Wonderful. Some comments based on my recent findings: For a near-miraculous yoop/chirp reduction -- at 40, with FT-243 and larger rocks; HC-6s are just too thin -- put a 25-k pot (wired as a rheostat) across the 47 k grid resistor and, with key down, adjust its value down from 25 k. In the region immediately above the point at which there's too-little R across the crystal to sustain oscillation, you will find a slight output-power peak -- _and_ you will find that the rig generally puts out more power than with the original 47 k grid R. _This is without any regulation on the screen._ Proper tuning of a crystal-oscillator rig is not about tuning the output for a plate-current dip; that's for an amplifier, but a single-tube oscillator is not an amplifier but rather a highly dynamic environment in which the tube supplies its own driving signal. The correct way to tune a single-tube-crystal-oscillator rig is to adjust TUNE and LOAD for maximum output _in conjunction with best keying_; there's little value (aside from eye candy) in devoting a permanently-installed meter to the job. For the 5763/6417, keying will be best on the lower-frequency side of "output max," at a point at which oscillation still starts reliably on key down. (And when it's connected to an actual antenna system, the "correct" settings will shift; I recommend monitoring your transmitted signal so you can find that sweet spot again and/or as you change crystals or rain falls and shifts your antenna system's impedance.)Beam power tubes are prone to intrinsic-negative-resistance-based oscillations in the plate and/or screen, so, in the order of importance: Install a 47- or 100-ohm resistor between the tube's screen socket terminal and screen bypass cap; remove that parallel RL VHF-killer choke and install a 47-ohm resistor at the tube's plate socket terminal, between the plate and anything else; and maybe up the value of that 10-ohm grid R to 47 ohms.But if you do only one thing, try reducing the resistance of the grid R as I've described and tuning the output for max output/best keying. Suddenly I can use my first-ever Novice transmitter construction circuit on 40 m without wincing! 73, Dave/amateur radio W9BRD
I remember this in an American ham radio book I borrowed from the library. A novice transmitter for 40 and 80 meters. HT was about 280 volts. It was my first transmitter and worked well. Next one was a 2 valve 6BW6 oscillator/multiplier 807 PA for 10/15/20 and 40m. That got better results as I had more power. The HT was 560 volts on the second rig.
A great nostalgic project for over the holidays. Well documented and very interesting video. I built a one valve EL84/PL84 transmitter some years ago and it had a lot of chirp. I think this has inspired me to get it back on the bench again and start experimenting. Well done Mike with another great video. :)
Great stuff! I would rather build then buy any day. At one time I had rooms full of spare parts but gave it away so I had to start all over again. Thanks, keep the great vids coming. Carl AB1ZI
Single active device transmitters are an interesting subject. I took my microwave oven, arranged waveguides and feeds for the antennas as well as keying for the magnetron with interesting results.
@@MIKROWAVE1 Of course I'm being silly, I wouldn't want to frazzle the recipients. Imagine how dangerous it might get if there's STRONG propagation enhancement! 🤣
Actually the 1mH choke has a very important function. When power is applied to the plate circuit the 0.001uF output coupling capacitor will charge up, and the current flow is through the 1mH choke from ground. When power is removed the same capacitor needs to discharge, again through the 1mH choke. If the choke were not there then some DC would appear on the antenna, unless that antenna used a grounding Balun. So without that choke, a shock hazard exists at the antenna or RF output jack. Another trick is to use a 4.7k ohm 1W resistor in place of the RFC. Takes a bit longer to charge and discharge the RF Coupling cap, but it sure is cheaper.
nice looking project, I made a similar one a few years ago for 40M but it was a one transistor oscillator and an RF match to the antenna, what I did not have was a harmonic filter, and i got a harmonic signal on 14M, which could not get rid of....de aa5oz
The RF choke on the output is not there only in case the plate-to-network capacitor fails. It's there to act as a pull-down across the loading capacitor -- in effect, to allow the plate-to-network capacitor to charge AND to keep the RF output line to the antenna jack at dc ground -- when a low-resistance load is not connected to the ANTENNA jack. (Without such a pull-down, the plate supply would charge the plate-to-network output C in series with the loading C, with most of the voltage appearing acoss the loading C.) I've seen a 1/2 watt, 10 k to 22 k resistor to provide this pull-down function instead of an RF choke; a resistor may provide more safety than an RF choke if the plate C fails, as the resulting current pulse might well cause an RFC to fail open, losing its protection, whereas plate-supply current through a small 10 k to 22 k resistor will cause the resistor to smoke, alerting the operator that something's wrong.
