how to learn low level RF design

[[email protected]]

I work as an EE, I don't have a degree, but I do have a working
knowledge of analog and digital electronics and have worked on a very
wide variety of circuits.

I have always wanted to learn low level RF "black art" circuit design,
but its just too difficult on my own, and believe me I have tried.

Whats the best kind of job or environment to get started in this? A
"furnace" to be forged in?

 

[No Spam]

I work as an EE, I don't have a degree, but I do have a working
knowledge of analog and digital electronics and have worked on a very
wide variety of circuits.

I have always wanted to learn low level RF "black art" circuit design,
but its just too difficult on my own, and believe me I have tried.

Whats the best kind of job or environment to get started in this? A
"furnace" to be forged in?

Assuming your talking about the more modern and harder to understand RF
in the microwave range.....

Try ham radio. There are allot of v/uhf books around and getting a tech
lic (in the USA) which will allow you on that band is only 25 SIMPLE
questions. Look for people who are hams that do microwave contesting and
"buddy" around with them. Honestly, they will be honored to help.

If your talking HF radio below 100Mhz, your not looking/working hard
enough

 

[EE123]

I work as an EE, I don't have a degree, but I do have a working
knowledge of analog and digital electronics and have worked on a very
wide variety of circuits.

I have always wanted to learn low level RF "black art" circuit design,
but its just too difficult on my own, and believe me I have tried.

Whats the best kind of job or environment to get started in this? A
"furnace" to be forged in?

RF is difficult. You really should have an MSEE to be proficient at
it.
THe big problem is that RF extends well into the GHz range.
Even if you stay in the upper 100's of MHz, it is fairly easy to get
tripped up
That would be police radios for example.

Post a question and I will try to answer it!

Dave

 

[Joerg]

Assuming your talking about the more modern and harder to understand RF
in the microwave range.....

Try ham radio. There are allot of v/uhf books around and getting a tech
lic (in the USA) which will allow you on that band is only 25 SIMPLE
questions. Look for people who are hams that do microwave contesting and
"buddy" around with them. Honestly, they will be honored to help.

If your talking HF radio below 100Mhz, your not looking/working hard
enough

Designing an HF receiver that can listen to a teeny signal 20kHz from a
station that makes a fluorescent lamp glow _is_ hard work

 

[[email protected]]

Designing an HF receiver that can listen to a teeny signal 20kHz from a
station that makes a fluorescent lamp glow _is_ hard work

- Hide quoted text -

- Show quoted text -

NICE. . What was the station?

I am talking about making a transmitter and receiver capable of
sending and receiving voice with 3khz bandwidth 1 mile line of sight,
so I suppose that puts me sub 100MHz, and also sub-par as far as my
effort to teach my self it according to one of you.

I figure if I could do that, from scratch, using discrete components,
that I would be able to accomplish all of my RF circuit goals for
life, which are basically farting around for fun.

Yeah you are right, I "tried" to do this on my own about 8 years ago
before I even started working as an EE. I've learned quite a bit since
then and I bet I could learn it on my own now. But I am never going to
underestimate the difficulty of successful, non-accidental success of
RF circuitry design. If you can do it, you are pretty much in the
highest rung of the EE ladder, IMHO.

The tricky part here is that I must be able to design the circuit from
scratch to have certain specific parameters, and not just monkey copy
something out of the ARRL book. Although that is an excellent
reference.

Heres a question for you:

Whats the hardest part about doing what I mentioned above? Opinions?

 

[[email protected]]

"I am talking about making a transmitter and receiver capable of
sending and receiving voice with 3khz bandwidth 1 mile line of sight,
so I suppose that puts me sub 100MHz, and also sub-par as far as my
effort to teach my self it according to one of you. "

Ignore those who are discouraging you.  While it's true that it's unlikely
you'll understand every last little bit of a transceiver design if a handful
of months, that doesn't mean you shouldn't still build one and gain
appreciable knowledge.

"I figure if I could do that, from scratch, using discrete components,
that I would be able to accomplish all of my RF circuit goals for
life, which are basically farting around for fun."

You might find this book useful:http://www.amazon.com/Build-Intelligent-Amateur-Radio-Transceiver/dp/...

