0
\$\begingroup\$

I'm working on a rocket project at my University, and am trying to find a point to point / point to multipoint radio capable of a hopefully 1-5 Mbps data rate between a ground station a directional antenna (~30 dbi), and an omnidirectional antenna on the rocket. The main design constraints are the path loss (~109.7 dB @ 2.4 GHz, ~95 dB @ 400 MHz), power budget (not more than a few watts), size (must fit in a 5.5" diameter rocket body).

I've already looked at a few possibilities such as Ubiquiti routers (such as this) and some LoRa devices (like this). However, the Ubiquiti devices use a little too much power, are fairly large, and don't work with custom antennae (the ones they produce aren't spherically omnidirectional). On the other hand, all of the LoRa radio's I've been able to find are too low bandwidth to be usable.

The rocket we're building is to be launched at the IREC competition in June. The high data rate is to hopefully transmit live telemetry (low data rate) and live video (high data rate) back to the ground station. The idea is to have a couple of sensors and a camera feeding information into a microcontroller like a Raspberry Pi which will talk through the radio link to the ground station. The antenna needs to be omnidirectional because the orientation of the antenna can't really be controlled. One issue might be doppler shift, as the rocket will reach radial velocities of up to a few hundred m/s, but I'm not well versed enough in radio communications to know whether that will make the signals unreadable.

My question is: are there any products that would fit this use case, or is it possible to build such a system ourselves? I am HAM licensed, and am not opposed to Amateur TV except that almost nobody produces modules for that anymore.

Much appreciated.

\$\endgroup\$
  • \$\begingroup\$ First thing comes to my mind is point to point microwaves using magnetron/klystron and waveguides and antenna. I've seen DIY articles on re-purposing cheaply available components for this. But it takes knowledge on your part to get things working well. (Or else using commercial units -- see this.) If you are a class A, might be fine (though the modern US class-A license requires very much less knowledge and practical know-how than it used to require a few decades back before they "renovated" the licenses.) \$\endgroup\$ – jonk Dec 31 '18 at 3:29
  • \$\begingroup\$ I think I've seen youtube videos where tech like this was used, but I don't remember a channel or anything. You might find it worth having a browse though. OC creators are often not hard to reach. \$\endgroup\$ – K H Dec 31 '18 at 4:09
  • \$\begingroup\$ You not going to have a 30dB Rx antenna maybe a 30dB pre-amp YOu can get in the high 20's with a servo tracked VHF antenna that looks like this bing.com/… You must start with a serious path loss and hard look at tracking errors and dropouts at apogee with the donut hole of your omni pointing in the wrong direction. ( toward or away from you ) \$\endgroup\$ – Sunnyskyguy EE75 Dec 31 '18 at 4:24
  • 1
    \$\begingroup\$ Then do a serious Friis Path loss with all your variables and cost budget as every dB counts a lot of $ when you don't have enough. When I did this we have a room full of the best Telemetry gear and quad servo-tracking Helix antenna. \$\endgroup\$ – Sunnyskyguy EE75 Dec 31 '18 at 4:32
  • \$\begingroup\$ Use a series of Drones, as radio relays, each being 1,000 feet higher up. \$\endgroup\$ – analogsystemsrf Dec 31 '18 at 4:43

Your Answer

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.

Browse other questions tagged or ask your own question.