Talk:Radio transmitter design

Tubes

Whats with all the tubes? Roger 21:03, 4 June 2007 (UTC)

High power transmitters (greater than, say, 10 kiloWatt) use tubes rather than transistors. Jaho (talk) 13:23, 20 December 2009 (UTC)

True, but an article on radio transmitter design shouldn't be focused on what are now highly specialized devices. -Roger (talk) 01:27, 21 December 2009 (UTC)

Tubes are mainly used only in HF and VHF transmitters in the higher power ranges 10 KW to 1000 Kw. Two of the three examples shown are obsolete, the third nearly so and the drawing for that one is very unconventional and hard to interpret. There have been a number of advanced AM/SW tube transmitters that should replace these. And, yes, using tubes in examples of low level circuits is not optimum. They should be transistors. My expertise is in high power short wave (AM and digital modulation)and I hope to improve the information or perhaps do a separate article on AM transmitter design. Suggestions welcome.JNRSTANLEY (talk) 19:21, 18 April 2013 (UTC)

What would be really cool and useful, from the point of view of giving an encyclopediac overview of the subject, is some kind of log-log plot of CW power on one axis and frequency on the other, with the regions marked for triode/tetrode tubes, bipolar transistors, FETs, travelling-wave tubes, magnetrons, IMPATT diodes, etc. and so on - it would give the reader a quick feeling for the current practices. --Wtshymanski (talk) 20:35, 18 April 2013 (UTC)

Good idea, I will give that some thought, or why don't you work that up. I can comment on the use of tubes above 1.8 Mhz part.

JNRSTANLEY (talk) 12:30, 27 April 2013 (UTC)

Semiconductors

At the present stage of development, semiconductors can be used in all stages, including high power output amplifiers. (Of course as parallel devices when necessary.) So I think this article (otherwise well balanced) should be reorganised to include the semiconductors. Nedim Ardoğa (talk) 12:00, 3 March 2010 (UTC)

See my comments on the issue above. (Tubes) Yes, solid state devices in parallel are technically possible at all power levels, but economically not, so tubes will be used for a while more, even in new designs. JNRSTANLEY (talk) 19:21, 18 April 2013 (UTC)

Opening paragraph

I find the opening paragraph to be quite strange with its reference to the need for two tuned circuits in transmitters and receivers, and the citation from a book about Tesla. This may put some readers off on the whole article which actually does contain some useful information. Unless someone shows up to defend that opening paragraph in a few days, I will probably redo it. JNRSTANLEY (talk) 21:47, 27 April 2013 (UTC)

Please do. The current version is silly. There's some truth to the point that one can't make a good reciever with a single-tuned filter, but no such requirement in the transmitter, as far as I can tell. Dicklyon (talk) 05:40, 28 April 2013 (UTC)

Local oscillators and unwanted mixing products

This section is flagged as having too much detail. I wonder if some of this material could be moved to the intermediate frequency article. A very brief summary of the subject would be left here with a link to that article. Any suggestions? JNRSTANLEY (talk) 19:39, 3 June 2013 (UTC)

I have now done major work on this section. JNRSTANLEY (talk) 13:17, 10 June 2013 (UTC)

Disorganized article

This is a very disorganized article, and some of the sections read more like a collection of how-to articles. There is no list of the component parts of a typical transmitter (as there is in Transmitter), there is no central breakdown of the different transmitter types, there is no list of the design specifications (freq, output power, modulation index, freq stability, spurious emissions) used to design transmitters. Under "Linking the transmitter to the antenna" there is no discussion of the central importance of impedance matching and SWR, and the requirement for an antenna tuner. There is also no mention of the important issue of high voltage safety: bleeder resistors and safety interlocks --Chetvorno^TALK 15:47, 12 February 2014 (UTC)

I agree with much of what you say, Chris. I believe the article is considerably better now than before I made a number of modifications, and hope you agree, but that said, it is far from perfect. As a relative newcomer to Wikipedia, I tried to retain as much as possible of the existing text and graphics and this is possibly part of the reason for the disorganization. It previously was basically a set of notes on building a 1950 vintage ham transmitter. Perhaps it is time for someone, (you?) to start from scratch, but I don't see much point in making it simply a re-hash of the Transmitter page, which, IMHO, is very good. My expertise is in broadcast transmitters, especially high power short wave, and in ham type amplifiers. I understand all of the points you raise and I can continue add content on some of the issues you mention above if you prefer that to doing it yourself. JNRSTANLEY (talk) 13:56, 14 February 2014 (UTC)

