Re: PLL for VHF receiver

From: SioL (Sio_spam_L_at_same.net)
Date: 07/09/04 

Date: Fri, 9 Jul 2004 15:56:57 +0200

"Damien Teney" <dteney@hotmail.com> wrote in message
> When I connect the PLL "normally"
> (http://www.mcarsweb.com/_divers/2sketch.jpg), it locks on the right
> frequency (good point!) but it seems really less sensitive
> (interferences ??) and I also have a small whistle in the background.

That whistle in the background could be reference feedthrough.
It means that your PLL steps are kind of small or your PLL filter is
not good enough to filter out the reference. The smaller the reference
frequency the harder it is to filter it out. Try to use higher pll steps just
for a test.

Also, if you hear interference on a given frequency that is probably
due to signals from the PLL. For example, 5.12x15 = 76,8. You'll
likely hear a carrier there or at other harmonics. To make things worse,
receivers are not perfect. You will hear a multitude of other signals,
if they're strong enough. Fvco+Fif and Fvco-Fif are just two usually
strongest, there are others.

You need really good shielding, remember to decouple power to the PLL.
Use a battery to power PLL only to test whether this is the problem.

How are you feeding the mixer in the receiver? Is the RF level the same?

SioL

Relevant Pages

  • Re: I cant drive 95....
    ... Louis Ohland wrote: ... UZ, XGA-2 has a whoppin' 4MHz xtal on it, probably to act as a reference ... Assume that the PLL is designed for stability. ... Oddly, for a PEL freq of 65MHz, the index would be 0, and for 128MHz, ...
    (comp.sys.ibm.ps2.hardware)
  • Re: PLL Basics
    ... mean a PLL is a filter, any more it is a VCO. ... The PLL does indeed act like a lowpass filter, provided that one thinks about the phase of the output as it is related to the phase of the reference. ... The "signal generator" aspect is a red herring; the maths works just as well if the output frequency is zero. ...
    (comp.dsp)
  • Re: 24-bit 100kHz A-D converter with optical output
    ... >> The 100kHz output rate is created using a 12.8MHz PLL oscillator ... Higher reference frequencies are better, ...
    (sci.electronics.design)
  • Re: Jitter measurement
    ... > was hoping to somehow quantify the residual phase variation, ... reference point for the measurement? ... If your reference is the 10kHz signal from the GPS receiver (your PLL ... input), then use the 10kHz signal as the scope trigger, and display the ...
    (sci.electronics.design)
  • Re: I cant drive 95....
    ... UZ, XGA-2 has a whoppin' 4MHz xtal on it, probably to act as a reference for the internal PLL. ... So the PLL native output is 16x to 32x of the xtal. ... FR Field Division Frequency Range ...
    (comp.sys.ibm.ps2.hardware)