Topband: Receivers, Noise Blankers and Key Clicks

[Tom Rauch]

Hi Joe,

You are correct. Close spaced performance has long been neglected for both
receivers and transmitters. That's why it important we keep pressure on the
ARRL to publish close spaced results in the main review pages, not in some
hidden "expanded test" that is difficult or impossible to read and
understand. The real problem is we have no way to know what is good or bad
until people start using the radio in large numbers!

I've tried to make it commonly known the FT1000 family (and other Yaesu's)
suffer from an engineering oversite. They have an FET amplifier hanging off
the IF amplifier before the narrow filters, and they don't turn that FET's
gain down when the NB is not used. What this does is deteriorate close
spaced IM performance a substantial amount when the FET has maximum gain,
even when the NB is OFF.

In the FT1000 and D, this occurs ALL the time. You have to make a change
inside the radio to stop the problem.

In the FT1000MP, you can cure almost all of it by turning the front panel NB
gain control to zero when not using the NB. No change is needed.

In the FT1000MP MK V, you have to go into a menu and change a NB setting to
reduce NB gain. The only reason the MK V tests so much worse than other
top-end Yaesu's for narrow spaced signal performance is the menu setting of
the NB. Moving one resistor to a new location eliminates the need to get
into the hidden menu to change NB gain.

I have mods telling how to fix the MK V and the 1000D on my website.

The same problem occured in a FT990 I looked at, so I'm pretty sure it is a
wide problem where the same basic NB is copied from one radio design to
another radio design without correction.

Of course leaving an IF NB on will kill any radio for close spaced (less
than 20kHz or so) performance.

As for DSP radios with wide roofing filters, it is pretty well known most
have substandard close-spaced performance. You only need to check tests to
see how they do.

73 Tom