Driver to drive?

[Joerg]

Hi Terry,

... Phrases like "We dont need a contract specifying deliverables,
just do..." now ring alarm bells.

Sometimes it is nearly impossible to foresee the scope of a redesign.
Under those circumstances there is only one mode in which I work. By the
hour.

They went broke a few years later...

That isn't surprising ;-)

Regards, Joerg

http://www.analogconsultants.com

 

[Charles Schuler]

"Dave" <db5151@hotmail.com> wrote in message
news:ckk9bu$28c@library2.airnews.net...

I am wanting to build a simple RF amplifier to boost the signal to my
television, and then use the knowledge I gained in that project to build a
second RF amplifier to boost and filter the signals I receive on my
Shortwave radio (which I connect to a random-wire antenna up on the roof.)
I have a background in electronics (with the exceptions listed earlier)
and
would like to keep on learning in this new direction. I do have a simple
workshop set up (again, after 20 years) and am basically seeking to pick
up
the hobby again.

Wideband RF amplifiers are not a beginner's project. Not trying to
discourage you, but to cover 54 to 800 MHz with decent noise performance and
gain is not easy. If you want to boost one channel (or so) that's more
manageable. Short wave covers 2 to 30 MHz and many preamps are already out
there. By the way, the sensitivity of many modern receivers is such that
little can be gained (pun) with a preamplifier. Ramsey electronics might
have some kits. Nothing wrong with kits for a beginner. Also, you can
Google for some schematics.

Again, the ARRL handbook is a gem if you really want to learn RF.
Electronics can be a fun hobby. It's just not as easy as it once was to
come up with anything significant at home.

 

[Joerg]

Hi John,

What smooths the chop into a sine? Leakage inductance in the
transformer?


Nowadays they do a fine PWM adjust over each half-cycle. With modern PWM

chips that wouldn't be a big deal and that is why I don't understand the
price difference. The sine is approximated by increasing and decreasing
duty cycle, or in some cases, bursts.

Just imagine you had an LM3478 with plenty of loop bandwidth and instead
of feeding the feedback pin directly you'd run this through an opamp
first where the other input is fed a sine wave from a DAC. With a uC
this is even easier because you can have the sine pattern laid down in
its flash memory, plus it can drive the H-bridge as well. That is where
a uC might be the most cost effective solution. Still, I wasn't aware
the inverter guys already did that.

Regards, Joerg

http://www.analogconsultants.com

 

[Dave]

"Charles Schuler" <charleschuler@comcast.net> wrote in message
news:RMmdnfmPCo81WPDcRVn-oA@comcast.com...

"Dave" <db5151@hotmail.com> wrote in message
news:ckk9bu$28c@library2.airnews.net...
I am wanting to build a simple RF amplifier to boost the signal to my
television, and then use the knowledge I gained in that project to build
a
second RF amplifier to boost and filter the signals I receive on my
Shortwave radio (which I connect to a random-wire antenna up on the
roof.)
I have a background in electronics (with the exceptions listed earlier)
and
would like to keep on learning in this new direction. I do have a
simple
workshop set up (again, after 20 years) and am basically seeking to pick
up
the hobby again.

Wideband RF amplifiers are not a beginner's project. Not trying to
discourage you, but to cover 54 to 800 MHz with decent noise performance
and
gain is not easy. If you want to boost one channel (or so) that's more
manageable. Short wave covers 2 to 30 MHz and many preamps are already
out
there. By the way, the sensitivity of many modern receivers is such that
little can be gained (pun) with a preamplifier. Ramsey electronics might
have some kits. Nothing wrong with kits for a beginner. Also, you can
Google for some schematics.

Again, the ARRL handbook is a gem if you really want to learn RF.
Electronics can be a fun hobby. It's just not as easy as it once was to
come up with anything significant at home.

