2 Valve Transmitter by SMØVPO
This transmitter is very stable and will deliver up to seven watts of power with the components and tubes shown. Do not be put-off by valves as they are VERY easy to work with and it seems that there are quite a few valves around.
http://sm0vpo.altervista.org/tx/2tubetx.htm

5-Watt Transmitter by SMØVPO
This is a very simple 5 watt CW TX based upon a TTL logic chip. There is just one "tricky" component and this is Cx. This component should have an impedance of about 10 - 50 ohms at the frequency of interest.
http://sm0vpo.altervista.org/tx/5watttx.htm

A Multimode Phasing Exciter for 1 to 500MHz by KK7B
The high-performance direct-conversion receivers described in the references may be easily paired with a CW transmitter to make a simple transceiver of very respectable performance.
http://www.arrl.org/files/file/Technology/tis/info/pdf/9304027.pdf

An Updated Universal QRP Transmitter by W7ZOI
Looking for a project that will let you try some of your own “scratch built” ideas? Here is a starter low power transmitter circuit for that pursuit.
http://www.arrl.org/files/file/Technology/tis/info/pdf/0604028.pdf

CigarBox Transmitter by SMØVPO
The text has been copied exactly as it was written when it was published, way back in March 1955 (Practical Wireless). I can clain NO originality for any part of this project. I have built it and it works using DL94 ...
http://sm0vpo.altervista.org/tx/cigartx.htm

Émetteur SSB 80 40 17 et 15 m by F5LVG
Lors de sa conception, cet émetteur a été prévu pour quatre bandes (80, 40,17 et 15 m), 100 W de puissance de sortie en SSB, réalisé intégralement avec des tubes, avec le schéma le plus simple possible.
http://oernst.f5lvg.free.fr/TX2013.pdf

Experiments with Broadband Noise Generators by N5ESE
I'm always on the lookout for useful gadgets that make it simple to do a big job. Well describe a few such products on this page. We'll look at how a very simple RF noise generator can be used to measure receiver filter response, for off-the-air antenna tuning, for making antenna measurements, and for troubleshooting electronic circuitry.
http://www.n5ese.com/noise.htm

Glowbug CW Transmitter by GØUPL
This one-valve (ECL82) CW Transmitter occupies a very special place in my amateur radio history. I was first licensed in 1994 but did not operate on air. I committed to only ever operate equipment which I had made myself.
http://www.hanssummers.com/cwtx.html

Homebrew Hi-Fi AM Driver Transmitter by W2DTC
I always wanted to build a simple 160-10 meter AM driver transmitter. Over the years I have built/gathered a remote variable power supply, a hi-fi modulator and an digital RF generator that made this project very easy.
http://w2dtc.com/w2dtc-homebrew-hi-fi-am-driver-transmitter-page.htm

Jersey Fireball 40 by WA2UNN
One of our club elmers, Clark Fishman, WA2UNN came up with a couple of twists on the popular theme of using a TTL crystal oscillator "can" as the heart of a milliwatt-level transmitter.
http://www.njqrp.club/fireball40/index.html

N7KSB Milliwatt transmitter that's easy to build by KJ5TF
N7KSB's experimental 1/2 watt CW transmitter uses a 74HC240 high-speed CMOS octal buffer, one section which serves as a crystal oscillator, four sections of which amplify this signal, and three sections of which are unused.
http://www.qsl.net/kj5tf/n7ksb.html

Single Valve Transmitter by SMØVPO
I recently purchased quite a lot of the old "battery valves" at a junk sale. It seems that there are quite a few of these valves around as it is common knowledge that valves are obsolete so no-one wants them.
http://sm0vpo.altervista.org/tx/1tubetx.htm

The 'Multi-Four' – a VXO Transmitter for 20/30/40/80m by GW4ALG
I've had an interest in building a simple VXO transmitter for many years, but was unsure that the limited tuning range usually associated with VXOs would be useful on the busy HF bands. However, the ability to switch a number of crystals, and cover a number of different bands in one transmitter greatly increases the chance of finding a clear frequency on which to operate.
http://www.alg.myzen.co.uk/radio/qrp/mf_tx.htm

The G4AON Companion Transmitter by G4AON
This transmitter design is based on the control circuitry of the Universal QRP Transmitter which appeared in the April 2006 edition of QST. The case, band pass filters and synthesiser are the same as those used in my Universal Receiver.
https://www.qsl.net/g4aon/g4aon_tx/

The G4AON SSB Transmitter by G4AON
Much of the circuitry in this transmitter is similar to my other TX and RX, being "3rd generation" means some of the design is an improvement over the earlier circuits.
https://www.qsl.net/g4aon/g4aon_ssb_tx/

The ONER HF Transmitter by GM3OXX
The Oner HF CW transmitter was first described by George, GM3OXX in Sprat number 45 and has been widely used as a simple but effective transmitter. It is so called because it can be built on a PCB just one inch square!
http://www.zerobeat.net/g3ycc/oner.htm

The "Oner" A Simple 1 Watt Transmitter by W5DOR
Started building the Oner. 1st I sketched a layout. For a good example of very neat manhattan style layout go to AA7EE's blog and scroll way down the page.
https://web.archive.org/web/20180828053055/http://w5dor.com/W5DOR-Oner.html

500mW CW Transmitter by KC6WDK
A very quick and easy way to get on the air is to build a "Michigan Mighty Mite" CW transmitter for 160, 80, 40 or 30 meters originated by Ed Knoll, W3FQJ and developed by Tom Jurgens, KY8I.
https://www.qsl.net/kc6wdk/QRP/transmitter.htm

The 'OXO' All Band Transmitter by GM3OXX
The OXO transmitter was originally described by George Burt GM3OXX in Sprat number 20 way back in 1979 and has proved to be a very popular little transmitter on it's own and as a basis for other rigs.
http://www.zerobeat.net/g3ycc/oxo.htm

The OXO An all bands VXO Transmitter by GM3OXX
The circuit is quite simple, but the oscillator and the PA are RF and DC coupled; the oscillator will not go without the PA,the 39 ohm and the 0.1uF in the PA emitter to ground.
http://www.qsl.net/g3pto/oxo.html

The VOXNER HF Tx by G4VAM
This clrcult is offered as an exerimental union of the OXO and ONER of GM3OXX fame! L1 has been included to increase VXO shift on 10 metres and higher bands.
http://www.zerobeat.net/g3ycc/voxner.htm

The W8EXI Wingfoot VFO Exciter by AA8V
The W8EXI Wingfoot VFO Exciter (transmitter) was built and designed by Jim Trutko, W8EXI (now, sadly, a silent key), in the middle to late 1950's with the assistance of the Goodyear Aerospace machine shop in Akron, Ohio.
https://www.frostburg.edu/personal/latta/ee/wing2e26xctr/exciterpics1.html