Garmin bills its new echoMAP CHIRP models as a series of “entry-level” combination sonar/GPS units with built-in CHIRP sonar technology, but I think the term “affordable” fits better.

We covered CHIRP here a while back, but let’s take another look at it and review why it’s important to our boating and fishing.

CHIRP stands for Compressed High-Intensity Radar Pulse. The technology first appeared in radar and might have stayed there if not for some engineers at Airmar Technology Corporation.

Airmar manufactures transducers and other sensors for recreational, commercial and military use. Apparently, somebody at Airmar was looking at CHIRP radar and, instead of just wondering if it could be adapted to sonar, he and some colleagues made it happen.

Here’s how it helps: Sonar has traditionally broadcast signals at one frequency, waited for echoes to return and then constructed readings from them. High-frequency signals tend to deliver better detail, separate targets better that are closer together, and perform better at higher boat speeds — and that’s a lot of “betters.”

Unfortunately, high frequencies don’t penetrate depth as well as lower frequencies. Also unfortunately, lower frequencies penetrate to greater depths with ease but don’t offer as much detail, can’t separate targets as well and have problems with higher boat speeds.

One approach to solving this problem has been to use dual-frequency units that could operate on a high frequency when detail was more important than depth reach and switch to a low frequency when looking deeper was more important than screen detail.

You could even use a split screen view to see both high and low frequency readings side by side.

Enter CHIRP. Instead of transmitting just one frequency CHIRP transmits a continuous sweep of frequencies, ranging from low to high and then interprets their echoes individually as they return.

So, CHIRP uses a whole range of frequencies and then digitally processes them to take advantage of the best attributes of each.

Since a range of frequencies provide a broader source of information, CHIRP can create crisper fish arches with greater target separation, even in deeper water — and do it all better at higher boat speeds.

Like Garmin’s previous echoMAP models, the echoMAP CHIRP series is available with 4-inch, 5-inch, 7-inch and 9-inch bright, color displays and are all keypad controlled.

Each has a built-in, high-sensitivity, GPS antenna that updates your location and heading five times per second. Model numbers with a “dv” suffix include Garmin’s CHIRP DownVü down-scanning technology with photo-like screen pictures in both freshwater and saltwater. Models ending with “sv” also have Garmin’s SideVü side-scanning feature offering the same photo-like detail off both sides of the boat.

All models have one NMEA input and output port.

The 7-inch and 9-inch models also support Garmin’s new Panoptix feature with real-time sonar imagery that can show fish up to 100 feet away swimming up and down, and nearer and farther away from the boat at video-like speed.

Models are available with preloaded cartography for U.S. or Canada LakeVü HD inland waters or U.S. BlueChart g2 coastal mapping. The U.S. LakeVü has a database of more than 17,000 inland lakes, reservoirs and rivers, including more than 13,000 lakes with high-definition, 1-foot contours shore-to-shore.

The echoMAP CHIRP series models all come standard with Garmin Quickdraw Contours, a software feature that lets you create personalized, high-definition fishing maps with 1-foot contours on nearly any body of water. You can make custom, up-to-date maps of your favorite spots and even correct coastal maps that haven’t been updated since the last hurricane.

The maps are formed as you move around and fish. You don’t have to send anything in and wait; the map just appears on your screen. These maps are yours, and you can share them or keep them to yourself at no cost.

Following is a breakdown of the differences between echoMAP CHIRP models.

The series starts with the basic 42dv ($299.99 MSRP with transducer). The first character in an echoMAP CHIRP unit’s model number designates its screen size, so this one has a 4-inch screen and all models with 4-inch screens have 482 by 272 pixel resolution.

The 42dv is CHIRP down-looking and CHIRP DownVü capable, but is available with or without a transducer. The second character in each model number indicates what kind of cartography comes with the unit. Those ending in “2” come without any special preloaded maps but — like all the models in the series — they have a port for one microSD card, and mapping can be added.

The echoMAP 43dv ($299.99) is a step-up model packaged with a one-piece CHIRP down-looking and DownVü transducer. Garmin’s U.S. LakeVü HD inland maps come preloaded.

Garmin’s echoMAP CHIRP 44dv ($349.99) is similar, but comes preloaded with BlueChart g2 U.S. Coastal charts.

Don’t order any echoMAP unit with a model number ending in “5” unless you want a unit preloaded with Canada LakeVü HD maps.

Want a bigger, 5-inch screen? The basic echoMAP CHIRP 52dv ($499.99 with transducer) has one with 480 by 480 pixel resolution. Like the 42dv, it comes with or without a transducer, and has no preloaded mapping but mapping can be added.

The model 53dv ($499.99) has the same screen and comes with a conventional down-looking/DownVü scanning CHIRP transducer, and is preloaded with Garmin’s LakeVü HD inland maps.

The echoMAP CHIRP 54dv ($499.99) is the same unit and transducer, but it is preloaded with BlueChart g2 U.S. Coastal cartography.

As we get to the models with wide, 7-inch screens, we also get 800 by 480 pixel resolution. The echoMAP CHIRP 72dv ($799.99 with transducer) includes a worldwide base map for general reference, and is available with or without a transducer.

All models with 7-inch or 9-inch screens support Garmin’s Panoptix LiveVü Forward feature when you add the optional Panoptix transducer. 

The 73dv ($699.99) comes with a CHIRP conventional down-looking and DownVü transducer, and is preloaded with U.S. LakeVü maps.

Garmin’s echoMAP CHIRP 74dv ($899.99) is similar, but comes preloaded with BlueChart g2 charts for the coastal U.S. 

Starting with the basic echoMAP CHIRP 72sv, the model numbers follow the same pattern but the “sv” designates that SideVü technology is also built-in.

The 72sv model has an MSRP of $1,099.99, including an all-purpose transducer for down-looking, DownVü and SideVü operation. It has only the worldwide base map for general nav reference.

The 73sv ($999.99) with transducer has preloaded U.S. LakeVü HD inland maps, and the 74sv ($1,099.99) with transducer comes with BlueChart g2 charts for the coastal U.S.

The units with 9-inch screens (800 by 480 pixel resolution) follow the same model numbering pattern, but all of them include SideVü capability.

The echoMAP CHIRP 92sv ($1,249.99) is the base version, with all-purpose transducer and with only the worldwide base map for general reference.

The 93sv ($1,199.99) includes the all-purpose transducer and is preloaded with U.S. LakeVü inland maps, while the 94sv ($1,299.99) with transducer is preloaded with BlueChart g2 U.S. coastal charts.

Visit garmin.com for more information on this new series and the features they offer.