Getting 1 mile video w/Gearcam

[the freshman]

Yesterday my SLI team had a successful test flight of our 4", ~7' rocket on a K570WW to an apogee of over 6200'. Dual-deployment with a Defy Gravity Tether went smoothly, and the rocket was recovered in good condition.

However, we didn't get a good enough signal from our Boostervision Gearcam onboard the rocket to record video of much more than the first hundred feet of liftoff. We were able to pick up a picture intermittantly while using the antenna to scan the cloudy sky for the rocket when it was near apogee; sound actually came through well the entire time.

I know our limiting factor is the low power output of the Gearcam, but since the Mile High Combo can work at over a mile in altitude, my thoughts on why ours didn't this particular time are:

-Our 14 db-gain patch antenna may not have given us enough gain
-Cloudy sky conditions prevented microwave transmission to the ground
-Our camera's antenna might have to be outside the rocket for the needed signal strength

I'm guessing the transmitter antenna position was the main problem. (Polarization was correct; both receiver antenna and camera rubber duck were horizontally polarized.) Unfortunately, the nature of the rubber duck antenna prevents it from being outside the airframe unless the entire camera is outside the airframe, and I want to avoid mounting the camera on the outside of the airframe.

Any suggestions?

 

[Art Upton]

Hi,

as shown on our website:

https://www.boostervision.com/boostervision/installation.asp

you need the GearCam antenna outside the rocket and in the instructions it talks about using a horizontal polarization or you will loose the signal at about 300 feet.

If you want the absolute best, the Mile High combo suggests that you place the antenna face up to the sky by the launcher.

I field emails for tech support daily, feel free to email me before you launch.

What you are learning is part of project management as well as science.

I suggest mounting the camera outside the rocket, we have done so even on L800 5" rockets.

 

[the freshman]

Thanks, Art. Polarization wasn't an issue (both receiving and transmitting antennas were horizontally polarized). I didn't know whether or not attenuation from the airframe would be too much to get a strong enough signal out; I agree that the attenuation from the rocket was main reason we had a bad signal. We'll make sure to mount the antenna on the ground near the launch pad next time, too.

Our experiment, design, and motor choice can't allow the increase in drag that comes with external mounting. What I'll probably do instead will be to use an internal mirror to have the camera pointing downward inside the rocket looking down at the mirror, while the rubber duck will be bent up to stick out of the airframe.

 

[Art Upton]

Thanks, Art. Polarization wasn't an issue (both receiving and transmitting antennas were horizontally polarized). I didn't know whether or not attenuation from the airframe would be too much to get a strong enough signal out; I agree that the attenuation from the rocket was main reason we had a bad signal. We'll make sure to mount the antenna on the ground near the launch pad next time, too.

Our experiment, design, and motor choice can't allow the increase in drag that comes with external mounting. What I'll probably do instead will be to use an internal mirror to have the camera pointing downward inside the rocket looking down at the mirror, while the rubber duck will be bent up to stick out of the airframe.

I don't think you will find any real noticable drag from putting the camera outside. It might reduce your altitude by about 3 or 4 feet.

Ok, maybe 30 or 40 feet instead of 3 or 4

 

[Pat Butler]

I have my camera mounted inside a payload bay and pointing at a mirror. That doesn't allow for the antenna to be outside of the rocket. I too have had problems with my reception.

 

[Art Upton]

That's why we recomend mounting it on the outside Pat.

 

[Pat Butler]

I'll try that. It would sure make it easier to prepare for launch. Right now I have to connect the battery then install everything inside my payload bay then put the nose cone and put in a few screws.

 

[troj]

FWIW, on the Redstone, we had the camera mounted in the birdhouse, with the antenna pointing straight out from the side. We had video of the entire flight, until just shy of touchdown, when the rocket was on the other side of a slight rise from the antenna sitting near the pad.

Art's got a pretty good clue how to make his equipment provide the best performance possible. We followed his recommendations, and that's our result.

-Kevin

 

[Art Upton]

Here is a document I made up and plan to publish on how I modify most of my model rocket size payloads to hold a Mini GearCam.

This one was the payload compartment of the Semroc Goliath

https://boostervision.com/files/modgoliath.pdf

Here is a picture of that payload on a 1/4 scale model of the Bruiser made from the Goliath

Here is a video of that rocket on an E30 motor using an 8db patch antenna

https://www.boostervision.com/minibruiser/minibruiser.wmv

The larger size Rockets can work the same way with the power cord out the Vent hole of the Electronics bay.

You can cover up the Cam with a 2/3 nose cone if it will go mach .8 or better.

I'm still arranging with Kevin for rights to the birdhouse