Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Old June 9th 18, 05:47 AM posted to sci.electronics.repair
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Default Selectivity vs. sensitivity

"Tuners that are beloved of the "FM DX" crowd will tend to have: "

I want one with continuously variable IF bandwidth on the front.


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Old June 10th 18, 02:02 AM posted to sci.electronics.repair
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Default Selectivity vs. sensitivity

wrote:


"Tuners that are beloved of the "FM DX" crowd will tend to have: "



I want one with continuously variable IF bandwidth on the front.



** Such a feature is useful with AM reception but not with broadcast FM.

The FM signal is inherently wide band, with +/-75 kHz deviation at peak audio level - if the IF bandwidth is less than 150kHz, distorted sound is the result.

I have a radio scanner ( AR 1000xlt ) with wide and narrow FM modes, 30kHz and 200kHz respectively. Listening to broadcast FM while in narrow mode is *intolerable*, in wide mode it sounds just fine.



..... Phil




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Old June 10th 18, 03:21 AM posted to sci.electronics.repair
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Default Selectivity vs. sensitivity

"** Such a feature is useful with AM reception but not with broadcast FM. "

I've had it in a couple of tuners and found it useful when DXing, and once in a great while other times but still DXing somewhat. Listening to strong local stations just leave it in wide though, then it practically worthless.
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Old June 10th 18, 03:40 AM posted to sci.electronics.repair
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Default Selectivity vs. sensitivity

wrote:


"Tuners that are beloved of the "FM DX" crowd will tend to have: "


" I want one with continuously variable IF bandwidth on the front. "



"** Such a feature is useful with AM reception but not with broadcast FM. "



The FM signal is inherently wide band, with +/-75 kHz deviation at peak audio level - if the IF bandwidth is less than 150kHz, distorted sound is the result.

I have a radio scanner ( AR 1000xlt ) with wide and narrow FM modes, 30kHz and 200kHz respectively. Listening to broadcast FM while in narrow mode is *intolerable*, in wide mode it sounds just fine.




I've had it in a couple of tuners and found it useful when DXing,



** Continuously variable ????

Or just a couple of settings.

FFS stop oversnipping !!!!



..... Phil


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Old June 10th 18, 04:38 AM posted to sci.electronics.repair
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Default Selectivity vs. sensitivity

"** Continuously variable ???? "

Sorry, switchable, narrow and wide. I heard of a tuner with three positions but never had one and don't remember the name or model.

Doing variable control in the analog domain would be an incredible bitch but that's how I want it. Actually it only has to be a couple of stages towards the front, maybe even just one, but still. Maybe Studer Revox would do something like this (maybe they have) but I doubt anyone else. Them engineers there I bet are showoffs. I'm not bitching, just saying. I saw the print of one of their tuners and said "WTF, are you sending the first mission to Mars or what here ?". I'm sure I still have it lurking around a drive here but it would probably be easier to find it online again than to look through all my backup.

Yes I am a nasty SOB who wants someone else to do what I can't. But they get paid for that.
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Old June 10th 18, 06:35 PM posted to sci.electronics.repair
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Default Selectivity vs. sensitivity

I had an 82 Toyota Celica. Radio was horrible. It looked like it was designed for an external antenna amplifier and when one was added, the number of stations received increased.

It was very "hissy" when the speakers were upgraded,

I have a 2000 Solara and the Radio is pretty nice. 5 CD changer, cassette and AM/FM.

==

House wise, I have a Technics Professional ST-9030. See http://audiokarma.org/forums/index.p...t-9030.363631/ I have been able to get 3 stations on the same frequency just by rotating the antenna.

The FM bandwidth is selectable from auto and wide. They probably should have made it auto and narrow. It may continuously change bandwidths in auto mode.

To make things more interesting, I added a Carver TX1-11 signal process which makes multipath noise "go away".

More interesting yet, I have a 4bx dynamic range expander with impact restoration.

The tuner had two outputs. One filtered at 15 kHz so it would not interfere with tape decks and one with a higher response.

I also owned a automotive Blaupunkt Tucson which was very good coupled with an active AM antenna.
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Old June 10th 18, 09:01 PM posted to sci.electronics.repair
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Default Selectivity vs. sensitivity

On Sunday, June 10, 2018 at 12:35:38 PM UTC-5, Ron D. wrote:
I had an 82 Toyota Celica. Radio was horrible. It looked like it was designed for an external antenna amplifier and when one was added, the number of stations received increased.

It was very "hissy" when the speakers were upgraded,


Ford and GM seemed to apply importance to their car stereos in the early 1980s. Amps with DPL (anti-clippping gain control), speakers from Bose, tuners from Hughes Aircraft which were also used in David Hafler tuners, and Blaupunkt for the cassette decks. Bose also made some amps for mainly Caddilacs, they were class D and ran into very low impedance. But that was no stranger to Bose, the speakers in the 901s are 0.9 ohms each. They get near 8 ohms being all in series.

And a buddy of mine has a 2005 Ford Taurus and that thing gets stations I can't even dream of getting. Two of them I really want, 94.9 and 97.5 out of Akron, which is not all that close. And he gets them clean. I might have to fell him over this. (jk)



House wise, I have a Technics Professional ST-9030. See http://audiokarma.org/forums/index.p...t-9030.363631/ I have been able to get 3 stations on the same frequency just by rotating the antenna.

