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On 04/11/2015 09:33 AM, scott wrote:
>> Huh. And here I was assuming that Apple would have used only the most
>> over-priced hardware components they could source...
>
> As Jim said they will put *a lot* of effort in to sourcing the absolute
> lowest price parts they can find that will "work". I suspect either
> there was a fault with the display you saw, or they had literally shown
> the same image for months on end.
I left a program running overnight. The next morning, even after booting
back into Mac OS, the text was still faintly visible.
>> While we're on the subject, what causes the weird diagonal lines that
>> all RF-modulated signals have?
>
> Non-perfect electronics :-)
Why lines though? Why not random snow or something?
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On Wed, 04 Nov 2015 18:41:26 +0000, Orchid Win7 v1 wrote:
>>> While we're on the subject, what causes the weird diagonal lines that
>>> all RF-modulated signals have?
>>
>> Non-perfect electronics :-)
>
> Why lines though? Why not random snow or something?
Because radio waves are waves, not "random noise". The proximity of the
transmission source means that the wave is stronger than the other random
RFI in the area, so it stands out.
Jim
--
"I learned long ago, never to wrestle with a pig. You get dirty, and
besides, the pig likes it." - George Bernard Shaw
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On 11/4/2015 7:49 PM, Jim Henderson wrote:
> On Wed, 04 Nov 2015 18:41:26 +0000, Orchid Win7 v1 wrote:
>
>>>> While we're on the subject, what causes the weird diagonal lines that
>>>> all RF-modulated signals have?
>>>
>>> Non-perfect electronics :-)
>>
>> Why lines though? Why not random snow or something?
>
> Because radio waves are waves, not "random noise". The proximity of the
> transmission source means that the wave is stronger than the other random
> RFI in the area, so it stands out.
>
I think it is more likely to be that the RF is not properly tuned.
As you and Scott pointed out:
>
> The basic rule of thumb is to buy the least expensive component that meets
> the specifications
The tuning pots are generally only 10 turn pots and it will be hit and
miss to get an exact match.
--
Regards
Stephen
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On Wed, 04 Nov 2015 20:20:20 +0000, Stephen wrote:
> On 11/4/2015 7:49 PM, Jim Henderson wrote:
>> On Wed, 04 Nov 2015 18:41:26 +0000, Orchid Win7 v1 wrote:
>>
>>>>> While we're on the subject, what causes the weird diagonal lines
>>>>> that all RF-modulated signals have?
>>>>
>>>> Non-perfect electronics :-)
>>>
>>> Why lines though? Why not random snow or something?
>>
>> Because radio waves are waves, not "random noise". The proximity of
>> the transmission source means that the wave is stronger than the other
>> random RFI in the area, so it stands out.
>>
> I think it is more likely to be that the RF is not properly tuned.
> As you and Scott pointed out:
>
>
>> The basic rule of thumb is to buy the least expensive component that
>> meets the specifications
>
> The tuning pots are generally only 10 turn pots and it will be hit and
> miss to get an exact match.
Could be - generally a harmonic frequency can cause weirdness as well - I
was more talking about why it's lines and not just snow. The proximity
of the transmitter to the "receiver" is what causes that.
Jim
--
"I learned long ago, never to wrestle with a pig. You get dirty, and
besides, the pig likes it." - George Bernard Shaw
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On 11/4/2015 9:32 PM, Jim Henderson wrote:
> On Wed, 04 Nov 2015 20:20:20 +0000, Stephen wrote:
>
>> On 11/4/2015 7:49 PM, Jim Henderson wrote:
>>> On Wed, 04 Nov 2015 18:41:26 +0000, Orchid Win7 v1 wrote:
>>>
>>>>>> While we're on the subject, what causes the weird diagonal lines
>>>>>> that all RF-modulated signals have?
>>>>>
>>>>> Non-perfect electronics :-)
>>>>
>>>> Why lines though? Why not random snow or something?
