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The coax center wire is terminated in the small cone

The small cone is connected to the larger one

The small cone is connected to the larger one. The coax center cable is terminated into the small cone and the coax shield into the larger outer cone.

The screenshots are from this video https://www.youtube.com/watch?v=Pu-o4u3VgR0

Another video from a different manufacturer - https://www.youtube.com/watch?v=y8ky1t3IfLE

They claim wideband coverage from 700 Mhz to 2.5ghz, but I suspect they simply do not do anything.

I have one of them and I think these are the reason my setup is failing.

Could they even work?

I couldn't find any teardown of any dome antenna from any of the big companies except this one - https://www.youtube.com/watch?v=7EB4wqawBv4 - but this seems to be a completely different design.

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    $\begingroup$ they call it an "omni" antenna which would lead more to a discone theory-of-operation than a horn. but of course "theory" vs. "practice" :-) keep in mind though that coax loss is pretty high at those frequencies — so while it's always good to have a healthy suspicion for antenna design and curiosity about the operation/tradeoffs, if your ultimate goal is to troubleshoot your setup you might also open a question re. that with more details (power levels, coax type/length, antenna environment, etc). $\endgroup$ Mar 1, 2023 at 18:41
  • $\begingroup$ @natevw-AF7TB I agree with you, this is a type of discone :-) My question is, How well will it respond to horizontally polarized TV signals if it hangs down ? It looks like it is designed to hang down from the ceiling? In any case, Mavin has asked an upvote-worthy question. $\endgroup$ Mar 1, 2023 at 19:11

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That design is a kind of wideband conical monopole, a fairly standard design.

The slightly conical groundplane should help raise the radiation towards the horizon. A monopole on a groundplane tends to radiate downwards (when mounted on the ceiling) which isn't ideal for the longest-range users. It may also improve the impedance.

If it's done right, it could certainly be an excellent antenna for 700-2500 or higher, with low VSWR and clean radiation patterns. Metal spinning (or just pressing) is a good way to make the parts.

But I'm horrified to see the grounding wire on one side though - this will distort the pattern and affect the VSWR. I suppose it's done to provide a DC short, which is a good idea and may be required by some systems or safety codes, but it will affect the pattern at all frequencies, and the VSWR at some frequencies (may be designed to only affect say 1000-1600 so it doesn't matter).

The coax, if it's a low-loss LMR-195 / HDF-195 will be well under 1 dB of loss, not significant in this case.

In what way is your setup not working? Are you using it for wifi or an indoor picocell or repeater? The best would be to measure the antenna with a VNA, to check the impedance is well behaved in spite of the shorting wire.

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  • $\begingroup$ It works mostly. I was trying to build a passive cellphone repeater. I have a 900Mhz yagi on the rooftop (mounted at 45 degrees to capture LTE. Apparently 90 degrees is still 2G and 3G is disbanded) pointing directly at the cellphone tower 100 meters away. There is 50ft of LMR400 cable till the ground floor where it connects to the above discone. Within 5 to 6 feet of the discone there is sufficient signal to get around 1Mbps speeds. Was wondering if there is anyway to improve performance to around 10 feet of the discone. $\endgroup$
    – Mavin
    Jan 21 at 12:25

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