Hi.
Looking for an integrated circuit, device or tiny module as RF receiver that can turn on a LED when a 123MHz transmitter is nearby. Simple, no heterodyning. To work around 3V. NO demodulating needed. No audio stage nor data output used. Just a LED indicating RF activity.

These similar show in a search results :
----> https://www.aliexpress.com/item/WR-...-Regenerative-Receiver-Module/1936209770.html
----> https://wxykpj.en.alibaba.com/produ...ative_receiver_module_with_decoding_2272.html
----> https://www.alibaba.com/product-det...spm=a2700.details.maylikehoz.1.2d9a7fcaVm07LQ
----> https://gts-ht.manufacturer.globals...le/1163082024/RF-wireless-receiver-module.htm

Or something else...

How would you do it ?

Edited... Cannot find data on IC SCSR121

 

Side note: Your chosen frequency is in an aircraft band and may interfere with aircraft, particularly in the vicinity of airports. You would be safer to use an ISM (Industrial, Scientific, Medical) band in which licenses are not required and the chances of interfering with critical services are small.

https://en.wikipedia.org/wiki/ISM_band

 

Thanks.
I know very well it is in the aircraft band, and that is the frequency I have to detect activity, not on ISM. Regenerative receivers emit interference ?

 

(Some text removed for clarity) Regenerative receivers emit interference ?

Yes they do. That is why many of them have a preamp ahead of the detector.

 

SCSR121 / SCR118. datasheets ( in Chinese)...
It works on 315MHz or 433MHz


http://www.ynovo.com.cn/index.php/en/ownproduct/lists/typeid/22.html

 

Unicom frequency. You looking to control airport lighting?

 

It's one of the things we love. A mystery project. Like, even if it were patentable, a fresh $Jackson would buy it. Loads of small fields have lights activated by a certain key sequence on one of the Unicom frequencies. What's "in the vicinity?" In the area of DFW that might mean something entirely different than in the area of KHYS.

 

Unicom frequency. You looking to control airport lighting?

Yes. Do you know other methods ?

Get a 'Forbidden access' to the chip link to find out if the 'demo board' is tuneable or not.

 

AliBaba is usually a min of 100pcs. On AliExpress though...
https://www.aliexpress.com/wholesal...regenerative+receiver+module&switch_new_app=y

 

Like the ones on post #1. Would like to know if those are modifiable/tuneable...

 

Have you considered buying an "air band receiver?" Several search terms needed, but eBay has them for <$20, example:https://www.ebay.com/itm/Air-band-r...335896?hash=item33fe2788d8:g:dCcAAOSwmfhcK941

 

Yes; bought two of these 3V :
----> https://www.banggood.com/DIY-FM-Rad....html?rmmds=buy&ID=224514182&cur_warehouse=CN
And assembled and modified successfully shifting band, working now on desired frequency but unfriendly to hack further (and shrink).

 

What you bought were FM radios. Maybe better luck buying AM radios as AM is used in aircraft communications.

 

A one-chip FM receiver might be a good starting point as long as the chip has an RSSI output.

 

First, I don't think a $1.38 regen receiver is going to crash aircraft communications anywhere ever, even if onboard a plane, in the cockpit, and inside the instrument panel. Second, this sounds to me like a modified crystal radio: tuned antenna coil, MOSFET preamp (depending on local field strength), seriously resonant tank, and a CMOS gate as a level detector. Am I missing something? I have a tuned-RF aircraft radio that is legal at all times on board because it doesn't emit anything, and this smells like its front end.

ak

 

What you bought were FM radios. Maybe better luck buying AM radios as AM is used in aircraft communications.

In post #1 :

NO demodulating needed. No audio stage nor data output used. Just a LED indicating RF activity.

 

Pedantic picking ...

Actually, *some* demodulation is needed. What you are doing basically is OOK - On/Off Keying, a grunt form of AM. Detecting the presence/absence of a carrier meets every aspect of what demodulation is. Granted, you don't want to recover any information modulated on the carrier, but still ...

ak

 

In post #1 :

Can you expand on your post #12. If the FM receivers are "working," what's the problem lighting an LED?

 

Can you expand on your post #12. If the FM receivers are "working," what's the problem lighting an LED?

unfriendly to hack further (and shrink).

My guess is that "unfriendly" means difficult. Looking at that kit, there is a whole lot of gorp he doesn't need for this application.

ak

 

Thanks. Where would you tap to get a RF carrier active -no audio- signal ? 123MHz antenna gets into pin 1; Pins 4,5,7,12,16 inactive, pin 14 is high. AGC is for 1MHz band