FlexRadio-8600 + Maestro C Test Results - Robert Sherwood, NC0B

Netas Ameba

Hi

http://sherweng.com/table.html

73

Netas Ameba

W2PP

ouch

Mike-VA3MW

Rob Sherwood's receiver test data table is one of the most cited resources in the ham radio world, but it's also one of the most misread, mostly because people jump straight to the "narrow spaced dynamic range" column and rank radios like a leaderboard without understanding what that number actually represents or where it stops being relevant.

Why it needs multi-parameter interpretation

The headline number, third order dynamic range at 2 kHz spacing, tells you how a receiver handles two strong signals close together, which matters a lot in contest and DXpedition pileup conditions but is nearly irrelevant for casual ragchewing on a quiet band. Sherwood also lists wide spaced dynamic range (20 kHz), which is a completely different scenario, closer to what you experience with a strong local AM broadcast station or a nearby ham running a kilowatt on another band segment. A receiver can be excellent at one spacing and mediocre at the other, so picking one column and ignoring the rest gives a distorted picture.

Then there's the noise floor (MDS), phase noise, IF filtering characteristics (roofing filter bandwidth and rolloff), and AGC behavior, all of which interact with each other. A radio with a fantastic dynamic range number but a mediocre roofing filter can still fall apart in a real pileup because the roofing filter is what actually protects the ADC and downstream stages from being swamped in the first place. Phase noise close to the noise floor matters enormously for weak signal work near a strong signal but barely shows up in the headline dynamic range spec at all.

There's also the practical reality that these numbers are measured under lab conditions at specific spacings and specific signal levels, so real world performance depends heavily on your actual RF environment. A station on a quiet rural QTH with no local contest stations nearby is never going to stress a receiver the way a multi-op contest environment does, so the "best" radio on Sherwood's list may be functionally indistinguishable from a mid pack radio for a lot of operators.

Also, keep in mind that these are bench tests. SuperHet Radios (anything not direct sampling such as FlexRadio) suffer from serious IMD products in crowded band conditions. You can actually hear the artifact when listening to a CW contest due to all the product mixing in the front end. This is why Roofing filters are so critical for a contest radio.

Direct Sampling radios, such as FlexRadio do not suffer from IMD mixing products since you are not mixing radio signals to get to the audio frequency you need to hear. In fact, the work better in crowded band conditions.

Gerald explains why here:

https://youtu.be/VN3uxuExIng

Why it says nothing about the transmitter

Sherwood's testing is purely a receive side evaluation, and that's by design, not an oversight. It measures the front end and IF chain performance of the receiver, which historically was the differentiator between radios because transmit chains were comparatively simple and well understood (drive a PA to rated output, keep distortion products down).

But a full station's on air quality and courtesy to other operators depends just as much on transmit side factors: ALC behavior, processor and compression settings, opposite sideband suppression, carrier suppression, IMD products from the PA, and how clean the signal is under SSB voice peaks or full break in CW keying. None of that shows up anywhere in the Sherwood table.

This matters practically because a station can have a top of chart receiver and still sound terrible on the air if the operator runs excessive audio processing or the PA is driven into compression, and conversely a radio lower on Sherwood's list can be a perfectly courteous, clean transmitting station. The list answers "how well does this radio hear" and nothing about "how well does this radio talk," which is really a separate and equally important half of the station's contribution to band conditions.

There is no discussion on these key parts:

• SmartSignal - Adaptive Predistortion
• CESSB - Controlled SSB for for RF power out
• Ease of Station Integration
• Remotability
• ESSB up to 10Khz if you desire

Let us know if you have any more questions.

John KB4DU

this relates to my main frustration with the chart. It cannot by sorted by column to see the relative rank order of the various parameters.

W2PP

Mike is of course correct. I had the top rated radio but as Bob Sherwood has said many times…. It’s ergonomics!! So if the radio is hard to use then what good is it?

Peter

Netas Ameba

Hi

Thanks to Mr. Michael, VA3MW for comprehensive commentary and all the information.

ARRL Lab. Tests Results, Mr. Sherwood Tests Reports - before buying, CQ WW DX & others - after. ☺️

73, Netas Ameba

Flex-8600-1f.pdf

NC0B-CTU-2026-2m.pdf

Netas Ameba

Hi

I'm sorry for off topic.

73, Netas Ameba

https://www.youtube.com/watch?v=COq7v5pk96w

Rob Sherwood

The Sherwood lab test of the Flex 8600 & Maestro does have data on SmartSignal.
It is possible to download the Sherwood table into Excel and sort on any column.
Some cleanup of the Excel spreadsheet may be required.

Andrew O'Brien

Good to have Rob's analysis . I watched one of Rob's videos about his measures a few months ago . My take is that a Flex compares well to many of the top 20 and that the average human brain operating a radio will see very little difference in perceived performance. With that in mind, my additional take is that the extra boost up the Top 20 Charts should go to Flex for convenience , and modern day "ergonomics" . That is why I came back to Flex after a 7610 , and back again after a FT-710 , I just missed how easy Flex hardware mixes with the software it is supported by . Andy K3UK