Cool Tube

Westinghouse WL-531/VT-141


I got this tube from Bob KD8ACU (one of my professors at OSU). I think this is a tad OVERKILL for my amp project HIHIHI. 50,000v for the plate, 20 amps@11.5v on the filament...OUCH!!!!!!!! The filament takes as much current as my rig does transmitting 100w HIHI. I'm sure this tube could run in the tens of kilowatts range. It was commonly used in SCR-270 radar units in the 40's-50's era. It is definitely a collectors item now! (I have no idea if the tube is still good)

Note: Please don't ask me if it is for sale. This one is a keeper.

Edit 12/20/08:

I tried to light up the fillament on this and there is a short, full continuity, between the leads. The tube is no good.

Homebrew Communications Speaker Project

I am taking a manufacturing class this quarter and our first "introductory" project is to build a box out of wood. This sounds pretty simple, but going with the manufacturing theme the box has to be designed (working drawings - dimensions, isometric), we have to have a bill of materials, and we need to lay out a plan of procedure for making the box. I have had this kind of stuff in the past and I am good with machines/building things so the project still seems a bit too easy.

I didn't just want to build a box. I wanted to put something in it. My first idea was to build a case for something. Then I couldn't think of anything to build a case for. Since I don't want a box to sit on my desk and look pretty or something to hold junk I tried to think of some function the box could have so I could USE it. Since I am a Ham radio operator I started thinking electronics. That's when the speaker idea hit me! I don't have a good speaker, and I don't have a whole lot of stuff that I have built in the station. So, it is a perfect project.


Since these are pencil drawings they didn't scan very well. This one gives you an idea of the finished product. It isn't an exact model/drawing though.

Gathering up the parts for the electronics has been a challenge. I don't want this to turn in to a really expensive project. I need to have some $$ to do my amp. I have spent the past 5 days or so on and off researching electronics kits to make this work.

I worked on the wiring diagrams all weekend. Let me tell you - this isn't a speaker box that you plug your wires in to a stereo and you get sound. Mine will have two speakers, a 10w/channel class AB stereo amp, switched capacitive filter (NEScaf) for bandwidth/shift control, a VU meter to monitor drive level (at the input), 4 mono inputs, and two stereo inputs. The 4 mono inputs can be switched individually to both speakers or one to one speaker and another to the other speaker. This way I can plug 4 radios in to it and switch between which ones I want to listen to. Only the mono channels can be routed through the filter board. The amp can be switched on/in or out/off so the line can be routed to a headphone connector on the front panel with the amp/speakers muted.


I just found one error on this - the dotted separation line should be above the power input on the right. I think I can work around that one.


I hope I can follow all those lines OK! It shouldn't be that hard, I understand how it is supposed to work.

I will work on the final drawings, bill of materials, and plan of procedure here and post my progress in the next couple days.

The speakers are 5" Dayton PA sound drivers. These aren't your average "speakers" - these are loudspeaker drivers. Note the price in the link there - $11.80 each, NOT BAD!! Now, why would I use loudspeaker drivers? Well, I am not trying to blow myself across the room when I tune in a signal on the radio. In fact, the speaker I am making isn't supposed to get loud at all. If you compare a PA sound driver to a car speaker the first thing you will notice is the ratio between the magnet size and the speaker size. The 5" Dayton drivers have a 4" magnet!!! This creates tighter, more hi-fi audio - which translates in to clearer sound. Car speakers are not as precise and would sound a little muddy or muffled. Same goes for "woofers". Although they have larger magnets, they are designed for low frequency response - below 600hz or so, usually (in a sound system the mid range takes over from here). This wouldn't do a communications speaker any good since the purpose is to hear the normal audio range of human speech - 500-2500hz or so (and tones, like Morse code).

Website reformatting?

I am working on website development in my communications class at OSU. I am working with a freeware program called "Sea Monkey". I am trying to re-configure the site so it is not a "blog" but a normal website where I have a homepage and navigable sub pages. I am not sure how long it is going to take to pull it off, but I am going to give it a shot!

