2.4 RF meters

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rudderonlybird
Posts: 35
Joined: 17 Feb 2018, 05:07

2.4 RF meters

Post by rudderonlybird »

Would any here know of a way to make an RF indicator-meter for 2.4? I acquired a Tower Hobbies six channel transmitter, and it has a switch just behind the antenna for selecting the panel meter to read battery voltage or RF output. Normally I wouldn't deal with Tower's junky products, except this one was made by Kraft, and has the Kraft sticks and what looks like the general layout of a Kraft product.

I thought I read somewhere, can't remember where, you can't use a simple diode detector for 2.4, but would need a circuit resembling a 2.4 receiver instead. This was brought on by my upcoming transmitter project, a World Engines 'Controlaire' four-channel tranny. This is the production version, not the kit-built 'M.A.N. 2-3-4' version, although I have one of those as well. Anyway, it has a meter hooked up to a resistor-diode circuit, shunted with a capacitor, connected to a short piece of resistor lead, about 1 1/4" long, and situated close to the center-loaded antenna, just as it comes down through the case top. I assume needed power to run the meter comes off the antenna.

My thought was, if such a circuit could be made, both the Controlaire and Tower transmitters could benefit from it. If not, I'll just use the normal ESV-type battery monitor meter.

Any information would be appreciated. I looked up 'display' in the search box and came up empty, so thought I'd ask here.

Marc
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Phil_G
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Re: 2.4 RF meters

Post by Phil_G »

You can use the same trad diode/capacitor arrangement Mark but use a UHF Schottky such as a 1SS99, lots on ebay but dont search for "microwave diode" as you'll be swamped with the power rectifier used in a microwave oven. Its not a brilliant solution as the envelope of a spread-spectrum system isnt constant like a 27, 35 or 72mhz carrier. Peak power on SS is less important than the spread average, the "area under the curve" on a spectrum analyser. But the diode/cap idea will give an indication.
Cheers
Phil
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RogerMacey
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Joined: 13 Nov 2020, 20:47

Re: 2.4 RF meters

Post by RogerMacey »

I don't know if this will be of any use to anyone, but may just give an indication of whether or not your 2.4GHz transmitter is radiating at all.
I've had for some time a "Microsafe" device which allegedly can check to see if your microwave oven is "leaking" radiation.
I recently read somewhere that this kind of device can also be used with our 2.4GHz R/C transmitters. When I hold my Futaba T6EX transmitter near to it, the meter on this device does deflect.
Being inquisitive, I opened up the device, to discover only two components - a meter and a diode.
If you're a DIY electronics type of person, the following may be of interest.
The meter is an SD-306, 250microAmp, 650ohm, -20~, +3dB, and the diode, which is unidentified, is soldered directly across the meter terminals (the diode leads are not cut short - maybe they serve as an antenna ?). I guess the diode needs to be a high frequency type, but beyond that I don't have the knowledge to say.
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RON
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Re: 2.4 RF meters

Post by RON »

I wonder why the big box ?
G0MBV Class A Radio Amateur, North Yorkshire
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Shaun
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Re: 2.4 RF meters

Post by Shaun »

It makes it look more expensive 😄
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Wayne_H
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Re: 2.4 RF meters

Post by Wayne_H »

RON wrote: 07 Jan 2021, 08:15 I wonder why the big box ?
Probably promoted as a safety feature to keep you as far as possible from "them thar killer rays" :ugeek:

Mind you, none of us has ever peered into the mickywave to make our dinner cook quicker, have we, hmmm?? No sir, never sir.... :lol:
Cheers,

Wayne
Once a Retrobate, always a Retrobate............ ;)
Dave
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Joined: 14 Feb 2022, 03:24

Re: 2.4 RF meters

Post by Dave »

Found this link on the Norcim website http://www.rcgroups.com/forums/showthread.php?t=1557232
rudderonlybird
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Joined: 17 Feb 2018, 05:07

Re: 2.4 RF meters

Post by rudderonlybird »

Thanks muchly, Dave. I'll give it a try. I see that thread is about eight years old, but still applies.

Marc
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Flynn
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Re: 2.4 RF meters

Post by Flynn »

Is there a particular reason for wanting a diode/milliamp meter type of detector? There are quite a few iterations of a 2.4GHz band scanner originally designed by Martin on here that will show you not only the 'pseudo' strength of your signal but on which frequenc(ies) it is on. I say pseudo because it is not actually a signal strength meter but does give quite a good indication of signal strength. Here is my attempt at fitting one in a tic-tac box, I notice Martin also did one in a tic-tac box but I managed to squeeze a lipo in mine too :)
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Currently showing the output from a FlySky AFHDS radio.

Lots of info on viewtopic.php?f=42&t=1008
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If it doesn't move when it should use the WD40 and if it moves and it shouldn't use the tape.
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