped (i have corrected this on the next round of boards). So just keep that in mind when it comes time to program your call sign.

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Awesome, thanks Michael. I think we’ve all been there with swapping Tx/Rx lines.



So I found 150ft^3 of He for $105, 1 week tank rental, if we show nonprofit status. (Will I need board cooperation for showing 501c3 status? If so, how hard would it be?)

Also the tank had no stem (I think that’s what the flow shoppers are called), so it doesn’t need anything screwed in to eject gas, just open the valve and it goes. They recommended holding the balloon over the screwhole (whatever it’s called), but I don’t think that will work since we will need a load to balance against. They didn’t have any good solutions for unregulated hoses; I’m guessing it probably wouldn’t be too difficult to find the correct thread at home depot, drill a hole down the middle, and epoxy a garden hose to it or something.

That was one shop here in Arlington.

I might Google tonight and see if I can find more specifics on other people’s solutions.



The space has my tank of helium, I would agree it would be a good use of it. @Robert_Davidson can confirm if its still in offsite storage.



Michael from Tracksoar has shipped us a prototype of his new APRS tracker, and I should have it in hand for our meeting on Tuesday!



I shipped your Tracksoar board today, it should be there by early next week. Attached is the Tracksoar manual, its a first draft so any suggestions or revisions are welcome.



Just a reminder, we’re meeting tomorrow night at 7PM in the common room. There has been some discussion that some group members of RBNO (Robot Builder’s Night Out) may be interested in our project, but the two groups meet at the same time. We’ll gauge interest tomorrow and if neccessary, find a better time to meet.

I think the robot builders can offer a lot of advise/experience and may want to help us create our high altitude robot!



I am sorry guys, but I won’t be able to make the meeting tonight. It sounds like the Tracksoar is the solution to our APRS problem.

I have a radio, TNC, and APRSDroid ready. I am currently shopping for a good VHF antenna to mount on my truck to help with the chase.




Notes from meeting, direct copy paste (sorry):

To do for next HAB meeting:

  • Electronics power needs

  • Electrical budget

  • Someone build a payload box

  • Simple, Home depot square foam

  • Say, 6” x 6” x 4”

  • If HD foam ½” thick, then about 50g

  • Buildup of internals

  • Internal components:

  • Pixhawk

  • GoPro Hero 2

  • FPV txBattery

  • Buzzer

  • Gps Antenna
    *Telemetry tx
    *APRS tracker
    *Hot wire cutter
    *180 grams total, 256 w/ batttery

  • Interfaces

  • Parachute (71g)

  • Cutter / main line

  • Window for camera

  • Mast / GPS location

  • Payload budget


  • Bought NiChrome

  • Will bring drone to Saturday and drop test weighted box



Robert, sounds good - sorry you weren’t able to attend tonight. Excellent on the APRS setup - we’ll need receiving stations of our own, in addition to relying on APRS Igates. I’ll plan to make a cable to use either my android tablet or laptop’s soundcard to my Baofeng radio for decoding APRS packets.



Chesley, thanks for sharing.

I also want to pass along a link to a blog I found while looking at payload images today, great writeup on everything from payload hardware, balloon calculations, to filing a NOTAM with the FCC: http://rocketsetc.com/high-altitude-balloon/hab-1



H.A.B. Payload Container

I had some time today and did a rough and simple CAD of the box. I expect we’ll modify this when we sit down to design on Saturday, but here’s an initial concept

Foam material: Owens Corning Fomular (Home Depot rigid foam)

  • Price: $11.75 for 4ft x 8ft sheet (1/2 thickness)
  • Weight 2.7lb / sheet, or .266g / square inch

My concept is for a 5" foam cube. This will be a very compact design.


  • House electronics, keeping securely fastened
  • Insulate electronics from cold of high altitudes (< -40°)
  • Protect electronics from potential hard impact with earth
  • Protect electronics from water exposure if landing in body of water, and provide bouancy


Front View

Side View

  • Dark Grey: GoPro
  • Black: Pixhawk
  • Yellow: Telemetry Radio
  • Green: Video transmitter
  • Blue: 12v 1300mAh LiPo
  • Red: AA battery holder (for APRS)
  • Light Grey: APRS Tracker
  • Orange: GPS

You can view/edit the design here: https://tinkercad.com/things/ceNWmkFnqxV

One downside of this design is much wasted space around the camera. It’s assumed the camera compartment may get flooded, and thus it’s walled off from the rest of the electronics. For more sophisticated designs, we could even laser cut the foam.

Foam Required for container: 143 Sq. In. (38g)

  • Top & Bottom: 5"x5"
  • Front & Back: 4"x5"
  • Left & Right Side: 4"x4"
  • Inside Wall (camera chamber seperation): 4"x4"