>>>
>>> Because radio waves are waves, not "random noise". The proximity of
>>> the transmission source means that the wave is stronger than the other
>>> random RFI in the area, so it stands out.
>>>
>> I think it is more likely to be that the RF is not properly tuned.
>> As you and Scott pointed out:
>>
>>
>>> The basic rule of thumb is to buy the least expensive component that
>>> meets the specifications
>>
>> The tuning pots are generally only 10 turn pots and it will be hit and
>> miss to get an exact match.
>
> Could be - generally a harmonic frequency can cause weirdness as well - I
> was more talking about why it's lines and not just snow. The proximity
> of the transmitter to the "receiver" is what causes that.
>
From the little I know only having worked, with Comms guys. You are
right but then you could tell me anything. It is all magic to me.
They even told me that our phone calls were bounced off the sky and the
sea. And I believed them.
--
Regards
Stephen
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On Wed, 04 Nov 2015 22:14:15 +0000, Stephen wrote:
>> Could be - generally a harmonic frequency can cause weirdness as well -
>> I
>> was more talking about why it's lines and not just snow. The proximity
>> of the transmitter to the "receiver" is what causes that.
>>
>>
> From the little I know only having worked, with Comms guys. You are
> right but then you could tell me anything. It is all magic to me.
> They even told me that our phone calls were bounced off the sky and the
> sea. And I believed them.
Well, I do have a radio license. ;)
Radio signal strength is a factor of power - with a falloff of 1/r^2
(when an antenna is in use, this can vary somewhat depending on the type
of antenna, but that's beyond my knowledge; I've read, for example, that
a dipole antenna ends up being somewhere between 1/r^2 and 1/r).
But that's the reason that proximity to the transmission point for the EM
waves matters - and a closer but power power (at transmission point)
overpower a signal that's farther away but stronger. With a 5W
transmitter that's not well filtered, an amateur radio operator can
disrupt commercial radio (AM/FM) and TV (VHF/UHF) transmissions quite
significantly. Every amateur radio operator has to learn at least a
little about this in the US, because we're responsible for dealing with
harmful interference we might cause with our gear.
Even with well-filtered equipment, though, if I put the transmission
source for my radio right next to a computer monitor or CRT display, I
can cause some interference.
Jim
--
"I learned long ago, never to wrestle with a pig. You get dirty, and
besides, the pig likes it." - George Bernard Shaw
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On 11/4/2015 10:53 PM, Jim Henderson wrote:
> On Wed, 04 Nov 2015 22:14:15 +0000, Stephen wrote:
>
>>> Could be - generally a harmonic frequency can cause weirdness as well -
>>> I
>>> was more talking about why it's lines and not just snow. The proximity
>>> of the transmitter to the "receiver" is what causes that.
>>>
>>>
>> From the little I know only having worked, with Comms guys. You are
>> right but then you could tell me anything. It is all magic to me.
>> They even told me that our phone calls were bounced off the sky and the
>> sea. And I believed them.
>
> Well, I do have a radio license. ;)
>
So do I. Albeit the lowest level (RT). I could use a marine radio on a
fishing vessel or stand in for the RO on an Oil Rig.
> But that's the reason that proximity to the transmission point for the EM
> waves matters - and a closer but power power (at transmission point)
> overpower a signal that's farther away but stronger. With a 5W
> transmitter that's not well filtered, an amateur radio operator can
> disrupt commercial radio (AM/FM) and TV (VHF/UHF) transmissions quite
> significantly. Every amateur radio operator has to learn at least a
> little about this in the US, because we're responsible for dealing with
> harmful interference we might cause with our gear.
>
It is quite a fearsome exam. With Morse code and regulations.
> Even with well-filtered equipment, though, if I put the transmission
> source for my radio right next to a computer monitor or CRT display, I
> can cause some interference.
