New 4-1000A modulated by 4-1000As AM Project - Fabio II Reborn

[kb3ouk]

Knowing my luck with radio gear, it would take me about 2 years to build it, 30 minutes to blow it up on the first run, then 2 years till I managed to get around to fixing it. I saw a 4-1000A today at the York, PA hamfest, should've got it but wasn't too sure about it by the looks of the glass, and that was the second time I saw that very same tube for sale, it was at Timonium last weekend (so was probably 90% of the rest of the stuff that the same seller had). Should've got the 50 cent 4X150A too, even if it would've turned out to be a dud, it still makes a cool paperweight.

[KA2DZT]

Maybe you need to acquire a nice Springer Spaniel...

Ralph,

That's what I'm beginning to think.  I'll bet that Yaz is doing some of the construction when Tommy is sleeping.

[KL7OF]

That dog has to be good with a drill motor and screwdriver...judging by the amount of radio construction that happens around there...

[John K5PRO]

Nice workmanship.

To water cool a tube, you need to keep the leakage current through the hose under a milliampere DC. Eimac and RCA used to have recommendations in their info. My experience is to keep it under 500 uA per hose. But this is for 24/7 long life gear at higher voltages that hams want to use. If leakage is high, expect slow electrolytic action that will eat your plumbing fittings at each side of the water pipe (HV and grounded ends). How to know what you have? You need to know the resistivity of your water, usually measured in Megohm-cm. There are instruments that measure this. Or might try and get a water quality lab or friendly chemist to do it. They usually measure conductivity, which is inverted of same number. Or rig up a piece of hose of known dimensions and a high R meter and measure it. Typical values to use are 0.5-1 Megohm-cm, or higher. Knowing the HV DC, you can calculate the resistor that your water pipe is, in ohms per cm length, using the area and resistivity. Then just make the pipes long enough, roll them, curl them, etc to get the value that will keep the current below the threshold you decide. If running deionized water, be sure to stick with copper or stainless steel, sometimes brass for fittings. I avoid PVC pipe due to the chlorine ions it has. It only takes a little bit to turn water into a conductor.

[Opcom]

Knowing my luck with radio gear, it would take me about 2 years to build it, 30 minutes to blow it up on the first run, then 2 years till I managed to get around to fixing it. I saw a 4-1000A today at the York, PA hamfest, should've got it but wasn't too sure about it by the looks of the glass, and that was the second time I saw that very same tube for sale, it was at Timonium last weekend (so was probably 90% of the rest of the stuff that the same seller had). Should've got the 50 cent 4X150A too, even if it would've turned out to be a dud, it still makes a cool paperweight.

Some guy had a 4-1000 at a hamfest with rather dark glass. Isn't that a measure of use? His price was $100 and he claimed it worked as new, but he kept after me to buy it and near the end it was $40. if there had been a way to check it, I'd have taken it but the situation seemed suspicious and in those days $40 was 2 tanks of gas in a 455-powered cutlass.

For the pros:  What's the story on the darkening of glass in big tubes, either around the plate or at the top and bottom where the electrons presumably can escape or 'leak' past the plate?

[W1ATR]

Yeah nice amp job, but I have a question.

How come all the parts are squeezed together on each deck? Is this a mobile amp or something? 

[K1JJ]

Yeah nice amp job, but I have a question.

How come all the parts are squeezed together on each deck? Is this a mobile amp or something?  

A mobile amp.. HA!   I see what you mean.  Though if you pull the cover off any modern ham amp, you will find it is much more compact than this. The exception is a broadcash rig, of course.

 Yes, it was something like a jig-zaw puzzle getting everything to fit in.  Though, a picture doesn't do it justice and the rigs are actually bigger in person - and every part is easily removed without a problem. There is no layering of parts.

Being a one-shot project, I did not make a mockup or prototype.  And things change as the project goes on and parts get added that take up more room.

But compact is certainly a good thing for RF, since we want short connections and parts close together.

