Digital Drive & New Rigs

Welcome and feel free to ask questions about class E, mosfet's, and AM.
You must be registered to post.

Digital Drive & New Rigs

Postby Brent » Mon Apr 13, 2009 9:14 am

I finally got the 10 fet E rigs converted to digital gate drive. The new DDS vfo required some buffering to drive the 74ac112.
Mark KA2QFX helped me get that straightened out and Steve helped me debug the 40 meter deck. I was able to get 90% efficiency out of all the decks. I did convert the 160/80 to 8 fets for 4 driver chip symmetry. All rigs putting out 375 watts.

I will try to get some pics on my web site soon.

Brent W1IA
Brent
PT Cruiser Tina
 
Posts: 110
Joined: Sun Feb 02, 2003 11:21 pm
Location: Derry, NH

Re: Digital Drive & New Rigs

Postby KD3CN » Tue Apr 14, 2009 7:03 am

FB Brent,
I need to get into higher gear here with the current e-rig projects, and your progress is great motivation.
Looking forward to seeing the pics.
73, Karl
KD3CN
Member
 
Posts: 41
Joined: Sat Apr 08, 2006 5:26 pm
Location: Strasburg, PA

Re: Digital Drive & New Rigs

Postby Brent » Tue Apr 14, 2009 7:24 am

KD3CN wrote:FB Brent,
I need to get into higher gear here with the current e-rig projects, and your progress is great motivation.
Looking forward to seeing the pics.
73, Karl

Thanks Carl,
It was back emf blowing out the chips..once I put some diodes across the relays problem solved.
Rigs work fine. I am going to convert the 20 fet 80 meter to 24 and 160/80 with digital drive. Then the big job of rewiring the station for master station keying.

God day to work on antennas.

73 Brent W1IA
Brent
PT Cruiser Tina
 
Posts: 110
Joined: Sun Feb 02, 2003 11:21 pm
Location: Derry, NH

Re: Digital Drive & New Rigs

Postby W1AC » Tue May 20, 2014 8:40 pm

Brent wrote:I finally got the 10 fet E rigs converted to digital gate drive. The new DDS vfo required some buffering to drive the 74ac112.


Brent,

I'm doing the same thing, converting a 10-FET RF deck to use gate drivers.

I'm using IXDD614 chips, but I wonder if there is an "inverting" version I can use that will save me the need for a phase splitter board?

TIA.

Bill, W1AC
Class E is a lot like life:
The trick is to avoid the hot spots!
W1AC
Member
 
Posts: 13
Joined: Sun Jan 28, 2007 9:38 pm
Location: Sharon MA

Re: Digital Drive & New Rigs

Postby Gilly » Wed May 21, 2014 5:25 am

Hi Bill

I will keep quiet for a while and give Brent a chance to reply.....

I cannot quite see your problem.....but I think I can...
Why not use what Steve has on the WEB site...that is a 74112 or even 7474 divider that gives you that 180 degrees phase difference.....required for Push Pull....

If this is the way your going I would make each bank either 4 FETs or 6 FETs....
This way one IXDD614 will drive 2 11N90....

Hope this helps to some extent......and its easy to do too...

You will need a variable frequency source as well.....


Wayne
Gilly
Class E Enthusiast
 
Posts: 167
Joined: Tue May 15, 2007 6:59 pm
Location: Mt.Eliza Victoria Australia

Re: Digital Drive & New Rigs

Postby W1AC » Wed May 21, 2014 12:15 pm

Gilly wrote:Why not use what Steve has on the WEB site...that is a 74112 or even 7474 divider that gives you that 180 degrees phase difference.....required for Push Pull....

If this is the way your going I would make each bank either 4 FETs or 6 FETs....
This way one IXDD614 will drive 2 11N90....


The deck I'm rebuilding was an experimental layout, using 5 FETs per bank, and I'm dropping it back to the usual four. That would require two IXDD614s per bank, of course, but it since the phase splitter boards are in short supply, I think I can use an "inverting" chip on one of the banks (i.e., two non-inverting and two inverting IXD_614 FETs) and feed them in phase to simplify the input.

There is a version of the IXD_614 that has an inverting output, but it doesn't have an enable lead, and I'm such a N00B at Class E that I don't know if it's usable. It's the IXDI614, and there's a spec sheet here: http://ixapps.ixys.com/DataSheet/IXD_614.pdf

Gilly wrote:Hope this helps to some extent......and its easy to do too...

You will need a variable frequency source as well.....


Of course it helps! Thank you! Every bit of information helps!

73,

Bill, W1AC
Class E is a lot like life:
The trick is to avoid the hot spots!
W1AC
Member
 
Posts: 13
Joined: Sun Jan 28, 2007 9:38 pm
Location: Sharon MA

Re: Digital Drive & New Rigs

Postby kf1z » Wed May 21, 2014 1:01 pm

It depends on how you plan to drive them.

