HF Radio Circuit Modifications and Repair Information
Find schematics, repair guides, and homebrew projects for various HF transceivers and receivers, including popular models from Icom, Kenwood, and Yaesu.
Many hams enjoy working on HF radios, whether it's building a new rig from scratch, modifying an existing transceiver, or bringing an older classic back to life. This category focuses on the technical aspects of HF equipment, offering practical advice for operators who like to get hands-on with their gear.
Operators can find schematics and construction details for homebrew QRP SSB transceivers and CW transmitters, like the 80m ceramic resonator VXO. There are also extensive resources for popular commercial radios, including modifications for improving power output on a Sierra transceiver, fan mods for the Icom 706MKIIG, and troubleshooting guides for common issues like the ICOM IC-746PRO's dead TX problem. You can also find detailed information and user groups for classic rigs such as the Yaesu FT-101 and Kenwood TS-830S.
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40 meter transmitter by K9GDT -
A semi-homebrew QRP CW transceiver project based on the ARK-40 kit, enhanced with a BASIC STAMP BS-II microcontroller for knob-type tuning and an LCD -
This circuit is unique in that it uses a power mosfet as a final rather than a conventional bipolar transistor. -
40 meters band 5 watts transmitter, uses a 6L6 with a 6X5 rectifier and a 0D3 voltage regulator tube on the screen. -
This is a SSB and CW transceiver for the 80m and 20m bands. It produces 25 Watts out and uses a digital frequency display. -
80 metre ceramic resonator VXO CW Transmitter by VK1PK -
This low power transmitter is developed for ARDF exercising purposes but of course can be used as super QRP transmitter either. With 1 or 2 meter wire as antenna and a ARDF receiver with ferrite-rod antenna the range is about 100m but with better antennas and a 'real' receiver the range is probably much larger. -
This a well performing, simple two band transceiver. The transceiver design is inspired by the S7C superhet. A dual-band transceiver with a crisp receiver and a clean SSB signal -
An easy to build 6 watts SSB transceiver for 14MHz. BITX is an easily assembled transceiver for the beginner with very clean performance. Using ordinary electronic components and improvising where specific components like toroids are not available, It has a minimum number of coils to be wound. -
OZ9FW CDG2000 High-end transceiver homebrew project -
Circuit diagrams drake tr7, Schaltbilder Drake Tr7, antenna tuners, baluns, and home brew power supplies, dual tone ssb test generator, zweiton ssb test generator, zweiton testgenerator, dual tone test generator by DK4DDS -
Yaesu FT-101 Users Group purpose and scope is to serve as a sort of benevolent, protective, mutual aid and social club, essentially for the purpose of interchanging information, ideas, experiences and problems. By and for owners of Yaesu amateur radio equipment. Founded in 1972 by Amateur Radio operator Milton Lowens N4ML -
How to keep from being out of band -
Visit the legendary FT-847 FAQ pages ! You'll find a huge knowledgebase especially for the Yaesu FT-847 Transceiver. -
Programming software, diagrams, radio mods, secrets, service manuals for Motorola, Yaesu, Kenwood, Icom, Alinco. A large collection of ham radio equipment data also known as Ham.dmz.ro -
XLS file with technical specifications about ham radio transceivers -
Continuos coverage HF Transceiver by I6WJB & I6YPK -
This page describes a homebrew QRP SSB transceiver built by WB9IPA. -
External Amplifier Keying from the IC-706 by Bob Wolbert, K6XX -
How to replace the lithium battery in this ICOM radio -
The ICOM 746-Pro has acquired a history of NEC 1678G (IC-151) MMIC and driver transistor 2SK2975 failures. The failure of IC-151 appears to be a combination of ESD damage from electrostatic charge on the antenna entering IC-151, and perhaps thermal heat. -
Detailed instructions for modifying the ICOM IC-706MKII transceiver to enable out-of-band transmit capabilities across HF, VHF, and UHF segments. -
The purpose of this web page is to try to investigate the ICOM IC-746PRO Dead TX problem reported by many radio amateurs through out the world; and unfortunately not properly taken care of by ICOM. If you are the owner of either the ICOM IC-746PRO or the IC-7400 you may already have experienced the Dead TX Issue. If not you may sooner or later. -
All about the JRC NRD-525 receiver. Modifications, review, manuals, tipd and tricks -
