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Author Topic: UHF interference- does it enter via the Rx or the Antenna?  (Read 1553 times)

Billy_boy_2010

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UHF interference- does it enter via the Rx or the Antenna?
« on: October 07, 2017, 07:30:40 PM »

Hi guys

I'm considering keeping my ezuhf rx close to the body of the plane and just routing the Rx out on the wing. How prone is the module to rx? If the majority of interference enters from the antenna I will route that on the wing only
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Schalonsus

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Re: UHF interference- does it enter via the Rx or the Antenna?
« Reply #1 on: October 07, 2017, 07:49:03 PM »

On my SkyFun the Fox800 and the EzUHF 4ch RX are just separated by 15-20cm and i fly 35km on 200mW EzUHF without problems
https://www.youtube.com/watch?v=Uf7wLnnS76w
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SnoozeDoggyDog

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Re: UHF interference- does it enter via the Rx or the Antenna?
« Reply #2 on: October 07, 2017, 08:11:52 PM »

I've had my antenna and Rx on the wing and both in the plane. Can't say I noticed any difference. Out to 15k

P
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Coyote

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Re: UHF interference- does it enter via the Rx or the Antenna?
« Reply #3 on: October 07, 2017, 08:17:48 PM »

Th Rx is pretty good at ignoring local rf to be fair, you shouldn't see any issues.
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Billy_boy_2010

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Re: UHF interference- does it enter via the Rx or the Antenna?
« Reply #4 on: October 07, 2017, 09:25:07 PM »

interesting giuys but you dont specify what frequencies you're using.....?

Th Rx is pretty good at ignoring local rf to be fair, you shouldn't see any issues.

interesting thanks Coyote- is that the case on all frequencies? Will i lose gain with perhaps 50cm of antenna cable on the ezuhf?
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SnoozeDoggyDog

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Re: UHF interference- does it enter via the Rx or the Antenna?
« Reply #5 on: October 07, 2017, 11:14:37 PM »

interesting giuys but you dont specify what frequencies you're using.....?

interesting thanks Coyote- is that the case on all frequencies? Will i lose gain with perhaps 50cm of antenna cable on the ezuhf?
Billy, on my first "long distance" I had the ezuhf stuffed in the back of the talon right next to to a bec, both elevon servo wires, the ESC main power cables. It was all just thrown in. I had the standard ezuhf shite antenna on the RX poking out the top of the talon access lid. I got out to 6k before RTH kicked in (it may have even miles as when I started flying I flew in miles on the osd). I have no doubt the RX antenna was to blame for the RTH and not all the shite around the RX. I also had a 800mw vtx on board on the nose. I was using extreme hoping, low power

I've change loads on my current setup. I have fpvpro dipoles on the wings directly attached to the vtx and Rx. I've a 2w ezuhf module on my taranis with a srh771 whip. Last time I could be arsed I was out to 13k on low power ... I turned round because I wanted to 😒

The question is how far do you want to fly?

Regards
P
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Coyote

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Re: UHF interference- does it enter via the Rx or the Antenna?
« Reply #6 on: October 08, 2017, 12:32:10 AM »

interesting giuys but you dont specify what frequencies you're using.....?

interesting thanks Coyote- is that the case on all frequencies? Will i lose gain with perhaps 50cm of antenna cable on the ezuhf?

With cable you will always lose gain, but it will be fractions of a dB so negligible really at that length. Try to keep the length at multiples of a wavelength to minimise losses.
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English Turbines

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Re: UHF interference- does it enter via the Rx or the Antenna?
« Reply #7 on: October 08, 2017, 01:30:38 AM »

On my SkyFun the Fox800 and the EzUHF 4ch RX are just separated by 15-20cm and i fly 35km on 200mW EzUHF without problems
https://www.youtube.com/watch?v=Uf7wLnnS76w

  That's an impressive flight for such a small rig....pretty remarkable Id say....:)


                                                                                                :vulture:
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Nothing beats the smell of Jet-A at 800 Celsius...:)
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Billy_boy_2010

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Re: UHF interference- does it enter via the Rx or the Antenna?
« Reply #8 on: October 09, 2017, 11:13:42 PM »

With cable you will always lose gain, but it will be fractions of a dB so negligible really at that length. Try to keep the length at multiples of a wavelength to minimise losses.

Interesting thanks mate :)
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Billy_boy_2010

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Re: UHF interference- does it enter via the Rx or the Antenna?
« Reply #9 on: November 25, 2017, 12:57:21 PM »


Try to keep the length at multiples of a wavelength to minimise losses.

Quick bump please Coyote

Do you include the sma connector as length or not?

And by multiples of the wavelength- is any fraction acceptable? or only quarters?

Thanks :)
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Schalonsus

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Re: UHF interference- does it enter via the Rx or the Antenna?
« Reply #10 on: November 25, 2017, 01:07:59 PM »

coaxial feed length multiple does not really matter if you trust Alex

Quote from: IBCrazy
Coaxial cable 1/4 wave Myths:

I have heard in numerous places that you need to avoid lengths of coaxial cable equal to an odd multiple of your quarter wave. This is a myth that started back in the early days of CB radio. So long as you use 50 ohm coaxial line you will be ok at any length that will fit on your plane. I would recommend keeping it short only to reduce spurious emissions and keep it light weight. Any type of coxial line will work, so choose whatever suits you best. For short lengths RG-58 is just as good as RG316.
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Billy_boy_2010

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Re: UHF interference- does it enter via the Rx or the Antenna?
« Reply #11 on: November 25, 2017, 03:55:31 PM »

Ibcrazy alex??
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Schalonsus

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Re: UHF interference- does it enter via the Rx or the Antenna?
« Reply #12 on: November 25, 2017, 04:33:35 PM »

Yes, IBCrazy
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Coyote

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Re: UHF interference- does it enter via the Rx or the Antenna?
« Reply #13 on: November 25, 2017, 11:50:36 PM »

Even though Alex has strong religious beliefs I don't take his word as gospel no :)

I would measure it from the SMA personally.
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Billy_boy_2010

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Re: UHF interference- does it enter via the Rx or the Antenna?
« Reply #14 on: November 26, 2017, 09:21:53 AM »

ok thanks Coyote :)

And is that as a fraction of the wavelength? So is 5/8ths acceptable?
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