Powered by Invision Power Board


Forum Rules Forum Rules (Please read before posting)
Pages:123 ( Go to first unread post ) Reply to this topicStart new topicStart Poll

> The Ad9850, Is it a VFO?
cgriggs
Posted: December 24, 2016 12:35 am
Reply to this postQuote Post


Member
****

Group: Trusted Members
Posts: 197
Member No.: 40,300
Joined: December 02, 2016




The item is: 0-55 Mhz Signal Generator - Digital Ham Radio VFO SSB RIT AD9850.
I see several of these listed on Ebay. Part of the description is "VFO". I am wanting to build a VFO for a crystal controlled 40 meter cw rig I put together decades ago and am wondering if this would fill the bill, or would it take an additional small fortune just to "finish" combining the project? Any ideas?
I've been out of the picture for over 20 years and am "starting over" with the higher tech items I see in today's projects. (Really a different world, folks! LOL)
Charlie
PMEmail Poster
Top
kellys_eye
Posted: December 24, 2016 04:23 pm
Reply to this postQuote Post


Forum Addict ++
*******

Group: Spamminator Taskforce
Posts: 11,418
Member No.: 2,735
Joined: June 21, 2005




Charlie.

These 'VFO' devices come in two varieties - one with push-buttons to increment/decrement the set value (frequency) and the better version that uses a rotary encoder with push-to-select via the same knob/shaft.

The one I use is a DIY one based on the AD9851 (essentially the same device) that was originally designed for use with a key pad as well as rotary encoder so you can 'type' in the set frequency. I don't require the keypad function so simply omitted it from the construction and use the rotary control to choose which DIGIT I increment thus allowing me to change the frequency by any step from 1Hz to 100kHz and any in between.

You can find the details of this DDS here http://www.hamradio.in/circuits/dds.php

If you use a decent rotary encoder (256 steps/revolution) you can sweep across a whole band at 10Hz or 100Hz resolution quite quickly/easily.

The additional functionality depends on your own personal needs and having the facility to add an offset or even to change between bands (the AB function) with one keypress.

Which DDS device you pick depends on what you want from it - I'd highly recommend the versions that use a rotary encoder though - more expensive but much more versatile.

Output frequency is accurate to something like 0.034Hz (also dependent on your crystal oscillator stability - generally good anyway) and can be used without filtering if you're 'mid band' of the DDS operating range (higher/lower ranges benefit from suitable filtering but this need only be simple RC or LC filter. Some of the cheaper DDS boards may not have adequate filtering but you can check this yourself quite easily.

The eBay versions are perfectly OK for VFO work and the price they quote is unbeatable - you couldn't purchase the parts locally yourself any cheaper I can assure you!



--------------------
May contain nuts
PMEmail PosterYahoo
Top
cgriggs
Posted: December 24, 2016 06:43 pm
Reply to this postQuote Post


Member
****

Group: Trusted Members
Posts: 197
Member No.: 40,300
Joined: December 02, 2016




Wow! I'm going to have to get an electronics Dictionary! LOL

I only want to use it from 7.0 to 7.3 for my 40 meter cw qrp rig. I'm wondering if the unit might be overkill. The DDS is nice, but I already have it incorporated. For that price though, I could afford to only use the VFO part. (I'll have to get a pic of my rig to show you what it looks like.)

I sold or gave away just about everything but this unit, I loved it so much. (Now I'm glad I did!!)

I think I'll send for it, (after the new year,) check it out and get back to you if/when I have a question. OK?

Oh! Number seven on the list said, "Two VFO's???" I'm going to have to get more info on this, I guess. I like to look over schematics and "figure them out" but it's a totally different world today.

I can see I have a lot of studying to do on electronic nomenclature! (If I can live long enough! LOL)

Charlie
PMEmail Poster
Top
kellys_eye
Posted: December 24, 2016 08:17 pm
Reply to this postQuote Post


Forum Addict ++
*******

Group: Spamminator Taskforce
Posts: 11,418
Member No.: 2,735
Joined: June 21, 2005




The span offered by a DDS VFO is a bonus, not a 'difficulty' - let's face it, ANY VFO can be used to cover any span if you change a few parts. The DDS version would still be cheaper than any standard VFO you can construct in the conventional manner but consider the simplicity of zero alignment, stability and calibration problems!