Hmm. I have a schematic I intend to follow for the SW part (MFJ 1020A) and
have already purchased the discrete components, but realized I don't know
much about actual construction, which is the basis of what I am wanting to
pursue. For the TV part, I am thinking only of channels 2-69, or something
like that. 54 - 450 Mhz is what I have in mind. The reasoning behind this
is that our old VCR gave us fantastic reception, but the new one doesn't
(same antenna but in a different location- it used to be mounted on the
carport, and is now in back.) I've been told repeatedly that VCR's don't
amplify the incoming signal, but that VCR did (signal quality dropped
significantly when I was taken out of the circuit.) For the TV RF amplifier
I am planning on using a couple of NTE10 VHF/UHF amplifiers, equivelant to
the 2SC3510. I figured I would come up with my own schematic after
digesting Wes Hayward's book, and perhaps Christopher Bowick's. (I have
time on my hands, and don't mind the research.) If you have a suggested
source for schematics I am all ears. For that matter, I'm all ears anyway.
I am just trying to pursue my old high-school hobby of tinkering and using
what I learn to build something usefull.

Thanks,

Dave
db5151@hotmail.com

 

[Nicholas O. Lindan]

I am wanting to build a simple RF amplifier to boost the signal to my
television,

You can buy a 4-output distribution amplifier for ~$25 (?) at Radio Shack.
This is useful to mitigate cable loss if you have a lot of TVs in your house.
It won't improve your reception.

'Building' an amplifier will teach you nothing but how to screw and solder.
Designing a wide-band RF amplifier for the VHF & UHF TV broadcast bands is
another
matter - a whole bunch of university level circuit design courses should about
do it. And you will need all sorts of very pricey RF instrumentation to
verify the design.

and then use the knowledge I gained in that project to build a
second RF amplifier to boost and filter the signals I receive on my
Shortwave radio (which I connect to a random-wire antenna up on the roof.)

A 'random wire' antenna? I had one of those when I was young, are they
mainstream nowadays?

A pre-amp will not help you receive signals. The only thing that will help
is a very _non-random_ set of antennas: an antenna for each band; directional;
rotatable; on the highest tower the zoning ordinance will let you get away
with; on the highest ground in the neighborhood.

Again, the ARRL handbook is a gem if you really want to learn RF.

Good idea. Start simple. Start in the 80 meter band where AOTE (Any
Old Test Equipment) will be adequate.

Get a novice license (do they still have novice licenses?).

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
Remove spaces etc. to reply: n o lindan at net com dot com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/

 

[Country Loon]

"Brian Raab" <kaisers_sun@yahoo.com> wrote in message
news:8d001dc6.0410071808.6e3f9c4f@posting.google.com...

Tested it on myself, unfortunately something went wrong and it reduced
my IQ from 150 to 15.

What can I do now?
Try supporting Man United.

Tom

 

[Ken Smith]

In article <LQibd.357$0O.16758@news.xtra.co.nz>,
Terry Given <my_name@ieee.org> wrote:
[...]

yep. Alas this was a buck-derived converter The argument was that it
was for charging batteries, which look like a cap. My argument was that
it has to meet EMC standards when attached to a battery by a pair of
wires (no doubt forming a nice big loop). And customers probably expect
DC out of a DC power supply

Someone I know missed the FCC spec by a mere 50dB with a design sort of
like that. The design started off as a class "D" with no output side
filter because "the load doesn't care". After much redesign and about 6
more poles, it met the spec.

have you ever built a zero-ripple cuk converter?

I've build an "almost no ripple on the input side when the voltage is just
so SEPIC design". It got the input ripple way down at the cost of some
added complexity. The system had a very restricted input ripple current
spec.

I had to draw just a smidge under 0.24A at all times. The ripple IIRC had
to be less than 0.02mA in the "band of interest".

I suspect no output
cap is theory only

I think no output cap lives in the same fairy tail land as the perfect
diode.

