Tube Shunt Regulators

The finished circuit board containing two positive shunt regulators (Operate & Tune) and a negative shunt regulator (Tube Bias). The current sense opto for the negative regulator has been left off the board until I figure what is going on. It seems the opto diode has been drawn with the wrong polarity by the designer.

If anyone is able do look at the schematic in the article "Positive Regulator" you may be able to see what I am getting at. The opto diode in the bridge circuit for the positive regulator seems to be drawn correctly but the opto diode in the negative regulator seems to be around the wrong way.

New Circuit Board.

The finished item. I use the Ferric Chloride solution cold so it takes about 4 hours to complete. A pot scrubber is used to clean the marking pen traces.

Art Work Complete.

Ready for etching.
Cost $32 for a doctors visit after several daily drawing sessions. The act of rubbling my elbow on the bench resulted in an inflamed and infected elbow.

Circuit Template

Another cardboard template and the resulting dot pattern. It is going to take a few days to hand draw this one.

1296 Amp

Rack case and other bits for the amp. The case originally contained a power supply built to supply bias for UHF tube amps (20 odd volts cathode bias). Left meter. 30v/10mA scale. Right meter 25W (Will be x 10) power meter. I will have to counter sink the cavity a bit to line up with the front panel hole that originally had the meter switch.

1296 100W 2C39 Cavity

I got my hands on a cavity and 4 tubes. One of those round-to-it projects where a round-to-it was never found.

I could not put it in to storage until I confronted the main issue.

No cathode / heater socket / plug / mounting hardware.

Head first into the junk box and several hours of cutting, etching, fiddling, etc. etc and the challenge is solved.

Once I have the power supply built I can revisit the project and find the teflon sheet, glass trimmers and other odds and sods.

Top: The cathode and heater socket / plug assembly.

Middle: The tube chamber, 1KV BNC and N Type link coupling.

Bottom: Boxed up ready for storage

Etch Kit.

It can be a messy business etching boards. Ferric Chloride pallets can be added to hot water for a quick etch however I prefer to turn it into a solution to minimize waste. Small boards can be placed under a light to speed up the process however large boards can take one or two hours with cold solution.

I made two double sided boards for my 1296 cavity.

Mini Tower

This mini tower is 3 meters high. The pole that slides up the center is 5.8 meters long and fits just below the guide at 1.9 meters up. I think this was an old windmill tower and worth its weight in gold just for the two castings that make up the top plate and guide.

It was in poor condition with the legs rusted out at the top plate. I flipped the legs due to a bend in one which was less pronounced, after some bashing with a sledge hammer, at the top and cut about 100mm off each leg. I drilled all new holes and a full set of new galvanized bolts finished the hardware.

Then came a full paint job with "Galvit" galvanizing paint and a heavy layer of water based paint. Now I have to figure out how to get it up with a 5 element tri bander on it.

70cm Preamp

Low Noise UHF Preamplifier.

The circuit is pretty standard fair, common emitter, bipolar and uses all surface mount apart from the inductors. All the caps are 0603. One 0805 resistor (base bias) and one 1206 resistor (collector current). The transistor used is a BFG67.

Power is supplied through a feed through capacitor mounted on the copper plate on the top side of the small box and sealed from the outside with wax.

The local engineer tapped the holes for the N connectors. The case has a neoprein seal and hopefully the whole thing will be moisture proof.

Low Voltage Regulators

This is the low voltage regulators for the amp supply. 24v, 12v, -12v and 5V. The 3 TO3 devices on the heat sink are a MJ2955 pass transistor for 24v. A 15v regulator to drop the 24v down a bit which supplies a 5v regulator. On the circuit board are three TO220 regulators. A 24v regulator, a -12v regulator and a 12v regulator with a TO220 MJE2955 pass transistor.

A 6 pin connector is used to connect AC from the two transformers and an additional 6 pin connector for the output voltages. The whole thing mounts in a card rack and the TO3 heatsink bolts onto the back of the card rack. A 6 pin connector allows the heatsink assembly to connect to the circuit card allowing the card to be pulled for repair.

Power Supply Images.

(1) Still lots left to do.

(2) A closer look.

(3) Top level moved forward to show next layer.

(4) Back panel moved to reveal the four transformers.

Finished Unit

Two new circuit boards assembled and mounted. This unit sits just above the transformers and below the HV recitifier/step start boards pictured elsewhere below.

