Hello.

I was wondering if anyone could help me with a little problem… I know this question sounds insane but is there any way to connect a frequency meter (Something such as a home built one based of a PIC) to a home built radio so I can determine what frequency it is working at?

Or is there some other way for me to easily work out the frequency that my radio is working at?


Dawn.

 

Assuming it's a superhet radio?, you can connect it to the local oscillator via a buffer (so as not to load it), this will then give the frequency either above, or below, by the IF frequency used. As it's a PIC based counter you could easily modify it to subtract or add the offset as required - it's a pretty common application.

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PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

If by frequency meter you mean a frequency counter, then yes it is quite possible.

As Nigel said, you have to make sure the FC has a high impedence input so as not to 'pull' the receiver's oscillator off frequency and you will have to manually add or subtract the intermediate frequency (IF) offset to get the actual receiver's tuned frequency.

Early digital display receivers used this method by actually having a internal frequency counter, but now most use micro based circuits to control and display the PLL or DDS type oscillator frequency.

Lefty

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Measurement changes behavior

 

Intermediate frequency

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

Damn spell checker

Lefty

__________________
Measurement changes behavior

 

Intermittent Frequency?

Thats what you get when the radio isn't working verry well.

JimB

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Experience is directly proportional to the value of the equipment ruined.

 

Hi Dawny,
please post a schematic of your Home made Radio ,
Mean time you try to browse for Frequency counters by IK3OIL using PIC16F84.It has selectable "IF" offsets .

I assembled one and is working fine .

I feel it can be interfaced to Home made radio with suitable shielded compartment for the counter part and having a buffer for picking up the Local oscillator ferequency.

Meantime, it is also possible perhaps to use a ready counter retrieved from cheap digital radios like Kchibo k9913- by taking suitable protection to the input so as not to blow up front end of counter.

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Regards,
Sarma.

 

After development of IT and computers, many might have forgotten the terms intermediate frequency (IF) and they interpret IF as "if" or Basic language"IF" or as pointed out Intermittent....

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Regards,
Sarma.

 

I know this circuit is really, really primitive but then again it seems to work...


Dawn.

P.S. Do you think it's time I went hunting for a better radio circuit to base a new experment off?

Attached Images

radio.jpg (29.0 KB, 15 views)

 

Yea, that isn't going to cut it. Not that it won't receive signals, but it's just a 'crystal radio' with modern active audio amplification added on. There is no local oscillator to measure the received signal frequency.

Lefty

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Measurement changes behavior