Transmitter Circuits Collection

 

• 10W 40m CW Transmitter

• 2m Band Beacon

• Beacon for 144 MHz

• Beacon for VHF

• HF QRP CW Transmitter

• VHF Beacon

• Wireless AM Microphone

• X-tal VHF FM Transmitter

• 7 MHz CW QRP Transmitter

• 14 MHz CW QRP Transmitter

• 145 MHz X-tal FM Transmitter

• 27 MHz AM/FM Transmitter

• HF QRP CW Transmitter VXO - W7ZOI

• FM Audio Transmitter with Monitor

• 0.5W FM Transmitter 88MHz-108MHz

• 7 MHz 5W QRP Transmitter

• 7 MHz 12W Transmitter - NB6M

• 10m VXO QRP Transmitter - NB6M

• 27 MHz 2W Transmitter

• 40m 5W CW Transmitter - N1HFX

• 75m Phasing SSB Exciter - WA7JHZ

• Miniature Tracking Transmitter

• 4W PLL FM Transmitter - XQ5FOD

• 20m 1W Transmitter - PA2OHH

• 40m CW Transmitter - PY2MG

• HF SSB Exciter - KD1JV

• 3 GHz Beacon - G4DDK

• 5.7 GHz Beacon - F6BVA

• SHF Micro-beacon - F4BAY

• 6m CW Transmitter - VE7GC

• 1W HF CW Transmitter

• 50 MHz QRP AM Transmitter

• 80m-40m 6W CW Transmitter

• 80m Beacon

• 144 MHz 1W FM Transmitter

• 144 MHz AM/FM VFO Controlled Transmitter

• 144 MHz Low Power Beacon - YO3AVE

• 432 MHz CW Transmitter

• 432 MHz QRP FM Transmitter

• 1296 MHz Simple Transmitter

• QRP Transmitters

• 1.65 MHz QRP AM Transmitter

• 88 MHz - 108 MHz FM Transmitter

• HF Low-Power AM Transmitter

• 88 MHz - 108 MHz X-tal controlled 1W FM Transmitter

• 30m CW Transmitter

• 80m CW VFO Transmitter

• VLF 15W Transmitter

• 9 MHz SSB Modulator

• 88 MHz - 108 MHz 0.5W FM Transmitter

• High-Quality AM Transmitter

• 27 MHz 4W AM Transmitter

• 2W Two-Bands Transmitter - VK3XU

• 7 MHz QRP VFO Transmitter - W7ZOI

• 14 MHz 1W VFO Transmitter - W8PJ

• 40m QRP CW Transmitter - WB8VGE

• 40m The-QRP-Key Transmitter - WA8MCQ

• All-Bands VXO Transmitter - KN1H

• 2m Low-Power CW Beacon

• 9 MHz SSB Modulator Phasing-Method - RSGB

• SSB Modulators Filter-Method - RSGB

• 88 MHz - 108 MHz 25mW FM Transmitter

• 88 MHz - 108 MHz 20W FM Transmitter

• 40m MicroT2 SSB/CW Transmitter

• HF MKII All-Band CW Transmitter

• 88 MHz - 108 MHz 20W PA - ON6MU

• 80m Fox Beacon

• AM Broadcast mini-Transmitter

• SSB Generator - JG1EAD

• 1 MHz - 500 MHz Multimode Phasing Exciter - KK7B

• 2.32 GHz 0.7W Beacon - LA3UHH

• 27 MHz QRP AM Transmitter

• Simple FM Sender MAX2606

• 144 MHz Fox-Hunt Transmitter

• 144 MHz CW-AM-FM QRP Transmitter - DJ8PG

• 144 MHz FM-AM Transmitter - DL3WR

• 144 MHz Transmitter - DC9MD

• 144 MHz 1W NBFM Transmitter

• 144 MHz 5W SSB TX - DJ9ZR

• 6m Beacon - WB2AMU

• 144 MHz 350mW Beacon - 9A4QV

• 10 GHz Beacon - W1GHZ

• 88MHz to 108 MHz Low Power Transmitter

• 10m SSB Transmitter - NZ5G

• 10 MHz 3W CW Transmitter - WB6VGE

• 50 MHz DSB Transmitter - KL7GLK

• 7 MHz 2.2W CW Transmitter

• 7 MHz 123mW CW Transmitter

• 14 MHz 4W VXO Transmitter

• Phased SSB Exciter

• SSB Generator

• 14 MHz to 21 MHz 5W CW Transmitter

• 10m Double Side Band Transmitter - WA4ADG

• 10m Double Side Band Transmitter - K4EPI

• 144 MHz FM Transmitter - WB6BIH

• FM 5W SENTOR Transmitter

• 7 MHz CW-AM Transmitter

• 50 MHz 30W Beacon - N6CA

• FM Transmitter 300mW

• 14 MHz 4W QSK Transmitter - WB8VGE