Technical reference about Accessories, Amplifiers, Antennas, Cable and Connectors, Filters, Geography, Grounding, Gunk, Matching Networks, Projects, Propagation Info Radios, RFI/EMI, Rotors, Station Setup, Towers. -
Kazmo’s Kustom Kreations a cool accessory - aka Outboard Heat Management Project by w4kaz -
An assortment of Amateur Radio-related technical articles written for the JUG, the newsletter of the Northern California Contest Club. Topics include unique but simple and useful radio modifications and accessories, and rig reviews. -
Lot's of info on 950sdx tranceiver by Jeff King ZL4AI/DU7 -
The Kenwood TS-950S and TS-950SD HF transceivers are fine radios. However, many, if not all, of them were produced with a design flaw which allows the RG GAIN control to cease function in the presence of a strong signal IF the AGC has been turned OFF -
Kenwood TS-830 manual, tips and fixes -
Contain schematic diagram of many different radio, and some operations instructions. -
Mizuho Tsushin Co. was a small Japanese manufacturer of QRP radios and kits, shortwave receiver accessories, and AM broadcast band receiver kits and antennas -
Designed to handle audio signal interfacing as well as transmit/receive switching Reviewed by Steve Ford, WB8IM -
The following transceivers can be susceptible to damage from a strong RF field (or RF-overload) IC-746 IC-746PRO IC-756 IC-756PRO IC-756PROII IC-756PROIII n1eq explain why -
Kenwood, Icom, Yaesu, Sony, Uniden Bearcat, Wilson MARK II & IV -
This is a collection of emails collected over time which indicate how to put some mods into your Sierra transceiver. Most of the mods have to do with improving the power output. -
Sommerkamp FTDX500 - Yaesu FTDX400 restoration -
An Homebrew 10 Meter transceiver -
Build a 5 watt, 80 meter QRP CW Transceiver Designed by N1HFX -
Increase TS 480 PEP power level -
A Yahoo! Group for Kenwood TS-850S HF transceiver owners, facilitating discussion, technical information sharing, and support among hams. -
Born as a companion transmitter for the Yaesu FRG-7 receiver has become a stand alone tramsmitter for 160 meters band -
How to build a complete Single-Sideband amateur radio transceiver from scratch. Article published on hackaday dot com includes an introduction to radio architectures, ssb receivers and tramsitter -
A quick fix for a Yaesu FT-757GXII blank display -
This article describes the construction of a high performance transmitter and receiver for SSB (voice) communication covering the 14MHz (20 meters) high frequency amateur radio band with output range 15 to 20 watts and a top audio sound quality both on transmit and receive. -
Kenwood schematics diagrams in high resolution format, includes Kenwood TS-830S , TS-820S and TS-520S -
This transmitter was first constructed in 1987 and provided the author with his first real rig, capable of distances of more than about 100 metres.Use a 6GV8 tube. -
Home made 40 meter transceiver project. The receiver is a Progressive Receiver with a few modifications. The Transmitter is a modified MFJ Cub circuit. Includes schematic and circuit diagrams for Receive Input Filter, 3-Pole 500 Hz Cohn Filter and 7 MHz Double Tuned Bandpass Filter -
Recently, at the Ballarat Hamfest, the author acquired an old Marine transceiver for just $10, charmed by its sturdy construction and waterproofing. Made by Findlay Communications in Sydney, this crystal-controlled transceiver had been dormant but was reinvigorated with minor fixes. A manual was sourced, and further repairs were made, including an ingenious crystal oscillator replacement using an Si5351a controlled by an Arduino. The refurbished radio, complete with a fresh coat of paint and added customizations, is now operational for 160m AM and 30m SSB. A successful and cost-effective restoration. -
This transmitter covers the 160, 80, 40 and 20 metre bands and provides both SSB and properly generated CW. The CW side of this transmitter is not compromised and produces excellent CW. On SSB the audio has been tailored to provide a rising response to 3 KHz, with a sharp drop above that frequency. There is RF speech clipping to both provide more "punch" and to limit the peak output. -
The FT101ZD DDS VFO project replaces the original VFO in the Yaesu FT101Z/ZD rigs with an AD9850 DDS module, providing enhanced frequency control. It uses the original optical encoder and clarifier for compatibility, with a custom 6V power supply modification. The project includes selectable step sizes, a frequency save function, and works with both RX and TX modes. The design involves mechanical and electronic modifications, including SMD components and a custom PIC processor. Calibration ensures accurate frequency output, with further improvements under consideration.
