FB7-NX Mini Receiver


General Information about the FB7-NX Mini Receiver

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.

The FB7- NX is offered with two coil sets when purchased. These are the designated Coil Set B and C. Coil Set B is focused on the 75/80 meter Amateur Band, while Coil Set C covers the 40 meter amateur band. Both offer some coverage of international shortwave frequencies on either side of the amateur radio bands. Once a coil set is inserted, a front panel switch allows selection of a more “general coverage” frequency range, or the desired amateur band that the coil set is designed for. See the technical specifications section for the frequency coverage of the coil sets. Additional coil sets will be provided in the future for other frequencies of interest.



Receiver Type: Single Conversion solid-state Super-Hetrodyne design, incorporating 3 IC’s, 2 FET transistors, and one bipolar transistor. Frequency is determined by the plug-in coil module inserted into the receiver.
Frequency Range:

Coil Set B
Approximately 2.7 MHz to 5 MHz in two front-panel switched positions. 

Coil Set C
Approximately 4.5 MHz to 7.8 MHz in two front-panel switched positions.

Tuning Drive: 6 to 1 planetary reduction drive.
Intermediate Frequency: 455 KHz.
IF Filter: Ceramic: Broad response about 9 KHz, Narrow response about 6 KHz

Minimum Discernable Signal (MDS): Approximately -107 dBm (1 micro-volt at 50 ohms), with receiver in CW/SSB mode.

Input level for +10 dB Signal to Noise response (SNR): Approx. 5 micro-volts (-94dBm)

Measurements made at 10 MHz on the engineering development prototype receiver.

Audio Output: Approximately 250 milliwatts into 8 ohms. Rear panel stereo jack (connected in parallel for monaural response) provided for interface with headphones, which must be provided by the customer.
RF Input Connector: BNC female
Front Panel Controls: Audio Volume, Beat Frequency Set, RF Preamp Peak, RF Gain, Band Switch, Filter Control Switch, Power Switch.
Rear Panel: RF Input BNC, Audio Output jack, Plug-in Coil jacks, 9Volt Battery connector, Battery Mount. 1/8 inch mono jack for High Frequency Oscillator output, 1/8 inch mono jack for receiver muting.
Power: Single 9 volt battery, either or Alkaline or Lithium recommended. Battery mounted on rear panel.
Mechanical Size: 4” wide, 5” long, 2” tall, plug-in assembly and battery attached.
Enclosure Material: Aluminum



Type FB7-NX mini-receiver with Coil Sets B and C $379.95
Shipping and Handling to within the US $10.00

An additional Shipping Charge will be required for all overseas orders and determined after receipt of the initial order.  The additional charge will be determined, based on the country where it will go, and the amount will be emailed to the customer at that time.

California residents will be required to pay sales tax.

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