PCS Electronics PCS Electronics - home page PCS Electronics  
RegisterSearchFAQAM & FM Radio transmitters shop UsergroupsLog in
Help me for problems with HEF4751V

 
Reply to topic    PCS-Electronics Forum Index » Schematics - help and ideas View previous topic
View next topic
Help me for problems with HEF4751V
Author Message
Ivand
New registered user
New registered user


Joined: 02 Mar 2004
Posts: 1

Post Help me for problems with HEF4751V Reply with quote
Hello, I have one problem using HEF4750V and HEF4751V

HEF4750V is Frequency synthesizer form Philips
http://www.semiconductors.philips.com/acrobat/datasheets/HEF4750V_CNV_3.pdf

HEF4751V is Universal divider form Philips
http://www.semiconductors.philips.com/acrobat/datasheets/HEF4751V_CNV_3.pdf

First at all I want to say that I have working synthesizer with above
schemes. I make it working on radio bands 1.8Mhz 3.5Mhz 7Mhz ... 28.5Mhz
The channels are to 1Khz and I using DAC to make sub channels to 10Hz
It works fine but has some errors.

I control the universal divider HEF4751V and DAC with PIC16F84.

In this PLL synthesizer the value of N, by which the output frequency is
divided in order to compare it with the reference frequency(1Khz) is construct
by this formula

N = A - B or
N = A - B + 10^6 (if A - B < 0)

A and B is numbers which can be programmed in HEF4751V

In my synthesizer I use only A number.
I put for A number this 35.600Mhz + 3.5Mhz = 39.100Mhz for my VCO.
in this situation N = 39.100 - (B=0)

THE PROBLEM:
I read in some other design of such synthesizer that I can program
B number in such way that I can just put in A direct frequency as 3.5Mhz and
N will be 39.100!

By my calculation B must be this

B = A - N + 10^6 = 3 500 - 39 100 + 10^6 = 964 400

Problem is that when I put this B = 964 400 in HEF4751V my PLL is locket
but the channels do not change :(
for example on 1.8 3.5 and 7Mhz it locks near on 40.500Mhz
I change A but it stay on one frequency

Has some one do such synthesizer and can help to me with above problem?
Tue Mar 02, 2004 7:31 am View user's profile Send private message
pcs
Site master
Site master


Joined: 18 Jan 2002
Posts: 3063
Location: Radio Land

Post Reply with quote
This chip is obsolete/really old. There's so much way better stuff
out there. Just not worth the trouble.

_________________
Best regards,
Marko - PCS Electronics
--------------------------------------------------------
Turn your PC into a FM radio station!
http://www.pcs-electronics.com
fax +386 4 2316 128
Sun Apr 04, 2004 2:52 pm View user's profile Send private message Visit poster's website
marinbnm
New registered user
New registered user


Joined: 23 Oct 2004
Posts: 3

Post Reply with quote
pcs wrote:
This chip is obsolete/really old. There's so much way better stuff
out there. Just not worth the trouble.


This chip is older but the HEF4750V frequency synthesizer is one of a pair of LOCMOS devices, primarily intended for use in high-performance frequency synthesizers, and is not worth to say that is not worth trouble.
I had a fm transmitter using this synth, and i get schematic for you, maybe then you can get some solution for you're problem.
Sat Oct 23, 2004 11:13 am View user's profile Send private message Visit poster's website
Display posts from previous:    
Reply to topic    PCS-Electronics Forum Index » Schematics - help and ideas All times are GMT + 1 Hour
Page 1 of 1

 
Jump to: 
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group