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Old 24th Nov 2020, 10:58 pm   #1
PWH
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Default Kenwood TS430s AM filter operation

I have overhauled the rig which did not have an AM filter fitted. I acquired a filter because the AM broadcast was sounding poor. I have fitted the filter, first removing the resistor and cutting the resistor on the control board according to instructions here.
https://www.manualsdir.com/manuals/6...s.html?page=20



There appears to be no difference is sound when switching between wide and narrow on AM. On SSB, you have to have the switch set to wide to hear anything on narrow all you get is a hiss.


I don't think this is normal. What should the switch do on AM/SSB?
Thanks
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Old 24th Nov 2020, 11:46 pm   #2
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Default Re: Kenwood TS430s AM filter operation

I'm probably only going to add to the confusion but I bought a brand new TS430S back in the 1980s. I ordered it with the FM board and I also ordered the 6kHz wide AM filter. It is a long time ago but I recall having a similar experience to you after I fitted the AM filter. I wasn't happy with the way it selected the filters depending on mode.

I think I ended up modifying the switch selection such that it did the following:


AM Wide (6kHz filter)
AM Narrow (2.2kHz filter)

I haven't used this radio for many, many years but I think that is how I arranged it. However, I'm not sure my switch wiring mods added any real value as I only ever selected the (new) 6kHz AM filter in wide mode anyway. I was a bit disappointed with the new wide AM filter. I think it would have been nicer if it was 8kHz rather than 6kHz wide.
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Old 25th Nov 2020, 8:51 am   #3
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Default Re: Kenwood TS430s AM filter operation

According to the manual here

https://www.radioscouter.se/onewebme...ser_manual.pdf

PDF page 18

There are THREE places that you cut out resistors?

Also a jumper wire needs moving

Fred G4BWP
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Old 25th Nov 2020, 3:20 pm   #4
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Default Re: Kenwood TS430s AM filter operation

Because I wasn't sure if I'd remembered correctly I dug my old 430S out and tried out the various wide and narrow filters on AM/SSB and this is what I ended up modifying it to.

AM Wide (6kHz filter)
AM Narrow (6kHz filter)

SSB Wide (6kHz filter in Rx)
SSB Narrow (2.4kHz filter)

It looks like I didn't bother trying to keep the narrow filter switch setting on AM and I just swapped the SSB modes. I really can't remember for sure but I think the standard fitting instructions for the wide AM filter mean that you get the wide AM filter on both wide and narrow settings. AM reception with the standard/narrow 2.4kHz filter was not pleasant at all so I don't miss it.

This was 35 years ago but I did some other mods at the same time. I put a stronger mixer on the FM board and changed the FM IF filter for a better one. I also changed the way the s meter was driven in FM mode as it was a bit of an all or nothing indication with the standard circuit. I also modded the synthesiser board to improve the phase noise on the first LO.
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Old 25th Nov 2020, 4:57 pm   #5
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Default Re: Kenwood TS430s AM filter operation

That's how my TS-430 is set up.

No Narrow Filter on AM.
Narrow and Wide both operate at 6 Khz.
i.e. No change.

Narrow only works on SSB.

This I think is quite a sensible arangement, unless you have a particular need
to resolve an AM transmission with less Bandwidth.


AM Broadcasts sound pretty Dire on a Narrow Filter anyway.

However an AM Broadcast received on SSB with a Narrow Filter can sound
good, especially in Noisey conditions.


EDIT: Just read the Instruction Manual Page 7, and it does say the SSB Filter should be switched in when
in AM Mode with the Filter in the Narrow position.