The TO220 packages are back to back diodes found in switch mode supplies. Way overrated for the circuit but they are free. The circuit switches three power supplies. Screen, Bias and heater. There are two seperate heater supplies. One is used for HF & VHF and the second for UHF. At UHF it is necessary to reduce heater voltage and this supply has an extra high power variable resistor in curcuit. Screen bias comes from a seperate board which supplies tune (105v) & operate (315v) voltages to the relay board. The last voltage is grid bias (-225v. Cutoff bias.) which is dropped down by a voltage divider to around -55 to -90 volts when the amps are switched to transmit.

Due to the nature of the beast the relay board has a unusual circuit. One set of relays (The group of 6) are connected in series pairs running 24v. The other group in parallel running 12v. All are switched to ground hence the need for the back to back diodes to isolate the two supplies (12 & 24v). This arrangement means the screen & bias are switched at the same time along with the heaters. It will all become clear as mud once I put the full circuit up here.

Estimated time to build... Four days. Day one & two. Maybe 6 hours each to draw the circuit boards including a 3D model of the relay (3D TO220 already in my library). Print and make templates. Day two. Punch and mark up the small board. 4 hours. (Rotory hoeing the garden takes priority this time of the year). Day 4. Mark large board, etch, drill and put together. About 10 hours. 26 hours all up.

Relay Boards

Circuit board construction.

Top. Blank board and template ready for marking up.

These two boards contain ten 12V relays for switching the HV (Screen & Bias) and heater supplies for the three linear amps.

(1) CAD layout of the circuit board.
(2) Print and glue onto card.
(2) Punch out datum points. Bottom left.
(3) Mark datum points on board.
(4) Hand drawn layout. Bottom right.
(5) Cover black area with cello tape.

Ready for etching.

Ceramic switch

It has been bugging me for some time. I keep looking at other options on the web and auction sites. Time to settle the matter once and for all. I have two nice ceramic switches. They came out of a Collins millitary linear amp running two 4CX250F tubes and the switches were controlled by a motor. The problem is that the switch position is controlled by a third waffer therefor has no manual position indexing.

Without positive feedback the switch is next to useless to me and I know that making something to do the job is pretty tricky. 18 positions. The switch layout takes up 9 positions. It is a funny switch. It is designed for capacitive arrays. C1 & C2 with a powered rollor inductor making up a plate tank circuit.

It is ideal for what I want to do. I have a C1 of 230pf duel section and C2 of 1300pf. For 160m C1 needs to be around 400pf so the two sections in parallel should work. Switching out the other section for 40m and above. C2 needs to be 2200pf or more reducing to 1500pf for 80m.

So mounting an indexing mechanism was the task at hand. A search of my junk collection located a likely candidate. An old two position switch with a ball bearing in a spring mount. I prized the spring mount from the end of the switch and found it was made of two pieces of spring steel. A quick rustle around in my nuts & bolts bin located another ball bearing.

I mounted these on a piece of aluminum added two standoffs and a cam made of phonelic circuit board with 18 drilled indents topped off with another piece of aluminum. It worked pretty well but maybe I will make another cam as the indents are a bit deep.

The standoff spacers will allow the whole thing to be mounted front and back and the only thing left to do is to find some way of adding start & stop tabs at the right positions in the switches travel.

Positive Regulator

Top: Up and running on the test bench.

Middle: Click on the circuit diagram for a larger picture.

Bottom: A closer look at the construction method used.

Five Over Five

Recently I have managed to aquire 2 TH5 DX antennas. The one in the foreground needs a new plastics kit and has suffered from electrolysis. As the saying goes... We can rebuild him. The one in the background (Traps boxed) has a new plastics kit and shows less signs of wear and tear. It is hard to say how old these antennas are but my guess is between 20 - 30 years old. The Thunderbird has a mighty fine reputation with countless stations using them to this day.

The plan is to put both of the TH5's on the tower below. One at 25 feet and the other at 50 feet. I have seen a couple of ideas for a matching network but I do not like either of them. I have a few ideas of my own that I may expand on later. It is going to take a few rainy day missions in the garage to clean them up. As with the TH3DX I have I will take to the TH5's with a wire brush (Brackets) and a poly pad (Pot scrourer). The TH5 has an average gain of 8.5db. Stacking a pair of them will add 3 - 4 db. Giving a total gain of around 12 db. Add 500 watts of RF and I will be one of the stronger stations in NZ on 20, 15 and 10 meters.

Tower

I have been doing some 3D Solid modeling. I bought a 15 meter tower in 5 sections. I want to turn in to a tilt over crank up tower.

Negative Regulator

I have been designing a negative regulator. I could not find any suitable circuits on the Internet so I have designed something around the LM431.

Click on the circuit diagram for a larger view.

Tier Two Amp Power Supply

Firstly this is a picture of my linear amp power supply. The supply has switching to change supplies over to whichever amp is being used.