But I think the main reason here for a compact layout is because I started with a standard 19" wide panel, and made the depth of the chassis for the longest rack I have, which is 29".   So, except for the height, which is already pretty high at 29", I really couldn't go much bigger.  I needed to fit the parts into that limited space.

Another thing -  I put all the low voltage power supplies, fil transformers and associated modules in too. Bottom line there are only two units for a complete class C plate modulated rig. The HV supply, which is as big as the rest of the rig, is already built and on the other side of the room, used for the other rigs too.

Fabio I, had modules and power supplies scattered all over the place. I wanted to do the opposite with II.

T

[WA3VJB]

Tom,  I think John/JN had it best with the layout seen in

The Bayou Desk Kilowatt

[K1JJ]

Tom,  I think John/JN had it best with the layout seen in

The Bayou Desk Kilowatt

Oh, the humanity!

A JS rig contest would become a popular topic.  Post legit photos of real rigs that border on sure death.  (To show how NOT to do it)

T


** I just received a few pics from another 4X1 X 833As rig owner.  Never saw this rig before. They are a proud lot, these builders. Not many homebrew 4X1s plate modulated out there these days.

Notice he did it up in Ole Buzzard Black.

[KM1H]

Way cool. Where do you get stuff like that?  Yeah, big flanger with w/c and blower ( for bottom seals I suppose). Tap water pressure and moderate flow rate ought to be plenty.  Distilled water, and changed out to prevent copper ions from running around, heh, heh

That was sitting on the floor in an electronics surplus shop in Manchester NH pretty much hidden in a corner.
It never had HV applied and it was used as a display/teaching item at the local technical college. Only the filament was lit along with a flow of tap water; I had to flush out the crud from the jacket

What you see is exactly what was used, right down to the filament transformer, socket, blower and foam shipping support. The tube alone is worth $1300 as a core and I paid $90 for all

Carl

[K1JJ]

The tetrode-connected 4X1 modulator is all wired and most circuits have been tested.  It features a regulated screen supply with cooling fan. (See heatsink)  

The mod iron and Heising chokes are all mounted on the chassis. Castor wheels used to ease movement.  Notice the HV resistive divider for monitoring HV. Also meters for fil, AC line and normal tube currents.

The modulator requires the input from the GFZ-designed solid state MOSFET audio driver unit into the 4X1 grids. This provides grid bias as well as audio drive.

Other than PTT, AC power, audio drive and HV, the unit is self contained.

There are spark gaps on the mod xfmr pri and sec, as well as on the Heising reactor.  The reactor is 75 Henries.

T

[K1JJ]

Top views and the business end of the mod iron...  That's an RCA 1KW 2.4:1  mod xfmr.   Weight: 144 pounds.

Can you see why I needed those sissor trays for "extra" parts?

[K1JJ]

Pic #1 -  Lower left is the audio negative feedback ladder that taps the sec of the mod xfmr and feeds it back to the low level SS audio driver. About 10 dB of NFB when adjusted right.

The mod xfmr, Heising reactor and Heising cap are all floating above ground and each other using Plexiglas.


Pic #3 -  The shack is a mess, but that's the price of progress, I guess.

I still need knobs for both decks.

T

[K1JJ]

While we're at it, keeping with the color scheme...

Pic #1 - Dr. Love

Pic #2 -  Fabio, the 8877 linear amp

Pic #3  -  Mr. Clean - 4CX-350FJ  class A linear amp


The 4X1 RF deck and modulator will have the same black lettering once I get caught up.

[K1JJ]

They showed up today. Regular visitors to the back yard.  Sometimes up to ten birds,  they clean out the bird feeders in a matter of minutes.

[W2NBC]

Mr T,


Your prolific transmitter creation reminds me of:

http://www.youtube.com/watch?v=qS_LwObwXAs

A day in the life of VU..

(Nice turkeys! Got about 13 that show up here)

[WB2CAU]

Tom, nice work!  Will you ever build a permanent transmitter? 

