WFBE's Home Brew Rig

[W3GMS]

For us that like the old buzzard stuff, you just can't beat this picture and article from the September 1, 2011 issue of Radio World. 

http://www.radioworld.com/article/wfbes-home-brew-rig/24317

Joe, W3GMS 

[W7TFO]

Yep, good history and photo in that blurb.

I've always loved 204-849-851 tubes for the 'get in your face' mounting and size.  No PW sigs there!

73DG

[W3GMS]

I have a bunch of 203A's but would love to find some good 204's.  They used 204's in the WQAA transmitter just down the road from me in Parkesburg, Pa back in 1922.  I would really like to build a working replica of that transmitter. 
73,
Joe, W3GMS

[Opcom]

With the construction open, one can almost 'see' the schematic. Its openness certainly reminded my of Ashtabula Bill's TX.

[KL7OF]

I really like the open construction of the TX  ....The ending paragraph about how ruthless A t&T was and how it bowed to public opinion shows what public opinion can do ...........

[W7TFO]

The ending paragraph about how ruthless A t&T was and how it bowed to public opinion shows what public opinion can do ...........

Public opinion and the unrelenting pressure of Sarnoff & RCA arriving on the scene, leaving a wake of bought-up patents.  Also them joining up with that charlatan DeForest to destroy Armstrong.

True early radio history was brutal in every country, not just the US.

My apologies to any that worked for RCA in later years.

73DG

[k4kyv]

In the early issues of the Frank C. Jones Radio Handbook you will see ads from Heinz-Kaufmann for "gridless" transmitting tubes.  The drawings show large glass bottles that look similar to 204As.  Instead of a control grid, they used a method of beam deflection to interrupt the electron stream from cathode to plate.  The ads claimed they were supposed to be more efficient than the control grid tubes and required zero driving power, but the real reason was an attempt to circumvent RCA's patent monopoly. They must not have been very successful, since they seem to have quietly disappeared with very little fanfare in the old radio literature, and H&K began manufacturing conventional tubes around 1936. That must have been when the patents expired, since other tube manufacturers like Amperex with their HF series sprang up that year.

[Todd, KA1KAQ]

Nice looking transmitter. Reminds me of an early Western Electric transmitter I saw in a museum in Yarmouth, N.S. some decades back. Been hoping to build a 204A/851 rig someday as my homebrew project. While the tubes are still around, tube bases are somewhat difficult to find. Think I've got 1.5 sets so far, and one dud 851. Missed a half dozen NOS 204As a couple years back. At least bases can be fabricated fairly easily.

Does RW still put out their paper magazine version, or is it only online now? My subscription didn't follow me when I moved south in 2008.

[k4kyv]

I still get my RW  in paper edition. But it has thinned down to a fraction of what it used to be.  The pages are smaller and there are fewer of them.  They went to a slightly better quality paper than the newsprint used in the older ones. But there isn't as much in them as there used to be.

Too bad about the 204As. I have seen a few here and there over the years, but never was able to run across any good ones at a reasonable price to purchase for myself.

Back in the mid 70s I missed out on a half dozen Amperex 849As (849s good up to about 20 mc/s) over a few lousy bucks gap between what I was willing to pay and what the seller was willing to let them go for.  I heard later that the seller, Young Engineering in Salem, MA, had hired some kids to tidy up the shop and they all got broken. He ended up getting zero for the tubes, and I wouldn't have missed the extra money had I bitten the bullet and paid him his asking price.

Homebrew sockets shouldn't be too difficult to construct. Heavy duty fuse clips for the filament pins, and use one of the female contacts from a knife switch for the grid connection.

Interesting that the WFBE photo shows the tubes mounted upright (plate upwards).  The RCA books all say the tube must be mounted upside down, with the filament base on top and the plate cap at the bottom. Don't know if that would make any difference in tube life (due to the convection of the heat from the filament maybe?), but I can't see how it would make any difference at all.

[KM1H]

An old QST had a shot of a couple of W6AM's PP 204A amps....KW my asss

He later went with 450T's and bigger....at a KW

[k4kyv]

Actually, a pair of 204As within its rating will just about run a KW input. RCA's 1 kw broadcast transmitter from the mid 30s used a quad of them in push-pull/parallel for the final, modulated by a single pair of 849s. Later versions of the transmitter went to the well-known pair of 833As modulated by another pair. Hams sometimes squeezed a KW input to a single 204A, but they weren't quite rated for that much power, particularly in plate modulated service, so that probably shortened their life.

A certain un-named AMer worked as CE at a broadcast station back in the 70s that still used one of those old RCA transmitters. While he was there, the station bought a retro-fit kit from RCA to convert the transmitter to 833As.  He installed the kit and either tossed out the 204As and 849s along with all the spares, or gave them away to another ham who never used them.

[Todd, KA1KAQ]

TNX for the RW update, Don. I'll have to re-subscribe. I have a stack of the earlier editions that were basically folded newpapers. The later ones were more like a copy of Nuts 'n Volts magazine.

I've always liked the looks of the 204A, a visually balanced, tough-looking tube. The 851 is even bigger but not as balanced with that massive girth and smallish ends. The half dozen 204As I missed out on sold for a little over $500 as I recall, but were NIB. They had 40s-50s date codes IIRC. Must've been spares for some old rigs the military still had on inventory, or maybe old BC transmitters. I do have a pair of 849s, at least one is a dud with filament pieces rattling around inside. The other is dark from use and protected in its original wooden box. Might have to go the 849 route if 204As don't materialize. Come to think of it, there aren't a lot of 851s floating around either. Did see an early globe-shaped 204 at Dayton a few years back.

