I prefer triodes because they tend to have linear plate modulation characteristics with out a lot of other circuitry. Tetrodes, on the other hand, not only require screen circuitry, but require a lot of audio level screen compensation in order to reach the same characteristics of the triode. But I'm very critical on passing the trapezoid pattern test.
I wrote an article similar to this point at http://www.qsl.net/wa5bxo/pptriodes/pptriodes.htm It is some what under construction still. So I have not made a link from the home page http://www.qsl.net/wa5bxo I was trying to clear up some things that or either not always clear in other books or not mentioned at all. Hope this helps someone. 73 John, WA5BXO -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Brett gazdzinski Sent: Wednesday, September 29, 2004 8:15 AM To: 'Discussion of AM Radio' Subject: RE: [AMRadio] Home Brew It sounds simple, and the RF stuff is simple, but it's the control and metering that adds complexity. Step start, push to talk, grid current and voltage metering, plate or cathode current and plate voltage meters, plate voltage control (variac or power trans primary taps),filiment voltage control and metering, protective bias plus grid leak bias, etc. But overall, it is quite simple, one step at a time... I like building a small deck just for the rf, and do the control on a separate deck, with lots of meters and knobs to twist. Big wire wound pots work great for grid leak resistors. Add in control grids and it gets more complex, with sequence starting, more power supplies and metering, overload circuits, etc. Its loads of fun to figure out what will work with what parts you have or can get. On the subject of meters (I use a lot of them), I use the cheap radio shack meters, they used to make 0-15 volts, 0-500 ma, and 0 to 1ma meters that took a very small hole in the panel. I just make the scales indicate whatever I want, 0-15 volts can be 0 to 150 volts, 0 to 1500 volts, 1.5 amps, 150 ma, etc. The scales come off, they are held on with glue, and you can make up your own numbers or transfer them from one meter to another, as I think they only sell the 0-15 volt meter now. I should use a computer program to make up real scales. So you can have a load of meters, all the same, cheap cost, small panel holes, and modern looking. Shunts will give any current you want, voltage dividers give whatever voltage you want. Black painted panels with P touch labels looks nice, and don't count on remembering what meter does what, or where its supposed to read after 10 years or more, or the next guy who gets the equipment! You can mark the correct voltage/current with a red felt tip marker. A pair of 813's takes how much grid drive? Screen current? Where did you run the plate current on the 4d32 rig? Are the 4x150a filaments 6 volts, or 6.3? Is this stuff fun or what? Brett N2DTS
