6.meter GS-35B EME amplifier..

[VK3ZL]

Hi again all...This is one of a pair of amplifiers I built recently for a ham in VK3...His main interests are EME work and playing with the high GHZ frequencies...He wanted amplifier's for 2 and 6 meters that would reliably withstand the hard wear that the data modes put a tube through but straight forward without bells and whistles..

As I have already designed a few of these amplifiers I was able to put this 6 meter amplifier together for him..The amplifier is built around a GS-35B Russian 1500 watt anode dissipation pulse triode....In my experience these tubes are rugged and reliable and only a fool will damage one..

From the pics you can see the simple construction...I machined a socket from 12mm thick aluminum stock and bolted it to the chassis floor...The tube slots into the socket and is secured with two simple "keepers"..The RF deck is sealed from the cathode sub chassis and is pressurised by a 5.5 inch Papst 12-28vdc fan..These fans are big and produce 285cfm...The air blows into the RF deck and evacuates through the massive copper tube cooler, through a Teflon chimney attached to the top cover..

The Pi-L output circuit uses a 1-10pf vacuum capacitor rated 12kv..I used an old WW2 150pf capacitor for loading...The cathode circuit uses a tuned T network as seen in the pictures...Ht power supply as a simple voltage doubling circuit using 6A10 rectifier diodes and 8 500pf 390mfd electrolytics...The amplifier uses one of my custom made Toroidal transformers..This unit is rates at 2kva and gives about 3800 vdc peak on the highest tap..I use the simple relay resistor step start system in all my amplifiers..The amplifier bias is developed through a small bias system developed by Tony King W4ZT (SK) ...I always bring the bias set control out to the front panel so that the correct idle current can be selected for the mode of operation...The input and output relays are standard off the shelf units....The output relay is a tiny 24 volt AC unit with two sets of 20 amp contacts with no internal wires..AC relays work quite happily with DC and this particular relay has never let me down in many amplifiers..

A couple of notes of interests for anyone home brewing using these Russian tubes..These tubes like the 8877 exhibit around 50 ohms driving resistance into the cathode..I have seen many times where hams have used these tubes and omitted to use a proper input matching network to the cathode...Usually they will then complain that the tubes are very inefficient and need heaps of drive....No short cuts can be taken and a properly tuned network is essential to get the best from these tubes...I use T networks on both my 6 and 2 meter amplifiers and trim them so that when properly adjusted to 1-1 input maximum output power is achieved ..With careful attention to details to both input and output networks the stated 13db is obtainable...It only takes 75 watts to run these tubes to 1500 watts output...Many state that they need 100 watts and I know exactly why..

These Russian triodes don't have the gain of a 8877 but for $120 they are excellent value and don't need all the complicated costly grid protection circuits..

Enjoy the following pictures..

Bob..VK3ZL..

[VK3ZL]

6 meters GS-35B.

This amplifier runs 800-1kw Data on EME...It will run 1600 watts SSB and CW mode..

Bob..VK3ZL..

[PA5COR]

Another beautifull specimen from you Bob, i really like to see the pictures and solutions you come up with..;)

[N2CHX]

Again, wow! I don't know what else to say.

[KA9MOT]

Out of curiosity, What does something like that cost?


8032

'Nuff said!

[VK3ZL]

Out of curiosity, What does something like that cost?


8032

'Nuff said!


Hi Steve, these amplifiers are $1800...Too costly to ship to the US, about $350 without the HT transformer..I only build these for local hams on request....

Bob..VK3ZL..

[KA9MOT]

Hello Bob,
I'm not in the market. However, the damn thing is so nice I became insanely curious about cost. Thanks for answering my question. In my opinion, they are worth any penny. Very nicely done... I'll run off and start your fan club now......

[AE1PT]

Bob, this sort of work epitomizes the spirit of the hams I knew growing up in the 60s--many who built everything that they were using to make an on-air presence. Your execution on these is stellar--keep us posted on the next run out of your custom factory!

[N2CHX]

Hi Steve, these amplifiers are $1800...Too costly to ship to the US, about $350 without the HT transformer..I only build these for local hams on request....

Bob..VK3ZL..

Wow, that's a lot less than I figured. I was curious about it as well.