And I would suggest getting your technician class amateur radio license, since
then you can (legally) transmit over many more frequencies than you can
without one.

"The tricky part here is that I must be able to design the circuit from
scratch to have certain specific parameters, and not just monkey copy
something out of the ARRL book. Although that is an excellent
reference."

The ARRL does have a couple of decent design-oriented books besides just the
big monkey-copy book... "Introduction to Radio Frequency Design" by Wes
Hayward is good, as is "Experimental Methods in RF Design."

---Joel

Thanks for the excellent reply Joel! Don't worry, I am not affected by
discouragers. If I was, I would probably never post here, since there
is always someone who replies "dont do it that way, dont do it at all,
etc.."

 

[Rich Grise]

Heres a question for you:

Whats the hardest part about doing what I mentioned above? Opinions?

Yeah, pretty much. ;-)

Cheers!
Rich

 

[Joerg]

A multi-multi ham contest. Meaning the dudes in the next tent were
blasting along on an antenna about 200ft from the one I was using.

Radio Tirana was another story. They blasted commie propaganda into
Europe from Albania, probably using up all the electricity there while
the population was starving. The usual :-(


But when one reaches 70 or 80 and the bones get shaky one quickly falls
off that rung again. Got a few decades, I guess ;-)


Can't see your whole original post (Can you use some better domain that
google.com?). But I don't see anything hard with a one-mile line of
sight audio com link. Even well above 100MHz.

"Introduction to Radio Frequency Design" by Hayward.

If you start with the 40 meter band (7MHz) you'll be able to get around
the world with 20 watts out on a good day on single sideband, and less
than a watt with Morse code.

And then the neighbor comes hollering that his super-cheap TV is falling
over backwards.

 

[[email protected]]

For less then 100 mhz, I'd go with

Experimental Methods in RF Design
-- by Wes Hayward, W7ZOI, Rick Campbell, KK7B, and Bob Larkin, W7PUA

Serious EE in that book as well as a lot of fun. My boss with 45 years
in EE but no interest in ham radio stole my copy and wont give it
back. For those sceptics out there, its not your normal ARRL/TAB
cookiecutter cookbook. But its not Artech House either.

Older over 100 mhz stuff,

The RSGB microwave handbook. The 60s-70-80s one, not the new
international one.

Not published any more, but still out there new.

Then get on the microwave mailing reflector and listen for a while.

Steve

 

[Phil Allison]

I work as an EE, I don't have a degree, but I do have a working
knowledge of analog and digital electronics and have worked on a very
wide variety of circuits.

I have always wanted to learn low level RF "black art" circuit design,
but its just too difficult on my own, and believe me I have tried.

Whats the best kind of job or environment to get started in this? A
"furnace" to be forged in?

** You will not likely get a job doing something you have no ability to do.

Suggest you start off building a "crystal set", these are more interesting
than you might think.

Built my first when I was 7 or 8 years old.

Then a one transistor radio, a one valve set tc.

Get yourself a nice RF generator too - essential really.

A frequency counter and spectrum analyser are also needed for working with
transmitters.

Also, and importantly - do not attempt to re-invent what others did long
ago, instead study what has been made and sold successfully and learn from
it.



...... Phil

 

[Joerg]

Google has plenty of hits on "stealth antennas." The ARRL even has books
on the topic!

Yes, but if you have repaired the umpteenth piece of electronics they
all know who dunnit ;-)

 

[Jasen Betts]

I am talking about making a transmitter and receiver capable of
sending and receiving voice with 3khz bandwidth 1 mile line of sight,
so I suppose that puts me sub 100MHz, and also sub-par as far as my
effort to teach my self it according to one of you.

Whats the hardest part about doing what I mentioned above? Opinions?

starting, persisting, and finishing.

some suggestions,

1: pick a frequency

2: If both ends are fixed locations, find a good design for directional
antennas.

 

[[email protected]]

I work as an EE, I don't have a degree, but I do have a working
knowledge of analog and digital electronics and have worked on a very
wide variety of circuits.

I have always wanted to learn low level RF "black art" circuit design,
but its just too difficult on my own, and believe me I have tried.

Whats the best kind of job or environment to get started in this? A
"furnace" to be forged in?

