Above 108MHz with FM radio (or other)?

[Roger Johansson]

Steve Evans <smevans@jif-lemon.co.mars> wrote:

And don't the original signals remain?

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

not normally, but Roger's proposing something rather _ab_normal!

If you look through radio amateur and DX magazines you will find ads for
small converter boxes you connect to the antenna to listen to frequencies
outside the radio's built-in bands. The box only contains a simple, but
stable, oscillator.

Theoretically, someone might say that the mixing of signals have to be
done in a non-linear component, like a diode or a transistor, and there
is no such component in the antenna.

But there usually is a non-linear component in the input stage of the
radio, and that's where the actual mixing takes place.



--
Roger J.

....what is really abnormal in the human society is what needs a lot of
training and violence to be "created", the male mind, for example.
that is what creationism is really about, the "creation" of the eternal
love and the holy matrimony, the holy ghost and the holy wrath, the
institution of the church and the mental training of young girls to
become convincing love machines..
...this leads to a dualistic society, heaven and earth, where a lot of
determinism, based on anger, is needed to have free will in social
life.. it will only cost you your soul and your sound judgement, but
what do you care about the soul, when love feels like a powerful drug.
Anger plus conviction becomes the God state of mind.
Holy cows are very convincing, and anger is what the tv is full of every night..
...sometimes the gods fail in "creating" a man, because he refuses to become
angry, then they crucify him and kill him instead..

 

[Richard The Troll]

On Mon, 13 Dec 2004 17:12:58 -0600, John Fields wrote:

On Mon, 13 Dec 2004 22:55:10 GMT, Steve Evans
On Mon, 13 Dec 2004 10:37:12 -0600, John Fields
On 13 Dec 2004 03:57:05 GMT, Roger Johansson <no-email@home.se> wrote:
When signals of different frequencies are mixed you get two resulting
frequencies, the sum and the difference between the two frequencies.
---
Don't you mean the sum _of_ and the difference between the two
frequencies?

yes.

And don't the original signals remain?

not normally, but Roger's proposing something rather _ab_normal!
---
If you heterodyne a couple of signals, f1 and f2, what you'll get out
of the mixer will be f1, f2, f1+f2, and f1-f2, so the original signals
_do_ remain; I was chiding Roger for his omission and for his little
grammatical error in the light of his recent native-English
speaker/America-bashing outbreak. Also, his proposal about mixing
with a second local oscillator was far from abnormal, it's done all
the time and it's called double conversion, as I recall.

This is "basics," right? I think it's worthwhile to point out the
difference between heterodyning and just plain old ordinary "mixing". If
you just send two signals through a circuit, if the circuit is linear, you
simply get the two input frequencies in the output. There has to be some
sort of nonlinearity to cause them to modulate each other to cause there
to be sum and difference frequencies. I'd think that this kind of spoils
the idea of just setting a 30 MHz oscillator next to your antenna, and
expecting to pick up 160 MHz transmissions at 100 MHz on your FM tuner.

The beat frequencies you hear when you're calibrating your short-wave
receiver actually get produced in the detector, which the tutorials always
show as just a diode.

Plus, you have to have some selectivity at the frequency of interest, in
this case, 160 MHz, and the mixing has to be done in a circuit that's
designed to cause them to heterodyne against each other. Just an
ordinary diode would work, if the 160 MHz signal swamps out everything
else at your location. Or maybe if the 30 MHz drives the RF amp or first
mixer into saturation every half-cycle. That'd be pretty non-linear.

Thanks!
Rich

 

[Jonathan Kirwan]

On Mon, 13 Dec 2004 22:55:09 GMT, Steve Evans <smevans@jif-lemon.co.mars> wrote:

"Dbowey" has never conrtibuted anything of value to _anything_ from
what i can gather.

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.

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.

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.

Jon

 

[John Fields]

On Tue, 14 Dec 2004 05:54:28 GMT, Richard The Troll <rtt@example.net>
wrote:

On Mon, 13 Dec 2004 17:12:58 -0600, John Fields wrote:
On Mon, 13 Dec 2004 22:55:10 GMT, Steve Evans
On Mon, 13 Dec 2004 10:37:12 -0600, John Fields
On 13 Dec 2004 03:57:05 GMT, Roger Johansson <no-email@home.se> wrote:
When signals of different frequencies are mixed you get two resulting
frequencies, the sum and the difference between the two frequencies.
---
Don't you mean the sum _of_ and the difference between the two
frequencies?

yes.

