Welcome to your 900Mhz Dipole Antenna!

[RCSubGuy]

Testing complete. Working on the video now. REALLY interesting findings, people.

[QuarterMaster]

To catch everyone else up on what Bob is doing after he and I were discussing due to an "Email Thread" started by Steve O'Connell.

What follows I've pulled from that email.

So before any of you respond...

1:I understand I AM NOT an RF or Antenna Engineer of any sort.
2. The following is merely MY interpretation of radiation patterns and how they appear to interact based on what I've taken the time to research.

'scuse the "Eddiegrams"

Such as I enjoy writing, this is a non-text discussion lol! Too many keystrokes can follow! But I'll at least say this...

Two main points to think about:

1-How much "more" performance is warranted? for 80% of the users, good enough works. Especially when you take into account the percentage of runtime in "clear" water supporting constant "at depth" running.

2-Basically it's a guideline, something to strive for, not obsess over. It's just good to be aware of it.

For the record, The Krick's 900Mhz antenna is laying horizontal, bent in a "crescent" shape! This past weekend at Fitz's Fun Float, Bob noticed my TX was set to the lowest TX power setting of 10mW!! I had been running for close to an hour with degradation only occurring when I dove > than its body length and that was 20' out, and it only gave loss of telemetry warnings while still operational so I didn't even know it. Bumped it up to 100mW to see any difference. Then Bob stole it from me and then attempted to own me by almost mastering a dynamic diver running at a consistent PD. Grrrrrr Bob!

BTW, as I bench test at 10mW (which I did a couple of days earlier) to not saturate or harm the RX, I need to add checking TX output power in the checklist!





The 900Mhz antenna in the X18/X20: So the emission "donut" wave pattern is perpendicular to the long axis of the handle. So if you're holding the TX between you and the boat as one normally does, and have the aforementioned long axis at right angles of the imaginary line to the boat, the "donut" is radiating at YOU and the boat up to the sky and down to the ground. As long as you're pointing that handle side to the boat, you're keeping it WITHIN the imaginary tire whose center is at the handle while pointing at you and the boat right angle to the horizon.

From my understanding of what I've been researching anyway.

Graphically represented like this...

The donut radiating from the TX naturally held pointed at the boat. You're at "Y", the long axis of the handle is represented by the "X" axis through the center of the donut. So the target boat is within the maximum radiation output of the TX. So would a drone be at 45 deg up or directly above you! For the record, this is in opposition to our 75 Mhz radios whose radiation donut is at right angle to this. Pointing those antennas at the boat as I've seen so many do is bad! Best way for those of course is keep the antenna pointed at the sky!



Here is what the dipole antenna would best "see" from the boat's perspective, if placed optimally. The boat has now good possible reception across the horizon in any direction she's headed. The next best thing would be to angle it 45 deg or so. If laid flat along the long axis of the hull, it would match the TX pattern and would see best athwartships, when she's running at right angles to you.





A good way to visualize best pattern matching as if the two "donut's" were two joined "links in a chain". TX vertical, RX horizontal.




The point being for best performance, sorta point the handle (top of the TX) in the direction of the boat. While one should orient the RX antenna as best as one can, it's NOT a deal breaker and we'll no doubt see this proven over time. If you turn in place bringing the boat off in either shoulder direction, you have the least performance. The nice thing is as long as the handle (screen end) is pointed toward the boat you can hold it vertically or horizontally. It probably doesn't help to be like me gesticulating like a madman when speaking. No, don't be an "Ed".




ALL RF Engineers I've worked with told me "FM" stands for "F#¢%ing Magic".

Again this is my understanding from what I've learned so far, and seems to make "sense". We'll learn more over time.

Now everyone is caught up, let's see what Logan and Bob discover.

As for me, I'm one with the "donut".

[RCSubGuy]

Logan and I are going to perform a test regarding antenna placement today (if I can find the time). We'll film the process and post up the results.
News at 11!

[QuarterMaster]

Ed, how are you dealing with the confined vertical space normally found in a WTC? I don't believe curving the antenna is a good idea, but even a good sized cylinder is probably shorter in the diameter than the dipole is long.

Think "outside the box".

Bob did.

[Nathan]

Ed, how are you dealing with the confined vertical space normally found in a WTC? I don't believe curving the antenna is a good idea, but even a good sized cylinder is probably shorter in the diameter than the dipole is long.

[Das Boot]

Did you get your transmission fixed or buy a new truck?

[QuarterMaster]

ALCON,

Spoke with KMc earlier on the "antenna" question. (Bet you didn't know there was one!).

It's our hope to "crack the nut" with respect to range/running depth, limiting output power (extend TX battery life) and simplifying the install. Kevin is plugging along researching this as well.

An interesting article on our new antennas. Might be a tad more difficult, but not insurmountable. How to Mount/Position Transmitter and Receiver Antenna on FPV Drone

I see we need to mount them vertically, not horizontally. Also using an external dipole on the TX (HOURUS vs X18/X20) and actually aligning in the direction you face will appear to help as well. Which a lot of people would do with the 75Mhz when they appear to have lost signal. Pointing it directly at the boat was bad, the radiation pattern of the monopole antennas should have you pointing them to Jesus as it's perpendicular to the antenna.

We need more crowd research here!

Mmmmmmm.....donuts!