A good RF Engineer needs to understand the following topics (Each
requiring a fair amount of study and work to understand):

1. Matching concepts. (Why is matching concepts so critical to RF -
must understand - it is a constant theme in RF)

1a. Matching with lumped elemenets
1b. Matching with distibutive elements

1b1. Understanding how distributive (Transmission lines)
elements work
(First step - a quarter wave short is an open

2. Noise, Noise bandwidths,
(as an example, why can you send a signal around the world
in
morse code with 1 watt, and you need a KW for voice?)

3. Amplifier system concepts , Noise figure, IM products, cascading
noise
figures

4. Feedback control theory. Concepts of stability, Loop bandwidth and
loop
response as a function of loop bandwidth.
You need to understand this to do Phase Lock Loops, and ALC
circuits.

5. Filtering concepts and filter designs. Need to understand Zverev
book of filter
tables and how to use it. Need to undersatand concepts of group
delay and
filter trade offs

6. Need to understand , inside and out, how to use a network analyzer
and a spectrum analyzer. Absolutelty must get access to these two
instruments and really , understnd them. (Must play around with
distributive elements on network analyzer)

7. Perhaps most importand is grounding concepts. I would say that in
my experience, 50% of all problems I have ever had ultimately boil
down to a grounding problem. Even to this day, and I know this, I
invariably chase down other issues before I chase grounding, and sure
enough, its a grounding problem.


These are your first steps, the circuit design concepts are not so
hard, but you must be willing to really really bang your head against
the wall to get your circuits to work. You must have tenacity.

 

[Joerg]

A good RF Engineer needs to understand the following topics (Each
requiring a fair amount of study and work to understand):

1. Matching concepts. (Why is matching concepts so critical to RF -
must understand - it is a constant theme in RF)

1a. Matching with lumped elemenets
1b. Matching with distibutive elements

1b1. Understanding how distributive (Transmission lines)
elements work
(First step - a quarter wave short is an open

2. Noise, Noise bandwidths,
(as an example, why can you send a signal around the world
in
morse code with 1 watt, and you need a KW for voice?)

3. Amplifier system concepts , Noise figure, IM products, cascading
noise
figures

4. Feedback control theory. Concepts of stability, Loop bandwidth and
loop
response as a function of loop bandwidth.
You need to understand this to do Phase Lock Loops, and ALC
circuits.

5. Filtering concepts and filter designs. Need to understand Zverev
book of filter
tables and how to use it. Need to undersatand concepts of group
delay and
filter trade offs

6. Need to understand , inside and out, how to use a network analyzer
and a spectrum analyzer. Absolutelty must get access to these two
instruments and really , understnd them. (Must play around with
distributive elements on network analyzer)

And always keep a good analog scope. Always. If the OP doesn't yet have
one I'd recommend the Tektronix 2465. Several of my clients followed
that recommendation and got them for around $500 off Ebay. "Wow, it's
like someone turned on the light!" was a common comment. Start every
measurement job with the analog scope first and use a DSO only when the
analog one really, really can't do the job. Like on data lines or very
low frequency erratic noise.

7. Perhaps most importand is grounding concepts. I would say that in
my experience, 50% of all problems I have ever had ultimately boil
down to a grounding problem. Even to this day, and I know this, I
invariably chase down other issues before I chase grounding, and sure
enough, its a grounding problem.

Sssssht! Don't take away my business base ... ;-)

These are your first steps, the circuit design concepts are not so
hard, but you must be willing to really really bang your head against
the wall to get your circuits to work. You must have tenacity.

You forgot one for the guys building analog power circuitry:

8. Always know where the next fire extinguisher is.

 

[[email protected]]

Good gear for RF is not expensive these days, but perhaps the OP would
like to start cheap:
Some useful toys:
:
The Poor Man's Spectrum Analysis kit:

http://www.science-workshop.com/

Ok, so its a slightly modified TV tuner, but for up to say 850 Mhz,
its a decent vision of whats going on, and you learn about birdies and
mixing and splatter and good RF construction practices. You build it
once and then rebuild it in die cast boxes to clean up the birdies.

You need a decent oscilloscope , say 10 mhz, solid state
deflection , CRT , minimum with it.