Ask any questions you like! Happy to help where I can and there are other forum members who have a lot more technical nous than me (step forward Tim aka Schematic).

Given the cheap (delivered) cost of those DDS VFO's it's worth purchasing one as a 'spare' and save on the (already-minimal) postage. They work right out of the box and you'll have more difficulty bending the metal to fit it in a box than with the electronics itself!

I'm sure you feel more at home in a Ford Taurus than a Ford Model T. We have to accept the improvements that time brings and sometimes 'forget' about what makes them tick.




--------------------
May contain nuts
PMEmail PosterYahoo
Top
cgriggs
Posted: December 26, 2016 12:16 am
Reply to this postQuote Post


Member
****

Group: Trusted Members
Posts: 197
Member No.: 40,300
Joined: December 02, 2016




As soon as I finish this note I'm sending in my order.
Many thanks for the info.
Charlie
On edit: TCO!

This post has been edited by cgriggs on December 26, 2016 12:22 am
PMEmail Poster
Top
cgriggs
Posted: December 27, 2016 12:17 am
Reply to this postQuote Post


Member
****

Group: Trusted Members
Posts: 197
Member No.: 40,300
Joined: December 02, 2016




From the article, "Freq setting in 1, 10, 100Hz, 1, 10, 100KHz, 1, 10 MHz by using a low cost mechanical encoder with a variable tuning rate."

And you said, "These 'VFO' devices come in two varieties - one with push-buttons to increment/decrement the set value (frequency) and the better version that uses a rotary encoder with push-to-select via the same knob/shaft."

Is this Rotary encoder something I'll have to purchase?

I had to learn a certain amount of Latin as an alter boy in the 40's, and I'm thinking that may have been a bit easier than learning today's electronic jargon. I haven't seen the word "Condenser" in anything I've read lately. I'm convinced that us minorities are to be pitied! LOL

Charlie
PMEmail Poster
Top
kellys_eye
Posted: December 27, 2016 11:38 am
Reply to this postQuote Post


Forum Addict ++
*******

Group: Spamminator Taskforce
Posts: 11,418
Member No.: 2,735
Joined: June 21, 2005




Usually, for eBay purchases, unless it specifically states it either comes with a rotary encoder or states it can WORK with a rotary encoder then the device will probably arrive with simple push-buttons (digit-select, up/down and enter).

There are two main versions of DDS module.

1. The type that are inclusive of software and display to enter and display frequency
2. A 'bare board' that is usually used with an external interface (user built and programmed).

The external interface version can be used with many designs that appear across the web - I linked to one in a previous post above - that either incorporate a rotary encoder or use a keypad etc. Unless you are prepared to program your own micro-controller (PIC) device then you'll have to find an outlet that provides a ready-programmed device. I don't doubt there are such DIY kits around but I've never used them myself, preferring to program my own chips instead.

Of course, the push-button version will do everything you require but with a small restriction on usability - although that's a matter for individual taste, some people LIKE using the push-button versions - so there's no real demand that you get the rotary encoder version if you want to get up and running as soon as you can.

The terminology and technology can sometimes seem daunting but when you get hold of the thing and see what is actually required the 'mystery' soon disappears.

I did a very quick Google search on DDS VFO's and came up with this:

http://www.pongrance.com/dds.html

which looks to be a very capable (and attractive!) solution, with the rotary encoder option fitted too - albeit sold out at the moment rolleyes.gif There WILL be other sellers offering such kits (and ready-built) versions across the world.

I suggest you do a reasonable search before committing as there will (may) be other suppliers with functionality that suits your own requirement. It's worth just reading the first paragraph of that advert to see how comprehensive and useful the seller finds it to be.


