Hello !
I own a second hand Luxman T-1 tuner.
It is suffering from hiss. At annoying level.
But I'm using an external antenna, the signal level indicator gives me 5 lighted LEDS.
On low frequency of the band, (at 88.1 MHz) the hiss is powerful enough to be heard very distinctly. On the upper band, at 103.5 MHz the hiss is so strong I can't listen to this channel because of the hiss. And the level is also at 5...
I can reduce it a lot by setting the tuner in mono mode. But this cancel the whole tuner point, isn't it .
Question : Is there something I can do to reduce this hiss or cancel it ?
Thank you for your help and advice on this matter !
I own a second hand Luxman T-1 tuner.
It is suffering from hiss. At annoying level.
But I'm using an external antenna, the signal level indicator gives me 5 lighted LEDS.
On low frequency of the band, (at 88.1 MHz) the hiss is powerful enough to be heard very distinctly. On the upper band, at 103.5 MHz the hiss is so strong I can't listen to this channel because of the hiss. And the level is also at 5...
I can reduce it a lot by setting the tuner in mono mode. But this cancel the whole tuner point, isn't it .
Question : Is there something I can do to reduce this hiss or cancel it ?
Thank you for your help and advice on this matter !
Some tuners with a five-LED signal strength indicator already turn on all LEDs when the signal is still quite weak. Do other FM stereo receivers give a much better signal to noise ratio (as well as a decent stereo effect) when connected to the same antenna and tuned to the same stations?
When the reception is weak, FM stereo has a 22 dB(A) worse signal to noise ratio than FM mono (with the European 50 us de-emphasis, in the USA the difference is even greater). That's simply due to the FM multiplex system.
When the reception is weak, FM stereo has a 22 dB(A) worse signal to noise ratio than FM mono (with the European 50 us de-emphasis, in the USA the difference is even greater). That's simply due to the FM multiplex system.
You need the right test signals to align it properly, that's pretty specialized test equipment.
The stereo decoder does not change with channel tuning, I would look at the alignment/tracking of the front end. This is a tedious process in need of an expert with the right RF alignment gear. I had a T-110 and it did 70-72 dB in stereo which was SOTA in the day.
I would try an RF attenuator... signal levels may be so strong that the frontend gets overloaded, not an uncommon occurrence with tuners of this vintage (1980) e.g. on cable (which only became popular a few years later). It was not common to use RF AGC in those days, and going by specs and images this guy is only using a 3-gang frontend.
Frontend schematics are, unfortunately, not included in the service manual, making coming up with an RF AGC mod substantially harder than it would have to be. Presumably the whole thing was bought from Mitsumi or Toko, as usual.
Analog tuners capable of coping with crowded European band conditions as-is do exist but are not a dime a dozen. The Technics ST-9030 comes to mind, or the Kenwood KT-1100. I've seen some 3-gang tuners with RF AGC, and in fact it turns out Luxman's own, fancier T-4 features it as well (though its filter complement would seem to be barely edging out the T-1 in "narrow", with "wide" being ridiculously wide - ah, classic Japanese tuner designs).
Frontend schematics are, unfortunately, not included in the service manual, making coming up with an RF AGC mod substantially harder than it would have to be. Presumably the whole thing was bought from Mitsumi or Toko, as usual.
Analog tuners capable of coping with crowded European band conditions as-is do exist but are not a dime a dozen. The Technics ST-9030 comes to mind, or the Kenwood KT-1100. I've seen some 3-gang tuners with RF AGC, and in fact it turns out Luxman's own, fancier T-4 features it as well (though its filter complement would seem to be barely edging out the T-1 in "narrow", with "wide" being ridiculously wide - ah, classic Japanese tuner designs).
Hi !
It has occurred to me that the signal strength might be the culprit.
I'm not far from a tower hosting a lot of FM emitters for various radios.
And if most of them are of no interest to me, two are. And, maybe, my Luxman tuner has trouble separating the good signal from the bad one. Somewhere I have a 10 dB attenuator I bought a long time ago for my mother's TV set because she was in direct line of sight of a very powerful TV emitter and her TV couldn't cope witht eh signal.
Once I find it, i'll try it.
As per trying another tuner instead of the Luxman, I only own tube radios with FM (and some with stereo) and they are better at discriminating strong signal so I can't try them to compare....
Stay tuned ;-)
It has occurred to me that the signal strength might be the culprit.