• 40m Rock-Bender 3W Transmitter - WI5W

• 88 MHz - 108 MHz FM Wireless Transmitter

• 137 kHz CW Transmitter - G3LDO

• 30m QRP CW Transmitter - WB8VGE

• 40m DSB/CW QRP Transmitter - WA5WWN

• 27 MHz 4W Class-D Transmitter

• 144 MHz 140mW Beacon Oscar-1

The NOGAnaut QRP Transmitter

 

The crystal oscillator is the simplest form of transmitter. Normally, oscillators are used to drive buffer amplifiers and power amplifiers, which provide increased output, as well as prevent the output circuit from adversely loading the oscillator.

Most transistors exhibit a characteristic impedance different from the 50-ohm impedance of a well-tuned antenna system. An improper match between the impedance of the transistor and the load (e.g. antenna system) can cause severe power degradation, and worse, can seriously affect the signal, including shifting the oscillator frequency in unpredictable ways.

In the NOGAnaut transmitter, the 2N2222A transistor, which exhibits a characteristic impedance of approximately 200 ohms, is matched to a 50-ohm load via the pi-network filter composed of C1, C2 and L2. The values of these components were chosen to provide a close match between the 200-ohm transistor and a 50-ohm antenna (it is therefore critical that a good 50-ohm antenna system be used with this transmitter). It so happens that these values also form the familiar half-wave harmonic filter, thus satisfying FCC spurious emissions requirements.

Figure 1. NOGAnaut 80M Transmitter Schematic.

Capacitor C5 provides the necessary feedback to begin oscillation. You may find that you can operate your NOGAnaut without this capacitor--stray capacitance in the circuit provides a certain amout of feedback without C5. However, it was found during development of this circuit that the oscillator can have troubles starting at times, therefore it is recommended that you leave C5 in the circuit.

The 0.01 uF capactor, C3, serves as a DC-blocking capactor. At 3.6864 MHz, this capacitor is essentially a dead-short to RF, but blocks the DC current from flowing into the load.

This is a familiar Colpitts oscillator, operated in "common-base mode." The usual base-bypass capacitor is replaced by the capacitance of the crystal. With a 15V supply, this transmitter has been measured to deliver as much as 134 milliwatts into a perfectly matched 50-ohm load ("your mileage may vary"). With a 9V supply, about 20-50 milliwatts should be expected.

The transmitter is keyed by interrupting the positive supply voltage. You can modify this to be grounded keying, if necessary (just interrupt the negative supply voltage instead of the positive voltage). This may be necessary if you use a keyer that expects grounded or negative keying.

For a very good description of crystal oscillators, check out Solid State Design for the Radio Amateur by Wes Hayward, W7ZOI, and Doug DeMaw, W1FB. This is one of the most popular amateur radio books ever written and is packed full of practical information about how solid state circuits behave. It is published by the ARRL, and can be purchased directly from them, as well as from many electronics retailers.