My plan was to build an open frame design like that old rack you have in your inventory, Don. Tubes would be mounted to the front panel with the old stand off meters for monitoring voltages, transformers hung on the back. Actually got a couple of the meters from 'JN a couple years back. HV zappage would be a big hazard of such a rig though, so the design in the photo Joe posted would be a good compromise: plenty of visual accessibility while keeping some level of frame in front for protection. Pay no attention to the tubing sticking out the side.

[KM1H]

Id rather use a pair of 860 or 861's; intro dates were 1929 and 1927 respectively. Still looking for 861's but they do show at times as they were used into the 60's on Navy ships.

[John K5PRO]

Would those be the same tubes that Robert Goddard (the liquid fueled rocket pioneer) patented, the Gammatrons? I recall seeing a display at the Roswell, NM history museum about those, since Goddard moved there later in his career to launch rockets without complaints from the police.

"In the early issues of the Frank C. Jones Radio Handbook you will see ads from Heinz-Kaufmann for "gridless" transmitting tubes.  The drawings show large glass bottles that look similar to 204As.  Instead of a control grid, they used a method of beam deflection to interrupt the electron stream from cathode to plate.  "

[k4kyv]

Yep, I think you're right.  I'll have to pull out my old Radio handbooks and review those ads.

[w1vtp]

Kept following the links and finally read the history of rectifiers.. MAN!  Imagine rocking a glass mercury-filled rectifier to strike an arc!!!  Talk about excitement.  The most excitement I could handle was the occasional arc-over of 866A rectifiers.  I finally got tired of that excitement and replaced the 866As with solid state direct plug in rectifiers.  Much quieter in the W1VTP shack.

Al

[k4kyv]

Would those be the same tubes that Robert Goddard (the liquid fueled rocket pioneer) patented, the Gammatrons? I recall seeing a display at the Roswell, NM history museum about those, since Goddard moved there later in his career to launch rockets without complaints from the police.

The most successful implementation of this approach was in the Gammatron line of Transmitter triodes from Heintz and Kaufman, starting in the early 1930's. These triodes have a low mu of 3, but very high current at low plate voltage. The reduced plate voltage makes up for the low mu to keep the grid swing comparable to the lower current conventional triodes. The plate current is so much higher that a much lower plate voltage can deliver the same power. Another important advantage of this electrode configuration is that the capacitance from the output plate to the input plate (i.e. control grid) can be much lower than for a comparable conventional triode, thus simplifying Miller capacitance neutralisation. US Patent 2071630 illustrates a dual triode variant for push-pull operation. US patent 2022212 illustrates a Gammatron triode that was optimized for very low input plate to output plate capacitance.

http://www.radiomuseum.org/forum/russian_subminiature_tubes.html

[Todd, KA1KAQ]

Art Collins used some of the Goddard designs back in the 30s when Sarnoff tried to Bill Gates him. Art wasn't going anywhere though, and went to the alternate designs (think he bought or at least, licensed several of the designs for Collins branded tubes). Sarnoff woke up and smelled the coffee.

Al, you can drop in 3B28s in place of the 866s and still have a nice tube in there without any of the MV hassles. They even make a nice purple glow.

[W3GMS]

Id rather use a pair of 860 or 861's; intro dates were 1929 and 1927 respectively. Still looking for 861's but they do show at times as they were used into the 60's on Navy ships.

My Navy CAY-52218 (TBM-12) transmitter uses a 861 in the final.  Fortunately I found two NOS ones and they are both in good shape.  A very impressive bottle for sure.

Joe, W3GMS

[w1vtp]

<snip>
Al, you can drop in 3B28s in place of the 866s and still have a nice tube in there without any of the MV hassles. They even make a nice purple glow.

Didn't know that at the time and I came into those SS dropins.  That PS is long gone.  I'll be doing rev. 2 after I retire.  Maybe will be using 872s just for the effect.  I do have a dozen 3B28 tho'.

Al

[KM1H]

My Navy CAY-52218 (TBM-12) transmitter uses a 861 in the final.  Fortunately I found two NOS ones and they are both in good shape.  A very impressive bottle for sure.

It sure is. Even more amazing is the 860 "VFO" with 1000V on the plate and rock solid stability and a sweet CW note.
I worked on several of the TBn family while floating around on the oceans. Thats what got me attracted to those tubes.

[Opcom]

Would those be the same tubes that Robert Goddard (the liquid fueled rocket pioneer) patented, the Gammatrons? I recall seeing a display at the Roswell, NM history museum about those, since Goddard moved there later in his career to launch rockets without complaints from the police.

"In the early issues of the Frank C. Jones Radio Handbook you will see ads from Heinz-Kaufmann for "gridless" transmitting tubes.  The drawings show large glass bottles that look similar to 204As.  Instead of a control grid, they used a method of beam deflection to interrupt the electron stream from cathode to plate.  "

It would be the same, however, unless they have corrected the display materials, it is wrong. They display a gridded tube advertisement and yet refer to the original Gammatron. The staff seemed aloof and made excuses when I pointed this out in 2010. Maybe they have fixed it since then.