Mark V

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Keyclick and Noise Blanker Mod for FT1000MP MK V by W8JI

Download Keyclick and NB Mod Information by PA1JR

Key Click Mod Report by IC8POF

 

Preliminary tests show very strong keyclicks +1kHz and -1kHz. The LSB clicks peak 500Hz below the TX frequency, and the USB clicks  (in the LSB mode) are very obnoxious because they are at twice the rate as LSB clicks (strong on both make and break).

The FT1000MK V shows a 1mS rise and a 2ms fall with sharp edges and a very poor rise and fall slope.

 

It's great to see a manufacturer offer improved close-spaced SSB transmit performance. The MK V Yaesu reverses other modern radio's downward spiral of transmitter SSB IM performance. Yaesu included a class-A mode. Unfortunately close-spaced receiver performance has been neglected, and this affects all modes. The transmitter also has nasty CW clicks. Stock MK V's appear to be as bad as or worse than older 1000 series radios in two important areas:

  • Clicks appear to be more severe than those from the notoriously poor 1000MP's

  • The noise blanker continues with the same circuit error as the FT1000/1000D/MP series

Since a portion of the keyclick mod requires accessing the same general area as the noise blanker, it would be prudent to fix the receiver and transmitter at the same time. This article offers a combined modification that patches both problems.

 

Keyclick Problem

Raised- sine rises and falls would provide the fastest possible CW speeds for a given bandwidth. With properly filtered rise and falls, we would hear little or no change or softness when listening on-frequency. Tuning off- frequency, clicks would quickly vanish.

If you want to hear the sound of proper shaping, listen to this click-free signal recording as I tune across the signal. Off- frequency (even a few hundred hertz), we hear no clicks at all. On- frequency the CW is "hard" sounding, allowing copy to 60-WPM or more. When the tone disappears in the deeper receive filter's skirts, clicks also disappear. In contrast, compare the MK V recording as I tune past the signal. This signal is from Europe on 40 meters!  There is a day-and-night difference off frequency between the no-click and loud-click signals. On-frequency both signals sound the same. 

 

MK V clicks are caused by excessively fast rise and fall, and very poor shape of the rise and fall.

Rumors sine-shaped waveforms impact tone or readability of signals are false, as are claims clicks rolling of at some "X-dB-per-octave rate" beyond a few hundred Hz are a necessary part of life. Such statements are misleading, likely being based on the incorrect assumption the receiver has very wide bandwidth and the transmitter is filtered through a single stage simple resistor-capacitor click filter.   

Unfortunately when we patch poor CW transmitter designs, we can not make perfect corrections. Without major modification we can not modulate the MK V ( or most other transceivers) with properly filtered (which also means perfectly shaped) rise and falls.  This modification, like the MP and 1000D click mods, is a patch...not a cure.

 

Patches Vs Cures

Because mods on existing radios are patches, the radio owner must make a choice. If the user operates speeds faster than 45 or 50 WPM, the rise and fall required for legal close- spaced operation may be less than ideal. This does not mean the ability to work weak signals at modest speeds (up to 30 WPM) would be compromised even the slightest amount. It means high- speed ops (speeds over 45-50 WPM) may find the CW slightly mushy when adequate for close-frequency operation.

If a 2 or 3 millisecond rise and fall is used for operation at very high CW speeds in a single-pole R/C filter (this radio uses a simple RC filter) a transmitter is almost guaranteed to interfere with less strong signals within 1kHz or so. Transmitters with fast rise and fall times should stay at least 1.5kHz away from operators working weak signals, especially when the CW transmitter has 1930-era transmitter CW  shaping.

Operators with stock MP MK V's should always try to operate at least 4kHz away from weak or moderate signal- level stations. Part  97 rules prohibiting keyclick emissions that interfere with adjacent frequency operations. The specific rule is 97.307(b) "Emissions outside the necessary bandwidth must not cause splatter or keyclick interference to operations on adjacent frequencies." 

 

The Click Mod

The actual click mod requires changing two stages. The first stage modified is on the IF board. The IF mod slows the rise and fall of mixer transistors Q2033 and Q2038. Note: This stage is easy to modify, and is located on the same board as the noise blanker. This allows the noise blanker to be corrected at the same time.

By itself, modification of the easy-to-reach IF board is NOT effective for substantially reducing clicks. A later stage on the RF board also has truncated rise-and-fall times with a very poor R/C edge-shaping system. This later stage continues to add clicks even after earlier stages are modified. RF amplifier stage Q1001 has the fastest rise and fall in the RF section. Q1001 must have proper gate bias shaping and timing to reduce clicks to acceptable levels. Removing D1002 and altering components around Q1002 slightly reduced clicking, but I concluded any effort wasn't worth the result with bias rise and fall more rounded at Q1002. 

