I have some new/old stock - unused 4CX300A and 4CX350A that are available if anyone has use for them anymore. John Lyles K5PRO Message: 1 Date: Fri, 19 Aug 2022 04:45:43 +0000 From: "Fuqua, William L
I saw you mention K5PRO, Don, so I had to come out of my shell. I have watched the 10 kW homebrew videos too. Admirable work, makes me long for time to do modern tube-based amplifier construction at
For high power systems, I prefer to put an intermediate dummy load with a coaxial patch panel to select load or driving the final stage. This is done as it is time consuming to have to break loose a
Thanks Karl-Arne and Don for sharing insights in tuning up high power communications xmtrs! John K5PRO -- Having worked with really big transmitters; Telefunken 100 kW ISB and Thomson-CSF 500 kW carr
To compliment what Karl-Arne said about MW and HF broadcasting transmitters, VHF high power transmitters have cavity resonators (sometimes called line circuits) that are in the range of 1/4 to a full
You can put negative bias V on control grid, with filament is hot. Avoid positive screen grid bias, however, unless there is some plate voltage first. The electron beam will otherwise all land on the
I was curious about extra shunt capacity to ground from the filament end if this fat assembly is placed close to chassis. The type 43 has some dielectric constant which increases the capacitance over
Looks good Jim. That ferrite choke definitely was too much extra C. I guess you had a hunk of RTV to clean out. Question: If the input is so flat, why even have variable caps there? I am guessing you
Over the past decade I designed a system with three high power transmitters that each use a pair of tetrodes in combined operation. These are TH628L, which run at 23 kV DC each, and produce about 1.5
If you look closely at the Amperex tube, you may note that the anode (plate) shape is different than the CPI/Eimac 3-500Z. Most of the Amperex/Covimag tubes have a wavy horizontal structure with a d
Rob and all, I apologize for the wierd WEtransfer link. On my desktop it works fine and is a simple storage location like Dropbox or Googledrive, for a temporary document or image file. On my Android
I have a 1955 and a 1971-72 Triad catalog. Also a 1952 Radio's Master buying guide from Leo Meyberg Co of Los Angeles. All list the same Triad transformers for plate power. Their commercial line of 1
A colleague in high power RF amplifier design for accelerators has asked me to see if there is interest in some custom Eimac 3CX10,000U7 striped-cathode UHF power triodes. These are perfect to go int
Beware that tubes marked Thompson are not the same as the classic Thomson tube company of France. Even that company is no longer Thomson, bean counters sold the name, and now its Thales, a major Fren
Thanks Jim for the informative summary presentation and paper on stub placement and design. I built a small 1/4wave shorted stub to protect GMRS base station receiver long ago in a remote location (l
The diode, resistor, capacitor parallel combo has been with us since the 1960s when 866s were starting to wane i popularity. Westinghouse, Amperex, International Rectifier all had it in their applica
The author originating this discussion said that they had one 3-500Z that was the vertical thin fin plate, Eimac original, and one 3-500G that has the graphite anode presumably with the horizontal he
The Collins 828C1, and Continental 314R1 1kW medium wave transmitter used a single 3-500Z as a switch tube running at 70 KHz switching frequency for pulse width modulated AM. It was very picky of the
Harald, Whatever you use, do not use the nichrome metal stock. It is high resistance for use in heater elements. It will get very hot from RF current as well. The best material is likely phosphor bro
I always use the Fourier series calculation based on using a selected load line on the constant current characteristic curves. Using a series of 8 - 10 points (i forget) along this load line, plug th