Request help with a range issue

Hi all,

I'm a noob to FPV and have recently put together my first kit of hardware. The setup operates well enough in most ways, but the useful range is only about 50m. This is not what I would expect with a 600mW transmitter.

Here's my setup:

500mm quad with CF frame

Boscam TS5828 video TX

Runcam 2 live video out as source

Bulkhead-mounted quadrifiliar antenna

4" RG316 cable to connect TX and antenna

Diversity monitor and FatShark Dominator goggles

I get the same performance with the cheap monitor and the goggles, so I'm inclined to think that the issue is on the transmitting end. My only lead is the antenna cable. RG316 is only good to 3GHz, but a 4" run should not cause nearly that much attenuation.

The transmitter gets about as warm as I would expect for such a device. It's clearly doing SOMETHING. I have already sorted out an issue with the telemetry radio and video TX bulkhead connectors shorting through the CF frame. Both radios were replaced after that, and are now electrically isolated.

Any input would help. Thanks for your time.

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Replies

  • It looks like the antenna relocation helped a little more. I think we can consider this case closed. Performance is still not what I would expect, but I also don't know how realistic my expectation is, not having much experience with FPV. Range now appears to exceed the boundary of the small field that I've been flying from. I need to find a larger field and greater confidence to send the quad longer distances and over obstacles.

  • Roger that. I understand. I thought that you were talking about the RC receiver.

    Still working on the LC filter. It requires major surgery to install. I'll report when I have a result.

    Thanks again for your help.

    Chris

    • I've installed LC filters on the +12V and +5V video rails. This removed a few lines from the image, but didn't improve range.

      The next test is to relocate the VTX antenna. It's currently about 4" from the telemetry antenna. This requires purchase of a cable, so it will be a week or two before I can respond to this.

      Thanks again for the advice.

      • Update: The 4" antenna separation figure was from memory. They were about 2" apart. I have relocated the VTX antenna to the rear of the airframe. I won't be able to test until the middle of next week.

        I also replaced the TX with an Immersion RC 600mW unit. I was able to test this yesterday and found performance improved considerably, but was not able to find a limit.

        I'll reply with another update when I have a result on the antenna relocation.

        Cherrs!

        Chris

  • Hi James,

    Thanks for the suggestions.

    My VTX and camera supply is supposed to be separately regulated, but I've never put a 'scope on it under load to see if it's clean. I have an LC filter that I can put on it, so I'll give that a go.

    I'm curious about your mention of VTX and RC RX interaction. I would think that this would only impact RC reception, but maybe I don't understand. Can you elaborate?

    I'm working on a couple of experiments of my own. I swapped out the super-duper quadrifiliar antenna on the VTX for the dipole that it came with and my range seems to have doubled. I get a whole 100m now! :-) I'm wondering if I bought some snake oil. I'll also be trying an FPV flight with the VTX antenna connected directly to the transmitter, rather than through a length of RG316. I have only brief flying windows in the early morning, so it will have to wait until tomorrow.

    Cheers!

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