Signal strength

AllanBertelsen

Senior Member
How do I measure signal strength from a radio receiver?
I build a little FM-radio transmitter that can transmit a tone generated by a 555 timer circuit. I can receive it by my clock radio. I want to build a receiver with a directional antenna. Then I want to measure signal strength to be able to optimize the direction of the directional antenna.
If possible the signal strength should be measurable by an ADC pin on a PICAXE.
 

Dippy

Moderator
You don't say what type of receiver module you have.
If you're lucky you'll have a pin on it marked RSSI. If you bought a cheapy it probably won't.
 

jmumby

Senior Member
Try searching the web for 'Field Strength Meter' or FSM. This an inductor and aerial with a basic amp. You could play round with the amp to create a full scale deflection of 5V.

I was going to do something similar but with 4 FSM's for a direction finder.
 

eclectic

Moderator
Allan, try this link please.

http://cs.okanagan.bc.ca/ve7ouc/eng/kc6wdk-mirror/fsm.html
<A href='http://cs.okanagan.bc.ca/ve7ouc/eng/kc6wdk-mirror/fsm.html' Target=_Blank>External Web Link</a>

The output looks as though it is measurable with a Picaxe.
e.





 

AllanBertelsen

Senior Member
Thank you jmumby lot of good hits.
eclectic - thanks for the link. It might be what I'm looking for. Just got to do a lot of reading to find out.
 

Michael 2727

Senior Member
Talking Electronics in Oz have done a couple
of them for FM Bugs, one is very simple only
a Diode, LED and Cap.
I'll try to locate a link and add it here.

Not an easy link to follow but try this -
<A href='http://www.talkingelectronics.com/te_interactive_index.html' Target=_Blank>External Web Link</a>
Then Go To Page P2 (page2 of the 4 page newsletter) and half way down hit the
Go now to our &quot;FM transmitter section&quot; which is hyperlinked then at the bottom of the page there are 2 projects use this link
- LED Power Meter - measures the output power 70&#162;
You could replace the DVM with a Picaxe
input and use the ADC, but remember to input
clamp the input of picaxe with a zener protection diode either 4.7V or 5.2V just incase.
All this for a measly $0.70 AUD, things are
tuff ain't they. ~ :eek:)

Edited by - Michael 2727 on 03/07/2006 14:49:01
 

AllanBertelsen

Senior Member
Thanks Michael
I found it. I also found a Field Strength Meter at the same site. It also gives 0-10V readings. But it also works at a distance.
 

eclectic

Moderator
Allan.
The meter in that article above appears to be designed for 100 - 300 MHz

Most licence-free low-power AM/FM transmitters work at 433 MHz.

What is the frequency of your &quot;home-made&quot; transmitter?

e.


Edited by - eclectic on 04/07/2006 06:05:13
 

Michael 2727

Senior Member
Allan that TE site has 20 or 30 different
size and style of FM Bugs, Transmitters and
even have a couple they set up for tracking
games like Fox Hunt over half a kilometer
or so. You may have to dig a little to find
the projects or info.
 

AllanBertelsen

Senior Member
Is's a Vellerman kit:
<A href='http://www.velleman.be/ot/en/product/view/?id=8892' Target=_Blank>External Web Link</a> It's 100-108MHz.
 
Top