What I see happening, is one phase ( the inverting side) staying on for a lot longer than the other... not a good scenario.


If I were going to try to go the minimalist approach...

I would use a transformer with center tapped secondary... diode on each output
and use each side to drive a phase.

That way the positive going 1/2 cycle will drive one phase, the negative going 1/2 cycle will drive the other phase.


If you go with an inverting IC, and one not... you'd have to double your input frequency first., ( I'm pretty sure...)
User avatar
kf1z
Senior Contributer
 
Posts: 558
Joined: Sat Mar 18, 2006 7:07 am
Location: Ely, NV.

Re: Digital Drive & New Rigs

Postby Gilly » Wed May 21, 2014 6:16 pm

Ohhh OK I see now....

Since this is your first build I would " throw them away " :mrgreen:

Like what Bruce said don't muck around with Inverters to fix the problem.....and you could use transformers ..... but this being your first build probably best to stick to Steve design as people will know then whats going on....

But this problem is easy to solve though..........Bruce has plenty of the IXDD414/614 and I'm sure he would be happy to help you out there.....

And you can still continue to rebuild your Transmitter using the IXD_614 as a mechanical guide in the outlay.....

If you are worried about your construction ability don't be :D as on 160M and 80M you can just about get away with anything.....40M is totally different ......


Wayne
Gilly
Class E Enthusiast
 
Posts: 167
Joined: Tue May 15, 2007 6:59 pm
Location: Mt.Eliza Victoria Australia

Re: Digital Drive & New Rigs

Postby W1AC » Wed May 21, 2014 10:24 pm

Gilly wrote:Like what Bruce said don't muck around with Inverters to fix the problem.....and you could use transformers ..... but this being your first build probably best to stick to Steve design as people will know then whats going on....

But this problem is easy to solve though..........Bruce has plenty of the IXDD414/614 and I'm sure he would be happy to help you out there.....


Wayne,

Thanks, I'm all set for FETs. I have four of the IXDD614 units in TO-220 cases, so I can put together the "standard" driver and 11N90 rig.

As things stand now, I'll be driving the IXDD614's from an FT-890 transceiver, which puts out 100 watts of CW, so I'm not worried about having enough drive: I'm removing the input tuned circuit that is used to be there in order to waste some power in the coils, which are already wound for push-pull feed.

I'll probably have to add a pad on the input, just to be safe, but I don't want to build a VFO just yet: On the one hand, it would duplicate a capability I already have, but on the other hand, a pad will take time and money too.

Anyway, thanks for your advice. I got the package from Digi-key today, so this weekend will be "layout" time.

Bill, W1AC
Class E is a lot like life:
The trick is to avoid the hot spots!
W1AC
Member
 
Posts: 13
Joined: Sun Jan 28, 2007 9:38 pm
Location: Sharon MA

Re: Digital Drive & New Rigs

Postby kf1z » Wed May 21, 2014 11:11 pm

You removed the input?

So.....
Now you have to re-add an input circuit.

one, to split into 2 phases, and two to let your transceiver "see" a 50 ohm load.

You cannot just run the output of your rig to the drivers..... that will not end well.

it takes a miniscule amount of RF to drive, the drivers!
( the 74ac112 flip-flop drives the ixdd614 just fine, and it's max rated for 50 mA @ 5 vdc)

But, because the Rf is sine-wave, you need a little more voltage to keep the drivers in the on state long enough....
So 2/3 of a watt to at most 1 watt is all you need.

I would have just left the entire input circuit, and tied it to the drivers...
Or for that matter, I believe that you would be better off leaving the whole thing as-is, without the drivers ( 614's)



or did I misunderstand?
User avatar
kf1z
Senior Contributer
 
Posts: 558
Joined: Sat Mar 18, 2006 7:07 am
Location: Ely, NV.

Re: Digital Drive & New Rigs

Postby Gilly » Thu May 22, 2014 12:45 am

Hi Bill

Bruce is 100% right.....your making this too complicated for what it is.......

I'm sorry Bill .... your way is not going to end well and will be over engineered and prone to disaster :oops:

Order a DDS from http://www.pongrance.com/ feed the output into a 7404 / 7414 to square it up and then into a 74112 Flip Flop.
The DDS will have to run 2 or 4 times the required frequency as the 74112 will divide it down etc:
The output from the Flip Flop will have 2 outputs 180 degrees out of phase ... these fed into the IXDD614 drivers...
All this is at TTL level .... very little power required.....

If you go the same way as on the WEB site the end result is a very reliable transmitter that you will be able to enjoy and use regularly.....