I have made another board (The blue caps). This board ties in the regulator and step start boards onto a frame which is part of the framing that connects the lower box to the top box. The EHV relay is on the right side below the EHV switch.

The gold box will contain the shunt regulators and monitoring circuits (Card frame in the front section. Hinged front). The rear section of this box will contain an air collection and distibution enclosure. The plan being to use a manual switch to send the air to whichever amp is being operated.

Above the transformers is a circuit board (Not shown) that will hold the relays to switch the HV supplies to the three amps.

The next stage is to design the shunt regulators. I just bought some LM431 regulators.

Step Start & Rectifier Boards

I have made two more circuit boards for my linear amp project. The left hand board contains an opto isolator, main power relay (NC), delay circuit and step start relay. The right hand board contains the fuses, MOV (Red), 1N5408 diodes and 0.01 1kv bypass caps. The main filter caps are going on another board.

The art work for the boards was designed in a CAD program and then printed out on plain paper, glued onto cardboard and then cut out with a Stanly knife. I then used the template to hand draw the layout onto the blank circuit board and used the standard etch solution to etch the board. As usual click on the image for a full sized view (800x600).

Home Brew Balun

Two ferrit rods wrapped with PVC tape. Wound as per the ARRL hand book.

For 1:1 (Shown on the left) I use a trifilar winding of enamel copper wire.

For 4:1 I use a bifilar winding of true rip speaker wire.

One rod can be used for low power however to ensure the ferrit is not saturated at high power two rods are used.

I use a loop of hard drawn wire to support the cut down plastic rat bait container and also the coax feeder to the shack. The dipole wire to balun joints are first wrapped in wire and then soldered. A 4:1 balun using the same design has been swinging without any support in the middle of my off center feed dipole for the last three years. Finally the whole thing is filled up with wax. Total cost less than $5.

EHV Rectifier

Here is the 2kv rectifier board for the linear amp power supply. I could not find any .01 3kv capacitors at a resonable price and had to pay $46 for the ones shown. The diodes are 1N5408 1000piv at 3amps and the resistors are 470k 2 watt carbon.

Rig & Me

Here are a couple of pictures of my rig etc. My radio shack is in the back of a 6x9m double garage and it gets a bit cold in the winter. At least it gets me out of the house. The shack is also set up with a large electronics work bench and a desk for my computers.

As you can see I am a no neck front row forward and a little over weight now days. Most certainly I have a no neck attitide when it comes to people I do not like.

Guess I got a lot of that from my father.

I spent a lot of time with dad, from about 7 years of age, in the bush hunting pigs and goats. Often he would put down the gun and wade in umongst the dogs and finish them off with a knife. I can remember many times pulling into the pub car park with a pig on the bonnet. A rasberry & lemonade for me and of course I would always be beaming from ear to ear after the buzz of the hunt.

QRO SPC Tuner

I have finished building this beast. It uses Cardwell capacitors and roller inductor. C1 has been modified to reduce its capacitance from 400pf per section to 110pf per section. Giving a total capacitance of 220pf.

The roller has an inductance of about 22uH and C2 is 400pf per section. The roller is a bit large as it only requires about 16 of the 27 turns at 160 meters. The original parts came out of a Red Cross Linear/Tuner rated at 5KW so I am sure it will handle the ZL legal limit of 500W.

At first I used a small inductor between C1 and the roller but found I could not tune into a dummy load on 10 meters so as per the ARRL Hand book I removed it and things worked just fine.

Also see further down for more specs. New Toys article.

Not shown are the top and bottom panels that I cut out of aluminium roofing sheets. I also extended the back of the rack case by about 40mm as the caps and roller stuck out the back once mounted.

Morse Key and Paddle

I am trying to learn morse code again. Back in the early 1980's I started to learn morse but gave it away. Now I am trying again. I have these two mounted on a base and after recent encouragement I have repaired the straight key. It had a lot of sideways play in the pivot and was somewhat erratic when used. I pulled it to bits and with a little filling and light tapping removed the play.

The two shown are a Galbraith GK-11 Paddle and a W.T. No 2 MKII straight key.

Both are classic morse keys and worth a lot more than the $11 I paid for them. Thanks Pete ZL2AUB for passing them on to me.

Rebuilt Cap

I rebuilt this cap from the two that are shown earlier on this blog (Some caps etc. The two on the table). They originally had plate spacing of 10mm and a C of 269pf. I pulled some spacers from several stuffed caps and drilled the stator spacers out and put the plates off one onto the other, 43 plates for the rotor and 42 for the stator. The new spacers are 4mm. As expected I have a very nice cap with a capacitance of 50 - 1300pf which I am going to use for the tune capacitor (C2 in the pie network) in the hf linear amp I am building. With a couple of fixed capacitors I expect the amp will be capable of going right down to 160 meters. I am very pleased.