>
Don't forget the cable. Bad connections can cause reflections. ;-)
--
Regards
Stephen
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On Thu, 05 Nov 2015 00:12:17 +0000, Stephen wrote:
> On 11/4/2015 10:53 PM, Jim Henderson wrote:
>> On Wed, 04 Nov 2015 22:14:15 +0000, Stephen wrote:
>>
>>>> Could be - generally a harmonic frequency can cause weirdness as well
>>>> -
>>>> I
>>>> was more talking about why it's lines and not just snow. The
>>>> proximity of the transmitter to the "receiver" is what causes that.
>>>>
>>>>
>>> From the little I know only having worked, with Comms guys. You are
>>> right but then you could tell me anything. It is all magic to me.
>>> They even told me that our phone calls were bounced off the sky and
>>> the sea. And I believed them.
>>
>> Well, I do have a radio license. ;)
>>
>>
> So do I. Albeit the lowest level (RT). I could use a marine radio on a
> fishing vessel or stand in for the RO on an Oil Rig.
I thought you did - so I was a little surprised. :)
>> But that's the reason that proximity to the transmission point for the
>> EM waves matters - and a closer but power power (at transmission point)
>> overpower a signal that's farther away but stronger. With a 5W
>> transmitter that's not well filtered, an amateur radio operator can
>> disrupt commercial radio (AM/FM) and TV (VHF/UHF) transmissions quite
>> significantly. Every amateur radio operator has to learn at least a
>> little about this in the US, because we're responsible for dealing with
>> harmful interference we might cause with our gear.
>>
>>
> It is quite a fearsome exam. With Morse code and regulations.
Code isn't required in the US any more - they dropped it out of (as I
understand it) fear that not enough people would join the hobby to
justify the spectrum use.
>> Even with well-filtered equipment, though, if I put the transmission
>> source for my radio right next to a computer monitor or CRT display, I
>> can cause some interference.
>>
>>
> Don't forget the cable. Bad connections can cause reflections. ;-)
Oh yes, absolutely. I also tend to pick up RF from my PCs on my
headphones (the ones plugged into the PC), even with a proper ground.
Jim
--
"I learned long ago, never to wrestle with a pig. You get dirty, and
besides, the pig likes it." - George Bernard Shaw
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> I left a program running overnight. The next morning, even after booting
> back into Mac OS, the text was still faintly visible.
That should go away after a while, but I'd be careful leaving a static
image for any longer on that screen if that happens already after just a
night.
>>> While we're on the subject, what causes the weird diagonal lines that
>>> all RF-modulated signals have?
>>
>> Non-perfect electronics :-)
>
> Why lines though? Why not random snow or something?
Designing RF stuff is tricky as every part of your circuit will blast
all the other parts with whatever signal is on it. I suspect it's just
some interference or some component creating harmonics, and they just
happen to manifest as diagonal lines.
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On 11/5/2015 1:08 AM, Jim Henderson wrote:
> On Thu, 05 Nov 2015 00:12:17 +0000, Stephen wrote:
>
>>>
>>> Well, I do have a radio license. ;)
>>>
>>>
>> So do I. Albeit the lowest level (RT). I could use a marine radio on a
>> fishing vessel or stand in for the RO on an Oil Rig.
>
> I thought you did - so I was a little surprised. :)
There is a big difference between being able to use a radio and design
and maintenance.
>>>
>>>
>> It is quite a fearsome exam. With Morse code and regulations.
>
> Code isn't required in the US any more - they dropped it out of (as I
> understand it) fear that not enough people would join the hobby to
> justify the spectrum use.
>
It's not? I thought it was an international requirement for a Ham
licence. Even at foundation level (5 wpm).
>>> Even with well-filtered equipment, though, if I put the transmission
>>> source for my radio right next to a computer monitor or CRT display, I
>>> can cause some interference.
>>>
>>>
>> Don't forget the cable. Bad connections can cause reflections. ;-)
>
> Oh yes, absolutely. I also tend to pick up RF from my PCs on my
> headphones (the ones plugged into the PC), even with a proper ground.
>
See, black magic. :-)
--
Regards
Stephen
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