--
--
kensmith@rahul.net forging knowledge

 

[Chaos Master]

Quoting Paul Burridge [pb@notthisbit.osiris1.co.uk], that posted to
sci.electronics.design on Wed, 13 Oct 2004 11:36:42 +0100:

Gosh! That's a bit effusive for you, John!
Seriously, I agree. Windoze is a non-starter. Apart from being a
flaky, bug-ridden, crash-prone pile of sh*t, it's also got too many
security holes and backdoors into it to be suitable for defence
purposes.

I would never use Windows on those applications. Nor Linux, as *nixes like to
core dump at the worst moments.

[]s
--
Chaos MasterŽ, posting from Brazil.
"I'd rather be hated for who I am, than loved for who I am not." -- Kurt Cobain

Evanescence: http://marreka.no-ip.com | Lies: http://tinyurl.com/46vru |
/dev/null: http://renan182.no-ip.org

 

[Terry Given]

John Larkin wrote:

On Thu, 14 Oct 2004 00:22:15 GMT, Joerg
notthisjoergsch@removethispacbell.net> wrote:


Hi John,


What smooths the chop into a sine? Leakage inductance in the
transformer?



Nowadays they do a fine PWM adjust over each half-cycle. With modern PWM
chips that wouldn't be a big deal and that is why I don't understand the
price difference. The sine is approximated by increasing and decreasing
duty cycle, or in some cases, bursts.

Just imagine you had an LM3478 with plenty of loop bandwidth and instead
of feeding the feedback pin directly you'd run this through an opamp
first where the other input is fed a sine wave from a DAC. With a uC
this is even easier because you can have the sine pattern laid down in
its flash memory, plus it can drive the H-bridge as well. That is where
a uC might be the most cost effective solution. Still, I wasn't aware
the inverter guys already did that.



There was a company, Nova I think, that did very nice pwm sine
inverters in the 1970's. But I was still wondering how they smooth the
chopping to a sine, given Chris' observation that "There is a small
unit made by TBS in Holland which uses 1 PIC, 2 IR2110 drivers
and a handfull of mosfets. This then feeds a line frequency
transformer. That's all there is in the box." Seems you'd need a
lowpass inductor or a transformer with high-quality leakage inductance
or something.

John

if the transformer leakage inductance was well controlled it could
easily form the inductive component of the required filter, along with
an output cap. Normally this would give the iron a real beating, but
there are ways of dealing with that too, including a tradeoff between
pwm frequency, core loss and cap size.

cheers
Terry

 

[Tam/WB2TT]

"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:9Tjbd.12728$nj.2865@newssvr13.news.prodigy.com...

Hi Richard,

I once saw the a digital filter that was based on one-shot timers. A
friend
of mine was given the project to redesign after the origianl designer had
been encouraged to seek employment elsewhere.

Or phase shifters made from prop delays on chips. Yeccch. I ripped out
that whole circuit and replaced it with an analog solution around the
SD5400. Lots of frowns at first because it was the only analog portion on
a large digital board. They really liked it once they realized that it
reduced cost big time and was totally reliable. The real joy set in when
the phase jitter was gone. Well, it wasn't really gone but went from
outrageous to barely measurable.

Regards, Joerg

http://www.analogconsultants.com

Yoerg,
I have been down that path. Bottom line is that the factory hated it because
they couldn't test it on their bed of nails gizmo.

Tam

 

[Jim Thompson]

On Mon, 11 Oct 2004 17:29:18 -0700, John Larkin
<jjlarkin@highSNIPlandTHIStechPLEASEnology.com> wrote:

OK, I confess that I'm personally involved with Democrats, too. I
sleep with one every night.

John

That must be fun ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Jim Thompson]

On Thu, 14 Oct 2004 00:22:18 -0400, Spehro Pefhany
<speffSNIP@interlogDOTyou.knowwhat> wrote:

On Wed, 13 Oct 2004 21:02:24 -0700, the renowned Jim Thompson
thegreatone@example.com> wrote:

On Mon, 11 Oct 2004 17:29:18 -0700, John Larkin
jjlarkin@highSNIPlandTHIStechPLEASEnology.com> wrote:


OK, I confess that I'm personally involved with Democrats, too. I
sleep with one every night.

