Jump to content
Sign in to follow this  
Airbender

Which Video Downlink frequency to use?

Recommended Posts

Friends,

I have completed building my camera ship and I am now faced with the dilemma of choosing the frequency for my downlink video.

I have a 600 ESP and I am waiting on the Askman AP mount to arrive. All of the downlink gear will be mounted as far away as possible from EMI & RFI sources. My current TX & RX is JR & Spektrum, so 2.4G for downlink is out of the question.

The downlink will be used for both FPV and/or recording directly to a DVR that I will have on the ground connected to the video receiver. The advantage is that it will allow me to use OSD devices mounted on the heli for graphics overlay. Therefore, I need a downlink system with good quality video because I will be selling the video+graphics information as part of my business model.

I realize there are limitations to all currently available downlink frequencies in the USA, i.e. motor noise, outside interference and line-of-sight, etc issues which would cause poor quality video.

From the hours, days & weeks of research I have done, it seems that (aside from 2.4 Ghz), 900 MHZ and 5.8 GHZ are the most likely candidates (here in the USA). Each has it's pros and cons:

900 MHZ:

PRO - cheaper equipment, more powerful TX's available, quality of video is acceptable (from the videos I have seen on the 'net), does not require much battery amperage to power the TX

CON - line-of-sight & range limited, more susceptible to outside interference

5.8 GHZ:

PRO - much better quality video, less susceptible to outside interference, further range with less issues regarding line-of-sight

CON-requires more battery amperage to power the TX's and the equipment is more expensive and there are fewer manufacturers=less competition amongst the manufacturers=prices are still high for the consumer

I'll be the first to admit that I may be wrong in my judgment and comparisons, but I am just looking for some sage advice from the experts on these forums.

Please let me know which direction to go here.

Thanks to all in advance

Share this post


Link to post
Share on other sites

sorry I don't have much time here so this may sound short.

900mhz has less line of sight issues, the higer the frequency the more line of sight it has to be.

Also you get more distance with 900mhz.

The only negative to 900 is the large patch ant. instead of a very small one for 5.8. video quality is the same

happy flying!

Share this post


Link to post
Share on other sites

From what I have seen 5.8Ghz will give a little better picture but $ for $ I think you will get a better 900Mhz system. Also the range of most 5.8Ghz systems is a bit limited but may not be an issue to you as its not for me.

Terry

Share this post


Link to post
Share on other sites

The 900MHz vs. 5.8Ghz question is hard to answer because every little detail of your application has an impact. Some comments:

(1) If your range requirements are typical for photography applications then it is usually within visual range. If that is the case, the 900Mhz range advantage won't matter much.

(2) If you are going to use it in areas that have many RF reflective surfaces (cars, buildings, metal fences, hard earthly structures, etc.) then 900Mhz will have less multipathing nuisance. If using 5.8Ghz, a diversity Rx would certainly help out in these environments.

(3) The 900Mhz A/V gear that is available today are old designs that were intended mostly for video surveillance. Those that I know that have tried 5.8Ghz A/V have commented that they noticed slightly better looking video quality. That is because the 5.8Ghz products are newer designs and their largest market is mostly consumer video sending applications where video quality is important.

(4) If your application involves a GPS receiver near the video Tx then 5.8Ghz will play much nicer with it. If you must use 900Mhz, and LOS range of under 1500 feet is required, then I'd suggest using a 200mW Tx to help minimize the EMI/RFI issues that higher RF power might invite.

(5) Current draw on either RF band, for similar RF power levels, shouldn't be vastly different. But antennas are a bit smaller with 5.8Ghz. That is nice when size/weight matter.

(6) If you intend to operate in the USA with full compliance to the FCC amateur radio (ham) regulations, then only one RF channel will be available to you on 900Mhz (910Mhz). On the other hand, you will have several channel choices on the 5.8Ghz gear (per the band allocations available on the ham license). In some foreign countries, the 900Mhz gear is not allowed, even to hams.

Bottom line is that the final choice is full of compromises. You have to decide what is most important to you and then go from there.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×