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AM-FM-SW Active Antenna - This simple little circuit can be used for AM, FM, and Shortwave (SW). On the shortwave band this active antenna is comparable to a 20 to 30 foot wire antenna. It is further more designed to be used on receivers that use untuned wire antennas, such as inexpensive units and car radios __ Designed by Tony van Roon VA3AVR
An 80 meter rig for the MAS contest by KD1JV - Designed to be competative in the DL 80M "Mininum Art Session" contest, this rig features a crystal controlled 2W transmitter and a sensitive regenerative receiver, using 51 discrete parts on a 3.5" x 2.5" circuit board. __ Designed by Steven Weber, KD1JV
An Audio Equalizer for Communications Use 234 kB PDF file - This five-band audio equalizer was originally designed for use at a multireciever site (a voting system hub). Originally published in the May 1990 QST __ Designed by Robin Humbolt WA4TEM
An Audio Limiter for NBFM use - This image is of a hard audio limiter used to limit the amount of deviation in an exciter. After the "knee" the compression ratio is infinite to 1 (hard limiter.) Smaller amounts of compression ratio can be achieved by inserting resistance between the output of the rectifier, and the DC input of the FET (gate.) This circuit can be used ahead of the processing in a standard exciter to add compression, or hard limiting.
The "R" and "G" are red and green led's. The op amp can be a 5532, LF-353, or TLO82. __ Designed by Kevin K. Custer W3KKC
An Audio-Noise-Based Voting - As hand-held transceivers (H-Ts) become smaller, and low power, battery conserving operation becomes more popular, the disparity between the transmitting range of a typical 100 watt repeater compared to the repeater accessing range of a typical 1 watt or less H-T becomes more and more apparent. How often have you found it difficult (or impossible) to access a repeater with a low power H-T even though you can hear the repeater at full quieting? This can happen even if the repeater is equipped with a high sensitivity, state-of-the-art receiver. __ Designed by Mark Kolber WB2WHC
An end-fed antenna - A piece of wire of almost any length can be used as an antenna on the HF bands. However, just because an antenna can be made to work is no guarantee that it will perform efficiently. This article will initially concentrate on the half wavelength of wire and its useamateur radio construction projects. __ Designed by Peter Parker VK3YE
An Inexpensive Tone Encoder - Figure 1 illustrates an easy circuit that can be constructed with mostly Radio Shack parts on any general purpose circuit board. The only rigid requirement is that capacitor C1 be stable over a wide temperature range. Use only Mylar, Polyester or Metal film for capacitor C1. The frequency is determined by the following formula: FREQUENCY = 1/R1C1The specified values should allow any tone between 100 to 300 Hz. Increase R1 or add another resistor in series with R1 for lower tone frequencies __ Designed by Radio Amateur Society of Norwich
AN-60-008 Operating precautions for RF Amplifiers - AN-60-008 App Note__ MiniCircuits.com
Antennas for Ham Transmitters - Describes how to construct various type of antenna for Ham Radio Transmitters
Audible S-Meter - hand-drawns schematic only __ Designed by byon Garrabrant N6BG
Audio Amplifier - SSB Transceiver-Receiver Section: The AF amp has about 60 to 70 dB of gain. The transistor is a BC109C. I might try replacing it with a lower gain device. A typical 59+ signal, gives more than a volt pp at the collector. The power amplifier IC is an LM380N (14 pin version). If you intend to use the rig on CW, the LM380N must be powered up on transmit as well as receive (for the sidetone osc.). __ Designed by EI9GQ homebrew radio
Audio Buffer & De-Emphasis - Use this circuit after a repeater receiver to de-emphasize the audio going to your controller. __ Designed by Lou Harris N1UEC offsite link
Audio Equalizer for Communications Use 234 kB PDF file - This five-band audio equalizer was originally designed for use at a multireciever site (a voting system hub). Originally published in the May 1990 QST __ Designed by Robin Humbolt WA4TEM
Audio Limiter for NBFM - This image is of a hard audio limiter used to limit the amount of deviation in an exciter. After the "knee" the compression ratio is infinite to 1 (hard limiter.) Smaller amounts of compression ratio can be achieved by inserting resistance between the output of the rectifier, and the DC input of the FET (gate.) This circuit can be used ahead of the processing in a standard exciter to add compression, or hard limiting.
The "R" and "G" are red and green led's. The op amp can be a 5532, LF-353, or TLO82. __ Designed by Kevin K. Custer W3KKC
Automicro RX3304 receiver Module schematic - Schematic Only __ Designed by Peter Jakab, Electrical Engineer, Engineer of Informatics
Aviation Band Receiver - Figure 1 shows a schematic diagram of the Aviation Receiver--a super heterodyne AM (Amplitude Modulated) unit built around four IC's: an NE602 double balanced mixer (U1) , an MC1350 linear IF amplifier (U2) , an LM324 quad op-amp (U3) , and an LM386 audio amplifier (U4). In operation, an antenna that plugs into J1 picks up the AM signal. That signal is then coupled through C1 to a three-section, tuned-filter network consisting of L1-L5 and C2-C6 __ Designed by Tony van Roon VA3AVR
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