--------------------
May contain nuts
PMEmail PosterYahoo
Top
cgriggs
Posted: December 29, 2016 03:25 am
Reply to this postQuote Post


Member
****

Group: Trusted Members
Posts: 197
Member No.: 40,300
Joined: December 02, 2016




http://www.ebay.com/itm/0-55MHz-DDS-Signal...XQAAOSwgQ9Vs~1c
Kelly,
At the risk of becoming a real pest, could you check this DDS and see if I've bought and bitten off more than I can chew? It said the "encoder is provided in product package". Does it mean switches or rotary? Can you tell?
TIA, Charlie
PS. I've also sent for a DDS book to try to get a bit acquainted with the subject. sigh LOL
PMEmail Poster
Top
MacFromOK
Posted: December 29, 2016 04:11 am
Reply to this postQuote Post


Forum Addict ++
*******

Group: Spamminator Taskforce
Posts: 15,264
Member No.: 5,314
Joined: June 04, 2006




QUOTE (cgriggs @ December 28, 2016 08:25 pm)
http://www.ebay.com/itm/0-55MHz-DDS-Signal...XQAAOSwgQ9Vs~1c
Kelly,
At the risk of becoming a real pest, could you check this DDS and see if I've bought and bitten off more than I can chew?

Hey Charlie,

If there's a definition of "a real pest" around here, it would probably be "MacFromOK," so stop trying to steal my thunder. biggrin.gif

Just kiddin', welcome to the forum. beer.gif


--------------------
Mac *

"Basic research is what I'm doing when I don't know what I'm doing." [Wernher Von Braun]

* is not responsible for errors, consequential damage, or... anything.
PMEmail Poster
Top
cgriggs
Posted: December 29, 2016 08:49 am
Reply to this postQuote Post


Member
****

Group: Trusted Members
Posts: 197
Member No.: 40,300
Joined: December 02, 2016




Mac,
I'm beginning to feel inadequate. Twenty (or so) years ago I was a 20+ WPM cw op, always with a home-brew project going, giving novice classes, ad nausium, and today I'm an electronic dunce. This electronic world has drastically changed! I need a "Henry" to lead me by the hand! (Judas Priest! Do these people even know what a "Henry" is?) LOL It's scary.
Technology keeps moving along and only gets more and more complicated.
"Buying Books" Charlie
On Edit: Judas Priest!!! Where in the world did "Henry" come from??? I meant "Elmer". ... sigh ... Old age is definitely not easy on the gray cells! LOL

This post has been edited by cgriggs on January 12, 2017 05:16 am
PMEmail Poster
Top
kellys_eye
Posted: December 29, 2016 10:26 am
Reply to this postQuote Post


Forum Addict ++
*******

Group: Spamminator Taskforce
Posts: 11,418
Member No.: 2,735
Joined: June 21, 2005




Charlie

with eBay I find that unless they specifically state they DO supply something then they DON'T! I can't see anywhere in that advert where they say 'yes, we include the encoder'.

Still, they are very cheap and plentiful anyway and the type you want is typically like this device:

http://www.ebay.com/itm/3Pcs-6mm-D-Shaft-1...PYAAOSwn8FXRj8b

The pinout corresponds to what they indicate in their VFO documentation so will work if connected as they suggest. The minimal cost means that if you order the VFO and an encoder IS included then you're not going to be out of pocket but will end up having a couple of spares in the box!

Dave


--------------------
May contain nuts
PMEmail PosterYahoo
Top
kellys_eye
Posted: December 29, 2016 10:35 am
Reply to this postQuote Post


Forum Addict ++
*******

Group: Spamminator Taskforce
Posts: 11,418
Member No.: 2,735
Joined: June 21, 2005




Forgot to mention - the book.....

Check out some basic online articles on DDS fundamentals or even download the manufacturers datasheet for the AD9850/1 where you'll see as much as you really need.

Here's a link to the DDS device manufacturers site and an application note that 'tells all'.

http://www.analog.com/media/en/training-se...ials/MT-085.pdf

The subject is 'dark arts' to me (well, I understand it but feel as if it's a pointless exercise to do so!) and find myself happier just using the devices rather than delving deep into their basic operation.

I tend to look at them as a means to an end on the basis that if the world goes t*ts up I can always revert to basics and design/build a VFO from scratch - something I wouldn't comprehend with a DDS box!


