TRANSCEIVER  PERFORMANCE:  

ANOTHER  LOOK

Adam Farson, VA7OJ / AB4OJ  has been professionally testing radio transceivers and receivers for over 50 years.  Though perhaps not as well known as some of the others, Adam's work reports some of the most valuable data availble to the amateur radio community.

Before looking at a brief summary of Adams work, followed by direct links to his extensive library of useful documents, let's first look at how others have been measuring receiver performance.

INTRODUCTION (by DJ0IP) :

For the past 15 years, hams interested in receiver performance (or a transceivers' RX performance) have consulted Rob Sherwood's Receiver Test Data list as the leading indication of receiver performance.

Rob's list is sorted according to the radios' two-tone third order dynamic range performance (DR3).  Indeed DR3 'was' a good indicator of receiver performance for a number of years.

In 2012, the ARRL began focusing on Recipricol Mixing Dynamic Range (RDMR), stating that in many cases, RMDR is the limiting performance factor, so this number is more representative of the radio's performance than DR3. 

Although they had been testing RDMR since 2007, they had not highlighted it as much as it deserved. In 2012 that changed.

In addition to RDMR and DR3, the ARRL also pointed out that Blocking Gain Compression Dynamic Range is also an important measurement.

More Info:  ARRL TEST PROCEDURE MANUAL 2010

Three Imortant Measurements  

Which one is most indicative of the radio's performance?

Simple answer:  ALL THREE .  .  . but wait, there's still more to the story:  "NPR"

N P R

Noise  Power  Ratio

The tests highlighted above are lab tests using two strong signals generated by a pair of high quality, low noise RF generators. 

Of course in real life, nobody uses their radio to listen to a pair of signal generators.

On-The-Air, things can be quite different from the conditions in the lab. 

On any weekend it seems there are hundreds of 59++ signals on the band.  On contests weekends there seems to be thousands of them!  Under these conditions, some radios with good lab measurements may still be a poor performer.  

Another lab measurement, NPR, stresses a radio similar to what we might expect to find on the band on a contest weekend.  Whereas DR3 and RMDR use a pair of 59+(?dB) signals, NPR tests with the equivilant of 1200 signals with 59+40dB signal strength.  This ultra-stress-test is clearly the better indicator of how a radio will perform on a crowded band.

Unfortunately, a radio with an outstanding DR3 or RMDR can still have a low NPR.  The FTdx5000 is a good example of this.

It is imortant to understand that no single performance measurement

is an absolute indication of the radio's true On-The-Air performance.  

In addition to the four performance measurements listed, there can be several other factors which determine the radio's ability to be used effectively over a longer period of time.  These include things like low audio distortion (on receive), intuitive menus, overall ease of use, etc.

And finally, according to Rob Sherwood, the NUMBER ONE determining factor in choosing a radio for 'YOU' is, you gotta enjoy using the radio!

The Bottom Line:  No single measurement and no list can fully represent receiver performance.  Anyone making purchasing decisions based on looking a a list is kidding themself and possibly throwing good money after bad performance!

Now let's look at what Adam says about Receiver Performance.