I'm not far from a tower hosting a lot of FM emitters for various radios.
And if most of them are of no interest to me, two are. And, maybe, my Luxman tuner has trouble separating the good signal from the bad one. Somewhere I have a 10 dB attenuator I bought a long time ago for my mother's TV set because she was in direct line of sight of a very powerful TV emitter and her TV couldn't cope witht eh signal.
Once I find it, i'll try it.
As per trying another tuner instead of the Luxman, I only own tube radios with FM (and some with stereo) and they are better at discriminating strong signal so I can't try them to compare....
Stay tuned ;-)
Try a foot (30cm) of plain wire on one of the FM ANT screws (or in the coax jack center).
30 inches (77cm) of wire is a "good" FM monopole. Something much shorter is a cheap "poor" antenna.
This will tell you if overload is a factor.
(I grew up in sight of a 50KW AM station. I could pick that up on a crystal radio with just a few inches of wet paper "antenna".)
30 inches (77cm) of wire is a "good" FM monopole. Something much shorter is a cheap "poor" antenna.
This will tell you if overload is a factor.
(I grew up in sight of a 50KW AM station. I could pick that up on a crystal radio with just a few inches of wet paper "antenna".)
I've found the 10 dB attenuation and installed it. It seems the hiss has gone.
Using Google Map i saw that I'm at less than 2 km away in strait line of the transmitter and it is in plain sight of my antenna.
I bet that if my saliva was more acidic I could get the radio direct in my tooth fillings....
Using Google Map i saw that I'm at less than 2 km away in strait line of the transmitter and it is in plain sight of my antenna.
I bet that if my saliva was more acidic I could get the radio direct in my tooth fillings....
Tested on the 103.5 station that was hissing a lot. The strength indicator serves as a VU meter : the fifth led blinks at the rate of the music or speech. But hissing is gone !
BTW, I've opened the set and the head is definitely a Toko one. it is on a separate circuit and a lot of parts are glued in wax. No markings nor part number. My tuner is an European version with MW and LW instead of the world wide FM+MW version.
And made in France, with wrapping instead of solder .... Very 70's ;-)
BTW, I've opened the set and the head is definitely a Toko one. it is on a separate circuit and a lot of parts are glued in wax. No markings nor part number. My tuner is an European version with MW and LW instead of the world wide FM+MW version.
And made in France, with wrapping instead of solder .... Very 70's ;-)
Well, I rejoiced too fast.
If I tune to a station near a commercial radio (Virgin), the hiss is very present.
So I checked all the stations I usually listen to : all are near a powerful commercial radio and all suffer from some hiss. This hiss had been greatly reduced by the attenuator but it remains.
So I bet my problem is double : Saturation of the front end, and lack of selection in the IF.
I bet, both are not easily fixable for an amateur with very limited means...
I should look for a better tuner... If money permits.
If I tune to a station near a commercial radio (Virgin), the hiss is very present.
So I checked all the stations I usually listen to : all are near a powerful commercial radio and all suffer from some hiss. This hiss had been greatly reduced by the attenuator but it remains.
So I bet my problem is double : Saturation of the front end, and lack of selection in the IF.
I bet, both are not easily fixable for an amateur with very limited means...
I should look for a better tuner... If money permits.
You may cascade line attenuators.
https://cpc.farnell.com/blake-uk/ac35-6/attenuator-inline-iec-6db/dp/AP03132
https://cpc.farnell.com/blake-uk/ac35-12/attenuator-inline-iec-12db/dp/AP03134
If you want to verify the root of the problem, you may get a 20-30 $ SDR dongle, set up the free software on your PC and watch the RF and I.F. spectrum and the spillage due to overmodulation of the offending commercial station.
PS. The dongle may finally perform better than your T-1 in your place as an FM (not only) tuner due to it's SW fully adjustable RF and IF bandwidth
George
https://cpc.farnell.com/blake-uk/ac35-6/attenuator-inline-iec-6db/dp/AP03132
https://cpc.farnell.com/blake-uk/ac35-12/attenuator-inline-iec-12db/dp/AP03134
If you want to verify the root of the problem, you may get a 20-30 $ SDR dongle, set up the free software on your PC and watch the RF and I.F. spectrum and the spillage due to overmodulation of the offending commercial station.
PS. The dongle may finally perform better than your T-1 in your place as an FM (not only) tuner due to it's SW fully adjustable RF and IF bandwidth
George
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