--------------------
May contain nuts
PMEmail PosterYahoo
Top
cgriggs
Posted: December 29, 2016 02:16 pm
Reply to this postQuote Post


Member
****

Group: Trusted Members
Posts: 197
Member No.: 40,300
Joined: December 02, 2016




Kelly,
In the 3rd and 4th pictures (click on to enlarge) it shows the encoder. A black, square item. It connects to pins 1, 2, 3 and 14, 17. Its 'rotary'.
I must admit, when I ask for a hand, you give an adequate applause! LOL Thank you. I printed out the DDS description. (Aarrgghh!) Lots to learn! Now I have to sit on my hands until the package comes. You can only imagine what the waiting does to an ADD just dying to heat up the soldering pencil!!! LOL
Charlie
PMEmail Poster
Top
kellys_eye
Posted: December 29, 2016 11:54 pm
Reply to this postQuote Post


Forum Addict ++
*******

Group: Spamminator Taskforce
Posts: 11,418
Member No.: 2,735
Joined: June 21, 2005




Pins 1 and 3 are the rotary signals (this is a quadrature i.e. phase shifted signal) with pin 2 being common to them both, usually a ground or logic high.

Pins 14 and 17 connect to a second switch (part of the encoder) that provides a closing contact when you push the shaft of the rotary encoder 'in'.

Worked together you then get left and right rotation (step) signals with a push-to-select function.

It's very intuitive when you get to use it - as you will (eventually laugh.gif ) find out.

The more I look at that AD9850 board the more I'm convinced it's a rip-off of the VFO project found here:

https://sites.google.com/a/hamradio.in/hamr...redirects=0&d=1

(download the files and open the zipped folder to see schematics etc).

The DDS4V0 project has all the functions the eBay board lists - LED band drivers, rotary and keypad inputs and the programming (user setup instructions) seem to be identical! Regardless, the VFO is very good if it is indeed the one I think it is - I'm using one as an RF signal generator - so you have no worries over its capabilities when you get it up and running.






--------------------
May contain nuts
PMEmail PosterYahoo
Top
cgriggs
Posted: January 11, 2017 04:20 pm
Reply to this postQuote Post


Member
****

Group: Trusted Members
Posts: 197
Member No.: 40,300
Joined: December 02, 2016




Kelly; I can't feel my hands!!! ... Oh, never mind! I've been sitting on them and the circulation is gone. LOL
Judas Priest! How long does it take to ship from China?? Aarrgghh! It's killing me!
Charlie
PMEmail Poster
Top
kellys_eye
Posted: January 11, 2017 08:12 pm
Reply to this postQuote Post


Forum Addict ++
*******

Group: Spamminator Taskforce
Posts: 11,418
Member No.: 2,735
Joined: June 21, 2005




laugh.gif

delivery from China seems to vary a lot. I've just received a number of orders that were placed in December (around the 23rd IIRC) so the average wait has been only 18 days - pretty darned good if you ask me especially considering their sale price is inclusive of delivery!

I can't send packages internally in the UK for less that the Chinese manage to ship the PAID FOR product to the UK!!!!! Even despite the fall in exchange rates I'm happy to spend more and more money ordering from China - the service (barring the waiting time) is impeccable.

Patience!!!!

(and if life teaches me anything, the moment one complains about delivery, the stuff arrives the following day!!)


--------------------
May contain nuts
PMEmail PosterYahoo
Top
cgriggs
Posted: January 14, 2017 10:00 pm
Reply to this postQuote Post


Member
****

Group: Trusted Members
Posts: 197
Member No.: 40,300
Joined: December 02, 2016




It came and I'm petrified! LOL It said the rotary controller was included, but it wasn't. I'll go back to ebay for one. Will that be the main frequency tuning for the VFO or not?
I'll have to figure out the nomenclature of the three "plugs"(?) to connect 1,2,3,14 and 17 and get them also.
I need to find better instructions than what I have so far too. ... It's a bit scary! A world of difference from tube (valve) days!
Charlie
PMEmail Poster
Top
kellys_eye
Posted: January 15, 2017 07:18 pm
Reply to this postQuote Post


Forum Addict ++
*******

Group: Spamminator Taskforce
Posts: 11,418
Member No.: 2,735
Joined: June 21, 2005




They are often called 'Dupont' plugs. You can buy the shells and pins separately or as made up leads in any number of 'ways' - from single pins to many 10's of pins. Obviously you need the 2-pin and 3-pin versions.