And don't the original signals remain?

not normally, but Roger's proposing something rather _ab_normal!
---
If you heterodyne a couple of signals, f1 and f2, what you'll get out
of the mixer will be f1, f2, f1+f2, and f1-f2, so the original signals
_do_ remain; I was chiding Roger for his omission and for his little
grammatical error in the light of his recent native-English
speaker/America-bashing outbreak. Also, his proposal about mixing
with a second local oscillator was far from abnormal, it's done all
the time and it's called double conversion, as I recall.

This is "basics," right? I think it's worthwhile to point out the
difference between heterodyning and just plain old ordinary "mixing". If
you just send two signals through a circuit, if the circuit is linear, you
simply get the two input frequencies in the output. There has to be some
sort of nonlinearity to cause them to modulate each other to cause there
to be sum and difference frequencies.

---
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.
---

I'd think that this kind of spoils
the idea of just setting a 30 MHz oscillator next to your antenna, and
expecting to pick up 160 MHz transmissions at 100 MHz on your FM tuner.

---
Then you'd think wrong, since all that's necessary for the sidebands
to be generated is for the gain of the front end to be made to vary by
the new 30MHz local oscillator.

In addition, it wasn't a 160MHz carrier which was being discussed, it
was 130MHz.

From the OP:

"I was wondering if there is any type of receiver I can find/purchase
that would be
capable of tuning above the FM band, like from say 100 to 130 MHz."

And Roger's reply:

"Connect a signal generator, or a home built oscillator, to the
antenna, set the oscillator to 30 MHz.

A signal of 130 MHz coming in to the antenna will be mixed with the 30
MHz from the oscillator and produce a 100 MHz signal and a 160 MHz
signal. The 100 MHz signal will be recieved by the radio as if it was
a
normal FM station."

which was correct.
---

The beat frequencies you hear when you're calibrating your short-wave
receiver actually get produced in the detector, which the tutorials always
show as just a diode.

---
So what? All that proves is that two carriers separated in frequency
by the frequency of the beat note are being allowed to propagate all
the way the through the RF and IF chain to the detector, where they
mix, or that a signal is being injected somewhere which eventually
yields the beat note. For instance, a CW carrier generating a 455kHz
IF will generate a 1kHz beat note if a 456kHz signal is injected into
the IF.
---

Plus, you have to have some selectivity at the frequency of interest, in
this case, 160 MHz, and the mixing has to be done in a circuit that's
designed to cause them to heterodyne against each other. Just an
ordinary diode would work, if the 160 MHz signal swamps out everything
else at your location. Or maybe if the 30 MHz drives the RF amp or first
mixer into saturation every half-cycle. That'd be pretty non-linear.

---
You need no selectivity, all you need is for the new 30MHz local
oscillator to change the gain of the front end so that it looks like a
mixer and beats the 130MHz carrier down to 100MHz. From that point
on, the RF section of the radio looks like a new IF and the radio
becomes, effectively a double conversion superhet with a wide-open
front end.

--
John Fields

 

[Clarence]

"Jonathan Kirwan" <jkirwan@easystreet.com> wrote in message
news:068tr0dauc8pkisgj8ba5kp0glvaepvvle@4ax.com...

On Mon, 13 Dec 2004 22:55:09 GMT, Steve Evans <smevans@jif-lemon.co.mars
wrote:

"Dbowey" has never contributed anything of value to _anything_ from
what I can gather.

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!

> Jon

 

[John Fields]

On Tue, 14 Dec 2004 16:21:49 GMT, "Clarence" <no@No.com> wrote:

"Jonathan Kirwan" <jkirwan@easystreet.com> wrote in message
news:068tr0dauc8pkisgj8ba5kp0glvaepvvle@4ax.com...
On Mon, 13 Dec 2004 22:55:09 GMT, Steve Evans <smevans@jif-lemon.co.mars
wrote:

"Dbowey" has never contributed anything of value to _anything_ from
what I can gather.

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!

---
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.
---

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.

---
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.
---

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!

---
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.

--
John Fields

 

[Bob Myers]

"John Fields" <jfields@austininstruments.com> wrote in message
newsr0ur05fva533etmpj9imjkab1cvmilvvj@4ax.com...

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.

 

[Jonathan Kirwan]

On Tue, 14 Dec 2004 23:51:52 GMT, Steve Evans <smevans@jif-lemon.co.mars> wrote:

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