Mailing List Archive: AIMS Labs radio card: frequency limit

AIMS Labs radio card: frequency limit

Jan 9, 1999, 1:53 PM

Post #1 of 8 (940 views)

Hi!
It seems that the video4linux driver for the AIMS Labs radio card
(or the equivalent Reveal RadioTrack) limits the usable frequency range
to 88-108 MHz. Why?
Here in K-Town, Germany, there are two radio stations with frequencies
below 88 Mhz (Deutschlandfunk and CFN Frankfurt). If I try to choose one
of them with the fm-tools I get the following error message:
"Frequency 87.6 out of range (88.0 - 108.0 MHz)".
I solved the problem by simply changing the rangelow value like this
(kernel 2.2.0pre6):
--- linux.orig/drivers/char/radio-aimslab.c Sat Jan 9 21:40:58 1999
+++ linux/drivers/char/radio-aimslab.c Sat Jan 9 18:02:50 1999
@@ -228,7 +228,7 @@
return -EFAULT;
if(v.tuner) /* Only 1 tuner */
return -EINVAL;
- v.rangelow=(88*16);
+ v.rangelow=(87*16);
v.rangehigh=(108*16);
v.flags=0;
v.mode=VIDEO_MODE_AUTO;
Ciao,
Kuehly
--
Andreas Kuehlmeyer ! "Do not meddle in the affairs of wizards, for
kuehly@gmx.de ! you are crunchy and good with ketchup."
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Re: AIMS Labs radio card: frequency limit [ In reply to ]

rkroll at exploits

Jan 10, 1999, 5:07 PM

Post #2 of 8 (939 views)

> From: kuehly@gmx.de
> It seems that the video4linux driver for the AIMS Labs radio card
> (or the equivalent Reveal RadioTrack) limits the usable frequency range
> to 88-108 MHz. Why?
I'm responsible for some of the code in that driver, so I'll field this
one. The commercial FM band over here is defined as a range from 87.9 to
107.9 using the odd tenths values. The 88-108 range never presented a
problem, so it stayed that way.
> I solved the problem by simply changing the rangelow value like this
> (kernel 2.2.0pre6):
That patch should be fine. I imagine other users will report similar
range issues as 2.2 spreads to other parts of the world and similar
changes will have to be applied then.
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Re: AIMS Labs radio card: frequency limit [ In reply to ]

vojtech-lists at twilight

Jan 13, 1999, 11:17 AM

Post #3 of 8 (937 views)

On Sun, Jan 10, 1999 at 05:07:35PM -0700, Russell Kroll wrote:
> I'm responsible for some of the code in that driver, so I'll field this
> one. The commercial FM band over here is defined as a range from 87.9 to
> 107.9 using the odd tenths values. The 88-108 range never presented a
> problem, so it stayed that way.
That reminds me that some stations in the countries of the eastern Europe
still broadcast in the OIRT frequency range, which is 64 - 73 MHz, below
the western CCIR range 88 - 108 MHz. Myself I think no artificial limits
should be set for the receiving frequency, and just let the hardware do what
it can.
Vojtech
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Re: AIMS Labs radio card: frequency limit [ In reply to ]

alan at lxorguk

Jan 13, 1999, 12:35 PM

Post #4 of 8 (936 views)

> That reminds me that some stations in the countries of the eastern Europe
> still broadcast in the OIRT frequency range, which is 64 - 73 MHz, below
> the western CCIR range 88 - 108 MHz. Myself I think no artificial limits
> should be set for the receiving frequency, and just let the hardware do what
> it can.
The API return is supposed to be what the card can take. Of course most radio
cards are reverse engineering jobs so its not always clear
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Re: AIMS Labs radio card: frequency limit [ In reply to ]

rkroll at exploits

Jan 13, 1999, 1:04 PM

Post #5 of 8 (941 views)

> > the western CCIR range 88 - 108 MHz. Myself I think no artificial limits
> > should be set for the receiving frequency, and just let the hardware do what
> > it can.
>
> The API return is supposed to be what the card can take. Of course most radio
> cards are reverse engineering jobs so its not always clear
Indeed. The best way IMO to establish exactly what the card can handle
would be to generate audio signals on arbitrary frequencies and then try
to tune them. Sometimes the data sheets lie ... also, I've found that a
board's implementation of the design often excludes a feature or two
that's technically available on the tuner chip or similar.
If someone finds that they can pick up a signal outside the range in the
kernel reliably, then expansion of that range is probably warranted.
Anything else is just guesswork unless it's based on some authoritative
source of information for the hardware in question.
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Re: AIMS Labs radio card: frequency limit [ In reply to ]

alan at lxorguk

Jan 15, 1999, 3:01 PM

Post #6 of 8 (940 views)

> Probably a better choice would be for the kernel to assume that it
> can, and report an error if the hardware says otherwise, at least as
> far as that is possible...
Believe me the PC radio cards are far far too stupid to know that
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Re: AIMS Labs radio card: frequency limit [ In reply to ]

rkroll at exploits

Jan 15, 1999, 4:11 PM

Post #7 of 8 (938 views)

> Probably a better choice would be for the kernel to assume that it
> can, and report an error if the hardware says otherwise, at least as
> far as that is possible...
That assumes that the radio card is able to indicate that a frequency is
unattainable. Unfortunately, when it comes to tuning, these things are
pretty stupid and don't report much back. The aztech, aimslab, and cadet
radio cards all suck down tuning bits but only the cadet will let you read
them back.
For most of these things, a human has to be in the loop doing experiments
to figure out exactly what the limits are. There are also modifications
possible to these cards that will alter the range, so a fixed value isn't
always good either.
I imagine that allowing "freqlow" and "freqhigh" as options for
insmod/modprobe would allow users in various locations to try different
frequencies to see what happens. This is obviously out of the question
right now, so I will pursue it when 2.3 development starts. It keeps the
idea of "let clued people change values" alive, which is always a good
thing.
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Re: AIMS Labs radio card: frequency limit [ In reply to ]

Jan 16, 1999, 5:54 AM

Post #8 of 8 (937 views)

Hi Alan.
>> Probably a better choice would be for the kernel to assume that it
>> can, and report an error if the hardware says otherwise, at least
>> as far as that is possible...
> Believe me the PC radio cards are far far too stupid to know that
Believe me, I'm somehow not surprised...
Best wishes from Riley.
---
* ftp://ftp.MemAlpha.cx/pub/rhw/Linux
* http://www.MemAlpha.cx/~rhw/kernel.versions.html
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