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Free programmable LOW/HIGH/BANDPASS FIR filter in the audio range 0-4kHz

K9AY loop antenna installed at PA6Z Contest group. This is a receiving antennas for the low bands (160m, 80m and 40m). Include schematics and info on a building the control box, preamplifier and low-pass filter

A free computer aided design program to help users without special expertise in filter design to create filters using Linear Technology's monolithic filter ICs. With FilterCAD, you can design lowpass, highpass, bandpass and notch filters

Duplexers for dual band radio are usually high pass filter and low pass filter combined in the same box. This circuit is a design within a cost of US$10.

CW Skimmer 2.1 employs a high-sensitivity CW decoding algorithm based on Bayesian statistics, enabling simultaneous decoding of up to 700 CW signals within a receiver's passband on a 3-GHz P4 system when paired with a wideband receiver. The software features a fast waterfall display with sufficient resolution for visual Morse Code interpretation, automatically extracting and labeling callsigns on the waterfall traces. Extracted callsigns are exported as DX cluster spots via an integrated Telnet cluster server. The application includes a DSP processor with a noise blanker, AGC, and a variable-bandwidth CW filter, alongside an I/Q Recorder and player. It supports both 3 kHz radio passbands and wideband SDR receivers like SoftRock, RF Space SDR-IQ/SDR-14, SRL QuickSilver (QS1R), HPSDR Mercury, and Microtelecom Perseus. System requirements specify Windows XP/7/8/10 (32-bit or 64-bit), a Pentium-4 2.5 GHz for wideband operation or 1 GHz for 3-kHz radios, a COM port for CAT control, and a stereo sound card supporting 48 kHz sampling. It integrates with Elecraft KX3, Icom IC-7300/IC-7610, and Flex 6000 series radios, with documentation available for various setup configurations.

Freeware real time DSP filter particularly for applications of amateur radios , IIR, FIR filter, low-pass, high-pass, band-pass filter, band suppressor (notch filter) individually adjustable

Stacking and phasing HF and 6m arrays antenna switches and contesting devices. Custom low band antenna arrays, bandpass filters,commercial/Mil STd filters,microwave components, commercial broadcast filters.

Manufacturer of communications antennas, bandpass filters, RF combiners, receiver multicouplers, diplexers, duplexers, RF connectors, RF circulators, RF isolators, RF couplers and SWR meters

Sharing beverage antennas with this switch boxes is possible. This article describes a 6-position remote antenna switch for Beverage antennas on 3 bands (160m, 80m, 40m). It allows selecting one of 6 antennas for each band without affecting other receivers. The system uses a control box with a rotary switch and a separate splitting box with bandpass filters for each band.

Do your multiple-transmitter field day or contest efforts suffer from intrastation interference ?

TVI and BCI bandpass and bandstop filters in SMD technique. Schematics and images.

HotPaw MorseDecoder, an iOS application, provides real-time translation of Morse Code audio signals into plain text, leveraging the device's microphone or headset input. It incorporates a DSP narrow-band audio filter, adjustable from 300 to 2400 Hz, to mitigate background noise and QRM, enhancing signal clarity for decoding. The application offers both an automatic decoding mode and manual controls for fine-tuning parameters such as audio filter frequency, WPM dot/dash speed, noise threshold, and Farnsworth timing. The WPM detection automatically adapts from 8 to 40 WPM, with a QRQ High Speed mode extending this range to 30-80 WPM for faster code. A built-in spectrogram aids in identifying the precise audio frequency of the CW tones. User feedback indicates effective performance with various transceivers like the Yaesu FT-857 and Icom IC-R8600, particularly when manual settings are optimized. The app's ability to visually tune stations within the passband and decode speeds beyond an operator's manual capability has proven beneficial during contests and general QRP operation.

These inexpensive, easily built filters can be the buffer you need between the signals you want to hear and send and those you don't!

The page provides detailed information on coax stub filters for multi-transmitter setups, including specific lengths for different bands and types of coax. It also references additional technical notes for further analysis.

Constructing a Lindenblad antenna for 137MHz NOAA satellite reception involves specific design considerations for optimal performance. The resource details the use of 4mm galvanised steel fencing wire, 300-ohm television ribbon cable, and wood/plastic components for the antenna structure. Key dimensions for a 137.58MHz-resonant antenna are provided, derived from the ARRL Satellite Handbook, specifying s, l, w, and d as 42, 926, 893, and 654mm respectively. The antenna is designed for Right Hand Circularly Polarised (RHCP) signals, requiring the four folded dipole elements to be tilted clockwise by 30 degrees. A significant aspect covered is impedance matching between the antenna's 75-ohm impedance and a typical 50-ohm receiver input. A twelfth-wave matching transformer, constructed from 117mm sections of 50-ohm RG-58 and 75-ohm RG-59 coax with a 0.66 velocity factor, is described. The article also addresses coaxial cable and connector selection, recommending 75-ohm Type-N connectors for RG-6 cable in professional setups and F56/F59 connectors for general use, while strongly advising against PL-259/SO-259 connectors for VHF. Strategies for mitigating Radio Frequency Interference (RFI) are discussed, including antenna placement to shield from local TV transmitters and the use of commercial or DIY band-pass filters, such as cavity resonators or helical notch filters, along with ferrite chokes on coaxial cables. Antenna orientation is explored, noting the Lindenblad's 'cone of silence' directly overhead and its maximized sensitivity towards the horizon. An experimental vertical tilt of 90 degrees is presented as a method to improve overhead reception and reduce interference from strong horizontal signals, particularly relevant in high RFI environments like the Siding Spring Observatory site.

