8511	2013-04-11 22:09:06	yz1gw	Design tracking PLL, help
Message	Date	From	Subject
Hi Wes and group, I'm trying to make a PLL VFO for my phasing DC receiver. I tried PLL design with 74hc4046, but i have loop oscillation problem. I would like to try similar design to offset tracking PLL with 74HC74 detector, from EMRFD fig 4.42, 4.45 and 4.57A, but I need help for specific loop filter components ("TBD" components from fig 4.57A). My goal is: VCO range: 28 to 28.4 MHz VCO gain: 120kHz/V (measured) VFO range: 4 to 4.4 MHz I will use OP AMP TL072 (i have not OP027) I would be grateful if someone could help. 73 de YT5RA Djole
8539	2013-04-15 12:02:44	Wes	Re: Design tracking PLL, help
Hello Djole and group, I have also had problems with the 74hc4046 and loop stability. I didn't pursue it very far. I have added a PLL design aid on my web site. This is a program within a Zip file, so it can be downloaded. Just go to http://w7zoi.net/ and then to the emrfd errata section. Then look at the book related items where you can click
8540	2013-04-15 12:25:03	Lasse Moell	Re: Design tracking PLL, help
Years ago I did some PLL design with the 74HC4046.. what I had problems with was the dead-zone where the phase detector goes into hi-z mode and the gain changes. The remedy was to have a 1Mohm resistor on output to draw current all the time. This worsen the phase noise a bit but made the loop much much more stable. One other thing that may cause problems is when one uses an active loop filter, the op-amp may have stability issues if input voltage is too high. /Lasse SM5GLC On 15 apr 2013 21:02 "Wes" <wesw7zoi@gmail.com> wrote: > > > Hello Djole and group, > > I have also had problems with the 74hc4046 and loop stability. I > didn't pursue it very far. > > I have added a PLL design aid on my web site. This is a program within > a Zip file, so it can be downloaded. Just go to <http://w7zoi.net/> > and then to the emrfd errata section. Then look at the book related > items where you can click
8541	2013-04-15 12:50:43	William Carver	Re: Design tracking PLL, help
I think it was Philips who otroduced a version of 4046 that didn't have that dead zone. I think that's now the NXP 74HCT9046A. I'm not sure how much that might have increased the phase detector spur in the output. W7AAZ On Mon, 2013-04-15 at 21:25 +0200, Lasse Moell wrote: > > Years ago I did some PLL design with the 74HC4046.. what I had > problems > with was the dead-zone where the phase detector goes into hi-z mode > and > the gain changes. The remedy was to have a 1Mohm resistor on output to > draw current all the time. This worsen the phase noise a bit but made > the loop much much more stable. > > One other thing that may cause problems is when one uses an active > loop > filter, the op-amp may have stability issues if input voltage is too > high. > > /Lasse SM5GLC > > On 15 apr 2013 21:02 "Wes" <wesw7zoi@gmail.com> wrote: > > > > > > > Hello Djole and group, > > > > I have also had problems with the 74hc4046 and loop stability. I > > didn't pursue it very far. > > > > I have added a PLL design aid on my web site. This is a program > within > > a Zip file, so it can be downloaded. Just go to <http://w7zoi.net/> > > and then to the emrfd errata section. Then look at the book related > > items where you can click
8542	2013-04-15 16:49:04	kb1gmx	Re: Design tracking PLL, help

8544	2013-04-15 18:02:01	rlramirez77	Re: Design tracking PLL, help
Has anyone had similar experiences with the Motorola MC14046BCP part? Only asking because this version is a bit different than the CD4xxx or 74HC4xxx parts. Russ K0WFS
8546	2013-04-15 18:02:02	Dana Myers	Re: Design tracking PLL, help

8551	2013-04-15 18:36:06	Chris Trask	Re: Design tracking PLL, help
> >> Years ago I did some PLL design with the 74HC4046.. what I had problems >> with was the dead-zone where the phase detector goes into hi-z mode and >> the gain changes. The remedy was to have a 1Mohm resistor on output to >> draw current all the time. This worsen the phase noise a bit but made >> the loop much much more stable. >> >> One other thing that may cause problems is when one uses an active loop >> filter, the op-amp may have stability issues if input voltage is too >> high. >> > >Has anyone had similar experiences with the Motorola MC14046BCP part? Only asking because this > version is a bit different than the CD4xxx or 74HC4xxx parts. > This is a situation where you might want to consider using the XOR phase detector (PC1out). It's essentially a quadrature phase detector. They work fine as long as your tracking bandwidth is less than an octave. Chris Trask N7ZWY / WDX3HLB Senior Member IEEE http://www.home.earthlink.net/~christrask/
8555	2013-04-16 02:34:08	Lasse Moell	Re: Design tracking PLL, help
I found it easier to use the old MC4044 and the faster sibling MC12040 rather than trying to push a 4046 into service at a high reference frequency. Today I would look into some more modern circuits from Analog Devices or similar. /Lasse
8563	2013-04-19 07:43:05	yz1gw	Re: Design tracking PLL, help
I thank you all for the helpful information, especially Wes for software which helped me a lot. I constructed PLL (ugly style) and it worked from the first time. Since I have no sophisticated instruments to check for phase noise, I used another receiver to listen to the VCO and I was very pleased with results, noise was much lower then with 4046 PLL. Second, when I connected VCO/PLL to my phasing receiver, listening to the strong transmitter signal(on dummy load), I did not noticed any PLL problem/harsh on the whole band. My VFO is stabilized with Huff&Puff and frequency stability is excellent. After this experience, I have many new ideas... 73, Djole / YT5RA