How to make your TS-940S sound (and hear) "bodacious"

[N8YX]

As delivered from Kenwood, the '940 incorporates a Murata CFJ455K-12 filter in the SSB transmit signal path. This filter has a 6dB B/W of 2.4KHz. The rig sounds "good".

It is a fairly easy proposition to widen the TX B/W up slightly (to 2.8KHz) and make the rig sound "great", all the while keeping the audio narrow enough to be neighborly.

Three ways to accomplish this:

1) Find a surplus CFJ455K-13 filter (eBay, private sale, etc) - $$$

2) Go to a Kenwood parts distributor and hope they still carry one - $$$$

3) Wait for a used TS-930S "signal board" to come up for sale then snatch it.

I opted for Item 3 - twice. My average price for one of these boards (complete with filters) is $70. Desolder the filter and swap with the one currently in your '940. Voila! Done.

Your '930 board should also have a YK-88S2 SSB filter installed. Desolder and swap it with the '940's YK-88S1. Your rig's SSB receive B/W will now be 2.7KHz instead of 2.4, and can be "tightened" as before via the Slope Tuning controls. This filter is selected on AM when one presses the 'NAR' switch. The wider filter results in easier copy of an AM signal but is still an effective QRM fighter. It's also much more pleasant to listen to than the stock SSB filter.

Easy, wasn't it?

[WØTKX]

That radio might be better than my TS-850/DSP-100. :dunno:

[N8YX]

That radio might be better than my TS-850/DSP-100. :dunno:
A lot of 850 owners whom I know are very pleased with their rigs. I've never had the chance to perform an A/B comparison.

Hang on to that DSP unit. It's worth as much as the radio now.

[WX7P]

As delivered from Kenwood, the '940 incorporates a Murata CFJ455K-12 filter in the SSB transmit signal path. This filter has a 6dB B/W of 2.4KHz. The rig sounds "good".

It is a fairly easy proposition to widen the TX B/W up slightly (to 2.8KHz) and make the rig sound "great", all the while keeping the audio narrow enough to be neighborly.

Three ways to accomplish this:

1) Find a surplus CFJ455K-13 filter (eBay, private sale, etc) - $$$

2) Go to a Kenwood parts distributor and hope they still carry one - $$$$

3) Wait for a used TS-930S "signal board" to come up for sale then snatch it.

I opted for Item 3 - twice. My average price for one of these boards (complete with filters) is $70. Desolder the filter and swap with the one currently in your '940. Voila! Done.

Your '930 board should also have a YK-88S2 SSB filter installed. Desolder and swap it with the '940's YK-88S1. Your rig's SSB receive B/W will now be 2.7KHz instead of 2.4, and can be "tightened" as before via the Slope Tuning controls. This filter is selected on AM when one presses the 'NAR' switch. The wider filter results in easier copy of an AM signal but is still an effective QRM fighter. It's also much more pleasant to listen to than the stock SSB filter.

Easy, wasn't it?

Interesting.

I've had two 930's, both were great radios. I had a late production model 940, which was a piece of garbage.

Now I now why.

[W3WN]

Interesting. I never heard of that one before.

The 930 was a great radio in it's day, but it wasn't perfect. The 940 was an improvement in many ways, but it was also a step backwards in others. Sometimes I wonder if the designers of that rig were a little bipolar.

[W5IEI]

I did the same thing with one of my Omni V's.
Put Inrad 2.8's in both I.F's.
Made mucho difference.

[N8YX]

I did the same thing with one of my Omni V's.
Put Inrad 2.8's in both I.F's.
Made mucho difference.
One can also do this with a TR-7. That radio (along with the companion R-7 receiver) has the advantage of being able to mode-independently select receiver filter bandwidth. Removing the stock 2.3KHz filter and replacing it with a 2.85 or 3KHz Sherwood filter will widen out the transmitter bandwidth, but not excessively so.

[N8YX]

Step Number Two. This modification converts the rig to RF predriver-level, full-carrier DSB AM instead of SSB AME (which routs through that narrow SSB TX filter - and when subject to excessive ALC action sounds like carp to boot).

http://www.amwindow.org/tech/htm/ts940s.htm

Disadvantages? You lose the ability to monitor your AM transmissions via the rig's 'Monitor' function, and the speech processor no longer works on AM.

B...F...D. Seeing how the rig already has ample mic gain, who cares about the latter? I can always run an outboard compressor in the form of an MC-85 mic. As for the Monitor function: an SM-220 or similar RF sampling scope should already be in line at your shack...

I have a bunch of parts and two '940s with which to experiment. Looks like I'll be upgrading at least one of these over the Christmas holidays.

[KA5PIU]

Hello.

Bodacious, a ham rig on 27.185 MHz. ;)

[NQ6U]

Somewhere along the line, someone made some modifications to my IC-736. It's not supposed to work on 60m, but it does. In fact, I've yet to find a frequency it won't transmit on, although I'll admit I haven't tried every frequency between 160m and 6m. I need to connect up the dummy load one of these days and test it out.

[N8YX]

Hello.

Bodacious, a ham rig on 27.185 MHz. ;)
That's covered in a separate article.

Please reference the WorldWide DX Forums for details.