You must have a junk box the size of the library of congress. I think I have enough parts in my junk box to build an led flasher. This is the problem with the Ham industry - many times parts are hard to come by. Ive been frustrated by lack of parts too many times to mention. I dont know how many incomplete projects have sailed out my window due to lack of parts. Its too bad there arent more kit producers interested in vintage equipment at reasonable prices. Elmers dont give radios away any more as you mentioned was so in the past in another video. However, my friend's grandfather was very happy to take my last 1973 25 dollars for an S-38 that bit me if I didnt wear dry shoes. Another pseudo Elmer was very happy to have me repair half the shingles on his roof for an old model 28 teletype machine. The ham store was very happy to sell me an HW-8 kit with a swift kick in the pants out the door.. Some ham at a flee market was very happy to have me hall away a Yaesu 101 for top dollar, then I had to send the goofy thing to the factory for a 300 dollar over hall.. A kid cant even build a crystal radio anymore because he cant find a 365pf variable cap. What's the secret to ham radio?? Perhaps one must be a greedy sob - I sure met my fair share. Of course this post is not a reflection on you... just my experiences. You want to know what virtual reality is?? I received virtually no radio hobby support from my parents or relatives or teachers.. I earned my extra the hard way - virtually alone - as most of the hams growing up today are apt to experience. Ham radio operators are a dime a dozen; real ham technicians are hard to find - and its no wonder - its just too darn difficult to find parts. On the other hand if you want to buy an $800 radio filled with SMTs so small you need a magnifier you will have no problem.
clyde bennish , if you can, try attending hamfests that have "flea markets" of electronic parts. I know that is hard to do because of the Covet-19 situation we currently are experiencing. Unfortunately, a lot of these old parts get thrown out when an old guy like me eventually becomes an "SK." I did my part to help a younger generation, by giving a whole bunch of tubes to a younger Ham who actively builds vintage radio stuff. Keep looking. You'll be amazed at what unexpectedly becomes available.
Dear Mikrowave1, I have bveenb searching the internet and youtube HIGH n LO for a 6m CW QRP kit, NOT some MFJ thing either. I cant find anything and if I do its poorly documented. Any ideas?
I wonder if this was a transmitter that WN1LRK a novice was trying to build from scratch, or was it a commercially made transmitter or kit. It looks like it was commercially made because the lettering looks very professional. Looks like the old FT-243 cleaned up the chirp for the most part.
It is really an excellent project,thank you very much.But my problem is in the calculation of output pi network so could you please give me precisely how to calculate it even to any tube or transistor.thank you.
Well a good approximation starts with calculating the impedance that the tube (or transistor) is presenting at its operating point during full power. So if we have a 250V supply and the meter reads 50 mA, the estimate is 5000 Ohms. This is 12.5 W input power by the way. So you are trying to transform 5K to 50 Ohms. Then pick the Q you want. Say 5 which is reasonable. Then just work the PI formulas at your frequency.
Charles Caringella, W6NJV, Easy-to-Build Ham Radio Projects (New Augusta, Indiana: Editors and Engineers, June 1967 CE), was the basis of this project, and he includes in another chapter, a 2E26 Amplifier stage which is the little brother of the 6146. This got you up to the 20 Watt level. But the Radio Amateur Handbooks of the 50's and 60's were full of 2 tube novice rigs, some using the cheap 1625 tubes that were available surplus and even TV sweep tubes. These could get you to the Novice legal limit.
If you convert the meter into a volt-meter, you can use common values to make the meter read correctly. Use a 4.7 (or any other low value resistor) shunt, then a resistor in series with the meter, or even a small pot so it can be calibrated easily. Which you describe at 14:10 Good example here: www.electronics-tutorials.com/test-equip/meter-shunt.htm 73 Jim W7RY
The fuse is to blow, should the anode .001uf fail thus putting B+DC into the Pi tank Network. The output RFC would ground and damage the B+ supply without a fuse. So if you do use the hole for something else, put a wire ended fuse holder or similar inside or in the power supply lead.