Further information about pi-network filters can be found in The ARRL Electronics Data Book, by Doug DeMaw, W1FB, also published by the ARRL. This book contains most of the nuts and bolts of basic circuit design, and is a must for any ham shack.

http://www.nogaqrp.org/projects/noganaut/circuitdescription.html

Homebrewed Off-Center Fed Dipole

 

Building A Homebrewed Off-Center Fed Dipole Scanner Antenna.

Aluminum/copper tubing construction:

You will need to check the fit of the tubing with the T connector and the caps while you are at the store. One combination that fits nicely is 3/4" copper pipe with 3/4" CPVC fittings (not to be confused with 3/4" PVC fittings which will be too large). The tubing/connector is held in place with 2 stainless steel sheet metal screws for connecting the balun to each element.

Find a "U" bolt to fit your mast. Drill two holes in the support pipe to fit the U bolt.The support pipe is 18" from the "T" to the mast.

Remember, bandwidth increases as diameter of the elements increases. I think, if I remember correctly, at the hardware store, that a few CPVC fittings will fit copper tubing perfectly!

Some say that the 18" element on top mounted works best,Some like the 48" element on top.It does'nt matter,it works the same.

If you use the copper tubing,be sure to paint it with some good,non-conductive paint.I used to paint mine light grey. -Have fun! (Teraycoda)

For an alternate/temporary mounting option, drill a hole in one of the end caps and put in an eye bolt with a nut on the underside of the cap to secure. Be sure to secure this end cap to the copper tubing somehow, perhaps with an additional small stainless sheet metal screw. Be sure that the eye bolt itself doesn't make electrical contact with the tubing. Also, drill a small weep hole in the bottom end cap to allow any moisture to escape that may accumulate inside. Use the eye bolt and some rope to pulley the antenna up high in a tree, or use a hook to hang it somewhere. Give careful consideration to safety and grounding depending on your particular usage scenario. (Qdude)

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Variation for Off-Center Fed Dipole Using Simple Wire and 75 to 300 ohm TV Balun Transformer

Electrically, this version is the same as the one using copper tubing (above) but can be assembled quickly and is quite portable. While not as broadbanded as an OCFD using copper tubing or other metal with a larger diameter, the OCFD made from simple wire turns in great receive performance in all the commonly scanned bands, as reported here on RR in multiple message threads.

The legs/ends of the dipole are simple bell wire and shown here coiled up. Uncoil them and hang them vertically; doesn't matter if the long or short leg is at the top... works the same either way. The wire terminal lugs shown at the end of the legs of the dipole antenna should NOT be connected electrically to the wires - just crimp them on over the wire insulation. They are used as convenient hangers for the antenna, and not meant for electrical connection. Obviously, the lugs at the TV transformer/balun ends of the wire should be stripped before crimping on the terminal lugs to ensure contact with the antenna wires when you attach the TV transformer. Ensure the 75 ohm coax feedline that you connect from the balun/transformer runs away from the antenna at as near a 90 degree angle as possible.

Building a radio in 10 minutes.

http://sci-toys.com/scitoys/scitoys/radio/ten_minute_radio.html 

For our 10 minute radio, we will need these parts:

• A ferrite loop antenna coil

  In our other crystal radios we wound the coil by hand. In this project we use a much smaller coil with a ferrite rod inside, from our catalog. The ferrite rod allows the coil to be smaller, and it can be moved in and out of the coil for coarse tuning.

• A variable capacitor (30 to 160 picofarads)

  We carry this in our catalog. You can also find them in old broken or discarded radios.

• A Germanium diode (1N34A)

  We carry this in our catalog.

• A piezoelectric earphone

  Also in our catalog.

• Two alligator jumper wires

  We use alligator jumper wires here for convenience. They are used to connect the ground and antenna wires to a good ground and a long wire antenna. We carry these in our catalog.

• About 50 to 100 feet of stranded insulated wire for an antenna.

  This is actually optional, since you can use a TV antenna or FM radio antenna by connecting our radio to one of the lead-in wires. But it's fun to throw your own wire up over a tree or on top of a house, and it makes the radio a little more portable.

• A block of wood or something similar for a base