Then you read this paper and clean up the IF response and extend the
range

http://www.arrl.org/qex/Henkel.pdf

I know there are better Spec An kits out there, but t 0-110 mhz
doesn't get you much these days.

I will also agree that a decent scope is the best starting point.

A older varacter TV tuner (external pll) with the lid off is a
wonderful place to start, even if your only other gear is a 99$
optoelectronics frequency counter.

I once asked Dr Wenzel to calibrate a diode for me, this paper was the
result:

http://www.techlib.com/files/detect.pdf

Then one of these:
http://www.aade.com/lcmeter.htm

Then one of these:

http://www.aade.com/dfd4.htm

if you have no budget left after the 1N914 diode, the scope, and the
spec an from the dead VCR, you go here:


http://web.telia.com/~u85920178/

Then some mini-circuits mmics and vcos.

The pro EEs here might laugh at me for this, but starting at this
level with the above stuff in college got me to 10 Ghz SSB phase
locked to a GPS reference.

If you have budget, a PTS160 from ebay is also a great bench tool

Steve Roberts

 

[Mark1]

to the OP

try the ARRL Handbook

and

http://www.amazon.com/RF-Circuit-Design-Christopher-Bowick/dp/0750699469

These are good practical guides to RF

Mark

 

[[email protected]]

Steve ...

The one thing "pros" will *NOT* do is laugh at somebody who has learned the
art and science of making cheap test equipment do the job of high-end
equipment, and who knows the limitations of that method.

Thanks, I needed that.

One more good ham radio resource, but written with Attitude:

Green Bay Packet Radio:

http://www.qsl.net/n9zia/

Steve

 

[[email protected]]

And always keep a good analog scope. Always. If the OP doesn't yet have
one I'd recommend the Tektronix 2465. Several of my clients followed
that recommendation and got them for around $500 off Ebay. "Wow, it's
like someone turned on the light!" was a common comment. Start every
measurement job with the analog scope first and use a DSO only when the
analog one really, really can't do the job. Like on data lines or very
low frequency erratic noise.

My experience is a crappy digital scope is better than a great digital
scope when you are looking at analog signals in an RF system.

An analog scope, as you point out, is often better than a digital
scope.

You forgot one for the guys building analog power circuitry:

8. Always know where the next fire extinguisher is.

And # 8- 2: Now, go get yourself a decent digital scope for power
supply design. Need to catch the one time transcients.

Brent

 

[[email protected]]

I'm excited!! Thanks for all the hints and tips folks! I am sure there
are many people like me who want to learn this and now all these
guidelines will be immortalized.

Im getting that Experimental methods in RF design book for sure,and I
will look at the other ones too. I found a library with it and I will
try to get the others too. Hope they dont mind if I keep it all for a
while

 

[Tim Williams]

Here's my understanding of it, I think, more or less possibly... wrote
this a little while ago, here's the quote:

Wideband stuff is pretty easy: resistors are, for the most part, well
behaved, and with resistance squashing the more unpleasant reactances
in the circuit, you're free to push the boundaries. In wideband
circuits, that means reducing those resistances until the reactances
just start to bite back, then tweaking the circuit (or layout, or...)
until the waveform simply looks good.

But in RF, you're intentionally tempting those parasitics with juicy
LCs, lumped constants that you so wish to be ideal. And they can be
pretty nice, with high Qs for high selectivity. But without that
resistance, parasitics like lead inductance are free to party. You
can try building an amplifier for one frequency, but if it works
better as an oscillator at any other frequency, its amplification is
pretty well doomed.

So I think it's exactly the fault of putting in a tuned circuit (most
likely the capacitor in particular) which creates all those horrible
VHF-UHF+ oscillations that so often spoil RF work. I think it's
valuable to have experience in wideband as well as tuned circuits,
especially where stability and power converge. When you're building a
wideband amp, it has to carry a lot of current, because it's class A
and it's fast. RF power outputs carry a lot of current because
they're outputs, and they're fast because that's the point, but what's
more, they're fast well above and below the one frequency you need
them, so they are both similar to, easier than and harder than a
wideband circuit!

Now, I haven't had much experience with tuned amplifiers, but I think
I've gotten enough of a feel for these things that this might actually
be right.

But I still say RF is black magic. ;-)

Tim