[CQ-Contest] How to rigorously test transmitter audio equalizer settings from [donovanf]

James Cain jamesdavidcain at gmail.com
Mon Oct 19 17:02:59 EDT 2020

This is what I get for having The Onion and cq-contest near each other in
my Favorites list.

cain K1TN


Hi Alan,

Have you applied for DXCC Challenge yet?
More than one hundred PVRC members have.
Sixty members have more than 2000 and six members have more than 3000
30 PVRC members have 6 meter DXCC.
Who says PVRC isn't a DX or a VHF club?

Your equalization practices are the same as mine. All of my microphones
are either ModMics or Heil HC-5s. The frequency response seems to be
essentially identical for both microphones. I don't use HC-4s any more,
but they were great for old generation radios without equalizers.

I don't change equalizer settings between operators, although that
might marginally improve our audio quality. Its just too complex
with dozens of operators.

We used a "blind" audio testing process to initially set my
K3 and FTdx5000 equalizers for HC-5s and ModMics.

What's blind audio testing?

The tester uses a transmitter (K3 or FTdx5000) into a dummy load.
It could also be done by transmitting into an antenna with the listener
at a different QTH on a dead band so you don't disturb anyone.

The tester has long list of audio equalization settings to test. Each setting
is tested at least three times, randomly scattered throughout the sequence
of equalizer settings to be tested.

The tester says "CQ Contest CQ Contest Whiskey Tree Lima Papa Lima Alpha"
for the first equalizer settings

Then "CQ Contest CQ Contest Whiskey Tree Lima Papa Lima Bravo"
for the equalizer settings to be compared to Alpha

He repeats this three times before going on to the next equalizer settings in
the list.

(in contests we never say three, we always say tree )

A skilled SSB operator listens on a separate receiver connected to an antenna
with normal background antenna noise. His only response to the tester
is Alpha (is better), Bravo" (is better) or X-ray (no discernable difference).
The listener is not allowed to know what equalizer settings correspond
to A and B. The tester writes down each A, B or X response from the listener

The listener hears about a S5 signal, only about one or two S-units above
the antenna noise.

The tester runs through a long list of alternative equalizer settings,
never telling the listener what the settings are. Each equalizer setting
is repeated randomly many times until the blind listener provides
consistent results.

The listener replies with only: Alpha or Bravo or X-ray

Voila: after about 15 minutes of A vs. B vs. X blind testing you get
your final equalizer settings!


More information about the CQ-Contest mailing list