Hi, I didn't mean to criticize anyone. I can see the article was in a really poor state when you began. Your additions seem really excellent; I certainly learned a lot. Not many WP articles are written by a professional in the field. Your description of modulators was really clear. and your comparison of the advantages of tubes and solid state; little points, like the power supplies have to be turned on in correct order (from exciter to final amplifier?). As you say, there's always a desire to keep what's useful. BTW, an alternative to improving an article in place is to create a work page on your user page, copy it there, perform major surgery, then put it back. I'm currently doing a rewrite of Negative resistance that way. I hope you don't give up on this article; I think you are the ideal person to write it. I don't know how much help I'd be here, I don't have any experience with transmitters, but if you'd like someone to bounce ideas off of contact me. I'll watchlist this page. --Chetvorno^TALK 16:04, 15 February 2014 (UTC)

Comparative Efficiency, Theoretical limits Vs. Actual Performance Cross Reference Table

In the May 1999 issue of Proceedings of the IEEE, page 759, reported efficiency nearing 65% was reported for a Russian Gyrotron producing one megawatt peak at 110 GHz with a 1.5 second pulse width using a single-stage depressed collector; 40% efficiency was reported for non-depressed collector operation. I came to Wikipedia hoping to compare this to a Class-C, CW, Valved transmitter. I seem to recall 65% efficiency was about what was achievable in practice. Traveling Wave Tubes for use in outer space recently achieved 65% efficiency--requiring ten stages of collector depression (don't publish this figure. I can't cite a source this instant. I will review and provide a documented value later). Non depressed collector operation was said to be sufficient. Single stage collector depression was said to be efficient. From what I saw in the manufacture of TWT amplifiers, three stage collector depression was where wall plug power consumption began to track RF power delivery. Wall plug efficiencies were typically below 50% in practice for X-band airborne and earth based TWT amplifiers (I should research documented data here too). I came to Wikipedia hoping to see a chart listing comparative efficiencies, both in practice and theoretical limits for various topologies. These could be listed using in tabular form for Valved/Solid State, CW FM/ Switching and Linear Modulated AM/ Linear Amplified SSB. Electron transit time limits Valved applicability to a cutoff frequency. A line might be used to divide the table, beyond which Linear-Beam and Cross Field devices predominate, whether Slow Wave structured or Fast-Wave/Relativistic, both CW and pulsed; of Grid and Cathode Modulated varieties, whether Soft-Tube/Line-Type or switched DC (by IGBTs or Hard-Tubes). Efficiency listings should include both theoretical and realized values covering ranges from Audio Frequency, Short Wave , HF, UHF, Microwave, Millimeter Wave, Terahertz, X-ray, through Gamma Ray portions of the spectrum (DC to daylight and beyond). Devices currently used might be listed in the leading column. Power supply and modulator loss might be considered in a column beside output stage efficiency. Listed in the second column or the last, I would like to see overall wall plug efficiency. If I can be of any less help, I'm all ears. Jeffreagan (talk) 18:44, 4 April 2017 (UTC)

Jeff, the closest I can find to what you are looking for is discussed somewhat in the article Amplifier figures of merit. A tabular listing as you suggest would be nice but quite a bit of work and there are many variables. Class C RF amps up to 30 MHz typically achieve between 75 and 83% plate efficiency. (ARRL Handbook) Pushing beyond that requires high drive power which decreases overall efficiency. Filament and screen supply power and tuned circuit losses also lower overall efficiency of course. JNRSTANLEY (talk) 12:10, 5 April 2017 (UTC)

Regarding a question on costs to run a transmitter in talk:FM broadcasting, I found this one about modern FM transmitters in the 67% range. Microwave ovens are in the 65% or 70% or so range now. Years ago, it was usual to say 50% for both radio transmitters and microwave power sources. I used to know about TWTs with one stage depressed collector, 10 is pretty amazing! Gah4 (talk) 17:30, 19 April 2020 (UTC)