[K7SGJ]

Another nice job, Bob. What do you use to cut the large hole with the recess for the tube socket? As I said before, the metal work is just amazing.

[NQ6U]

Another nice job, Bob. What do you use to cut the large hole with the recess for the tube socket? As I said before, the metal work is just amazing.

I believe he previously mentioned he owned a lathe. What I want to know is how he spun that big chunk of aluminum. Four-jaw chuck?

[K7SGJ]

I believe he previously mentioned he owned a lathe. What I want to know is how he spun that big chunk of aluminum. Four-jaw chuck?


I don't think Chuck works with him any more.

[VK3ZL]

I cut out all the holes by hand...First I scribe a circle of the appropriate hole....I scribe another circle 1/8 inch inside the first circle...I then use an 1/8 drill and drill holes around the inner circle...I then carefully cut out the metal using a small pair of side cutters...I use a half round file to remove the rough edges and take it to the outside circle...This is hard work and bloody tedious but I can cut and finish a hole in a perfect circle...I use this method on all the panels for sockets, meters etc...

Now you all know why I am a grumpy old geezer...

Bob..VK3ZL..

[K7SGJ]

Jezzus, talk about patience and a labor of love. I think after about 30 minutes of that shit, I'd just finish the hole with my 12 Ga shotgun.

[VK3ZL]

Jezzus, talk about patience and a labor of love. I think after about 30 minutes of that shit, I'd just finish the hole with my 12 Ga shotgun.

One must have infinite patience when doing these jobs...A friend of mine told me years ago to always do a job to the best of your ability..I have had years of practice...There are many things I still have to learn and each of these amplifiers add to my knowledge..Unfortunately the old ham ways are disappearing..I have a million things I could pass on but I'm afraid that most will die with me..

Bob..VK3ZL..

[KB3LAZ]

One must have infinite patience when doing these jobs...A friend of mine told me years ago to always do a job to the best of your ability..I have had years of practice...There are many things I still have to learn and each of these amplifiers add to my knowledge..Unfortunately the old ham ways are disappearing..I have a million things I could pass on but I'm afraid that most will die with me..

Bob..VK3ZL..


There are defiantly many things that you could pass on to others. However, there is also raw talent in there that one either posses or does not. Yes, learned skill but there is an art about your work that is yours. I can use a tool to draw a circle on construction paper but no matter how many times I try, I just cant seem to cut it out perfectly. That is with paper, forget about anything more solid.

Also, you had previously mentioned that due to costly shipping, even less the transformer that exporting one of your projects to the states would be too costly. I suppose that is a matter of perspective. One of a kind, hand crafted, and by a friend and fellow ham VS mass production speaks volumes itself. Besides, in the end, one would still have a small fortune less invested when compared to something like an Alpha.

As I said, hand made and attention to detail alone are only but a few things to look at.

I suppose it would boil down to not only a tool but a conversation piece and memento for a lifetime.

As always, I enjoy seeing your work.

[W5GA]

Carl, to do that on a lathe you would clamp the metal to a face plate....and turn it slowly.

[NQ6U]

Carl, to do that on a lathe you would clamp the metal to a face plate....and turn it slowly.

Yeah, that makes sense. I never think about using a faceplate because I never had access to a lathe that was equipped with one. All I know is that I hated setting up stock in a four-jaw chuck.

[KB3LAZ]

Bob, just curious, do you have any photos of home brewed gear other than amps? Rigs, specifically.

[wa6mhz]

I will be doing that soon again too. Cutting big round holes in a panel. I bought a circle cutter from harbor Frieght, but it is absolutely useless. Only good for cutting holes in WOOD!!!

My 2 holes will be about 2 inches in diameter, but fortunately, if they are ill cut, the meters will hide any defects. I plan to drill a series of holes around the circle and then file it to fit. What an incredibly tedious amount of hard work! I need to find a circle cutter that will hold up to Aluminum!

[K7SGJ]

I will be doing that soon again too. Cutting big round holes in a panel. I bought a circle cutter from harbor Frieght, but it is absolutely useless. Only good for cutting holes in WOOD!!!