Band-pass filters can be critical components in competitive stations. This setup may help put your station on the map.

High speed silicn diodes work well as RF switches. This article describes how to use diodes for selecting two or more filters ARRL QST article by W1FB

This is a 6 band receive only filter designed to protect your receiver front end and provide 45dB reject at the stop bands. This is a 6-band receive only filter designed to protect your receiver front end and provide 45dB reject at the stop bands. Stop band reject may be limited by the relay isolation. Worse case isolation is at 28 MHz or 35 dB or better. Relay K3/K8 protects the filter during transmit via the PTT line. A 25-50ms delay must be used between transmit and PTT. Do not rely on your radio to provide adequate delay with out using the PTT. You logging software must be set to allow a delay between PTT and time of 1st transmit. This filter will not work with VOX or QSK keying as you will damage the filter.

The document is a technical guide on designing RF filters for radio frequency applications. It covers topics such as interference suppression, band-pass filters, and low pass filters, with a focus on filter design and circuit filters.

Manufacturer of single band and multiband transceiver bandpass filters for HF. High pass filters, two radoi headphones mix and switch, 6 meter portable antenna, antenna remote switching and steering.

Part 2 You're now much closer to saying goodbye to your unwanted signal problems!

UK manufacturer of ham radio accessories, including TNX, SDR receivers, RF Diplexers Triplexers, bandpass filters, iambic memory keyers.

Diplexer is a passive device, a special filter circuit that seperates 2 different bands, not to be confused with the duplexer that usually separate 2 different frequencies on the same band.

The Rock-Mite is a 40m CW kit offered by Small Wonder Labs . It features built-in keyer, direct conversion receiver with a crystal RF bandpass filter, 500 milliwatts of power, and switchable frequency offsets to work around QRM

A home made antenna tuner based on the W6JJZ basic concept that ,atches balanced loads without the use of lossy baluns, can provide band-pass filtering and harmonic attenuation.

A homemade tunable bandpass filter for all HF bands from 160m to 10m

Fill out the form to design a bandpass filter as described in the January 1985 issue of Ham Radio Magazine. These filters are generally limited to frequencies above 200 MHZ because their size is slightly longer than 1/4 wavelength

Project of receive only filters optimized for minimal loss and very high rejection of frequencies below 75% of the filter center frequency by K1TTT

Project to build sets of band pass transmitting filters for reducing the interference between HF transceivers operated in close proximity

A K9AY loop antenna project done with Far Circuits pc boards for the antenna switch and bandpass filter and preamp by K7SFN

Third-order Cauer filters can boost performance of multi-transmitter, multi-operator contest stations to the next level. The filters are practical and you don’t need expensive test equipment to align them.

Tips on winding wire coils used as inductive loads, traps, band-pass filters, are implemented in a number of amateur radio projects especially antenna projects

Australia's largest range of Electronic Kits & Components In Stock for the Radio Experimenter, ATV, microwaves, HF Band pass filters

A simple project for an effective home made band pass filter, designed for the portable field day usage

How to design narrowband bandpass filters

ScopeIIR: an Infinite Impulse Response (IIR) digital filter design tool for Windows. It designs high-order IIR filters based on analog filter prototypes, and can design lowpass, highpass, bandpass, and bandstop filters.

The direct conversion receiver described consists of only a bandpass filter, mixer IC, VFO and audio filter. With only 22 parts, this simple circuit should take a few hours at the weekend to construct.

Clean Up Your Signals with Band-Pass Filters

HF receiving systems and components, band pass filters, array controllers, HI-Z pre amplifiers

Will additional coax stubs improve Band Pass Filter performance?

Band pass filters, for radio frequency interference problems.

A homemade band pass filter for the 30 meter band based on the original VE7BPO design

HF Radio Preselectors,BCB filters,Low Pass filters,Band Pass filter

VHF Broadcast Passband Filter (88 108 MHz) by DF9CY

Homebrew Amateur Radio 440Mhz Interdigital Bandpass Filter

Passive Band-Pass Filter, low-pass filter calculator

Hand made RF sweeper made to adjust the pass band of crystal filter

These are QRP rated 3 Pole Butterworth filters based on a design by K4VX, feature simplicity, almost no insertion loss, and reasonable rejection on the other ham bands.

R3KBO is an amateur radio club producing and developing amateur radio kits and assembled products including HF VHF Power Amplifiers or RF Power Kits and amplifier parts, low pass filfers, band pass filters, sourge protections, splitters and combiners, antenna switches

The program can be used to calculate inductors (coils) and their number of turns on ferrite cores, ferrite shells and air coils. These can be used for baluns, Ununs, bandpass filters, low pass filters, resonant circuits, and more. The technical specifications of the cores are already integrated in the program. Application is free and runs on Windows 32 bit versions only. To make it run on Windows 10 64 bit need to be unzipped in a single folder.