TS-850S + YK-88S2 "wide" SSB filter = mid-fi?

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K7DKE
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TS-850S + YK-88S2 "wide" SSB filter = mid-fi?

Post by K7DKE » Thu Dec 01, 2011 2:50 pm

I am new to the board and have already learned a lot about my new (to me) TS-850S. Lots of big brains here with a lot of combined experiece with hi-fi audio.

I'd like to try to set up a decent mid-fi station on a shoe-string budget. My TS-850 does not have a DSP-100 to mate with, and probably won't for awhile due to the exceedingly high price of the DSP unit. So that leaves me with trying to squeeze out what I can from the 850 standalone.

I'd like to try to get what I can out of the TX. Already I have a Heil HM-12 that has a wide response from 80Hz to 14Hz, so I think I'm good in the mic department. However, the filter bandwidth is pretty narrow. 2.7k indicated, but I think this translates only to about 2.4k real-world audio range with 300Hz and 2700Hz cutoffs (but I haven't yet measured this on a sprectrum analyzer to be sure).

On SSB the TX is run through the narrow 455 ceramic filter to strip the unwanted sideband. That's why you need the DSP unit if you use one of the wider filters on TX via the hidden menu. So that got me to thinking (always dangerous):

If I put a slightly wider filter in one of the optional slots and then selected it for use on TX via the hidden menu, then I could get some extra audio bandwidth without the DSP and for just the cost of the filter. Filter candidates would be 1) the Kenwood YK-88S2 3.2k "wide" SSB filter (yes I knw I would have to solder it in), 2) the Inrad 2.8k filter (the extra 100kHz hardly seems worth it but has sharper skirts), or 3) I could simply replace the stock 455 Murata ceramic filter with either a wider Murata ceramic filter or some other wider filter wired in remotely to the 2.7k 455 slot using 174 coax. I'm not sure which Murata filter I would have to go to, but have read unsubtantiated rumors that a CFJ455K13 is upwards of 3.2k wide.

This wouldn't give me essb by any stretch, but it would give me upwards of 500-800Hz of extra of TX audio over stock. A "poor man's" mid-fi.

Do I then need to adjust the carrier set point to a decent cutoff of 100Hz or so on the low end and 3.3kHz on the high end? Is this how you do it or is the filter bandwidth set, in which case maybe I could somehow use the slope tune internal coils to put the new bandwidth where I want it?

If I could pull this off, it'd be a marked improvement over the current cutoffs of 300Hz and 2.7kHz and would make better use of the HM-12 mic freq response.

What do the old hands here on the voodoo board think of my scheme? Hare-brained or possibly workable?

Thanks,
Darren

m0kvr
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Post by m0kvr » Sat Feb 16, 2013 9:01 am

I have also considered doing this...

Do any of you guys know if the above would be possible?

Would the 4khz Inrad #475 allow tx at 4khz bandwidth with adjustment of the carrier point?

The dsp-100 unit is so difficult to come by, and the price is sky-high!!

Andy
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Post by Voodoo Guru » Mon Feb 18, 2013 8:40 am

Howdy Darren,

It has been several, several years since we have messed around with the TS-850, so our memory is not that great on it. The answer will be very general.

We have never experimented with adding wider TX Filters into the TS-850 as there was always a DSP-100 involved.

The 455kc 2.7 ceramic filter does look like the one that removes the opposite sideband component from the DSB Signal generated by the Balanced Modulator.

The most important thing to consider is the Carrier Offset Control. You can install as wide a filter as you want to but the Carrier Offset Control MUST have enough adjustment to reset the Carrier Point to that filter or you will start to go into Double Sideband. The thing is, we can't remember if there is actually a carrier offset adjustment for the 455Kc Filter bank, but there is one for the 8.83Mc filter bank.

If there is an adjustment for the 455Kc filter bank, you would have to measure this and see how wide a filter you could actually use.

Another thing to consider is this, there is not a separate adjustment for Transmit and Receive Carrier Points, nor for each individual filter. So when you adjust the 455Kc carrier point to match the filter your Transmitting on, it will affect the Bandwidths of the others in that filter bank.

Take Care,
Voodoo Guru
From Deep in the IDD of the Sub-Harmonix Realm

tbd
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Post by tbd » Wed Jun 26, 2013 6:31 pm

m0kvr wrote:I have also considered doing this...

Do any of you guys know if the above would be possible?

Would the 4khz Inrad #475 allow tx at 4khz bandwidth with adjustment of the carrier point?

The dsp-100 unit is so difficult to come by, and the price is sky-high!!

Andy
M0KVR
Do it you will not regret, I just did it with my TS850 and the audio now is
Awsome.

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