Amplifier ideas

I am re-visiting an amplifier construction project. I have been thinking about building an amp for quite some time. It would be an excellent piece of home-brew gear in the shack and it is the only piece of equipment I don't have (minus various test equipment. I have rigs, a tuner/transmatch/impedance matcher (HI - read my post on tuners from a couple months ago), power supply, coax, and antennas. The only piece of gear (in the transmit/receive line) I don't have is an amp.

I'll be right up front with this - I don't, at this moment in time, have the knowledge to build an amp. I do have the knowledge, ambition, and desire to learn how to do it. I just got my Extra class license in the past month or so. That said, the reason for revisiting the project is because I have a RARE opportunity at hand. I am a student at OSU and have a professor who is a ham and has enough knowledge and electronics experience to guide me through it. I am taking his design class this winter (and his 1st electronics course in the spring) and have the OK on the amp for my project. I knew this was a possibility about half way through last quarter, so I have been researching things with this project in the back of my mind since then. Now that school started back up this is all starting to roll!

The project details aren't laid down yet. That is what I am in the process of - and partially why I wrote this post. Please feel free to e-mail or comment with any suggestions.

I work the HF bands mostly, but I am an avid VHF'er (if you have read a few of my other posts on here then you know what I mean HI). I would like to cover all bands QRO. Right now I can get on 160-2m and 70cm. I know this is impossible to cram in to one amp because of the differences in circuit design (component values/sizes). I know I can get 160-10m in one box. There are a zillion 160-10m amp designs out there. Everything from a few tens of watts to legal limit and then some, transistors and tubes alike. However, I can't say that I have ever seen a tube amp covering 160-6m that is QRO. If I am going to build an amp then I would much rather build an AMP - legal limit. I can always knock the power down, but I can't go the other way.

Transistors would be GREAT to use - they are tiny, light weight, and more reliable in service than a tube (given they are used within their specs). The down side is they are VERY EXPENSIVE!!!!!!! That is a major issue. So, I am going to resort to using a tube. This isn't a bad deal, though. Tubes are very popular (more so than transistors, probably because of the cost issue) so there are many to choose from and many places to get them.

Right now, I have a 3cx/3cpx1500A7 (8877) in mind. Just one is all I need and I won't need to run it "hot" for legal limit. This is subject to change, however. I need to track one down first. If you know where I can get a (working) pull for cheap let me know!

I want to cover 160-6m. Now, if you build or have any knowledge about amps, I know what you are probably thinking - I'm crazy. Well, yes, maybe a little. I know 10/12m are hard to tune. Getting to 6m is going to be even harder. An 8877 will run up to 2m, maybe 1.25m, so the tube isn't the problem. Getting the tank to resonate on 6m, while also down on HF, is going to be a real trick. I will have to dig in to the circuitry design to see what my options are.

As part of the design I want to have expandable, separate boxes, for the VHF+ bands. This means the amp should be rack mountable - most likely 19" since that is the "standard". The power supply can probably be shared between all the other boxes, so that would keep the cost and build effort down on the expansion bands. I don't know if I want to build the power supply in to the HF amp or not. If I do then I have one self-contained unit, which would simplify mobility for operating events like field day and other contests. That would also, most likely, take up less space on the rack than having two boxes. The amp/ps combo would be bigger than just the amp or ps box, however.

If you did read this, or just skimmed over it, and have any suggestions/comments, whatever, PLEASE let me know! All input is greatly appreciated. Leave a comment (preferred so I can post it on the site for others to read) or e-mail me: sjdamico@gmail.com

Edit 1/6/08:

I am researching HF/6m tube amps to see what I can come up with. I am going to compile a list below for my own records but surely others will benefit from my research. This should be an interesting search!

ACOM1000 single GU-74b 1000w
N4IS amp homebrew - looks like a pair of 3cx800's, no construction/spec details

Edit 1/20/08:

I think I am going to switch over to a GS-35b tube instead. They are a lot cheaper than an 8877 (even a pulled one) and I should be able to get 1500w out of one. I can also use them all the way up through the UHF bands.

I have a PS. I am not sure of the specs and don't have a schematic of it, though. I know it came from a Motorola repeater and the big transformer is 3500v on the secondary. I was told it was in a Micor repeater, of what era I am not sure.