So AM should be 6Khz / 2.7 Khz (Wide/Narrow) depending on which Filters are installed


Ian

Last edited by Superscope; 25th Nov 2020 at 5:18 pm.
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Old 25th Nov 2020, 6:14 pm   #6
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Default Re: Kenwood TS430s AM filter operation

Thank you everyone.
I will try the mod's from Dodgy-dxer's manual including moving the wire and report back.
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Old 25th Nov 2020, 8:11 pm   #7
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Default Re: Kenwood TS430s AM filter operation

I have done the additional mods but with no change. I am wondering if there may be a fault with the SSB filter part. On NAR, nothing happens, there is just a hiss. On wide I can hear all the RF noises.
Any pointers??
Unfortunately there is no SSB to listen to around here at the moment even the speaking clock on 10/15KHZ is not coming through
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Old 25th Nov 2020, 8:51 pm   #8
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Default Re: Kenwood TS430s AM filter operation

Just to be cler after the additional mods..
AM: Wide/Nar no difference in either position (but seems clearer than it was).
SSB Wide: is lively lots of expected static and noise
SSB Nar: just hiss

Listening to an AM station with SSB switched in
Wide : expected hetrodyne whistle and "SSB audio" and you can tune it for perfectly clear audio
Nar: just hiss.
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Old 25th Nov 2020, 10:13 pm   #9
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Default Re: Kenwood TS430s AM filter operation

Could be the Filter itself, but hopefully not.

Might be worth checking the Switch and double checking
for Dry Joints on the Filter first.




Ian
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Old 26th Nov 2020, 9:46 am   #10
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Default Re: Kenwood TS430s AM filter operation

You could remove the suspect filter and put in a link to bypass it, just to find whether the rest of the signal path is intact and the switching is correct. But look out for tricks like them using DC paths in filters as part of diode switch networks. These people would do anything to save a resistor.

The last time I changed filter in a TS430S was in the mid 80's so I don't trust memories for specific details.

David
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Old 26th Nov 2020, 1:48 pm   #11
G0HZU_JMR
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Default Re: Kenwood TS430s AM filter operation

Does your radio have the optional 1.8kHz wide SSB NARROW filter fitted? if not and you want to avoid hearing dead hiss on SSB NARROW you will have to buy and fit the (optional) narrow 1.8kHz BW filter. At least that is how I remember things when I first bought my TS430S.
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Old 26th Nov 2020, 8:10 pm   #12
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Default Re: Kenwood TS430s AM filter operation

Thank you all for your contributions.
I don't have the optional 1.8Khz filter just the normal ssb and now AM filter fitted. I have reworked all the joints around the ssb filter and AM filter. How do you test a filter? I believe the switch is working as things change (hiss/signal)
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Old 18th Dec 2020, 1:20 am   #13
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Default Re: Kenwood TS430s AM filter operation

Anyone have any further thoughts?
I can't believe that all one can hear on narrow is a hiss...
Thank you
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Old 19th Dec 2020, 12:48 pm   #14
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Default Re: Kenwood TS430s AM filter operation

How to test an unknown filter....

Ideally you need a spectrum analyser with a tracking generator, or a network analyser.
You could use a signal generator, if you have a good, stable (probably synthesised) one and some sort of sensitive detector, but stepping through by hand is very very very tedious.

Just connect up and do some scans to find where the passband is. Slow the scans down because narrow filters do not respond quickly and your trace will be 'smeared'

It still won't look right, because they are critically dependent on having the right source and terminating impedance so their response will be all wrong, but at least you now know where to focus your scans in future.

Next you need to fiddle with the source and load resistors. This is where the spectrum analyser earns its spurs. There is ludicrous sensitivity, so you can afford inefficient, resistive termination pads to go from Zo of your test gear (50 ohms) towhere you guess the filter is set for. You also make sure your coax test cables are reasonably well matched.

You make many networks, refining your guess of the filter's design impedance, deciding on whether the filter shape is starting to look like something intentional... minimum ripple is the usual give-away.

I bought dozens of crystal filters at surplus prices in the eighties and had to sort them all out. As a result I have sets of just about all bandwidths I could want for 1.4MHz IF.

If fiddling with R load gets you close to something, but no cigar, mess around with adding a little capacitance.

This is a lot of work, but good fun and educational to boot.

David
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