I did some more testing with the 4 way diversity box from HK with the four 12.6 db helical antennas I made and it's been working brilliantly.
I found I could fly anywhere in McCoy park with out even a hint of loosing the video link at quite low level too which is not an easy thing. With a bit of height I'm sure it would have greater range than the RC Link. I'm very happy with it.
There is one thing with it tho it only does a limited range of frequencies in 5G8 which means it's not compatible with the immersion RC gear which is a great shame!! It is compatible with many others tho'
here's a list of Channel frequencies that it works with and some other specs
Receiver frequency:
CH1: 5705MHz
CH2: 5685MHz
CH3: 5665MHz
CH4: 5645MHz
CH5: 5885MHz
CH6: 5905MHz
CH7: 5925MHz
CH8: 5945MHz
Video output: 75Ω/1Vp-p
Audio output: 10KΩ/500mVp-p
TV system: PAL/NTSC/SECAM
Input voltage: 8 to 12V/500mA
Antenna connection: SMA
http://hobbyking.com/hobbyking/store/__3...r_FPV.html
It works well with this VTX this can transmit on all 32 channels in the 5.8 band
http://hobbyking.com/hobbyking/store/__6...itter.html
I also have one of these VTX's and it works nicely as well
http://hobbyking.com/hobbyking/store/__4...P_SMA.html
Here's a list of channels for most of the Skyzone gear but it pays to check the specs of any one your considering they are not all the same.
Frequency range:
FR1 5865,5845,5825,5805,5785,5765,5745,5725
FR2 5733,5752,5771,5790,5809,5828,5847,5866
FR3 5707,5685,5665,5645,5885,5905,5925,5945
FR4 5740,5760,5780,5800,5820,5840,5860,5880
The Immersion RC Channels seem to be
5740, 5760, 5780, 5800, 5820, 5840, 5860MHz
I have a suspicion that the Immersion RC gear is very good but for a diversity system they only offer a 2 channel unit and it's around the same price as 4ch skyzone VRX
Two channel diversity can work quite well with a high gain and an Omni directional antenna. A lot of people are using this kind of set up with good results. The diversity box selects the best out put signal from the two antennas and routs that to the video goggled or screen
I guess I should post a quick explanation of what a diversity system is
Basically it's a 2 or more receivers each with a separate antenna and some electronics that looks at the output of each receiver and decides which has the best signal. The receiver with the best signal is switched automatically to the output where the video goggles or screen is connected.
It's continually checking all receivers and choosing the one with the best picture for you to view.
A very brief explanation of antenna gain:
Since there's no free lunch to get more gain (range) from an antenna you have to sacrifice something. In simple terms what you do is sacrifice coverage so by changing the design of the antenna you can have lots of gain in one direction and very little in another. You take advantage of this by arranging the antennas to point in a useful direction. Think of it like a torch beam compared to a light globe. The light globe illuminates the whole area but not for very far and the torch beam reaches out the distance but only illuminates one spot because it produces a narrow beam. It doesn't have a lot of coverage but it goes a long way. Antennas can be designed either way a light globe can be compared to an Omni direction antenna and a torch beam to a helical or patch antenna. It's a much simplified version of what's going on and there's a whole bunch of other factors but it gives a basic starting point.
This means that with a 4 channel system you can have 4 narrow beam high gain antennas pointing in different directions and as the aircraft flies from an area covered by one antenna to the area covered by another you are automatically switched over to the best antenna and receiver to suit the location of the aircraft.
With a two channel system you can use a wide coverage and a narrow beam antenna, like a light globe and a torch beam combined. Just point the beam in the direction where you want to go far away and stay in the wider coverage of the Omni (light bulb) when you are close. Remember the beam gets wider as you get farther so the area covered gets more the farther out you go. A reasonable shaped area of coverage can happily be obtained with a two channel diversity set up.
With directional antennas the lower the gain the wider the beam. With no diversity ie just a single receiver you can use an Omni antenna but you must stay in close or you can use a lower gain direction antenna (wide beam) and go a little further or you can use a high gain antenna and fly in the beam.
If the antenna is mounted on your goggles and you know which way you are facing you can turn you head to face the where the aircraft is and keep it in the beam. This takes a bit of getting used to and is much easier if you remind your spotter to help out with this. You also have to resist the tendency to look down because this might point the antenna at the ground which is not the best for reception. It actually takes a bit of brain space to think about pointing your beam antenna while your flying so not a good way to start out. There's enough to worry about just keeping it in the air at first. But certainly fun to try once you get a handel on things
I really hope this is of some help, If I can share some of my experience it might make it easier and more fun for others to have a go.