If you have or know where I can get a schematic and all the specifications of this PS I would greatly appreciate it!

Remote control of Ham stations, also - Echo Link What do you think?

I was reading the reviews on the Ten Tec Omni VII on Eham.net. For those of you that don't know what an Omni VII is, it is a new Ten Tec radio (within the past year or two) that has built-in Ethernet compatibility. That means you can plug the radio directly in to CAT-5 cable and through your network router in to the Internet - just as you would a computer in your home - and access the radio through the Internet to operate it remotely.

One guy posted on there about having another QTH and wanting to put one of these rigs there. When the propagation at his normal QTH is bad he can connect to the other rig through the Internet and bingo-blamo have an instant new QTH HIHI.

Isn't the "hobby" of Ham radio supposed to be wireless and usable when all other means are down? Where, then, does Internet remote control and Echo Link fall in the grand scheme of things?

My opinion is Ham radio is radios, and all that term encompasses (antennas, power supplies, transmission lines, user-interfaces (IE, CW key, mic, computer - digital modes/logging/computer control)). When you toss in an Internet connection you immediately suck the life out of Ham radio, in my honest opinion. How can you sit in front of a laptop miles from your QTH in Boise, ID, while on vacation at, say, Argentina, and be talking on the radio saying you are in Boise, ID??? Or, even WORSE - the other way around.

I also don't like the concept of Echo Link. I used to talk on that before I was able to get on HF. I used a repeater system and was able to dial in other repeater systems around the world. This gave me my "fix" on international communications, but boy was it short lived. For emergency communications or reliable every-day communications it is great. Dial in the code for whatever repeater or station (given they are echo link capable) and you can talk to someone on that system. It's almost like a telephone. However, in normal situations a telephone or Internet connection is going to be the better choice, I think.

What really disgusted me with Echo Link is the Internet. When you talk to another Ham through that system the Internet is taking your signal from here to there. Not radio waves and propagation. There is no skill or "magic" to dialing up a repeater on echo link and picking up a microphone and saying "hey buddy whats the weather like over there?". There IS, however, skill and "magic" in directly scrolling through the frequencies on HF and listening to the radio spectrum AS IT IS and finding that station to talk to.

I can wrap my brain around the concept of the remote station - the station is where it is, thus that is the origin of your signal - not Argentina. I just find the concept to be dumb - it sucks out the magic and the true meaning of Ham radio.

I don't mean to slam Ten Tec in their efforts, and I don't mean to speak badly about the Omni VII. Ten Tec is a fabulous company. If you don't think so I think you need to re-study their history and sit down with their current HF radios/receivers. I just think that the use of the Internet as a link in your communications system is a joke.

What do you think?

CW Progress

I am making some headway with my CW (Morse code). I am pretty much staying between 10 and 13wpm. I try to send between a 13 and 15wpm character speed and space it out so I have more reaction time between letters. I have found, though, that going too slow is just as bad as going too fast. If the spacing is too far then I can get the letters but I can't subconsciously hear the words. I am stuck "sounding out" the words and don't comprehend the message being sent. If I am at the right speed and miss a letter then I get discombobulated and mess up the word, or worse, the whole sequence. If the transmitting station is going too fast then all I hear are occasional letters. I can't seem to find a happy medium between the two. I can pick out names, signal reports, and states pretty easily at up to about 25wpm - mostly because they are repeated or are standard.

One thing I find interesting is the variability in how people reply to my CQ's. I send my call sign in my CQ's the exact speed and spacing I want someone to reply with. However, I get everything from someone sending 3-4wpm slower than my character speed with long spacing to someone sending much faster - both character speed and spacing. I might be a picky CW operator, but how hard is it to match someone else's speed/spacing? HI.

I have found, though, that it is very easy to ask someone to change their speed. Everyone I QSO with, that I have done a speed adjustment with, has been very helpful. This is one of the great aspects of Ham radio - experienced operators take the time and effort to help the non-experienced operators (myself with copying CW).

Since I cut the use of my computer for decoding I have had quite a few QSO's (I think a couple log pages, at least 1.5). I have not had any help with decoding and I have not had an SSB QSO since Thanksgiving. Now I just have to keep things rolling!