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Grogster

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Joined: 31/12/2012
Location: New Zealand
Posts: 9306

Posted: 03:13am 13 Jun 2022

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Hello all.

I need an amp for 433MHz, that is as small as possible, so I can integrate it into an existing design. I had considered one of those super-broadband amp modules from eBay such as something like this, but although this is small, it is not small enough. That one does not specify what the maximum input power is, but most of them seem to be around 1mW or so, so driving them with 20mW or so will probably result in nasty performance and/or harmonics on the output etc. I could put a passive resistor-type T-attenuator or something on the input to bleed the 20mW in down to around 1mW etc, but as I say - these little modules are too big anyway.

I really need something tiny like one of those can-type 433MHz things, that are inside many key FOB things - about 10mm wide, and about 6mm thick. Does anyone know where I can find those can-type things? I don't even know what they call them, but they probably have a special name which would be helpful to know.

Here is a photo of the can-type thing I am talking about.

Input power will be about 20mW, and I want about 100mW out. 5v supply would be nice, but will consider anything. Ideal device would also have an enable pin, so it can be turned off and on by an MCU pin, but that is not mandatory, as I can do that with an external MOSFET if I have to.

Technically, 100mW @ 433MHz is outside of limits, but I want to use this on a farm in the middle of nowhere, and use is sporadic, so it's extremely unlikely to be upsetting anyone else, and would mean I can use an existing system I already have in place. If I was to use something based on the HC12 for example, it will not be compatible with the base station, as the HC12 uses a different RF protocol. This system uses "Dumb" RF modules.

So, a simple 433MHz can-style blower would be perfect if I can find such a thing.
If anyone can help, please do post a reply. Thanks.

Smoke makes things work. When the smoke gets out, it stops!

phil99

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Joined: 11/02/2018
Location: Australia
Posts: 2135

Posted: 07:01am 13 Jun 2022

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http://oatleyelectronics.com//product_info.php?products_id=747

Is the above any good?

"TX01 LONG RANGE TRANSMITTER MODULE
[TX01] $9.00 $3.00

Pre-built 433MHz SAW resonator locked transmitter module

When used with our RX9 the pair can give a range of approx. 1.5km, even with some obstructions, when the transmitter is powered by 12VDC.

Transmit Power: 15mW @ 12V

Modulation: AM

Voltage: 3-12VDC

Size: 11 X 11mm
connecting holes are 0.1" apart.

This module can also be used with our PVJ6WC."

The little can things in key-fobs are transmitters not amplifiers. They won't accept RF input. Similar to above.
Edited 2022-06-13 17:22 by phil99

TassyJim

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Joined: 07/08/2011
Location: Australia
Posts: 6098

Posted: 07:21am 13 Jun 2022

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https://www.aliexpress.com/item/32238392004.html

VK7JH
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phil99

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Joined: 11/02/2018
Location: Australia
Posts: 2135

Posted: 07:39am 13 Jun 2022

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Does it need to be omni directional or could a Yagi at one or both ends provide the gain you need?

CaptainBoing

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Joined: 07/09/2016
Location: United Kingdom
Posts: 2075

Posted: 08:53am 13 Jun 2022

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some Qs

How far between the Tx & Rx? is it bidirectional. Is it line-of sight?

Try a directional antenna to maximise the power you have and minimise over-spill to other users.

I saw a vid where a guy used a laser module for one way data comms (found it) . played music down it(!) If you can get line of sight, range is largely down to the power of the emitter (as with anything). Laser would be guaranteed not to upset other 433MHz users. The beam spread was pretty large at distance but still good enough for reliable transmission. You should use some error detection + redundancy etc just in case.

Laser can really extend range and would look cool ... might spook the cows when it begins a transmission

Edited 2022-06-13 19:35 by CaptainBoing

InPhase

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Joined: 15/12/2020
Location: United States
Posts: 178

Posted: 07:43pm 13 Jun 2022

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I wonder if this isn't a problem that couldn't be solved by good antenna design vs. higher output power?

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