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Well I have had it. I'm tired of trying to fit 10 lbs. of shit into a 9 lb. bag. Yeah I know the saying is a 5 pound bag but in this case 9 pounds more closely reflects just how close I am to getting things to fit. In fact I can get everything to fit but some things are too close or oriented the wrong way ie. the tank coil should be parallel to the tune/load caps to minimize coupling but I can't do that. The solution is to build a separate RF deck and power supply. The RF deck will go into the cabinet pictured above quite nicely without any power supply components hogging the room. This gives me some room for options. I have a couple old steel chassis that held some VHF airband tube gear that once belonged to the Canadian airforce.They look pretty buzzardly but that just adds to the charm. I picked them up about 20 years ago and thankfully never got rid of them. They also contain a pair of plate transformers and a pair of filament transformers as well as power supply chokes etc. Everything is Hammond and built to RCAF military spec,in other words under rated. The pair of plate xmfr's in series so I can run on 240 volts will give me a DC output of 1800 volts no load at .75 amps continously.The filament xmfr's are rated at 10 amps each so I can parallel them and get all the amps I need and then some for the 572B's. On the other hand I have a plate xmfr from an old Collins 500 watt (?) broadcast TX and it's companion choke.The problem is that the volts may be a bit too high for the 572B's with this setup. It is 6400 volts output centre tapped to ground. This means 3200 volts into a full wave rectifier (not a bridge) and then into the choke.Total DC output may be in the order of 2800-3000 volts which is too high for the 572B's. Looks like its time to set things up and do some voltage tests. Typing that last line reminded me of the last time I messed around with that xmfr.The details are in the following thread.

Watch those meter leads!


This time do have the proper leads. Hopefully in the next day or two I will test the xmfr's and decide which ones to use and in what config. Separating the RF deck and power supply leaves me with a lot more options. Pictures to follow after more voltage tests are done.

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Front/back ratio comes from the antenna. Forward gain comes from the wall socket.

Sounds like progress bro!.
That should work with out any problems. We do what we have to do.
Now you will have two big oled heavey boxes!

1150 x 1.41 equals 1621.5 with a full wave bridge not 2000 volts

Yes, I am aware that the DC output is equal to the applied AC voltage times the square root of 2. That was one of the first things I learned during my electronics training which lead me to become a commercial broadcast engineer for 22 years . I believe you missed the part where I said it has taps for "HI" and "LO". See included picture attached to that post. Selecting the 1150 AND the "HI" tap yields about 1400 volts AC output. Trust me. I wired it up on the kitchen table and tested the voltage, or as we say in the business about anything that high, the joltage.

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Front/back ratio comes from the antenna. Forward gain comes from the wall socket.

Not much of an update this time. Lots of things to do before winter sets in. The last update saw me decide to build a separate power supply and RF deck. Here is the old chassis I plan to use for the power supply. I forgot to take a picture of it before I cut out the old steel deck. It had about a dozen holes in it from where rectifier tubes and transformers/chokes/capacitors etc. were mounted. It was an old power supply chassis from some air force air band equipment. Although it was air band it was ground based and was 60 Hz stuff. At least I can use the filament transformers that were in it. Here is the chassis after cutting out the old deck panel and prior to installing thge new one.





Here is the front panel. Note lots of holes for fuses along the bottom. The two elongated holes are fro breakers that I may be able to use as well. The two large round holes near the top are large pilot lamps,one red the other green. I figure the red will be filaments and the green for the plates. that way with the filaments on but no plate voltage the supply will indicate a ready but standby no-go status with the red light.




It also has rack mount handles for the front. It has had a coat of paint and hopefully tomorrow I can post a picture of it with the front panel components installed. It will have an enclosure built to cover the beast and the whole thing will possibly be on wheels if I floor mount it. Hopefully if the paint dries overnight I can layout the components for the power supply and get some voltage measurements made so I can determine just what configuration I will use.

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Front/back ratio comes from the antenna. Forward gain comes from the wall socket.

