• This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn more.

Plans for 900mhz rx antennas??

#1
Hey all!
Im getting into fpv here real soon. i plan to use a 200mW video system on 900mhz. my area has lots of trees and hills, and i would like to go around those things. I would like to use a cloverleaf antenna on the AIRCRAFT, and a helical on the ground station. I cant seem to find instructions for building the 900mhz helical. Im not sure of wire length, wire thickness, number of turns, diameter or the wire rotations, ect. Can someone help me find instructions to make the helical 900mhz? Ive found instructions for the cloverleaf, but not the helical. my last resort would be buying antennas. Thanks for the info!
 
#4
http://www.rcgroups.com/forums/showthread.php?t=1377791
Better check local cell phone service to make sure it doesn't use 900MHz.

Thurmond
will do. if so, ill go 1.2 instead. But i wont be flying in a city environment ever. but my local feild is a school which i used to go to. i know for a fact that the whole place is a cell phone dead zone. texting in class barely ever worked ;) so ill research the area a bit. thanks!
edit: did fast research. found out 2 out of 4 main cell phone companies here use the frequencies 700mhz and 850mhz. the other frequencies they use are things like 1.7 or 2.1ghz. im looking to start with the hobbyking 900mhz 200mW v. tx/rx combo. but when i look at the specs on it, and i see the "frequency" specs, why are there multiple frequencies?

http://www.hobbyking.com/hobbyking/store/__13438__900MHZ_200mW_Tx_Rx_1_3_inch_CCD_Camera_NTSC.html
Which frequency will the product i get run on? is it random? I also noticed too that ALL of the listed frequencies on the HK product page are higher than the cell phone frequency. the HK page shows that their product can run on .9, .91, .98, 1.01, or 1.04ghz. all of which are a distance from 850mhz. based on my knowledge of 27mhz rc transmitters, the different channels, or slightly different frequencies do not disturb eachother. I researched, and the different channels on 27mhz radios are only 0.05ghz apart! so why would 850mhz affect .9ghz or even 1.04ghz>? would it? i dont think so! comments, please! would like all the help i can get from experienced people! Thanks!
 
Last edited:

squishy

Pirate ParkFlyer
#5
That's the best way to know, if you have cell coverage, be cautious with 900mhz or avoid it all together...The only guys near me with any luck flying it, drive up to the mountains to fly...

If I were you, I would just go with 1.2 based on the abundance of products and support...
 
#6
yeah my area is pretty populated all together with cellphones and whatnot. i could try 1.2 then. recommendations on 1.2 systems that are cheap and simple? for beginners! ideas? Thanks!
 
#8
Thanks! on that page you showed me, will any of those 1.3 ghz VTX units work with either of those VRX units there? are they ALL compatible with eachother? Thanks!
 

squishy

Pirate ParkFlyer
#9
Generally you need to look at the channels offered in each and make sure the frequencies match. The two most common frequencies in that range are 1280MHz and 1258MHz. As long as your vTX and vRX can use the same frequency/s then they will work together. And yes, everything on that page works together.

I like to take his vTX's out of the case and stick on a headsink, he sells those too. This makes the vTX much lighter...
 
#10
Thanks! ill look into that equipment and look into making some 1.3 antennas. Thanks for the help! ill update this is if i run into a bit of trouble. Thanks!
 
#14
how come u dont need the liscense when you use 2.4 ghz? it says for frequencies over 30mhz

edit: also had another question! Ive recently seen the "fan" style circular polarized antenna for fpv. it looks really simple! all strait bends, and id like to try to make it! but the dimensions are no where to be found. ideas? answers? Thanks!
 
Last edited:

Tritium

Amateur Extra Class K5TWM
#15
2.4GHz is the band used by many low power consumer electronics ( wifi routers, RC Transmitters, Blue Tooth devices etc.). The Technician License is VERY easy to get. All the study materials are free online.

For antenna plans, do a search for IBCrazy at rcgroups.com and fpvlabs.com/forums

Thurmond
 
Last edited:
#16
Hey! Had another quick question. The wire leads we use for making FPV antennas, I am going to buy one and make an antenna. Is there size specifications for the cable? Which end goes on the antenna? The female or male? Can someone tell me exactly what I could tell a guy at a hardware store to get exactly what I need? Thanks!
 

squishy

Pirate ParkFlyer
#17
Generally speaking the antenna has a Male SMA connector

Some manufactures us SMA some use RP-SMA, so pay attention to this, it's like two completely different connectors...make sure you get adapters to go between them if you don't know what your vTX and vRX will be using...

Here's the adapters:
http://www.sierrarc.com/index.php?main_page=product_info&cPath=67_88&products_id=252
http://www.sierrarc.com/index.php?main_page=product_info&cPath=67_88&products_id=259

And I have purchased SMA connectors with wire bare ends for making antenna I just can't remember where I bought them from, someone around here knows...or you could just cut a small extension cable and get two of them for making two antennas.
 
#18
my friend has the hobbyking entry class 900mhz 200mW fpv system, and he will be using this antenna. so it would be used on this kit:
http://www.hobbyking.com/hobbyking/...0mW_Tx_Rx_1_3_inch_CCD_Camera_PAL_420TVL.html
Do you know what connectors are on these units? Thanks!

also had another question. looking to build the "virevent" antenna for this unit. heres the tutorial im going to use to build it:
http://www.truerc.net/images/tutorials/Vireventtutor.pdf
unfortunately it has conflicting wire size dimensions! at the bottom with the dimensions, it says i have to use .6mm wire. at the top it says to use .8mm wire. which should i use? can you tell from the picture what wire they used? Help! Thanks!
 
Last edited:

squishy

Pirate ParkFlyer
#19
That system has SMA connectors.

And you should go ask TrueRC (the owner can be found on FPVlabs) about the wire size discrepancy, I can't answer that.