Wayne
Gilly
Class E Enthusiast
 
Posts: 167
Joined: Tue May 15, 2007 6:59 pm
Location: Mt.Eliza Victoria Australia

Re: Digital Drive & New Rigs

Postby kf1z » Thu May 22, 2014 12:21 pm

That's where I disagree with you Wayne......

I had no good luck with N3ZI kits....

I would opt for instead of DDS, a unit based on the Si570
Like this one
http://www.qsl.net/k5bcq/Kits/Kits.html
The Si570 Controller and Frequency Generator Kit #2

The one-knob operation is a little weird,
but I use this one myself.
User avatar
kf1z
Senior Contributer
 
Posts: 558
Joined: Sat Mar 18, 2006 7:07 am
Location: Ely, NV.

Re: Digital Drive & New Rigs

Postby W1AC » Thu May 22, 2014 1:55 pm

kf1z wrote:You removed the input?

So.....
Now you have to re-add an input circuit.

one, to split into 2 phases, and two to let your transceiver "see" a 50 ohm load.


Well, I haven't done that yet: the components are still there.

kf1z wrote:You cannot just run the output of your rig to the drivers..... that will not end well. ... it takes a miniscule amount of RF to drive, the drivers!
( the 74ac112 flip-flop drives the ixdd614 just fine, and it's max rated for 50 mA @ 5 vdc)

But, because the Rf is sine-wave, you need a little more voltage to keep the drivers in the on state long enough.... So 2/3 of a watt to at most 1 watt is all you need.

I would have just left the entire input circuit, and tied it to the drivers...
Or for that matter, I believe that you would be better off leaving the whole thing as-is, without the drivers ( 614's) ... or did I misunderstand?


No, you didn't, and I apologize for not explaining my needs more clearly. I'd better back up and give you guys the "back story".

I'm a big fan of simple designs and using as few parts as needed. However, my "RF" experience is all from forty years ago (yikes!), when I was a broadcast engineer in AM and FM stations on both coasts. Needless to say, it's from the days of high-voltage, low-current, big iron.

To top it off, I had a job as a telephone equipment engineer at Verizon: a place where everything is specified to the nth degree, with debate about even the smallest engineering decisions. It made me overly-cautious and prone to hyper-vigilance, and I freely admit it.

But ...

The Class E RF deck I have was a gift from a friend, who told me that it had been an experiment and would need rebuilding. The existing deck was set up for sine-wave drive, with two banks of five 11N90 FETs in push-pull. My friend recommended that I use a more conservative design, with driver chips, and that's what I'm trying to do.

I'm perfectly happy to run the rig with drive right from my FT-890 if that will work reliably: the Yaesu can be dialed back to just a few watts of CW, so if that would work without burning things out, I'd be happy to do it. I'd also be happy to build or buy a pad to get the Yaesu's output down to a manageable level. That's one possibility.

OTOH, I'd also be happy to buy a DDS VFO and put it in if your advice is to do so: I don't know which solution I want to use, but I want to use whichever is the most simple, so long as it's the one that won't cause me problems later on.

I know that there are many ways to go, but I'm in a difficult situation: I want to preserve as much of the original work as I can, provided it can be made to work reliably, and minimize changes that I might make just because I don't know any better.

I hope that makes my situation more clear, especially if you read between the lines: if you need more pictures, more background, or any other info, feel free to PM me or email or call.

Thank you for your help. I appreciate your time.

Bill, W1AC
339-364-8487
bill at <lastname> dot net
Class E is a lot like life:
The trick is to avoid the hot spots!
W1AC
Member
 
Posts: 13
Joined: Sun Jan 28, 2007 9:38 pm
Location: Sharon MA

Re: Digital Drive & New Rigs

Postby kf1z » Thu May 22, 2014 3:55 pm

Oh I get it ok.

Less work, less money.... quick and easy. :-)

I really think you ought to use the board Steve has.

I emailed him, to see if he has any, but have not had a reply yet.
kinda strange, usually he returns my emails fairly quickly.
But, I don't know what he's up to either....
User avatar
kf1z
Senior Contributer
 
Posts: 558
Joined: Sat Mar 18, 2006 7:07 am
Location: Ely, NV.

Re: Digital Drive & New Rigs

Postby kf1z » Thu May 22, 2014 3:57 pm

Oh...

I am a big fan of taking on a project that I have never done before following the 'proven method' FIRST.

THEN start experimenting after it's together and working.

but, not everyone thinks the way I do.

( thank goodness for THAT. :-) )
User avatar
kf1z
Senior Contributer
 
Posts: 558
Joined: Sat Mar 18, 2006 7:07 am
Location: Ely, NV.

Next

Return to Class E Discussion

Who is online

Users browsing this forum: No registered users and 3 guests

cron