Note that you might be better off purchasing a packet of assorted 'ways' as they are too cheap to only bother with a 'one-off' purchase.

The VFO will tune anything - from under 1MHz to around 50MHz, whatever you require.

What I suspect you will need to do is set it for 14MHz (using the 1MHz, 100kHz, 10kHz etc step options) then set the 'dial' to tune in 100Hz steps then you can scan across the band as you please.

Don't worry! We'll help you through this thumbsup.gif


--------------------
May contain nuts
PMEmail PosterYahoo
Top
cgriggs
Posted: January 15, 2017 08:34 pm
Reply to this postQuote Post


Member
****

Group: Trusted Members
Posts: 197
Member No.: 40,300
Joined: December 02, 2016




I'm going to look up "Dupont Plugs" on ebay . I want to use the 7 Mc band (40 Meters) This unit has three white receptacles {1 through 18}, a 5 pin, a 6 pin, a 7 pin and a large, black, double row with 14 pins.
Back later.
Charlie
On edit: I think I won't need to find the "socket plugs", but only need to get the female shells. That'll be easy. Are they of a common size or should I mike the pins for size?
I sent for three rotary controllers last night.


This post has been edited by cgriggs on January 15, 2017 08:47 pm
PMEmail Poster
Top
cgriggs
Posted: January 16, 2017 04:38 pm
Reply to this postQuote Post


Member
****

Group: Trusted Members
Posts: 197
Member No.: 40,300
Joined: December 02, 2016




You know what scares me? The realization that this is starting to make sense! The more I look at the digital monster in my hand and read what you've said and check out ebay for things mentioned, it fits.
Nomenclature is numbing my brain, but I think by the time I get this working I'll not need too large an electronic dictionary. LOL
In another forum I spotted a question about the Nixie 40 meter rig, checked it out, since I purchased one for 'later', and found out more about this DDS unit. It mentioned "LED's for 6 bands". On my assembly I see the 6 items mentioned, but are those tiny things LED's??? Judas Priest! How small do they get?? LOL
You'll never know how grateful a dunce can be jumping into the deep end of the electronic pool and finding that, over the years, he's forgotten how to swim! Totally helpless, I'll tell you! Many thanks!
I've sent for the Dumont connector wires, 40 for less that 2 dollars. Cheap, but this waiting is making an old man out of me. ... uh ... wait! Too late! LOL
Charlie
PMEmail Poster
Top
kellys_eye
Posted: January 16, 2017 10:13 pm
Reply to this postQuote Post


Forum Addict ++
*******

Group: Spamminator Taskforce
Posts: 11,418
Member No.: 2,735
Joined: June 21, 2005




Mind that when you order the plug parts that they come with the sockets or pins that fit them. Often the shells are sold separately and are useless without the relevant insert. Wire is crimped onto the separate plug pin (or socket) using a special tool then the pin/socket is pushed into the housing where it locks in place. Crimping can be done using small pliers but isn't anywhere as neat.

For any permanent fixture there's no real requirement to use plugs - you can happily solder straight to the pins on the DDS board and cover using heat-shrink.

The incredibly small part size is key to the low cost and manufacture of these devices and the parts you see are NOT the smallest they do! There are surface mount components as small as 10 thou by 5 thou in size shock.gif Good luck in soldering those in! (the point being is that mechanical placement is the ONLY way to go and the resultant cost reduction is beneficial - probably)

The mark of a true ham/amateur is the ability to take 'strange' electronics and simply LOOK at it until things click into place. Full understanding may come eventually but enough understanding is made to make the device usable.



