TS 440s AM Mods - new web page

[WBear2GCR]

Thanks Steve for the link to W2APE's mods...

They seem generally on the right track, but I think there is more to this... so I put up a web page with these thoughts...

http://www.bearlabs.com/TS440/TS440.html

One of the biggest issues revolves around the xmit vs. receive path through the filters... and which caps to change to what values.

The other point I was trying to make is that I believe I have a source for drop-in CF2 (the Ceramic AM Filters) in the right bandwidth and with the superior shape factor.

Dave suggests a way to use Collins Mechanical Filters, which are good, but not a good physical option for the 440, imho. I suspect that these silly little ceramic filters perform sufficiently well to meet or exceed the performance of the Collins filter, certainly if cascaded (I haven't looked at a Collins filter spec in decades, so I don't recall truthfully... maybe they're >100dB skirts?) they should look like >100dB off the skirts... and they fit in the existing hole if you can stand 60dB skirts.

The rest is up on the new web page.

I'd be happy to discuss the ideas and particulars here or via email with anyone who wishes...

   73's

     _-_-Wbear2GCR

[Steve - WB3HUZ]

Looks interesting. I'm curious as to why you chose not to bypass the filter all together on transmit?

[WBear2GCR]

If you bypass the filter entirely on transmit then ur xmit bandwith is essentially unlimited.

There's no mod iron to limit ur bandwidth in a solid state rig. So, at least imho, you'd have to employ careful multi-pole rolloffs in the audio chain to prevent all sorts of nasties from appearing in the output.

Even if you're doing the mods and limit urself in the audio chain externally, it's not a good idea to put up mods that will give unlimited bandwidth not knowing who is going to do what with them if they are followed explicitly.

On the other hand, it's unclear to me having not really spent that much time with the schematic looking at the electronic switching IF the CF filters are being used AT ALL during transmit. The block diagram seems to say "yes" but I seem to recall that they are NOT being used durning AM xmit from memory of figuring this out some years back. It bears further investigation...

PS. I'll add a little text on the audio section today...

[Glenn NY4NC]

Wouldn't a 3 section op-amp lowpass filter (Mrs Butterworth) employed at the output of the audio stage be a lot easier and cheaper than IF filters?

you'd have to employ careful multi-pole rolloffs in the audio chain to prevent all sorts of nasties from appearing in the output.

[Steve - WB3HUZ]

It will sound better too. Crystal filters induce phase delay.

[w3jn]

Not to mention passband ripple.

[WBear2GCR]

Nice "hat" for that dog...

The ripple in the audio passband from one of these filters is negligible in practice, imho... spe'd 3dB max.
Less for the +/-4.5dB CF, that one is 2dB max.

But, one could use an opamp LP filter... I'd opt for a 4 pole though...

The ceramic filter is a drop in...

And, as I said, I'll have to look carefully at the circuit operation to see if there is *any* use of the CFs during xmit...

       _-_-bear

[W2JBL]

    a good transmitter should have flat audio response from "dc to daylight". EQ and bandwidth limting should take place in your processing chain. adding crystal, mechanical, or cermaic filters to narrow things up after modulation takes place is at best a patch, and filters introduce phase and amplitude distortion issues that should never have to come up in a well designed system. why build something that you have to add extra EQ to just get get flat response when you have the oportunity to do it right when the transmitter is being built?

[WBear2GCR]

a good transmitter should have flat audio response from "dc to daylight". EQ and bandwidth limting should take place in your processing chain. adding crystal, mechanical, or cermaic filters to narrow things up after modulation takes place is at best a patch, and filters introduce phase and amplitude distortion issues that should never have to come up in a well designed system. why build something that you have to add extra EQ to just get get flat response when you have the oportunity to do it right when the transmitter is being built?

That is pretty much utter nonsense.

Nothing that is being discussed here has to do with "narrowing up" something via the use of filters per se.

All of that "audio" processing gear has both phase shift and introduces amplitude distortions.
Take a look at the phase shift of the "EQ and bandwith limiting" in *your* processing chain and report back as far as what you find.

