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DIGITAL VFOS




 
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Author Topic: DIGITAL VFOS  (Read 7356 times)
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ka4koe
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It's alive. IT'S ALIVE!!!


« on: July 02, 2013, 09:48:39 AM »

Despite heroic efforts, the Valiant still drifts!!! Are we surprised? Anyway, I wonder if anyone here has tinkered with feeding in a signal from a digital VFO? I assume one would inject the signal at the crystal socket.

Just playing with ideas here.

Philip
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WD5JKO
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WD5JKO


« Reply #1 on: July 02, 2013, 11:18:47 AM »


Phillip,

   Take a look at Jim Hagerty's web pages here:

http://wa1ffl.com/index.html#

He addresses the Valiant's frequency needs with an optional switch board, and a buffer board to drive a tube rig.

Jim
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KB2WIG
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« Reply #2 on: July 02, 2013, 11:28:58 AM »

How about getting a BC 221 hetrodyne freq meter. They are stable, and ya can sometimes find 'em for around $20 at fests.


klc
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W9BHI
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« Reply #3 on: July 02, 2013, 11:41:50 AM »

Look at the N4YG DDS vfo site.
Then check out the W9BHI (my) version of his VFO.
I had him custom program the processor for me and I did the construction.
He now offers this kit as a replacement for Johnson and Heathkit VFO's.
I am using it on my Valiant II and has plenty of drive with it's built in buffer amp.
Works from 10 thru 160 perfectly.

Don W9BHI
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W3GMS
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« Reply #4 on: July 02, 2013, 10:39:04 PM »

I know several locals that have bought this one and all were very pleased.  In some cases, a single stage gain stage is  needed in cases where the injection voltage needs to be higher. 

http://www.pongrance.com/

Joe, GMS 
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WD5JKO
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WD5JKO


« Reply #5 on: July 03, 2013, 05:30:35 PM »


Phillip,

  Lots of options these days on the DDS front. There are also options to stabilize the old pesky Valiant VFO. This would be a challenge, and you will never be DDS stable, but you can certainly improve things a bunch. This would be a case of your time being free, and you have plenty to spare.  Huh

  I am attaching a PDF on what I did to my old Knight Kit V44 vacuum tube VFO. The content within can apply to many other vintage VFO's. The idea is to leave the VFO on all the time, shield the output, and have the frequency shifted away during receive. Then use the Cumbria X-Lock 3.0 where the RIT option will record both key up and key down frequencies, and maintain them within a 10 Hz +/- window.

Jim
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W3GMS
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« Reply #6 on: July 04, 2013, 10:04:27 AM »

Hi Jim,

Very interesting on the Knight VFO modifications.  I have that VFO and your suggestions are appreciated.  So I really don't see any details about the X-Lock.  I do see the diodes and well understand the cap change with applied DC voltage using them as varactor's,  but whats the circuit look like that is feeding them?  I would imagine it measure the initial frequency that you set the VFO and then create an error voltage to keep the VFO on the original set frequency by sending a correction voltage to the diodes.    So in essence its continuing to lock onto the selected frequency. 

Joe, W3GMS 
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WD5JKO
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WD5JKO


« Reply #7 on: July 04, 2013, 11:14:35 AM »

Hi Jim,

Very interesting on the Knight VFO modifications.  I have that VFO and your suggestions are appreciated.  So I really don't see any details about the X-Lock.  I do see the diodes and well understand the cap change with applied DC voltage using them as varactor's,  but whats the circuit look like that is feeding them?  I would imagine it measure the initial frequency that you set the VFO and then create an error voltage to keep the VFO on the original set frequency by sending a correction voltage to the diodes.    So in essence its continuing to lock onto the selected frequency.  

Joe, W3GMS  

   Joe, I didn't mean to hi-jack this thread...just to give Phillip another alternative to DDS for his mighty Valiant transmitter VFO. Your questions and many more are answered on a recent thread at AMFOREVER dot COM.

   I added a system schematic of an earlier implementation of X-Lock on a tube VFO below for clarity of concept.

Jim
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* System_Schematic.JPG (79.85 KB, 920x628 - viewed 490 times.)
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W3GMS
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« Reply #8 on: July 04, 2013, 04:24:03 PM »


   Joe, I didn't mean to hi-jack this thread...just to give Phillip another alternative to DDS for his mighty Valiant transmitter VFO. Your questions and many more are answered on a recent thread at AMFOREVER dot COM.
   I added a system schematic of an earlier implementation of X-Lock on a tube VFO below for clarity of concept.
Jim
WD5JKO
[/quote]

Thanks Jim. 

I think its related and not a hi jack of the thread.  Its all about how to make something more stable.  DDS or possible other solutions that Phil did not consider. 

Thanks for the info and I will look on the WEB about the product to which your referring to.    Not sure what AMForever is.  Hopefully that means that AM is not dead!

Joe, W3GMS
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Detroit47
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« Reply #9 on: July 04, 2013, 05:30:53 PM »

Not wanting to hijack thread, but any thoughts on the infamous GLEN 326-G DIGITAL VFO. I read the instructions and I think it would work on a Viking 1 or 2. I have seen the working nice on tube CB radios. But never on a ham transmitter.

John N8QPC
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WD8KDG
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« Reply #10 on: July 04, 2013, 11:38:13 PM »

Not wanting to hijack thread, but any thoughts on the infamous GLEN 326-G DIGITAL VFO. I read the instructions and I think it would work on a Viking 1 or 2. I have seen the working nice on tube CB radios. But never on a ham transmitter.

John N8QPC

Got one of those Glen 326-G digital controllers in the shack. The VFO is really a voltage controlled oscilator. No PLL. Think the lowest frequency output is around 7.6MHz. Then there is a little switch on the back that takes (in steps) the VCO up to about/near/some where nearby 26 MHz. Then there is a slide switch for an output X2 about 52 MHz.

It was given to me years ago from a gud buddy CBer sometime in the 80's. Power transformer was toast, found something at RatShack for the 5V supply and built a voltage tripler plus an other Xformer for a 15V supply. Shoehorned it in the bottom section.

Was using it just as a freq counter till last week, quit counting. At this point all leads are pointing toward a JK flip-flop. If a new IC will fix it; still worth using as an el'cheapo counter.

Craig,
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WBear2GCR
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« Reply #11 on: July 05, 2013, 12:48:18 AM »


There are a ton of tunable "DDS frequency generators" around now, for low $$, most based on one of the Analog Devices chips, some on programmed uproc and other chips.

Wonder if these have the requisite clean-ness for VFO usage?
Obviously, they need a buffer in most cases.

Small, self contained, simple power and digital readouts.

                             
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« Reply #12 on: July 05, 2013, 06:19:15 PM »

Quote
Not sure what AMForever is.
    Grin
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