My 2 holes will be about 2 inches in diameter, but fortunately, if they are ill cut, the meters will hide any defects. I plan to drill a series of holes around the circle and then file it to fit. What an incredibly tedious amount of hard work! I need to find a circle cutter that will hold up to Aluminum!

HD has bi-metal hole saws made by Milwaukee that will do the job if you go slowly. They are about 10 bucks or so, a little more with the arbor if you don't have one.

[VK3ZL]

I notice the comments about cutting holes for meters etc...I was just finishing off a cover panel for the cathode enclosure on a new 6 meter amp today...This has two 3.5 inch 240 volt muffin fans attached to the panel..I decided to take a couple of pics to show you how simple it is to make perfectly round holes..

This requires little effort..Pics show the scribed circle of the wanted diameter with another circle 1/8 inch smaller inside the material that needs to be removed..Using a drill press or even a hand drill using a 1/8 inch drill bit, carefully drill holes all the way around following the inner circle being careful not to drill outside the outer scribed circle..

Once you have a complete circle drilled, using a pair of small clippers remove the inner disc...Then all you need to do is file away the rough edge out to the scribed line...

I know this probably sounds a lot of work just for holes for meters etc but with patience one soon becomes practiced and rewarded with a perfect job every time..I tried a fly cutter once and it nearly gave me a vasectomy...Bloody dangerous things in the hands of fools..

I hope the pics give an understanding of my poor mans efforts..

Bob..VK3ZL..

[VK3ZL]

Bob, just curious, do you have any photos of home brewed gear other than amps? Rigs, specifically.

I haven't kept many pics of other than amplifiers but I found a little 100 watt 160 meter CW transmitter I built using old WW2 metal tubes...There are a couple of modern tubes in this transmitter also mainly the 6146 finals and a couple of VR regulator tubes..

The VFO uses a 6SG7 from memory with a 6C5 triode buffer then a 6AG7 amplifier into another 6AG7 driver once more from memory....The VFO is perfectly stable and drift free after 10 minutes warm up in fact better than any Kenwood or Yaesu 520 or 101E..I have a voltage control on the driver screen to allow the power output to be varied when driving an amplifier..

All the metal tubes were salvaged from the junkbox..I sanded and cleaned off the original black paint and re sprayed the tubes with a metallic grey paint then added rub on lettering designating tube types..

This little transmitter has been running for years and I often use it for a change to the 1000D..I have added an automatic keyer using a Curtis chip since I built the transmitter..I use both a home brew iambic key and a Black Widow key I got in kit form from the US.. Bob..VK3ZL..

[KB3LAZ]

I haven't kept many pics of other than amplifiers but I found a little 100 watt 160 meter CW transmitter I built using old WW2 metal tubes...There are a couple of modern tubes in this transmitter also mainly the 6146 finals and a couple of VR regulator tubes..

The VFO uses a 6SG7 from memory with a 6C5 triode buffer then a 6AG7 amplifier into another 6AG7 driver once more from memory....The VFO is perfectly stable and drift free after 10 minutes warm up in fact better than any Kenwood or Yaesu 520 or 101E..I have a voltage control on the driver screen to allow the power output to be varied when driving an amplifier..

All the metal tubes were salvaged from the junkbox..I sanded and cleaned off the original black paint and re sprayed the tubes with a metallic grey paint then added rub on lettering designating tube types..

This little transmitter has been running for years and I often use it for a change to the 1000D..I have added an automatic keyer using a Curtis chip since I built the transmitter..I use both a home brew iambic key and a Black Widow key I got in kit form from the US.. Bob..VK3ZL..

Thank you for sharing, I love it! I can see that sitting next to one of your amps (in my head), what a nice looking picture it makes.

[K7SGJ]

Very nice. I had an RME receiver that used the 6xx series of tubes. I think they were the loctal base as I remember. I still have a Collins ARR 15 from a B25 that has the metal tubes in it. I used to have a whole mess of them. Probably worth a fortune these days.

[N8YX]

Very good work. I'm tempted to do something along the lines of a 4CX1500A for each band (HF 15-12-10, 6M, 2M, 432) that my FT-726Rs can cover. Maybe 222 thrown in for the time when I get a '736 or some sort of transverter.

Put 400v on the screen, drive the control grid with 10w and a '1500A will give you legal limit out.