National RF, Inc
National RF Inc offers State of the Art Radio Frequency and Unique Electronic Devices
- 858-565-1319
- 858-571-5909
- 7969 Engineer Road
Ste. 102
San Diego, CA 92111
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ELT STALKER Vector-finder
VF-121
The Vector-Finder Types VF-121 and VF 121A are unique in the Vector-finder series of direction finding antennas. They incorporate a proven design, electro statically shielded loop sensing element with modern solid state low noise analog and digital technology to allow detection and location of aircraft band signals. Both the VF-121 and the VF 121A incorporate a unique digital modulator which allows the user to more easily home-in on unmodulated carriers. Such cases occur at airports when transmitter may be accidentally keyed on during aircraft overnight layovers. The VF-121 is specifically designed to be used on airport premises where signal strengths are high. To compensate for very strong signals, an integral attenuator is also incorporated to allow the user to operate the unit close-in to aircraft. The VF-121A differs in that a high gain, low-noise preamplifier is utilized with the sensing element in order to hunt signals that may be weak or at a distance. The unit is ideally suited for the location of ELT transmitters in the field. Both units are tunable over the 118 MHz to 130 MHz aircraft frequencies and interface directly to the user’s aircraft band receiver or transceiver via the antenna jack. With the antenna system connected to the receiver, the user will hear the desired signal. If the signal is unmodulated, the digital modulator will generate a tone on the carrier. When the handheld unit is rotated about, an audible null on the received signal or the generated tone will be heard. This null aligns with the axis of the equipment case and represents the direction of the received signal. This direction may be read from the black dial compass mounted on the top of the enclosure. As the response is bi-directional, triangulation may be used to determine the true bearing when the true direction is not known.
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VHF Radio Direction Finding Antennas
Vector-Finder Series
The Vector-Finder Series of VHF direction finding antennas provide a compact, lightweight, active antenna, suitable for use in the field with handheld transceivers and scanning radios. The mechanical design allows the sense antennas to be folded back to provide a compact unit, easily stowed or transported in any vehicle. The system interfaces with any FM receiver or transceiver via the antenna jack and the earphone jack. Several different models are available to suit your pocketbook or unique field application, all of which operate on the phase shift technique. The VF-142Q models incorporate left-right indicators as well as an audible response from which the user can determine the true direction of the radio signal. The other types utilize the audible response generated by the equipment and heard on the user’s receiver or transceiver. All models operate from a 9-volt battery.
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Analog Power Supply
Type NPS-2412
National RF's Type NPS-2412 analog power supply was designed to be used in communication equipment where radiated switching inverter noise from conventional “switching type” supplies is not acceptable. The power supply consists of a standard rectified transformer output driving a pair of voltage regulators and filtering networks. The 2412 offers an adjustable voltage output between 2 and 24 volts as well as a fixed voltage output of 12 volts. A maximum of 20 Watts of DC power can be supplied from the unit. As the voltage regulators dissipate power in the regulation process, the power to the load is derated accordingly, dependent on the set voltage to the load. The adjustable regulator is a standard LM-317T integrated circuit device. The fixed regulator is a standard LM 7812 device. Upon customer request, the LM 7812 device may be changed to any voltage rating within the the LM-78xx series of regulators. Contact National RF for this modification if desired.
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GEOPHYSICS, SEISMIC, and ATMOSPHERICS RESEARCH RECEIVER
Type RAS-1
Called the RAS-1, the receiver is designed for ultra low and very low frequency scientific research work, including the exploration of low frequency emissions due to seismic and earth-quake activity, study of atmospheric phenomenon such as "whistlers", and low frequency Sudden Ionospheric Disturbance (SID) and electromagnetics phenomenon. The RAS-1 will receive signals from under 200 Hz. To over 250 KHz in both narrow bandwidth modes as well as broad badnwidth reception.
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FREQUENCY DISPLAY UNIT
TYPE NFD-1
The National RF Type NFD-1 Frequency Display Unit was designed for use with vintage and classic communications equipment, to display the received or transmitted radio frequency. The unit incorporates an internal processor that allows the intermediate frequency (IF) to be counted out by the frequency counter. The resultant display is the actual frequency that the equipment is receiving or operating at.
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MOD MONITOR
TYPE HFX-1
The Type HFX-1 Modulation Monitor is an ancillary piece of equipment, which is used with narrow bandwidth, or older oscilloscopes to allow viewing of RF signals and particularly modulated signals as high as 55MHz. The equipment contains an RF signal source and a broadband mixing circuit which converts the high frequency signal to an intermediate frequency within the oscilloscope’s range. The frequency control dial is simply adjusted until the RF signal is viewed on the scope. BNC connectors are mounted on the rear panel to allow interconnect to the scope and RF probe. This product was previously called "oscilloscope frequency extender" and may be used to view other high frequency signals on older or narrow band scopes.
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Resonance Dip Meter
NRM-2
National RF’s Resonance Dip Meter is a test instrument used to determine the resonant frequency of a tuned circuit or resonant network, such as an antenna system. In addition, the unit may function as an RF detector, or a secondary frequency source. The instrument is analogous to the older vacuum tube “grid dip meter,” once popular in every electronic laboratory or radio station. Unique to this updated version is a buffered output that may drive a digital frequency counter for exact measurement of resonant frequency, or connected to an oscilloscope to be used as an RF detector and waveform/modulation monitor.
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Portaquad
Type 2-MQ
The Type 2-MQ Portaquad is a high-gain, full size 2-meter quad antenna designed for portable operations. The mechanical design allows it to fold for stowage or transportation in a container. The container also acts as the antenna’s support base when the antenna is erected. After familiarity with the device is achieved, the antenna may be erected or collapsed in approximately one minute.
