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Cavity filters are tipically circuitry behind a duplexer that allow only certain frequencies to pass

Homemade LC Bandpass Filters for 20M, 30M, 40M In multi-station environments like special events, field day, portable operating, is very important to protect receivers from excessively strong signals. Bandpass filters help to protect your transceivers.

Building the W3NQN bandpass filters

2 filter designs a 3-pole and a 5-pole

Couplings Designer for iPhone. Modern advanced filter synthesis using coupling matrix techniques. There's a free LITE version limited to 4th order filters.

Martek Power designs and manufactures a wide of high performance power supplies for various industries. Power supplies AC-DC, DC-AC inverters, DC-DC, EMI Filters

Offer performance comparable to tin-box filters, and except for being bigger, stack up pretty well with those expensive little helical jobs. You just have to be able to make your own PC boards.

The TVI filters described in this page worked very well in curing a TVI problem on 2m abd 70cm

Producers of custom name tags, luggage tags, club badges, Employee Name Tags, Special Event Badges, but also Comtech Amateur Radio Television Transmitters and Receivers D480 filters, Video cameras and accessories.

Examples of absorbtive low-pass filters in which the unwanted high-frequency energy is separated from the wanted output and then dissipated in matched resistors

How to limit unwanted harmonics from your raspberry Pi radio transmitter by introducing filters.

Modem Telephone Super Filters For HF and AM Radio Interference.

Custom EMI Filters, AC DC Three phase filters by Filter Concepts Inc.

Realization of confortable communications. RF Filters

Icom 706MkIIG Filters, Make a narrow CW filter work in SSB for the digital modes

A complete guide on using the HF amateur radio bands, and the differences with VHF, using filters, influence of solar weather, the split mode and phonetic alphabets.

an overview, introduction or tutorial about the basics of electronics filters including the types of filter and the various filter design considerations and parameters

Antuino is an accurate instrument that can be used in the field to measure SWR, field strength, modulation, etc. In the lab, it can be used to sweep filters, measure gain, distortion, frequency response, etc. It works upto 150 Mhz. On the third harmonic, it is usable on 435 Mhz band as well (with reduced sensitivity).

TyQSL is a modern Logbook by Hams, for Hams. A Place for other hams to take a look at your QSO statistics as well as search for QSOs in your Logbook that you made public. Just click onto your name in the Menu Bar when you are logged in to get to your public profile. Soma features includes Shows the users Valid Callsigns Look at QSO Statistics, Search Public Logbooks, Filters are avaliable to find QSOs fast Just share the Link on Social Media, QRZ, or Similar with other

Lightning Arrestors, High current filters manufacturer

WiFi Antenna, WiFi Amplifier, RF Splitters, RF FIlters, Adapter, Video Cable and Custom Connectivity Products

How to receive NOAA weather satellite with a home made QFH Antenna. This project includes some easy and efficient notch filters to suppress noise from FM frequencies

Anatech Electronics manufactures RF filters for communication systems, Military and commercial, as well as RF filters for Wireless applications. Products include, Band pass filters, Duplexers, Low pass, high pass and bandstop filters. Additional products such as RF cable assembly also available.

DC filters from radius power are specifically optimized for applications with DC supply like e.g. photovoltaic inverters. Radius Power provides total power solutions, EMI filters solutions from design to manufacturing, Three Phase, Single Phase, Power Line, IEC inlet, Power entry modules Filters.

Ceramic capacitors, inductor ferrite products, high frequency dielectric components like chip antenna and filters.

When operating contest in a multi transceiver environment interferences between the 40m and 20m are guaranteed. An easy and inexpensive way to reduce interferences is to add coax stub filters

Filters and replacement parts for the Drake R-4C receiver by Sherwood Engineering Inc

These band filters are based on 3 or 5 sections Butterworth band pass filters, maintaining 50 Ohm impedance, and when built around toroidal inductors, can be made very compact.

Telnet client for DXCluster, Sorts, colours and filters DX Spots by (2) bands, wanted DX Station, who spotted the DX, local to your area and more, Can spot automatically after logging a contact if you are using ZCZ Log, Look up call on QRZ.com

HyEnd is a dutch amateur radio antenna manufacturer. Makers of the popular HyEndFeed Antennas, produce Baluns, bandpass filters and selle Line isolators, coax cables and connectors.