Power Supply Front Panel

Thank goodness for my little tank cutter. The left hand meter was mounted by the previous owner. I only had to make five 50mm holes in the thick aluminium front panel. It would be nice to have the modern day equivalant to the armstrong one that fits my Brace & Bit.

The tool can also cut out washers. It comes with three tools. The largest tool, not shown, is for cutting holes with what I call an inside radius. As in the tool cuts away the metal inside the radius. The other two are used to cut the inner and outer radius of a washer.

Rack case for tuner

Just when you least expect it... I went to a sale last night and low and behold a rack mount case was on sale. Winning bid $11.00. It is a tight squeeze and the case needs extending at the back but it will work. I can use the scales and knobs from the caps with the two 2.5/1 vernier drives I have been sitting on. Turns counter and insulated shaft couplers and I have most of it apart from a couple of PL259 sockets the rest is just mounting hardware.

I can feel a Tim Allen moment coming on... O o o

New Toys

I have added these very nice high voltage bits to my collection.

2 x Cardwell Johnson dual gang variable capacitors Part # 153-505 ... 38-496pF per section, 3500V

1 x Multronics, EF Johnson, Cardwell 226-001-1 rotary inductor - 27.5 turns, 3.5" diameter, 22.5uH

http://www.cardwellcondenser.com/PAGES/jcm153series.html
http://www.cardwellcondenser.com/PAGES/jcsp15.html
http://www.cardwellcondenser.com/PAGES/md04k.html

Yellow Steel Box

I came across this interesting piece of information on the net thanks to sm5bsz. The interesting bit as far as I am concerned is the note about yellowish steel. I am using a box like this to mount the 4CX250B tubes in. I have other boxes that will be used in the project. It is good that I do not have to shield these boxes when used in RF gear. I think these boxes where used for microwave equipment.

Material Relative losses
Silver plating 0.96*X
Copper 1.00*X
Aluminium (pure) 1.25*X
Brass 1.87*X
Aluminium (worst case) 2.17*X
Steel 25*X or more

Steel with a yellowish surface treatment, common in electronics, has losses similar to brass. I do not know what this surface is, but it is easy to verify the dramatic reduction of losses that it gives.

Hammarlund 230pf per section

This is a very nice cap. I think it will stay in my junk box for the time being.

It will make a fine load cap for an antenna tuner.

It is a Hammarlund with a plate spacing of 2.5mm and max capacitance of 230pf per section.

When I got it it was frozen up so I pulled it apart, gave it a good clean and put it back together again.

Some caps etc.

Scored more caps as per the pictures. The switch was what I was really interested in from the first picture. I am going to use this to switch the 2kv supply between the three linear amps.

This second lot is a bit messy. Looks like they have been stored in a damp place. Still with a bit of spit and polish they will come up OK. A hand full of ceramic stand off insulators was a welcome bonus.

QSL Cards

I am finally geared up to make my own QSL cards. I print the cards with an Epson colour printer, cut the 4 cards from the A4 sheet, laminate them and then cut the 4 cards up again. Time consuming but for me better than going to a printer.

The artwork was created with Corel and before printing I fill in the blanks.

I can finally send out the long overdue cards for those who have sent me theirs.

4CX250B Linear Amp Circuit Diagram.

Click on the image for a full sized view.
















This is a circuit diagram of the HF linear amp I am building.

Linear Amp Power Supply

Here is a picture of the power supply I am building.

Black object is the Toshiba 2kv transformer. Taps for 1500, 1600 and 1700 volts rms @ 0.5 amps (1KW continuous rated). Caps are 8uf 2,500 volts DC (24uf total). Transformers at the back from left to right. (1) 6.3 vac heater 4 windings each capable of 2.5 amps plus several low voltage windings +12 0 -12 volts to power regulator electronics. (2) HV transformer with 300, 225, 170 and 110 volt rms windings. (3) 24 volts for relays. (4) 12 volts for relays. Mounted vertically between the EHV transformer and the caps is the EHV rectifier board. Obscured behind the font panel is the resistor network for the EHV meter. There are still various sockets to be mounted on the back panel. Shown are the power on/off switch, power filter, 2 fuses, 12 pin Jones socket for HV and other power voltages and three uhf type connectors for heater voltage. The supply is to power three seperate amps each running a pair of 4CX250B's. The supply is not capable of running all amps at the same time but there is most certainly enough grunt to run each amp up to full rated power of about 600 plus watts.