The FM bandwidth is selectable from auto and wide. They probably should have made it auto and narrow. It may continuously change bandwidths in auto mode.


I ould like auto, narrow and wide if I can't have a variable control. In fact I wouldn't mind auto because signal conditions change.



To make things more interesting, I added a Carver TX1-11 signal process which makes multipath noise "go away".


I bet all that is is a stereo blend with logic. Bob did alot of "magic" that way. Those asymmetrical charged coupled device tuners of his were not the cat's ass. All it did was to detect what it thought was distortion along maybe with multipath which is easy to detect and start blending left and right and adding a digitally delayed signal to the L-R.


More interesting yet, I have a 4bx dynamic range expander with impact restoration.


I am going to build something like that one day if I live long enough, and all in discrete components.


The tuner had two outputs. One filtered at 15 kHz so it would not interfere with tape decks and one with a higher response.


Regular FM stereo is capable of 19 KHz but it takes some doing. It takes a very accurate pilot cancel circuit with a PLL generated null signal to assure a perfect sine wave. Interference to the wave would be reproduced, but also prevented from interfering with the phase lock of the MPX decoder oscillator. I don't want the job, maybe Revox.



I also owned a automotive Blaupunkt Tucson which was very good coupled with an active AM antenna.


Seems like you're into AM. Well, it is more people's media because it is much cheaper to have an AM station than FM, and forget TV. Maybe, for the common good we should support AM radio.

I'll have to give that some thought.
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Old June 11th 18, 08:43 PM posted to sci.electronics.repair
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Default Selectivity vs. sensitivity

On Sat, 9 Jun 2018 18:02:00 -0700 (PDT), Phil Allison
wrote:

wrote:
I want one with continuously variable IF bandwidth on the front.


** Such a feature is useful with AM reception but not with broadcast FM.
The FM signal is inherently wide band, with +/-75 kHz deviation at peak audio level - if the IF bandwidth is less than 150kHz, distorted sound is the result.
I have a radio scanner ( AR 1000xlt ) with wide and narrow FM modes, 30kHz and 200kHz respectively. Listening to broadcast FM while in narrow mode is *intolerable*, in wide mode it sounds just fine.
.... Phil


A bit of hair-splitting here. The FM channel allocation in the USA is
at 200 KHz intervals. However, if one adds the digital (HD Radio,
IBOC, iBiquity, etc) modulation, the bandwidth is now 400 KHz wide:
https://en.wikipedia.org/wiki/In-band_on-channel
This is what it looks like on a spectrum analyzer:
http://www.learnbydestroying.com/jeffl/crud/KBRG-100_3.jpg
http://www.learnbydestroying.com/jeffl/crud/KCSM.jpg

In most HD Radio receivers, the IF bandwidth is set by a digital
filter. For conventional FM, it's 200 KHz wide. For digital FM, it's
400 KHz wide. I suppose it could be front panel set by the user, but
methinks it makes more sense to have the IF bandwidth automagically
set by the mode and sub-channel.

Measuring Your IBOC Spectrum
http://www.nautel.com/wp-content/uploads/2011/08/NAB-Measuring-Your-IBOC-Spectrum-David-Maxson.pdf

--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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Old June 12th 18, 03:54 AM posted to sci.electronics.repair
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Default Selectivity vs. sensitivity

On Sat, 9 Jun 2018, Phil Allison wrote:

wrote:


"Tuners that are beloved of the "FM DX" crowd will tend to have: "



I want one with continuously variable IF bandwidth on the front.



** Such a feature is useful with AM reception but not with broadcast FM.

The FM signal is inherently wide band, with +/-75 kHz deviation at peak
audio level - if the IF bandwidth is less than 150kHz, distorted sound
is the result.

I have a radio scanner ( AR 1000xlt ) with wide and narrow FM modes,
30kHz and 200kHz respectively. Listening to broadcast FM while in narrow
mode is *intolerable*, in wide mode it sounds just fine.

Continuously variable for FM doesn't make sense. But there have been some
FM tuners that could be switched between "wide" and "narrow", in relative
terms. So for strong signals, wider bandwidth is fine. But for weaker
signals, narrower bandwidth avoids interference from adjacent signals that
are stronger. It wasn't uncommon for FM DXers to swap the ceramic filters
in their FM receivers from the often 280KHz bandwidth to down about
180KHz, at one time one could go to a catalog and order Murata ceramic
filters in a range of bandwidths. If you don't need FM, you can get by
with narrower, though of course nt in the tens of KHz wide.

The scanner wants "narrow" for two way communication which is narrow
deviation, 10KHz or smaller in recent years. The wide is for broadcast FM
and maybe some other things, since yes, the "narrow" in this case is way
too narrow for FM broadcast. Of course, the wider bandwidth can be useful
for things like receiving weather satellites, which may have a wider
deviation of something like 40KHz, but also because of doppler shift, an
even wider bandwidth makes things easier. I know I've seen modifications
for scanners to use with weather satellites, and they bypass the narrow
filter at 455KHz, which leaves an FM broadcast band type ceramic filter at
the first IF of 10.7MHz.

There was a time twenty years ago when I was bringing home lots of Delco
car radios from garage sales. I'm not sure what the FM filter is in
there, but they certainly seemed to have better skirt selectivity than
other FM radios I'm familiar with. The AM filters seeemd sharper too.

Michael



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