Eric

[K1JJ]

Tom, nice work!  Will you ever build a permanent transmitter?  

Eric

Thanks, Eric !

Probably the longest I've ever kept a homebrew rig going is five years. At that point my homebrewing skills evolve and I want to tear it down and do better.

In the last ten years I've gotten access to scrap yard aluminum, bought a drill press, bandsaw, lathe, etc.,  so this has caused me to tear down and rebuild the complete station several times since.

As usual, we think we are done, but I doubt it...     I've been working on these series of projects since November and am pretty well burned out from building.  Just need to optimize and test everything and hopefully do some operating.   For this AM project I still need to set up the sequencer, audio driver and interface it all to the station. Then testing, testing, optimization.


Jeff, I wonder how many people over 40 use those 5-hour pep drinks?  After giving up coffee, cigarettes, coca cola and all those other stimulants, one of those pep drinks would send me speeding outa my mind.  

My secret to production is to do a little each day and stay focused... even if I am not in the mood. It adds up over time. Even one hour a night after work can knock out a full blown amplifier in a month or two.   For some reason, when I have a hot project going, I just can't sit and talk on the air until I finish it.

T

[W3RSW]

Yeah Tom, the energy of youth has a lot to do with it. I remember sitting on the floor for hours, up to 3:00 AM building stuff, parts scattered in a trail of solder splashes on the rug of the boarding house when I was in college, not even realizing I'd missed meals (as I created a very long sentence here). 

..Remember being so focused, I'd walk across town just to oogle at the parts in the only ham store for miles.  B&w big xmitter parts on display in the counter case..  "Uh, a 5Y3 please."

Way to go and you have a great idea for staying the course, I. E.,  Just keep plugging and sooner or later in the session, your hooked again.

[K1JJ]

Just finished testing the WA1GFZ-designed MOSFET solid state audio driver and 4-step relay sequencer.  Both checked out good.  Mounted the SS driver and sequencer on their own chassis and will make a closed cabinet for the SS driver to prevent stray RF from getting in.

Now on to inter-connecting the RF deck, modulator and other modules into a working system. Then testing.

T



SS Audio Unit to drive the 4X1 grids and  Sequencer:

[K1JJ]

More pics:

[K1JJ]

The built-in ~50 ohm simple link input to the grid of the 4X1 RF deck sometimes has an swr as high as 2:1 on some bands.  There is no variable cap or way to adjust it.   My FT-1000D solid state RF driver usually likes < 2:1 or it starts folding back.  I use about 10 watts of dead carrier to drive the 4X1.  So, I built up a simple 50 ohm to whatever? unbalanced T-Matcher to put between the driver and 4X1 input.  It has 17 inductor taps to be sure there is plenty of range.  I tested it on 10-160M using various loads between 20 - 200 ohms and it matched to 1:1 swr beautifully.

I was going to buy a small MFJ 900 tuner for the job, but figgered I could do a better job myself.  Had all the parts.

It's so much fun to have access to ready-made junk parts. Can you imagine if we had to build all these parts from scratch, tubes included?

I still need to find some decent knobs for these projects.  I'd like to get some of those knurled aluminum fancy type.  That wud be slick.

T

[K1JJ]

And the rear-end.  That's Teflon wire used for the bandswitch connections. (of course  )

I was lucky to find an 18 position rotary switch in the JunqueBoxx

[KA2DZT]

I was going to buy a small MFJ 900 for the job, but figgered I could do a better job myself.  Had all the parts.

It's so much fun to have access to ready-made junk parts. Can you imagine if we had to build all these parts from scratch, tubes included?

T

Now you know why it took me over 10 years to build my rig.  I made all the parts.

Fred

[W3GMS]

Tom,
I got a kick out of the SS audio driver!  Its big enough to be a tube driver with a pair of 2A3's!  Looks great and can't want to hear it on the air.  Make sure you get on the air before you tear it down to build something different. 

And yes, junk boxes are wonderful things to have!

Joe, GMS