John


That must be fun ;-)

...Jim Thompson

He didn't say a *different* one every night. ;-)


Best regards,
Spehro Pefhany

I didn't mean a *different* one every night. Spirit definitely leads
to pleasure ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Clarence]

"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:Swjbd.3556$6q2.2726@newssvr14.news.prodigy.com...

Hi Terry,

... Phrases like "We dont need a contract specifying deliverables,
just do..." now ring alarm bells.

Sometimes it is nearly impossible to foresee the scope of a redesign.
Under those circumstances there is only one mode in which I work. By the
hour.

They went broke a few years later...

That isn't surprising ;-)

Regards, Joerg

Also quite common, I've encountered the phenomena several times.

Clarence

 

[Tom Del Rosso]

"John Larkin" <jjlarkin@highSNIPlandTHIStechPLEASEnology.com> wrote in
message news:ancom0tkqer8738s390u28i7iadj71j1rc@4ax.com...

Windows is good for the tugboat industry:

http://feed.proteinos.com/001229.html

When the author says...

"In the end, what you ask caused such a colossal failure on the Yorktown?
According to a military memo, "the Yorktown lost control of its propulsion
system because its computers were unable to divide by the number zero."

....I get the impression that he thinks, "a half decent computer should *at
least* be able to do *that*".

Anyway, apart from the need to execute the political appointees who chose
NT, isn't a RTOS more suitable than Unix for running a ship?

 

[Dave VanHorn]

That's the king size edition. I never had anything that could run above
12MHz. Everything else was out of the $$$ range.

Remember the CPU clock is 8 MHz.

This would be the leather seats that I usually can't use. Any uC with a
decent ADC on board I saw was over $2 in qties.

$1.44 in 100's from Digikey

That's where I've had the least problems. (none!) ...

Probably you were the HW designer and also did the firmware. Then it's
under your control. It can become challenging when you are asked to join
the uC party as an additional tenant.

Yes, I was

It's not just batteries, electrolytic capacitors can also put on quite a
pyrotechnic show. Wonder where fireworks were invented ;-)

Well, I do find the formula that Jim Williams gives, to be quite useful.

You can prevent saturation on the ol' bipolar transistors with a Schottky
or other pulldown when the collector goes below base. But the beta still
puts a damper on things if you want to do the whole switching with that
one transistor.

Yeah, in this case the driver was a cheap and easy solution.

--
KC6ETE Dave's Engineering Page, www.dvanhorn.org
Microcontroller Consultant, specializing in Atmel AVR

 

[Terry Pinnell]

"Dave" <db5151@hotmail.com> wrote:

I am wanting to build a simple RF amplifier to boost the signal to my
television, and then use the knowledge I gained in that project to build a
second RF amplifier to boost and filter the signals I receive on my
Shortwave radio (which I connect to a random-wire antenna up on the roof.)
I have a background in electronics (with the exceptions listed earlier) and
would like to keep on learning in this new direction. I do have a simple
workshop set up (again, after 20 years) and am basically seeking to pick up
the hobby again.

I realize I started out by making a fool of myself, but really am serious
and would appreciate any help anyone could offer.

Thanks,

Dave

Tim and I already answered your specific question about '||'. That
means 'in parallel', and I gave some examples.

As for '&', now that I see the document, it plainly means simply
'and'! The formula was presumably badly typeset, and should have had a
blank space on both sides of the '&'.

But isn't that obvious from the context? I don't think you're being
careful enough in your reading. In your reply to Paul Burridge you
said: "There is no Rb in the circuit illustration, and R1 is *not*
parrallel with R2."

Directly above the formula in question, the author says:
"The Thevnin equivalent of VCC, R1 and R2 in circuit # 3 is Vin and Rb
in circuit # 2." If you scroll back up to Circuit 2, which you
presumably read earlier, you'll see Rb.

