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Author Topic: Kenwood TS-440S - Question on the YK-88A AM filter  (Read 40590 times)
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WBear2GCR
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« Reply #25 on: March 22, 2011, 09:45:11 AM »

Yes.

You have to put in in the right direction and the right place of course.

It's on the top board when you open the top of the rig (iirc) and it is the square top black thingie in the upper right quadrant (if you imagine that you drew a + through the board) and toward the center a bit. There are holes already there for the longer "new" filter. So I suspect that the Kenwood designers either intended to use the "better" filter or just left the provision in case the cheaper one became hard to source... but for whatever reason the holes are there! Cheesy

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This is a receive ONLY mod...
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« Reply #26 on: March 22, 2011, 10:07:06 AM »

That 455 KC filter is used on both xmit and receive.
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WBear2GCR
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« Reply #27 on: March 24, 2011, 12:01:52 AM »

Hmmm... interesting Dave... 

I got no change in signal fidelity received reported when I did the mod... now I am confusered totally. Ok... fog lifts, the nominal bandwidth is the same then, just my skirts got way better. That must be it.

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« Reply #28 on: March 24, 2011, 07:56:09 AM »

If you are only using the rig for transmit on AM and not rx you can just yank the ceramic filter and put in a wire and do all your bandwidth limiting in the audio like any other AM rig.
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« Reply #29 on: March 24, 2011, 08:42:33 AM »

Yes, the filter can be bypassed with use of another receiver but there are better ways...
One is to duplicate the diode switched filters with an additional set of components and a 1K resistor in place of the filter. The internal AMT (am transmit) logic bus gets removed from itsk present location and hooked tot he switching diodes of the new section.layout will be critical here to minimise filter blowby.
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WBear2GCR
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« Reply #30 on: March 24, 2011, 09:28:23 AM »


Well this still is not making much sense... unless there is a LP in the speech amp section (is there??) at least on my 440 the xmit audio did not appear to be any 6kc wide... I was under the (false?) impression that the 440 tries to run the xmit audio through the default Xtal filter - IF it is present? In my rig it is present. So maybe without the default filter (I have another secondary SSB filter in it too...) one gets full width??

I know QFX came up with a way to add a few components so one gets wide xmit audio in AM only. I don't recall if it switched the filter back in for receive. But that would be ideal, I guess.

This replacement ceramic filter does a bang up job on receive, I'd hate to give it up.

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« Reply #31 on: March 24, 2011, 12:02:22 PM »

There was a time when the design assumption in engineering plastic SSB transceivers was that everyone would be using a hand mic and would want space shuttle audio (I guess now that the Space Shuttle is no more we have to call it something else, maybe subway PA audio) so the mic preamps built into the rigs often had passive compoenents that would roll off the lows and highs in the audio.   So it helps a lot if you work out a way to feed the balanced modulator (which is unbalanced for AM of course) directly with a cap in series.  You have to find the right pin on the bal. mod. chip and tack a cap lead on it and connect the other end to a coaxial audio cable to a RCA jack on the back panel with the shield grounded to the PC board ground (and/or the cabinet--I can't remember which way solves the pin 1 problem).  the cap can be something like .01 uF poly 25 v. for s.s. rigs.  you may have to do some experimenting.  It helps to have the service manual for the rig.   The caveat is that if you go this route you have to be set up to monitor what the rig is doing, i.e. you have to hear the tx audio off air, see it with something like a SB610 and/or scope, limit the peaks, and roll off the high end sharply at 4.5 or 5 kc by about 40 dB, and watch the ALC, because the rig isn't going to do anything for you but take everything you give it and send it out.   Its response should be very flat though and in my opinion, controlling response at baseband is better anyway.
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« Reply #32 on: March 24, 2011, 12:08:29 PM »

Probably time to study the block diagram.

Several people have good mods for this rig. Some on this board were running them and sounding good almost 25 years ago.

The 8.83 crystal mhz I.F. filters do nothing on transmit in this radio. They are used on transmit in other Kenwood models.

If one takes the time to sweep the speech stages one will figure out exactly what parts need to be changed. Hint: SPICE GIGO. Estimates and numbers pulled out of outer space don't tell us anything.

I'll be writing a white paper someday.


Well this still is not making much sense... unless there is a LP in the speech amp section (is there??) at least on my 440 the xmit audio did not appear to be any 6kc wide... I was under the (false?) impression that the 440 tries to run the xmit audio through the default Xtal filter - IF it is present? In my rig it is present. So maybe without the default filter (I have another secondary SSB filter in it too...) one gets full width??

I know QFX came up with a way to add a few components so one gets wide xmit audio in AM only. I don't recall if it switched the filter back in for receive. But that would be ideal, I guess.

This replacement ceramic filter does a bang up job on receive, I'd hate to give it up.

                           _-_-bear
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« Reply #33 on: March 25, 2011, 12:38:02 PM »

 " space shuttle audio "

Burger king audio??
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WBear2GCR
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« Reply #34 on: March 27, 2011, 10:45:46 PM »



dave, thanks for the kick... not necessary is it?

the SPICE simulation I did many years ago used the original parts values, and was intended as an exercise and experiment, not as some sort of definitive work fwiw.

I don't mind being 'wrong' - or being corrected, it's an opportunity to learn something.

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« Reply #35 on: March 28, 2011, 04:33:30 AM »



dave, thanks for the kick... not necessary is it?

the SPICE simulation I did many years ago used the original parts values, and was intended as an exercise and experiment, not as some sort of definitive work fwiw.

I don't mind being 'wrong' - or being corrected, it's an opportunity to learn something.

                      _-_-bear             

Call me when you have some real time, energy and expense developing mods for these.
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WBear2GCR
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« Reply #36 on: March 28, 2011, 10:47:11 PM »



Ok, I am totally confused. No idea what ur thinking. Please PM or email me if you've got something to say that is personal and/or does not add to the understanding of the topic in the thread.

Let me add, I don't claim any special expertise in ham radio. Not offering a commercial kit or modification. I'm just another ham. Talking about ideas. Sometimes I get it right, sometimes I don't. Plenty of folks on here know a whole lot more than I do. Perhaps you have a superior understanding, if you don't share it and are unwilling to explain or be specific, then what's the point?

If this isn't going to be fun or enjoyable, then what's the point anyhow?

So how about it Dave?

         
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« Reply #37 on: April 01, 2011, 07:07:20 PM »

I had cause to take a look at the webpage I had put up 5-6 years ago on this filter. That page was more or less a "blog" of what I was doing with it at the time... Seems like I preferred and am running the nominal +/-4.5 filter over the +/-6.0 filter. That's what's in the rig today. With the skirts being better than the stock and not as good as a high quality mechanical filter or similar, it does sound wide enough to me.  Fyi, and fwiw, etc.

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