So what does frequency range have to do with antenna? I just thought that if I have a 5db 2.4GHz antenna it just becomes a 3 db 900 MHz antenna or something. I can't really fit anything exceedingly long inside the rocket because of space limitation. Is this a function of antenna shape or material?
Would getting a Yagi antenna for the LCD receiver help?
To transmit power, an antenna need to resonate (be tuned) to the transmitter frequency. For example f = 1 GhZ = 1,000,000,000 HZ = 1 x 10^9 Hz. Radio wave travel at the speed of light with is c = 3 x 10^10 cm/s = 30 x 10^9 cm/s. The wavelength is wl = c/f = 30 x 10^9 cm/s /1 x 10^9 /s= 30 cm.
The simplest antenna is a 1/4 wavelength so a 1/4 wave @ 1 GHz = 30 cm/4 = 7.5 cm = 3". This is the electrical length. The physical length could be short is the wire is coiled as some rubber duckies are, but when the physical length = the electrical length you get the best performance.
So a 1/4 wave 900 Mhz band antenna (900-930 Mhz) will be ~7.5/.915 = 8.2 cm long and a 2.4 GHz band antenna (2.4-2.6 GHz) will be ~30/2.5 = 3 cm long.
A 1/4 antenna is an omnidirectional antenna having approximately the same signal strength in all directions. If you make the antenna longer in 1/4 wave increments (simple antennas) it will become more directional. In microwave frequencies we tend to use flat panel (patch) antennas to get directionality and gain.
https://www.l-com.com/wireless-antenna-900-mhz-antennas
https://www.l-com.com/wireless-antenna-24-ghz-wifi-antennas https://www.l-com.com/wireless-antenna-24-ghz-patch-antennas
Without going into detail and 8 db patch antenna on the receiver will greatly increase the reception range.
https://www.l-com.com/wireless-antenna-24-ghz-8-dbi-flat-patch-antenna If you mount the antenna horizontally on a tripod, the coverage will be a 35 degree half angle overhead cone. Increasing the signal strength by 6 db doubles the range, by 12 db quadrupoles the range. As an antenna gain goes up the solid ange (collection volume) decrease proportionally so more agin only helps if you track you rocket.
The approximate 2.4 GHz WiFi signal range is shown here for various antennal gains.
https://www.tomsguide.com/us/2,review-125.html The range is also dependent on the data rate. A 9600 bps data rate signal will have a long range than a 115 kbps data rate signal.
Instead of posting radio questions, try googling your questions. There are hundreds of ham websites that discuss all of this in detail.
Bob