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Spectrum Marker Generator
NSG-2
National RF, Inc. is pleased to announce the production of a new device, the Type NSG-2 Spectrum Marker Generator. The generator is intended to be used with either spectrum analyzers or communications receivers to mark specific frequency intervals in the RF spectrum. When used with receivers, it is essentially a frequency calibrator, thus making it attractive for use with vintage receivers with analog dials. The NSG-2 provides a leveled amplitude output over nearly 100 MHz of RF spectrum, thus making it ideal to mark frequencies and signal levels on spectrum analyzers. In addition, it may be used with a spectrum analyzer, in lieu of a sweeping type generator, to align lowpass, highpass, and bandpass filters with passbands greater than 20 KHz.
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Attenuators
The National RF line of attenuators are compact, affordable attenuators which are ideal for insertion between a direction finding antenna and a receiver/transceiver, to aid in the DF process. In addition, they may be used in the laboratory for a low-power, in-line attenuation purposes. The affordable price is achieved by utilizing standard 5% tolerance resistors and commercial hardware. For laboratory purposes, an attenuation versus frequency curve (to 500mMHz) is provided.
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Mini Receiver
FB7-NX
In about 1935, the National Radio Company of Malden, Mass., brought out a “hot” high frequency receiver, called the FB7, and the subsequent FB-7X. It featured a super-hetrodyne design with plug-in coils that gave it a broad frequency range. The “X” model also incorporated a crystal filter in the intermediate frequency section, thus giving it additional selectivity. The receiver was viewed by radio amateurs as a technological breakthrough, and it was also used commercially for point to point high frequency communications. As the receiver did not have an internal RF amplifier section, a separately tunable RF amplifier was later provided in a separate enclosure for additional performance capabilities. Now, National RF, Inc., is resurrecting the fabled receiver name with an all solid-state, hot mini receiver, which also utilizes plug-in coils to cover the HF spectrum. The mini-receiver is designed for use by radio amateurs as well as serious short-wave listeners, and allows reception of AM, CW, and SSB signals. It incorporates a super-hetrodyne design with a dual gate FET built-in RF preamplifier and a ceramic filter for selectivity, often required when used in a crowded amateur radio band. In addition, the receiver has a buffered rear panel output of the high frequency oscillator for use with either a frequency counter for exact receive frequency display, or for interface with an outboard transmitter. A rear panel jack is also provided for muting the receiver when a transmitter is placed into the transmit mode. And, the receiver is small enough to fit into carry-on luggage and taken on trips when it is desired to “keep an ear” on amateur radio or other high frequency activity. The receiver utilizes rear panel plug-in coil assemblies which contain the RF amplifier, mixer, and oscillator tuned circuits. Each plug-in coil assembly also comes with a separate dial scale, which is inserted onto the front panel for displaying the tuned frequency. A very smooth 6 to 1 planetary drive is used for tuning the receiver. Other front panel controls include RF preamplifier peak, volume control, Beat Frequency Oscillator adjustment, and RF gain control. Other switches include filter bandwidth, AM/CW/SSB selection, Power, and a general coverage/band spread control for certain plug-in assemblies. The receiver is intended to drive head-phones via a rear panel jack, but has sufficient output to drive a small external speaker.
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VHF/UHF Handheld Signal Location Antennas
Type NVF-2
The Type NVF-2 series of handheld directional antennas are used to locate interfering signals or noise in either the 420 – 470 MHz (Type NVF-2A) or the 900 MHz ISM band or cellular telephone bands (Type NVF-2B). Both models incorporate a solid reflector positioned behind a resonated half wave driven element, both elements being mounted on a fiberglass rod with an integral pistol grip. The configuration of the reflector and driven element are such that a deep null in the signal being received will occur when the antenna is pointed in the direction of the signal being radiated. A T-pad resistive attenuator is also incorporated in the antenna mounting enclosure to aid in the direction finding process on very strong signals or when excessive reflections present multiple returns.
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POWER ATTENUATORS
TYPE ATF
National RF’s Type ATF Power Attenuators were designed to allow interfacing of linear power amplifiers to RF exciters, where a specific amount of drive to the amplifier is prescribed. Often, however, drive from the RF exciter exceeds this minimum prescribed level and some form of power attenuation must be used in order to not damage the input of the power amplifier. National RF’s type ATF-3 offers 3 dB of power attenuation (1/2 of the power) when used between the exciter and the amplifier and will handle an input power of 132 Watts, RMS (continuous power) while providing about 66 Watts RMS output power, when it is terminated into 50 ohms. In practice, the ATF-3 attenuator will handle exciters achieving Peak Envelope Power levels (PEP) in the area of 200 to 250 Watts while providing half of that power to the load. For less attenuation requirements, the ATF-1 and ATF-2 offer 1 and 2 dB of attenuation, respectively.
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Reference Antennas
Type NRD
Reference antennas are precision dipole antennas that offer a fixed 2.15 dB of gain over an isotropic antenna along the major lobe axis at specified frequencies (2.15 dBi). They are intended to be used for antenna field pattern and gain measurements, or general RF sensing in the laboratory.
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TURBO-TENNA 137 MHz Weather Satellite Antennas
WX-137 SERIES
The WX-137 series of antennas are marine-grade 137 MHz circularly polarized antennas designed to receive weather satellite images from the polar orbiting NOAA and Meteor satellites. Manufactured from stainless steel and ABS plastics, the assemblies are sealed and designed to survive marine service, although they may be used on land as well. Each antenna is available with or without a gasfet preamplifier which provides about 16 dB of gain and is physically located adjacent to the antenna.