The flatness of response you seem to be talking about is mythical. What you go for is a "good sounding" response. Find me a mic that has a "flat response" that any ham you know is using? None. Find me a rig with dead flat response and that uses a mic with dead flat response, and I'll show you a sound that you probably won't like.

And in this case, the Japanese designed and built the rig - not me. So how does that comment apply?
(rhetorical question)...

And, btw, I did not particularly appreciate the sarcastic comments on the related thread either. What's your point? What's ur beef?

     _-_-WBear2GCR

[flintstone mop]

Hello AM Good Sound Guys,
The sound we hear on the air waves is a personal thing. There are guys using slightly modified DX 100's and a D104 with no audio processing and it is a beautiful sound. Many of us are  NOT radio announcers and do not have that third BA, but there are guys with the condenser mics or the RE27's and a lot of processing and they can 'make' their Tx audio sound like a 50KW radio station. It's that personal touch and the HUMAN EAR. It's not from test equipment magical theory.
You'll meet them in person at a Fester and you can hardly recognize their voice, because of the processing from radio QSO's.
I agree with BEAR that a FLAT response (to me) sounds very dry and dead. I ALMOST agree with some engineers that the EQ settings (sliders) might look like a smiley face, because of the normal crappy response of the human ear, remember the "Munsen Effect?"
It just seems that some folks want to take a very complicated route to 'make' something sound good. The filter magic mentioned on some websites just might introduce more problems down the chain to the "Ether".
I love my TS440/APE radio.
G'day
Another $.02 thopught
Fred

[W2JBL]

 well, it looks like Bear missed the point. i was not speaking of running perfectly flat audio. the point was that if you are taking the time time build or modify transmitter it should be flat over the entire range desired, and beyond. doing so means you do not have to introduce any extra EQ into the system to correct for defects. putting filters in line after the modulator is shooting yourself in the foot i you are aiming for decent fidelity.  and as i have often observed, many folks on these forums have absolutely no sense of humor.

[WBear2GCR]

Dear KD2XA,

The point was a mod to a Japanese transciever - the TS-440.

If you are building a rig, and it is plate modulated, there won't be any place for "filters after the audio"... they don't go there. The proper place, in the rig, is in the low level stages.
If you are building a class E rig and it is PWM it must contain filters by definintion.
If it is Class H modulated, you had better provide something somewhere for bandwidth limiting... somewhere. Myself, I'd design it into the modulator. You can do yours, your way.

Any plate modulated rig using a plate transformer is a filter already, as all transformers have limited bandwidth - especially mod iron - and significant phase shifts at the frequency extremes, plus hysteresis from the inductance/core...

Otoh, screen modulated rigs won't suffer from the issue of mod iron, but the screen tends to be horribly non-linear for most tubes, and causes other problems...

I don't know of any means to put "filters in the line after the modulator". So, I surmise ur still confused about the nature of the TS-440 and how most "modern" transcievers work by converting the signal to an IF frequency before it is converted to a specific output frequency. In the case of the 440S they convert to first 455kHz and then up to 8.83mHz before (in this case) coming out the business end at 3.850 MHz!!

The "filters" are RF filters. The 455 can be a Ceramic Filter, or a Mechanical Filter, and the 8.83Mhz. filter is usually a Crystal Filter. It's exactly the same filter you probably have in one or more of your receivers. I hope this make clear what the discussion about "filters" in my post is all about??

The web page that I posted is an analysis of the AUDIO section of the TS-440. Since the rig was designed with SSB and "intellegibility" in mind , this is needed if you want to figure out what to do in order to get closer to an "AM" fidelity.

Running "flat to the entire range and beyond" insures that you will be running so wide that you will be interfereing with other QSOs for no beneficial reason - one needs to limit the audio bandwidth in a reasonable way (dependent upon band conditions of course). There is no reason NOT to use in line audio processing/EQ to cut off your HF response to fit, and designing the modulator to be a nominal 20-20kHz (if you can manage to get mod iron to do that - IF) but that has nothing to do with modifying a Japanese Transciever, now does it? And that is the topic.

    _-_-WBear2GCR

PS. I found nothing funny about your swipe (replying to my other post) at "high-end" audio, and there is a whole lot that is funny about "high-end" audio. So, if you say something that I find humorous, I'll let you know.