Maker Pro
Maker Pro

Above 108MHz with FM radio (or other)?

C

Clarence

Jan 1, 1970
0
Jonathan Kirwan said:
I exclude anything from Clarence, so I'm luckily never bothered with any of it
except when others follow up. Oh, well. So I missed some of the exchange until
now.

I am delighted to think you would ignore me. I know I lost all interest in
your insipid insults long ago, and will ask that no one respond to this so you
will never know how delighted I am!
Regarding this exchange, Steve, I can tell you that when I was wrestling with
ideas for a phone indicator that relied on the phone line for power, dbowey was
very well informed on the subject and told me some things I was wrong in
assuming about it. More, he took the time and trouble to drive quite some
distance and meet me personally to help me further by giving me an original of
the appropriate specifications I needed to read. I still have those on my shelf
and I've spent time going though the parts I needed to read.

Well since I have only designed four PBX systems, including one for the
Airforce, I have little to contribute. Especially with the poor conduce I have
experienced from you and your leftist associates.

You don't get help like that, often, and he provided something that really isn't
all that easy to go find, either. He offered without my asking and I think he's
very generous when someone shows even a little effort. And that's as much as
any of us deserve to hope for, really.

Your comment is just malicious.
And entirely accurate!
 
J

John Fields

Jan 1, 1970
0
Jonathan Kirwan said:
I am delighted to think you would ignore me. I know I lost all interest in
your insipid insults long ago, and will ask that no one respond to this so you
will never know how delighted I am!

---
A method which assures that communication can't occur is to refrain
from communicating. You, however, can't bear not to throw what you'd
like to be a unilateral barb, and would like to enlist others to play
your stupid game.

Yes, stupid. You're basically a one-trick pony with aspirations to
mediocrity, and your one trick is posturing.
---
Well since I have only designed four PBX systems, including one for the
Airforce, I have little to contribute.

---
Apparently.

What you may or may not have done in the past is of no consequence
when your technical performance here is shabby and littered with your
obvious inadequacies.
---
Especially with the poor conduce I have experienced from you and your leftist associates.

---
Perhaps you meant "conduct"?

Before you cast aspersions, you should take a look at your own posting
history. Look at it objectively and you'll discover a dossier of
rudeness posted by a minor intellect.
---
And entirely accurate!

---
Your admission of its obviouisly malicious nature and yours, by
association, is accepted.

Your claims, without proof, as to its accuracy are not.
Barium titanate _is_ used as a capacitor dielectric.
 
B

Bob Myers

Jan 1, 1970
0
John Fields said:
You seem to have neglected to point out that in the context of _this_
thread, and in generally accepted RF terminology, 'mixing' refers to a
process which results in previously nonesistent sidebands being
generated. Were audio recording being discussed in this thread, then
'mixing' might, in that context, refer to the algebraic summation of
various signals, not to the multiplication required for modulation.

A slight nit to pick here, John; there's "mixing" in the sense
that you use it here, and then there's modulation based on
multiplication, which may be something else entirely. A
"mixer", meaning the specific sort of circuit that this term is
generally applied to, does preserve the original frequencies.
However, a "balanced mixer" does not, and the difference is
that the latter actually DOES perform an operation that is
solely a multiplication. In mathematical terms:

sin(A) * sin(B) = 1/2[cos(A-B) - cos(A+B)]

which clearly doesn't have the original frequencies in the output.
So pure multiplication results in DSBSC, which is then often
converted to SSB by filtering out one of the sidebands.
To get the original carrier back, a constant term has to be introduced,
i.e.,

sin(A) * [K + sin(B)]

Here, the K term corresponds to the DC offset which exists
when , for instance, the modulating signal (here, sin(B)) is applied
to the carrier (sin (A)) via a modulation transformer (classically,
in the "plate" circuit of a class C output stage), as is the case very
commonly in commercial AM installations. The result is
conventional "AM", with a "full" carrier.

Just to clarify that for those who may be trying to follow the
terminology, since this IS sci.electronics.basics after all. I
know YOU know this stuff already...

Bob M.
 
S

Steve Evans

Jan 1, 1970
0
You don't get help like that, often, and he provided something that really isn't
all that easy to go find, either. He offered without my asking and I think he's
very generous when someone shows even a little effort. And that's as much as
any of us deserve to hope for, really.

Your comment is just malicious.

whkatever.. i'm so happy for you.. it still doesn't alther the fact
that the majoritiy of his remarks I found on Google were simply
disparaging one-liners often made without the slightest provokation.
 
S

Steve Evans

Jan 1, 1970
0
Yes they do, but they are of no significance in this case, the sum- or
difference-signal is what interests us after the mixing.

sorry, roger, but I think Bob Myers is the only person here to have
got it absolutely right.
 
R

Roger Johansson

Jan 1, 1970
0
sorry, roger, but I think Bob Myers is the only person here to have
got it absolutely right.


Even a double balanced mixer cannot completely remove the two
frequencies we start with, only lower their level a lot.

In this case there is no need for that level of detail. The OP just
wanted a simple way to tune in the air band on a common FM radio.

If he had asked for a very high quality communications receiver class
solution there would have been a need to talk about double balanced
mixers.
 
J

Jonathan Kirwan

Jan 1, 1970
0
whkatever.. i'm so happy for you.. it still doesn't alther the fact
that the majoritiy of his remarks I found on Google were simply
disparaging one-liners often made without the slightest provokation.

It's the "disparaging" and "without the slightest provocation" parts that I'd
probably not see eye to eye with you, about. When I first wrote my question
(and you can check google) on these phone indicators that I wanted to operate
without a battery, his reply wasn't exactly sugar and honey -- but it was
exactly the kind of information I didn't have and needed to hear about:
A 220uA on-hook loop current is too much. You should use the 4.7M resistor.
The FCC R&R require a minimum of 5M of customer premises equipment loop
resistance in the on-hook state. Also. at 220uA some Central Offices will
declare a line fault and remove the line from service.

He made the job really hard for me to properly achieve. But then, learning to
get the job done well and right, even for a hobbyist, isn't a bad thing. One
grows from it and learns better why the standards *are* standards, too. In the
end, I developed a circuit that presents 20M continuous (it doesn't present
different momentary loads) to the phone line and still provides me with an LED
indicator. Don's challenge to me was from someone who knew the material and I
worked to meet it.

I think Don is brusk when people start asking about pirate broadcasting or else
receiving broadcasts on bands where they aren't supposed to (for experimental
purposes when you are licensed it is one thing, but for general tapping in it is
another), when it looks even something like that's what the question is about.
He pushes those considering such ideas to find another avenue, just as I'm
certain he was pressing me to not improperly hook up equipment to my phone lines
that was ignorant of the intended use and might otherwise interfere with it.

I can respect that.

In any case, he's helped at least one person I know of. Me.

Jon
 
S

Steve Evans

Jan 1, 1970
0
In any case, he's helped at least one person I know of. Me.

thats fair enouugh, Johathan. You gotta speak as you find.
 
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