OK the paint finally dried. Trem Clad makes some good paint but it is a bitch to use if you are in a hurry. First pic is of the newly painted front panel with all the original components installed with the exception of the two silver switches which were add-ons from another project but will be usefull.Red lamp for filaments on, green lamp for plate voltage on and ready to go.Plate voltage will be locked out until filaments are turned on first. A pair of breakers and six fuse holders along with two switches complete the front panel.The black wrinkle finish just says "Old Buzzard gear" all over. For those of you NOT familiar with the term "buzzardly" I direct you to the dictionary of the one and only Tim Smith aka Timtron aka W-A-1-H-Yell-R . Tim is found most nights tearing up and down the 75m AM window.


Category:Timtron - HF Underground






Here is the rear view of the chassis with new deck plate installed.




An finally the complete chassis with what I believe to be the final component layout.






The plate transformer in the upper right is from a Collin's broadcast transmitter of I believe 500 watts carrier rating. It puts out 3200 volts AC either side of centre tap.The rectifier will be of the conventional full wave non bridge type. The black choke in the upper left is the power supply filter choke for the high voltage. This power supply will be choke input and will be smoothed by the pair of 6 µF@4000 volt capacitors seen in the bottom left of the picture.Both caps will go in parallel after the filter choke. This should make a fairly stiff supply which is required for SSB service.The bottom right shows the two filament transformers that were originally with this piece of surplus gear when I picked it up 25 years ago. They will work quite nicely with this project.since i decided to go with an outboard PSU I figured why scrimp on component values and go with something that is more than suited for the task rather than use something that is borderline. Not sure what the final weight of the PSU is but the plate tranny itself weighs about 55 pounds. It is easily over 100-120 pounds total weight. And to think that this is the light weight supply compared to the one for the 3-500 or 4-400 project down the road. The last picture shows two of four rectifier stacks that were part of the now defunct RCA transmitter I scrapped. Two of these rectifiers will be used as a full wave rectifier with this power supply.They are rated at 10,000 volts at 3 amps each.





Next comes the scary part,bench testing everything to see what the final plate voltage will be. I also have a large 250 watt wire wound ceramic rheostat that can be installed in the plate circuit to lower plate voltage if I need too. It also came from the RCA tx.This supply will also have a step start circuit to limit both filament and plate inrush current. Time to call it quits for a while now. I work the next several days and my hand is still giving me grief. It was all I could stand to do to use the hand power drill this morning and just placing those heavy components around was a bitch. I can't keep a good grip on heavy things.The wife keeps talking about therapy for it and I keep saying it's getting better. What does SHE know. She's just a nurse,it's MY hand.

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Front/back ratio comes from the antenna. Forward gain comes from the wall socket.

You may want to reposition both filter caps after the choke. This will reduce B+.

If the choke has a good hipot rating it can be resonated for excellent transient regulation. Details are on AMFONE.

All you need for the filament current limiting is one of those R.F. Parts CL-XX thermistor current limiters on the primary of the filament xfmr. If there's no room for a filament variac see if you can rig a rheostat on the primary also.

Thanks for picking up on that! Corrected above.The other way would have seen the supply look like a capacitor input supply with an LC filter following it. this would have produced a MUCH higher voltage than I want. I was just looking at how RCA did that in their tx and was not paying attention to actual voltages present in the chain. I would like to think I would have caught that when the actual time comes to wire it up.

As for the inrush limiting ,I was planning on the old relay switched series resistor in the primary thing for both fils and plate voltage but had considered the thermistor route. I saw the discussion about it on AMFONE. The plate transformer and the filter choke were mated together in an old Collins broadcast transmitter so they should work together quite well. It is just a matter of choosing the proper values of C to improve the performance of the choke. I have a couple other HV rated caps of differant values that may be better than what I have proposed to use. It's all a matter of math at this point what I use.

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Front/back ratio comes from the antenna. Forward gain comes from the wall socket.

Just a coupla thoughts:

The broadcast rig has a constant load on the supply in the R.F. amp. The modulator is the dynamic load. Properly sized power supply components can be somewhat smaller with the constant load. If you use the amp on single slimeband the situation will be quite different.

The modulation reactor in the broadcast rig will also remove some supply ripple. A little more capacitance and revisiting the critical bleeder current might be worthwhile.