ACC2 on my TS440

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Draxx
Voodoo Audio Head
Posts: 15
Joined: Thu Oct 16, 2014 7:04 am

ACC2 on my TS440

Post by Draxx » Fri Oct 17, 2014 5:27 pm

I just recently picked up a mint TS 440. I would like to run my rack gear through the ACC2 rear jack. I know the 440 is probably not the best rig to do this on but I'm wondering if it will still give improved audio quality. I realize that I'm limited to the IF Filter as far as bandwidth along with some other capacitance for bass roll off but just wondering if it's still worth it. Would love to get some of that oh so smooth voodoo audio going. Thanks for your replies and thoughts.
kB6ZYJ
Scott

BillPaul
Digital Voodoo Guru
Posts: 66
Joined: Wed Jan 19, 2011 11:52 am

Post by BillPaul » Tue Oct 21, 2014 11:14 am

First, get a copy of the TS-440S service manual. I think there's several PDF scans of them out there on the web which you can find with minimal googling. I also have this one:

http://people.freebsd.org/~wpaul/statio ... Manual.pdf

Follow the ACC2 audio input path (which if I remember right is pin 11). Follow the audio path until it gets to pin 1 of the AN612 balanced modulator. I haven't gone through it in a while, but I think the path is fairly direct, with maybe only one or two coupling caps in the way. The coupling caps are usually 1uF. These should probably be increased to 4.7uF to improve the low end. You can also feed pin 1 on the AN612 directly through a 4.7uF cap.

For the treble, you're correct in that the limitation is the IF filters. Since the TS-440 is a purely analog rig, what you may be able to do is bypass the 455Khz filter and replace the existing 2.7KHz filter in the 8.83Mhz IF stage with a 4KHz one from INRAD:

http://www.inrad.net/product.php?produc ... =56&page=1

You could also go really nuts and use a regular 6KHz AM one.

If you do this, then there are some caveats:

- You will need to reset the carrier point adjustments. It's also possible that the adjustable trimmer caps won't have enough range and you'll need to replace them, or add some additional capacitance in parallel with them. YMMV

- Even with the carrier points set correctly, you may still leak a little bit of the alternate sideband signal. The DSP filtering can be widened while still remaining fairly sharp, which is why people go for DSP or SDR rigs for eSSB most of the time.

I was talking with Tyler KA0KA recently on 40 meters and he told me that he had done this sort of thing with a TS-820. He mentioned that he had to change out the carrier point trimmer caps because the filter he used was wide enough that the existing ones didn't have enough range. (I guess it makes sense that this should be the case, though never having tried it myself it never occurred to me that it could be a problem.)

Resetting the carrier point settings _correctly_ may be a little hard to do without proper equipment, in this case a two-tone generator and a scope. (Ideally you'd like to have a spectrum analyzer too.)

-Bill, N1GPT

Draxx
Voodoo Audio Head
Posts: 15
Joined: Thu Oct 16, 2014 7:04 am

Post by Draxx » Fri Oct 24, 2014 9:05 pm

Thanks for all the great input Bill, it's greatly appreciated. I really love this rig and would like to give it that deep "Kenwood" sound . Il take a look at the circuit and see what I can find there.

Take care,

73's

Scott

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