Vesper Cortex after a few months

The Vesper Cortex has been one of the most anticipated devices in the marine world for over a year. I've had one for a couple of months now, and have had the opportunity to use it daily while out cruising.

This is a companion discussion topic for the original entry at

Hi Steve - the site looks nice! I really like your home page drone shot :slight_smile:

Regarding both the Cortex and VHF radios in general, it would sure be nice if we could figure out a way to do a meaningful technical evaluation of the radio itself. By this I mean stuff like power output - frequency accuracy/stability, receiver sensitivity AND selectivity, IMD performance, etc. This would be a good place to see what’s up with the squelch settings, too :slight_smile:

So much of these reviews are (of necessity, sadly) subjective - and what seems fine for you in your area might be a disaster for me in mine (particularly things like receiver performance). In my case, I removed a GX1600 from my helm and put in an IC-M506, because the IMD and other noxious noises I was getting in populated areas was making me crazy! The difference has been significant.

Thanks for all the free ice cream!

S/V Atsa

Hi @Hartley - thanks for the kind words!

It would be nice to have a rig to test all of the radios side by side. Even then, though, a lot of performance would still be dependent on mounting location, quality of power/connections, and of course cabling and antennas - location, placement, quality, etc.

At least for me, I try to test these things with one change at a time, and with the same base hardware and environmental conditions possible. For instance, I used the same antenna and cabling with the Vesper Cortex, Standard Horizon GX-2400, and an ICOM model that I’ve forgotten (can look it up in the test data) to see how things performed.

Even longer term than that, I’ve been using the Cortex since early 2020 with the Standard Horizon GX-2400 attached to the splitter port on the Cortex, and both radios on pretty much 24x7. The Standard Horizon out performs the Vesper in terms of transmit, receive, and of course in squelch control. Hopefully over time Vesper will tweak this, but a lot of it is dependent on the hardware they already have in the system.

They have been talking about some really nice features coming where you can “listen” to multiple channels simultaneously - not scanning like current radios do. That could open up some better features and functions, but ultimately if they don’t fix the squelch issues, it won’t really matter.

Hi @Steve!

Performance will always be dependent on installation specifics, though as you have done, comparisons using the same antenna, vessel, etc. do help. But there are waaay too many radio models to try to install them all in one vessel to compare, and then you would only be looking at the specific challenges that vessel faces.

In the 2-way radio world (where I came from), manufacturers are expected to publish a number of relevant specifications, as measured by the EIA/TIA-603 standard (for FM radios). This allows a potential purchaser to examine which equipment performs best with the challenges they feel are most important. Things like IMD susceptibility or spurious receiver response might be of considerable interest, for example, to an urban-area user, while power output and receiver sensitivity might be of greater concern to a rural user. Some users might be more concerned with temperature stability or ruggedness - everybody is a bit different :slight_smile:
Unfortunately, manufacturers of marine VHF radios do not often publish the more difficult-to-measure specs, so we’re left rather in the dark.

For sure the Cortex’ squelch difficulties should be a huge black mark for such an expensive bit of kit - basic radio functions should work flawlessly at this price point (IMHO) and no amount of fancy features compensates for this.

I hope you are enjoying an wonderful Thanksgiving with your family today!


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True, but you could test the top 5 radios in relatively the same conditions and have some very useful data. One of my day jobs for years was performance testing networking equipment, and while that sort of testing is useful to see overall maximum performance, the products never really performed that way in the real world. I think using things in real world conditions is more interesting for many reasons, but it is true that one could not test every radio all of the time.

Very true, and it would be great to have more information from them.

The way squelch works has been discussed as a designed feature. Instead of someone having to tune it manually, Vesper wants you to let the radio do it for you. They also said it was done in a way to simplify it for common users - instead of having to learn about squelch, they can just pick one.

While I have seen some people not understand squelch, it’s not a hard concept to learn, and relatively easy to tune. I don’t generally mess with mine that much unless I am trying to hear something very distant or with a poor signal.

Nevertheless, the way it works now makes for a lot of missed audio and Vesper needs to offer an alternative - even a manual adjustment for “advanced” users would be better than what we have now.

I ate far too much! I hope you had an enjoyable day as well!

Hi Steve!

[Man it sure gets busy this time of year!] I even got to pay a visit to Atsa, which is languishing on the hard in freezy-cold Maryland. It seems we forgot to bring our HD tarp with us, so I had to bring it North and install it. Took the rest of the time doing yet more prep work for the LiFePO4 install, which will happen whenever Victron gets the battery itself there…

In a “normal” FM receiver, squelch works by measuring the amount of “quieting” (i.e., reduction of noise) at an audio frequency well above that used for voice comms - something maybe in the 8-12 kHz range. Since quieting is a fairly good representation of signal strength/quality, they work fairly well and predictably. Drifting EMI, of course, can fool them into thinking there is a legit signal present, and the presence of high-frequency noise in the detected audio (from interference mixing, for example) can cause them to close on a readable signal. If Vesper can use DSP to make a better squelch, that’s a good thing, but if users are aware that the squelch is malfunctioning, that’s not a good sign.
On HF-SSB, a reliable squelch can be surprisingly difficult, since the “quieting” approach doesn’t work on AM. Olde-tyme HF radios used a signal-strength squelch, but they really weren’t very good (ask an ancient mariner how the squelch on his olde 2-6 MHz AM Marine radio circa 1955 worked and you’ll get an earful!) Some modern SSB radios use a DSP squelch that attempts to discern a human voice from all the beeps and gronks that infest the HF airwaves - the squelch in the Mobat MICOM-3 radios we use at work is not bad, really - though it isn’t perfect. There’s a reason why digital calling schemes abound (not just DSC) for HF comms.

I think we agree that it would be nice to have manufacturers supply more in-depth specs for their radios - even if relatively few users understand or would use them. For someone with a specific interest - say, operating in an RF-intense location (like a major city harbor) could try to isolate the best radio for their mission. Alas, I fear we won’t see much change here :frowning:

And it would take a fair investment in equipment to do much in-depth testing - stuff like power output, current draw and transmit frequency accuracy are fairly easy, but receiver performance measurement beyond raw sensitivity is much more intense.

So have a Merry Christmas and a Happy New Year out there and we’ll see what 'ol Santa has in store for us next year!


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Well, I was looking around the Internet today, and it seems I will need to eat my own words! I was looking at fixed VHF radios, and every one of the models Defender carries had at least some useful specifications listed! Some, like the new Icom M510, had a very complete list of specs (and this allows you to see why the M510 costs 3X what the GX1800 does :)) Progress!


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Well that is good news!

I’ve had an M510 for a couple of months and am really liking it. I’ll do a write up on it soon.

I figured you would find the WiFi remote hookup irresistible :slight_smile:

I’m actually not a fan of any WiFi bits in VHF radios other than the Cortex, and even the Cortex has some issues. Most of the other VHF radios have implemented it poorly, mostly for remote handsets, and charge lots of additional $ for their antennas or other bits you need. They never seem to work reliably, and always have some issue.

I was really interested in the M510 for the excellent ICOM reputation and the clear display. The little wireless add-on box has been not that reliable, and while nice, is definitely another example of a poorly implemented WiFi thing on a VHF radio.