Passive Bandpass Filter online calculator and filter formulas. Active Inverting Op Amp Bandpass Filters, Active Noninverting Op Amp Bandpass Filter, just enter the Low ir High Cutoff Frequency

A spectrum analyzer is always an usefull amateur radio test equipment that should be present in a radio shack. Hams can use it for testing frequency response of filters, amplifiers, and other two-port RF devices. This article illustrate a tracking generator compatible with any spectrum analyzer in the Tektronix 490- and 2750-series lineups

Ucchino is an Italian manufacturer of electronic cirucits inclunding Digiham amateur radio USB interface for digital modes, morse code oscillator, filters and RF protectors

Start by getting your audio levels sorted out, Having your levels correct is critical to maximum effectiveness in both TX quality and also for being able to decode signals properly. Guide to Filters and other Rig Settings to optimize your output signal

This multiband transverter project features power output at 13,8V 50MHz 15W, 70MHz 10W, second harmonic < 65dBc. Single N connector of antenna, suitable for a dual band Yagi. Article include Block Diagram for Dual Transverter and low pass filters

If your multiple transceiver station is suffering of intrastation interference, this handy and inexpensive band pass filters and help you. QST article Sept 1988

Online antenna parts store, providing many accessories for amateur radio antenna homebrewing. Boom joiners, aluminium parts, elements clamps, filters, ferrites, fasteners, plasti caps, dipole elements. Based in UL

Icom IC-R9500 Professional Receiver with 5 roofing filters, 48 kHz DSP

DXLook is a free, web-based propagation platform that delivers comprehensive, real-time insight into HF and VHF conditions directly from any modern browser. It aggregates live spots from PSK Reporter, WSPRnet, RBN, and DX Cluster, complemented by NOAA space-weather metrics such as SFI, K/A indices, and geomagnetic alerts. Integrated VOACAP predictions allow practical "theory versus reality" comparisons, while the interactive world map with filters, gray line, and grid overlays enhances situational awareness. With no installation or maintenance required, DXLook provides a convenient, accurate, and accessible solution for everyday operating and propagation analysis.

Amateur Radio goodies for not only the Shack, but also a range of outdoor/portable kit. Ferrite toroids, RTL SDR, Un-uns and Baluns for antennas and RF Filters. Based in the UK.

How to replace IF filters on a Yaesu FT 857. This document explains how to desolder old deteriorated filters and replace with brand new ones.

Transmission lines have many uses other than simply transferring RF power from one point to another. Impedance matching, baluns and filters are probable the most common of these.

Worldwide Map of shortwave transmitters. Based on shortwave schedule database, this website let you serarch using filters for broadcasts schedule and at the same time to diplay the transmitter map.

How to install INRAD filters on the FT 847

Custom built high and low power power band pass Filters, low band triplexers, triplexers and diplexers

This document details the construction, programming, and operation of a modular WSPR transmitter. The transmitter utilizes an ESP8266 NodeMCU, an SI5351 synthesizer with a TCXO for stability, and selectable low pass filters. Construction involves soldering headers, components, and assembling filter module. The ESP8266 is programmed via the Arduino IDE, requiring library installations and code modifications, including network credentials, callsign, and frequency . The transmitter is powered by USB or Vin terminals and its frequency is selected by jumpers and software settings. The document also covers FCC restrictions and how to use the WSPR network

This PDF article introduces a series of dual-tuned bandpass filters designed for input tuning in amateur band receivers. Developed by Stefen Niewiadomski, these filters feature 50-ohm input/output impedance and can be cascaded for improved roll-off outside the passband. The designs use readily available TOKO coils, with taps on the tuned winding for matching input circuits with impedances around 1k ohm. The inductors are core-tuned, with average inductance values provided for easier matching to other inductors.

Replacing two ceramin filters of a Yaesu FT-857 by desoldering and soldering new ones.

TFilter is a free online tool for designing linear phase, optimal, equiripple finite impulse response (FIR) digital filters. It utilizes the Parks-McClellan algorithm implemented in JavaScript. Users can specify the sampling frequency, desired number of taps, passbands, and stopbands to generate a filter. An example configuration is provided for easy testing.

This article explores the nuanced design challenges of Band Pass Filters (BPF) in radio receivers, balancing low insertion loss, high stop band rejection, and narrow bandwidth. The focus is on the "Series-Trap, Shunt-C" topology, resonator count impact, and meticulous layout design for superior stop band performance across various frequency bands