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Exploring the Inovonics 674 AM Monitor Receiver

Useful features should appeal to those working with or for AM broadcasters

As the radio broadcast ecosphere shifts towards streaming and digital delivery, the number of new products for the AM broadcaster seems to be on the decline. That’s why it was a delight when Inovonics unveiled their 674 AM Monitor Receiver in 2019. Part of the INOmini series, the 674 fills the niche for a versatile but inexpensive AM confidence monitor.

This software-defined DSP receiver has many cool features. 

As a global product, it can either tune in 10 kHz increments for the Americas, or 9 kHz increments for Europe. Audio outs are available in analog and digital, each with independent level adjustments. 

The multicolor, backlit LED display continuously shows received signal strength and audio levels. Combined with the jog wheel, this display also facilitates system setup. The 674’s programmable front-panel alarms with rear-panel tallies indicate low or no signal and audio program loss. 

Alarm conditions also cause the display to flash against a red background, a move guaranteed to get your attention. Tweaks and upgrades to the firmware are easily uploaded through the front-panel USB port.

Around back, there’s an F connector for the 50 ohm antenna input as well as terminals for the alarm tallies, including ground, +5 volts, low signal and audio loss. There’s also an AES digital audio output and analog line outputs labeled left and right. 

And no, analog AM stereo is not making a comeback, these are really dual monaural outputs that are adjustable from –15 dBu to +15 dBu. The logic behind the left/right nomenclature is that most studios are wired for stereo, whether the programming is or not. 

Finally, two paralleled coaxial power connectors can take the +12 VDC and daisy-chain it to two additional INOmini devices, useful if the 674 is rack mounted with two companion units.

The front-panel headphone jack will accommodate any stereo phones with a 3.5 mm plug. When the headphones are plugged in, the LCD menu will automatically switch to the headphone volume screen, and you can adjust volume with the knob. Press the knob again and you’re returned to the previous menu. 

Menu screen 6 gives a bargraph presentation of program audio level. The meters are peak-responding with a floating peak-hold function. One-hundred percentcarrier modulation corresponds to 0 dB. 


As  a practical matter, the 674 can operate with just about any type of antenna. The 50 ohm antenna connector is insulated from the rear panel to create a quasi-balanced configuration. The instructions recommend connecting the shield to an external ground. 

Getting a strong, interference- and noise-free signal can be difficult in some locations, and Inovonics offers as an option the 637-01 passive AM loop antenna, with a figure 8 pattern, which can assist with some of the more challenging AM reception environments. 

Two menu screens determine how the 674 will sound. The standard NRSC truncated 75 µs de-emphasis may be switched in or out. The manual suggests making a decision based on which sounds best to you. A second screen enables selection of  IF bandwidth. Your options are 2, 3, 4 and 6 kHz. These settings mark the –6 dB points. 

Your selection is really a tradeoff between background noise and fidelity, with the 6 kHz setting being as close to high fidelity as you’re going to get. 

The days when you could troubleshoot broadcast equipment and make the repairs yourself are long gone. As with most modern gear, the Inovonics 674 is designed around surface-mount technology and chips with firmware, so the company recommends returning equipment to the factory for repairs. 

Nevertheless, curiosity dictates that it be taken apart just to see what it looks like inside. The board work, sheet metal and paint jobs are all up to Inovonics’ usual high standards.

Our evaluation 674 performed well with a long-wire outdoor antenna. The use of the traditional cold water pipe as an antenna ground turned out to be ill-advised. Smart meters dump large amounts of noise into the ground wiring. A stake driven into the ground outside the window worked much better. 

As expected, local stations could be set for NRSC off and 6 kHz with good fidelity and no noise. The AGC range of the 674 is broad enough to seamlessly handle day/night power reductions and antenna pattern changes. Although not intended for DXing, distant stations can easily be received, and are listenable with NRSC on and reduced bandwidth. Of course, noise from summer electrical storms is always a problem.

While the firmware in the 674 works as expected, other features could make it much better. As it stands, there is no way to store settings for multiple stations. That could make it inconvenient for users who work for a cluster. A preset function would also be useful if you want to do an A-B comparison between your station and the competition for the purpose of setting up audio processing

While the 674 is geared to a global market, the display is only offered in English. A menu selection of languages might make it more user-friendly outside the United States and other English-speaking countries.

Your happiness with the 674’s performance may depend to a large degree on how much thought and planning has been put into its antenna. Back in the day, a frightening number of stations used a short piece of wire and a clip lead as an AM antenna for EBS and EAS boxes, and even for mod monitors. It was never a good idea. 

Today, the proliferation of smart meters, LED and fluorescent lights, computers and switching power supplies all combine to create very high noise levels across the LW, MW and SW frequency bands. An outdoor antenna connected to the 674 via coax is almost mandatory for good reception. 

PRODUCT CAPSULE: Inovonics 674

Monitor Receiver

Thumbs Up

+ Independent audio level controls for analog and digital outputs

+ Programmable front alarms with rear-panel tallies for low signal and audio program loss

+ De-emphasis and IF bandwidth options for best audio quality

Thumbs Down

– English-only display

– No presets or easy to A-B compare stations

Price: MSRP $880


Contact: Gary Luhrman at Inovonics at 1-831-458-0552 or visit