QuadZilla sees first light - Quad 4X1's - pictures

[WB2YGF]

Tom was pretty good, but Don KYV gets my vote for the strappinest signal into NJ last night.

[Steve - WB3HUZ]

Three dB or so shouldn't be noticeable, given the right time constant(s). Some have done this in past decades with rigs like the DX-60, etc. I recall one guy who had his set up so he could vary from full carrier control to none (pure screen modulation).

... I have (to me) an new additional wrinkle .. I have come up with a way to vary the amount of controlled carrier from none to "some" in a plate modulated tx .. some tbd .. I am incorporating it in my current construction project ... I hope to have it ready to test soon ...73 ...John

John:  I'd be curious how you will be swinging the controlled carrier. Is it a grid driven amplifier with control of the screen and/or grid voltage you're accomplishing this with?  Might be a little harder with straight GG unless it is done in the low level stage, like at the FT-102 driver. Now that wud be fun to experiment with I think.

The only thing with controlled carrier is the annoying up and down sound of hedrodynes when using it.... :-)  Everything is a compromise or I guess we'd all be using the same thang eventually.

T

Tom, as far as I know this may be new ground ... I don't have access to the old magazines so it is possible that this is a "revisit" of an old idea and is relatively simple

I decided a while back that having control of the amount of controlled carrier would be a good thing .. I think 3 db would be unnoticed, 6 db would be noticed by some, etc.  The reason for going after this is when following the plate mod low power tx with an amplifier, controlling the carrier  level when unmodulated reduces heat production (3db = 1/2, 6db = 3/4 )

this may wind up being a compound scheme for increased + direction modulation index

let me see how this works and if promising I will release to the public domain

idea first disclosed to Jack, WB8BFS January 2009

73 John WB4BFS

[w4bfs]

yes I agree with 3 db as an easy figure of merit ... time constants I am trying are .5 msec attack and 100 msec release ... what I am trying is similar to what you are discussing with the NE602 circuit but with a 6S4 in the screen circuit of 2 - 6146 .... first attempts will be dc shifts and then if that works well may also try a bit of audio as well ...we shall see ...73 ...John

p.s. I AM NOT trying to steal your thread ... just kicked off this idea   ... by the way Steve, the stock DX 60's seen to generate about 9 or so db of controlled carrier and at times is annoying and other times is impressive ... a most curious hobby, this   ... beefus

[WA1GFZ]

Tom
I would think you could rectify the positive peak and feed the voltage into the dc carrier voltage as an offset. The trick would to be selecting an attack and decay time that didn't introduce distortion. Email me your circuit.
Tom, you missed out on two 4-1000As at the flea. $75 each

[K1JJ]

Tom
I would think you could rectify the positive peak and feed the voltage into the dc carrier voltage as an offset. The trick would to be selecting an attack and decay time that didn't introduce distortion. Email me your circuit.
Tom, you missed out on two 4-1000As at the flea. $75 each

Frank,

Here's the NE-602 circuit.  It appears that pin 2 wud be the place to inject the controlled carrier signal.  I agree that using the positive peak rectified is a good idea. We wud want a "linear" ramp up as the voice signal increased. 

http://www.amwindow.org/tech/htm/602mod.htm

A sample of the audio from pin 1 then rectified thru an R/C time constant is what's needed.  Not sure if we wud need another IC or transistor for isolation and gain.

Let me know and I'll modify my NE-602 in the FT-102 and test it at 20W before trying it with Quadzilla... :-)


John: No problem with "hijacking" the thread. I think the opposite way...I've always considered it a compliment whenever someone comments within one of my threads, no matter what the subject. It's that way in the real world and subjects are always changing, so why not?  :-)  Keep the new ideas flowing, no matter what they are.


Good luck with the tube version of the CC idea.  For linear (or low efficiency) operation it really is a great idea - if it can be set up transparently. Even for plate modulation, I'll bet it cud be useful as well.

I'd like to play with this circuit and see how far we can push it before introducing meaningful distortion. I figure one pot for the db carrier level insertion and another two more pots to play with attack and decay time constants - at least until it can be dialed in.

BTW, Frank, OK on the $75 4X1's.  I already have two on the way for $90 each, so I'm all 4X1ed out... :-)   Any other gud stuff there? How was the crowd?


T

 

[WA1GFZ]

Plenty of AMers but not a lot of stuff worth looking at. Lunch well attended but food was poor. Too much salt and service sucked. I must have done a quart of water when I got home. It was fun though.
let me study that schematic a while. I'll get back later.
Warren picked me up a slab of copper so I can mount erb2 holer and do more testing with the HPSDR set up.

[w4bfs]

a good idea with the NE602 ... my experience with signal processing (vox circuits especially) would have me wanting a full wave rectifier for the offset voltage  .... tends to remove 'gappiness' from the response ... don' t know if you have balanced or unbalanced audio available ... could be a good time to incorporate balanced ...just some thots ...by the way, thanks for the joining in from all... very rare these days ...73 ...John

[WA1GFZ]

Tom,
The carrier inject pot. Which way do you go to increase the carrier output.
Does higher resistance increase the output? Q 1 is not biased properly. It is set up like a switch not a linear audio amp. I bet it is temperature sensitive  the way it is.  I would add a 220 ohm resistor in series with the emitter and change the 100 K Base resistor to 10 K. This will make it biased in the center of the voltage swing and give it temperature compensation with a gain of 10. If that is too much gain increase the 220 resistor. Need more gain decrease it.

