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Modem Circuits
 

Last Updated: October 09, 2017 03:39 PM


Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

300/1200 baud BAYCOM MoDEM (revision & improved) -  Schematic only, no circuit description __ Designed by Guy Roels ON6MU

56K RF Modem -  This is a prototype of the WA4DSY 56KB RF modem.  It is intended for use on amateur packet radio networks.  The modem generates RF in the 28 to 30 mhz range and requires and linear transverter to convert the signal to a UHF or microwave ham band.  The digital interface is synchronous serial.  The modem supplies TX and RX clocks.  For more details see the various links below.   __ Designed by Dale Heatherington's Ham Radio, Electronics and Robotics Web Site

9 pin (Female) Nullmodem Cable -  Circuit only, no circuit description included.   __ Designed by Tony van Roon  VA3AVR

9600 Baud Packet Radio Modem -  The conventional packet VHF/UHF radio data rate is 1200 baud because all TNCs provide an internal modem for this speed, and the two-tone AFSK audio spectrum suits unmodified voiceband radios comfortably.  However all TNCs can generate much higher data rates, and most FM radios have an unrealised audio bandwidth of some 7-8 kHz or more.  So in many cases 9600 baud radio transmission is entirely practical with them. __ Designed by James Miller G3RUH

ADSL Modems that Use the LT1886 as a Line Driver Yield Long Reach & Fast Data Rates -  DN240 Design Notes__ Linear Technology/Analog Devices

AeroComm CL4490 Experiments -  Wireless data networking experiments using AeroComm modules and data modems.  __ Amateur Radio circuits from Green Bay Professional Packet Radio

AFSK 1200 Modem Based on PIC16c620 -  Schematic Only__ 

Build a HamComm Data Slicer -  Until recently many of the ham radio operating modes required specialist equipment that most often had to by build and was exclusive to the task.  Enter the Personal Computer.  The PC made life a little easier for the ham as it was now able to take over some of the jobs that bespoke hardware did.  But it still wasn't quite there yet.  The task of the PC was mainly to be a 'front end' to a now multi capable bespoke box__ 

Connect a Modem to a Basic Stamp -  09/16/99 EDN-Design Ideas - The 2400-bps modem in Figure 1 makes it easy to connect a Basic Stamp (Parallax Inc, www.parallaxinc.com) to a telephone modem.  Using this circuit, you can call home via your PC and find out if the house is still there.  The Basic Stamp2, BS2-IC, has the necessary programming space, and a 64-kbyte StampMEM memory-storage board enhances site data collection.    __ Circuit Design  by Ken Gracey

DSL Filter (phone-line) -  The above diagram is a standard low-pass telephone line filter (L1, C1, L3, C2).  L2 and L4 are needed since we're dealing with the 'Tip' and 'Ring' of a phone line which may carry up to 90VAC! __ Designed by Tony van Roon  VA3AVR

E10-G RS232 Modem -  How to connect a PC RS232 moden to you Pocket PC__ Vassilis Serasidis

FSK Modem with PIC16C84 -  schematic only __ Designed by shaunwilson19 @ yahoo.com

HAMCOM & SoundCard MODEM interface for digital modes using serial- or soundcard audio -  Ham Radio - Modems and Soundcard interfaces - schematic __ Designed by Guy Roels ON6MU

HAMCOM (SSTV, RTTY, FAX, PSK31...) modem using PC-speaker for TX -  Ham Radio - Modems and Soundcard interfaces __ Designed by Guy Roels ON6MU

HAMCOM (SSTV, RTTY, FAX...) modem using serial audio for TX -  Ham Radio - Schematic - Modems and Soundcard interfaces __ Designed by Guy Roels ON6MU

HamComm Modem interface -  I have recently done quite a lot of work on RTTY, using the HamComm program and been so impressed that I made a PCB to support the program.  I think that I will continue to use the software, so I have registered it with the programs author: W.  F.  Schroeder, DL5YEC has obviosly put so much work into it.  The program will send and receive RTTY up to 300 bauds as well as sending and receiving CW.  I am very impressed with the programs ability to __ Designed by Harry Lythall-SM0VPO

KD2BD Pacsat Modem -  The KD2BD Pacsat Modem is a low cost, high performance 1200 bps BPSK modem designed to interface between a packet radio terminal node controller (TNC) and an amateur satellite ground station, and allows full-duplex access to the 1200 baud "Pacsat" constellation of amateur satellites. __ Designed by John A. Magliacane, KD2BD

Modem-access adapter reduces interference -  EDN-Design Ideas - 07/22/1999   The modem-access adapter (MAA) in Figure 1 has features that reduce problems when modems and phones share the same line.  The design also overcomes the shortcomings of modem interference protectors.    __ Circuit Design  by Thomas Schmidt

Null Modem cable 9-pin -  Circuit only, no circuit description included.   __ Designed by Tony van Roon  VA3AVR

PTT and soundcard interface for the TM255/455 -  Ham Radio - Modems and Soundcard interfaces __ Designed by Guy Roels ON6MU

PTT and/or soundcard interface -  Ham Radio - Modems and Soundcard interfaces __ Designed by Guy Roels ON6MU

Supervisory Monitors-modem connection -  04/09/98 EDN-Design Ideas - (Scroll to find this circuit) In telemetry or security applications in which a modem connection automatically establishes itself between two systems, a failure in one of the systems can interrupt the data exchange while the connection remains established until someone physically breaks the line or restarts the failed system.  This situation __ Circuit Design  by J Basilio Simies and Jorge Landeck, Instrumentation Center of the University of Coimbra, Coimbra, Portugal

The KD2BD Pacsat Modem -  The KD2BD Pacsat Modem is a low cost, high performance 1200 bps BPSK modem designed to interface between a packet radio terminal node controller (TNC) and an amateur satellite ground station, and allows full-duplex access to the 1200 baud "Pacsat" constellation of amateur satellites. __ Designed by John A. Magliacane, KD2BD

TM-441 9k6 packet Modification -  Schematic only __ Designed by Guy Roels ON6MU


Modem Circuits

 


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