 

As designed, Yaesu uses a square wave very rich in harmonics to drive a simple R/C filter. This poorly filtered square wave amplitude modulates the RF and IF sections. The poor basic filtering design, combined with non-linear amplitude response, requires great care in component selection. It also means we never will achieve the optimum bandwidth for any give rise and fall time and ultimate CW speed.

 

The NB Problem

Signals inside the wide roofing filter BW of the MK V reach the gate of Q2009 through C2043. This point precedes the narrow 8MHz IF filtering, allowing a rather wide swath of unwanted signals to reach the gate of Q2009. Q2009 is left operating even when the noise blanker is turned off, and can have substantial gain depending on bias voltages at TP2001. Bias voltages at TP2001 can be varied by changing menu settings for NB gain, but never fully turn off Q2009. 

The accumulated level of all signals reaching the gate of Q2009 produce a large net voltage at the drain of Q2009. This voltage (and resulting net current) causes overload and distortion in the non-linear characteristics of Q2009 and 2010 (my manual has very poor printing, but I believe it says 2010). 

New signals created by this distortion and the resulting mixing products are fed back through C2043 to the IF strip. The IM products appear as "phantom splatter" on SSB and " phantom signals" on CW. We can not actually hear the distortion on frequency of strong signals. Instead the IM products appear in the form of artificial interference when we attempt to copy weaker signals within 10kHz of a mixture of signals containing a few moderately strong signals.

 

The NB Patch

The NB mod is a simple effective mod, and improves close-spaced IM3 dynamic range around 10dB. A simple factory change of moving one foil trace would have made the MK V receiver noticeably better, but fortunately this mod is fairly easy for owners.

The NB correction removes the surface mounted  220-ohm resistor (R2046) from the source of Q2009, replacing it with a 220 ohm resistor connected between Q2009's source at C2027 and Q2016's (2SC4047) collector and the junction of R2049 (220-ohm also).

 

Making the Mod

This mod is a little more complex than the FT1000MP mod because the chassis of the MK V is a little more complex and unfriendly. Like any service work, having a clean open bench and a spot to separately store screws and other hardware removed in every step in order will make the job smooth and easy. (If someone sends step-by-step text, I'll put it on this page.)

Some may wish to remove and change parts, but I prefer to wire the click-mod to a single terminal strip. This will allow you to customize the mod, switch the mod in and out, or correct any errors without dismantling the entire radio.   

You'll need the following parts:

(1) one foot each of two small insulated wires, #20-#26 one ( preferably) green and one blue to make connections

(1) four-lug (with ground) terminal strip

(3) .1uF 50 volt disc capacitors (C1-C3)

(1) 22k 1/4w fixed resistor (R2)

(1) 680k 1/4w fixed resistor (R1)

(1) 220-ohm 1/4w fixed resistor

In addition you need a well-lit bench, along with some hand-tools such as soldering pencil and solder, screwdrivers, and cutters and strippers.

Populate the terminal strip as follows:

 

Remove top and bottom covers to gain access to internal circuitry

Remove the screws holding the IF board in place, and the minimal amount of plugs to allow flipping the IF board over. Draw a roadmap of all plugs that must be disconnected. This will help you remember where everything goes!

 

(click here to download expanded IF board if needed)

                                                                   

Attach one end of the blue wire to the ungrounded end of C2148, let the other end float

        

Locate and remove R2046.

Add the 220-ohm resistor to the Q2009/C2027 source and capacitor connection point 

Connect the other lead of this resistor to the junction of Q2016's collector and R2048.

Reinstall the IF board with the flying lead exiting the closest edge of the PC board. 

(Take care to avoid pinching any wires.) 

Remove all hardware necessary to access the RF board

Remove the RF board

(Click here to download an expanded view of  RF board if needed)

                                                                                                  

Attach the green wire to the junction of C1004 and R1003/R1004 at the gate of Q1001

Route this wire up to the area of the IF board

Reinstall the RF board and all other hardware taking care to not pinch any wires, and to reconnect all unplugged wires in proper locations 

Select a clear area on the IF board and mount the terminal strip under the screws

Connect the green wire (from RF board) to C3, and the blue wire from IF board to the junction of C1 and R1. R1 is a 680k resistor, and R2 is a 22k resistor

Test the radio and reinstall the covers

 

 

This site was last updated 08/21/07