[K1JJ]

Tom,
The carrier inject pot. Which way do you go to increase the carrier output.
Does higher resistance increase the output? Q 1 is not biased properly. It is set up like a switch not a linear audio amp. I bet it is temperature sensitive  the way it is.  I would add a 220 ohm resistor in series with the emitter and change the 100 K Base resistor to 10 K. This will make it biased in the center of the voltage swing and give it temperature compensation with a gain of 10. If that is too much gain increase the 220 resistor. Need more gain decrease it.

Frank,

I measured the carrier inject pot. As the wiper of the 1 meg pot is moved away from ground, the carrier power output of the FT-102 goes up. 
So, higher R at pin 2 = higher carrier power output.

OK on Q1. I didn't use Q1 in my rigs. I didn't need it cuz I've got 1 v audio and it's enuff to drive the NE-602.  I think Bill added that afterwards.


I just checked the FT-102 / NE-602 freq response and found it's flat from about 1 cycle (as low as my sig gen goes)  up to 60kc.  It looks like a perfect waveform with the little "wavelets" when the modulation goes over 100% negative.  The modulation percentage is virtually unlimited, depending on where the carrier level is set.   ie, 20 watts carrier w/ 150 w peak  or 5 watts carrier at 150w peak, etc.

I will be using the 1 volt audio level from the input jack of the board for the rectified audio feed. You can take it from there.

Tnx.

T

[Steve - WB3HUZ]

There's no problem with Q1. Many, including myself, have been using it for years with no problems. I measured response out past 500 kHz with the the 602 circuit. When installed in the 102, the response was still good out to 100 kHz or so.

[WA1GFZ]

Steve,
Not the way I learned to bias a transistor to work over a wide temperature range. Gain is usually Rc/Re . Imagine the resting collector voltage over temperature. What is the gain of the stage as it is over say 25 degrees.
Tom ok on the 1 volt of audio. Let me give sleep on it.  I think you will need a diode or two a transistor and a cap.

[w1vtp]

I like the turns counter on your roller inductor!!  How graphic can you get?

Al

[K1JJ]

Steve,
Tom ok on the 1 volt of audio. Let me give sleep on it.  I think you will need a diode or two a transistor and a cap.

OK Frank -

Should we add in an RC attack and decay circuit with pots at this point to find the best time contants or just get it going first?  John suggested time constants of 0.5 msec attack and 100 msec release ... Maybe we shud start with those numbers.

I'll build it on an outboard PCB so we can experiment. 

I actually measured 3 volts p-p of audio available.


* I built up your power snubber tonight. I'll try it out tmw. For diodes I used those same big ones from the MOSFET solid state PDM rig project,  STAA3006P  / CO349.  Steve/QIX said they were quite fast.   I used two small 18V transorbs in series to make 36V. They will probably blow out, but at least I can test it at QRP -  I'll order some bigger ones if it works OK.    Built +- 25V supply for bias.


Al:  That's a  Guestimate brand turns counter.... :-)    Actually, the red marker dots get me exactly to the match on each band quickly.  But I do have another counter - I shud add it in now that it's bell and whistle time.
T

[WA1GFZ]

Tom,
Check the junction C of those diodes they may act like caps and run warm and suck your drive down. I sent you a marked up schematic. There is an error though. The emitter resistor is too large try 1K. You can easily outboard it. I hope it doesn't load your audio too much. Monitor the transistor base voltage to see the time constants. fc

[Steve - WB3HUZ]

LOL. No need to imagine. The circuit has been in use by many for about 10 years. If there was a problem with it, I'm sure it would have showed up by now.

Steve,
Not the way I learned to bias a transistor to work over a wide temperature range. Gain is usually Rc/Re . Imagine the resting collector voltage over temperature. What is the gain of the stage as it is over say 25 degrees.
Tom ok on the 1 volt of audio. Let me give sleep on it.  I think you will need a diode or two a transistor and a cap.

[WA1GFZ]

Do what you like but a beta limited switch has a small linear range and unstable over temperature..

[WB2YGF]

Copycat 

[W3RSW]

Derb named it.

It was from his subconcious, NOT a copy, don'cha know. 

[Steve - WB3HUZ]

Someone from Tiger Direct has been reading this forum or listening in on 75 meters. 

[K1JJ]

My people have already contacted their people concerning a Quadzilla infringement.  We'll probably settle for $1 billion (slush fund) and celebrate by taking everyone on the AM BB to Maui for a much-needed, month long vacation.  

T

[W3RSW]

be sure to invite Sir Francois De Slabsinister of Nottingham first!

[K1JJ]

Frank,

BTW, for the RF snubber/ power limiter to drive the 600w MosFet amp, I ended up using a simple resistive pad to go from 100w down to about 15w pep.  I added a small switch to adjust it slightly for various rigs.  Used a 60 ohm glow bar and some carbon resistors.  Got a pretty close 1:1 for the exciter.

So now the FT-1000D at 200w and the FT-102 at 125W won't blow out the MRF-150's no matter what. 

I think someone here suggested the straight pad - don't remember who, but it was a good idea.... fool proof.

T

[Todd, KA1KAQ]

I won't believe any of it until I see the Plexi-King trademark up in lights!