--------------------
May contain nuts
PMEmail PosterYahoo
Top
cgriggs
Posted: January 17, 2017 12:39 am
Reply to this postQuote Post


Member
****

Group: Trusted Members
Posts: 197
Member No.: 40,300
Joined: December 02, 2016




The six shafts are associated with the six bands I see. I also imagine they come into play with the "setting up" of the unit, but what will do the actual frequency tuning for the rig, a separate capacitor, pot, the rotary controller, or what? (It gets confusing.)
I would, if only for looks, like to find the 5, 6 and 7 female pin plugs, but have no idea where to look or what to call the completed assemblies.
I had to chuckle with the idea of soldering onto the pins themselves. At my age and ability I can picture a solid glob of solder filling the "sockets". LOL
Ah, my favorite overworked words come to mind: "I usta could"!
Charlie

This post has been edited by cgriggs on January 17, 2017 09:33 am
PMEmail Poster
Top
kellys_eye
Posted: January 17, 2017 05:59 pm
Reply to this postQuote Post


Forum Addict ++
*******

Group: Spamminator Taskforce
Posts: 11,418
Member No.: 2,735
Joined: June 21, 2005




Pins 1, 2 and 3 go straight to the rotary encoder.

The 'push-to-make' part of the encoder (the two pins on the other side) go to 14 and 17.

Using this control alone you can chose which digit of the display (the 'active' digit will be underlined) you want to increment. Press the rotary encode shaft 'in' and turn it to move the underline to the digit you want to change then, when you let go of the button the rotary control will increment that digit up/down according to the direction you turn it.

The display will increment/decrement accordingly and will also automatically take the 'carry over' to the next digit if you go past 9 or 'carry under' if you go under 0.

When you switch it on it will start at a predefined frequency so shift the underline (cursor) to each digit in turn and select the required number until the display reads whatever frequency you want it to start at. The device remembers the last setting you use so it will start up exactly as you left it after powering down.

Then move the cursor to the digit you want to increment by - say the 100Hz digit - and you can then 'tune' from the base frequency you set it at up and down either side of that frequency in 100Hz steps.

The LEDs light according to the band you are tuning in. Outside of the pre-defined band ranges NONE of the LEDs will be lit. The pins labelled 'frequency band output range compensation' rolleyes.gif are actually pins that go logic 'high' according to the band LED that is lit and are included to allow the board to select external tuned filter circuits accordingly. As per the LEDs, these pins will all be 'low' (i.e. off) any time you're out of band.

If you are lucky the board will be preset to CW mode so no other switches will be needed but if you need - or want - to change other settings then additional push buttons will be needed although a temporary shorting link using croc clip and wire can do most everything you'll need.

I suggest you photograph the board when you get it and post the image on here just in case there are other peculiarities - quite common with these Chinese kits as their Chinglish instructions are often difficult to decode and occasionally totally wrong!


--------------------
May contain nuts
PMEmail PosterYahoo
Top
cgriggs
Posted: January 17, 2017 06:12 pm
Reply to this postQuote Post


Member
****

Group: Trusted Members
Posts: 197
Member No.: 40,300
Joined: December 02, 2016




I'm printing out your responses as I get them and keep referring back to them. I can't trust my memory.
Now I need to know how to post a picture here. I'll look through the "Newbie" postings.
I'm amazed at the changes since leaving the hobby. Miniaturization is a wonderful thing for 20-20 eyes. LOL
You might want to check out my posting called "Taken For Granted?" in the General(?) listing.
PMEmail Poster
Top
kellys_eye
Posted: January 17, 2017 07:56 pm
Reply to this postQuote Post


Forum Addict ++
*******

Group: Spamminator Taskforce
Posts: 11,418
Member No.: 2,735
Joined: June 21, 2005




I haven't reached the dizzy heights of 60 never mind 80 but I'm already using magnifying glasses and digital microscopes to make and repair stuff laugh.gif

To post pictures here you have to use a hosting service like Photobucket. You upload the photos to the host service then copy/paste a link from there into your text on here.

I'll check out your other post too thumbsup.gif


--------------------
May contain nuts
PMEmail PosterYahoo
Top
0 User(s) are reading this topic (0 Guests and 0 Anonymous Users)
0 Members:

Topic OptionsPages:123 Reply to this topicStart new topicStart Poll

 


:: support us ::




ElectronicsSkin by DutchDork & The-Force