Looking for help adding a frequency counter to airband receiver

Status
Not open for further replies.
A

avz

Member
Hi. I've built a kit of an airband receiver purchased from Aliexpress. surprisingly, it even works. I've seen on youtube a clip demonstrating adding a frequency counter that displays the frequency. unfortunately, it's all in Russian, which of course I don't understand. attached are the circuit diagram of the receiver (it's the last page) and the link to the frequency counter (from Aliexpress, as well) that I would like to connect to it. could you tell me to which points on the receiver I have to connect the counter's input?
the link- **broken link removed**
Thanx.
 

Attachments

  • Aviation.pdf
    783.7 KB · Views: 362
The tuning is controlled by the local oscillator; I'd expect the take-off point for a frequency display to be from pin 7 of the NE602, via a buffer amp to minimise loading on that.

However, you the LO is offset from the receive frequency by the IF frequency, 10.7 MHz.
To display actual receive frequency it needs a counter that allows for that offset.

Possibly the Russian article for the display mod was offering an alternate PIC that had that included?
 
Thanx for your response. could you please explain in more plain English the second paragraph?
as per the Russian clip, all he showed how he put together on a wood base the receiver, the counter (which as much I was able to see was connected directly to the receiver - without any buffer) and a 9V battery.
 
I think "rjenkinsgb" assumed the frequency counter module only displayed the frequency applied to it's input. If that was the case it would display the local oscillator frequency rather than the received frequency. If that was the case the firmware in the PIC used in the frequency counter module would have to be modified to add or subtract (Depending if the LO was on the low side or the high side of the received frequency.) 10.7 Mhz to the local oscillator frequency. I found information in english for the frequency counter module and that implies that the display can be offset by the IF frequency. This is the link to the english version
https://www.aliexpress.com/item/400...earchweb0_0,searchweb201602_,searchweb201603_


Les.
 
Les Jones said:
I found information in english for the frequency counter module and that implies that the display can be offset by the IF frequency.
Click to expand...
Well spotted!
I actually see that link in Italian for some reason, but it definitely mentions an IF offset capability in that page, so should do the job perfectly.
 
Re post #6. I think it must use a prescaler chip to divide down the input frequency. (I would guess at a divide by 32.) There was a design in the EPE magzine November 2008 using a PIC16F628A (Same as PIC16F648 but less memory.) the read up to 50 Mhz using the TMR0 counter input.

Les.
 
upand_at_them said:
That thing can measure up to 1.2GHz using a PIC16F648A??
Click to expand...

Presumably it uses a prescaler to divide it down - but an 8 bit PIC on it's own, running at only 4MHz, can work as a frequency counter at over 50MHz. There was a VERY old and famous application note at MicroChip for just such a project. It's been copied and updated MANY times over the years (the original used 7 segment LED's, and an OTP PIC). It wasn't long before it was moved over to the 16C84 and Hitachi type LCD displays.

As this uses a very similar PIC (the 648 is a later - but old now - version of the 84), it's probably based on that application note.
 
I did not mean the internal prescaler on the PIC. I should have made it clearer saying using a separate prescaler chip.

Les.
 

Thanks for that citation. I'll check my back issues, I forget when I let my subscription lapse.
 
Nigel Goodwin said:
There was a VERY old and famous application note at MicroChip for just such a project. It's been copied and updated MANY times over the years (the original used 7 segment LED's, and an OTP PIC).
Click to expand...

AN592 ("Frequency Counter Using PIC16C5X"), I think. I printed it out, along with AN545 ("Using the Capture Module") for bedtime reading. :thumbs up:
 
My two 'penneth .. .. .. .

Here is an Airband Receiver I built from a very similar kit to which I fitted a frequency counter identical to the one Ron is detailing. I'm sorry the picture is poor - to protect the LCD I fitted an acrylic cover that reflects light beautifully, especially when you don't need it to !

MM
 

Attachments

  • Airband WIP 1.JPG
    107.2 KB · Views: 337
  • Airband FC.JPG
    1.3 MB · Views: 329
Hi Ron

I've attached the manual that came with the kit which includes a schematic. Unfortunately, it's a.pdf file so I can't edit it .. .. .. .. ..

The counter is connected very close to NE 602 pin 7. Why ? Because I know very little about RF and that's where the kind gentleman who was helping me told to put it .. .. .. .

MM
 

Attachments

  • AviationReceiverManual.pdf
    783.7 KB · Views: 315
Status
Not open for further replies.

Similar threads

I
Need help adding a manual temp-on pushbutton switch to an alexa controlled relay.
Replies
8
Views
608
Les Jones
L
  • Question
Adding an aux input to a microphone
Replies
1
Views
952
aliarifat794
A
E
Looking for suggestions on how to approach switching power to a series of EM Coils along a rail (EM Launcher)
Replies
7
Views
4K
rjenkinsgb
D
Adding switches for rear windows to passenger side of car.
Replies
0
Views
2K
Diver300
D
B
Looking for an optical odometry chip
2
Replies
21
Views
7K
BobW
B
Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…