Note that some care is needed when using symbols like 'RB'; in his
Circuit 2 the 'B' is actually a little smaller than the 'R', but it's
not well-positioned. I'd have written 'Rb'. That's particularly
sensible when you have no subscript symbols available, as is the case
in these newsgroup threads.

As for R1 || R2, Thevenin is about *equivalences*. Presumably you've
read up on his Theorem? (One of hundreds of relevant links is:
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/thevenin.html )

So, the 'R1||R2' part of the formula is meant to be read as 'the value
of R1 and R2 in parallel.

The author has also consistently mis-spelt 'Thevenin'.

--
Terry Pinnell
Hobbyist, West Sussex, UK

 

[Rich Grise]

On Wednesday 13 October 2004 04:52 pm, Dave did deign to grace us with the
following:
[please snip better!]

"Tim Wescott" <tim@wescottnospamdesign.com> wrote in message

The "Bf" is forward beta, and is usually denoted with a real, actual
Greek letter beta and a subscripted 'f'; that guy really needs to learn
how to use an equation editor. The "V_f" (he actually managed a real
subscript that time!) is the forward diode drop of the transistor -- one
often just assumes a number like 0.65V and designs as if it won't
change, which works as long as you remember that it _does_ change with
temperature.

Okay, that I can see. Crap. Confusing.

Thanks for your help. Now if I can just figure the rest out...

There might be something in here that might help:
http://www.google.com/search?q=thevenin+equivalent&btnG=Search+the+Web

Good Luck!
Rich

 

[ChrisGibboGibson]

John Larkin wrote:

On 13 Oct 2004 21:42:19 GMT, chrisgibbogibson@aol.com
(ChrisGibboGibson) wrote:


There is a small unit made by TBS in Holland which uses 1 PIC, 2 IR2110
drivers
and a handfull of mosfets. This then feeds a line frequency transformer.
That's
all there is in the box. Pure sinewave output. Fully protected against
overload. Very fast regulation. Very reliable.


What smooths the chop into a sine? Leakage inductance in the
transformer?

Yes. Similar to many line frequency converter UPS units. The transformer is
deliberately built with a higher leakage inductance.

Gibbo

 

[ChrisGibboGibson]

Joerg wrote:

[snip]

I wonder why the true-sine units are four times the price. Is there
really that much more in materials in them? Or is it just 50% more and
the rest is due to low market share?

It's not really related to the cost of manufacture.

It's due to the way the market and the technology has evolved.

When modified sinewave inverters got good, say about 20 years ago, it took a
lot of electronics to build a good one. Have a look inside, say, a Heart
Interface Freedom unit for an example of a top flight modified sinewave unit
from almost 20 years ago (and still in production).

No one in their right mind would design a modified sinewave inverter these days
as a commercial product, but if they did it could be built with far less
components, obviously.

The same thing happened with sine wave units. When they first appeared
commerially it took a lot of electronics to produce them. Consequently the
price was high. As better components have come on line, and engineering
techniques have been honed, the units require less and less internally.

However as they can still charge more, they do.

They genuinely are sold at "what will the market stand", as opposed to "what's
the cheapest I can sell this for?"

On top of all this, the field leaders somehow have to get back their RnD costs
which will be considerable on something like, for example, the ProSine.

Times are changing though. The price of pure sinewave units is falling almost
weekly now. I guess in about another year they will be the same price as
modified sine wave units.

Then the modified sinewave units will disappear.

2 years ago the cost of a sinewave unit was, in some situations, prohibitive. I
don't believe that to be the case anymore.

Gibbo

 

[Terry Pinnell]

"Dave" <db5151@hotmail.com> wrote:

Yeah, okay, I see it now. Damn I've gotten dense. Sorry to be such a
bother and so hard to convince. I haven't even touched any of this in over
20 years, and that has apparently affected my ability to reason and actually
think. Can't tell you all how much I appreciate your patience. And your
persistance. I've got a lot of catching up to do. Thank you.

Don't worry, most of us have BTampersandDT <g>.

--
Terry Pinnell
Hobbyist, West Sussex, UK