Transitioning to RF

[M. Hamed]

Hello there,

I am a digital engineer by education and practice. However, something possessed me lately and I have a new found love for RF. I would like to start designing radios and have amassed a good number of RF books.

1) Is it doable?

2) Can I work up the knowledge just by reading books and experimenting. I'm interested in designing RF circuits not just home-brewing stuff from magazines or buying ready made equipment.

3) Any suggestions for RF/Radio beginner newsgroups and forums.

I appreciate any information / encouragement / reality checks etc.

Thanks

 

[Phil Allison]

"Jan Panteltje"

Start by building a simple crystal receiver for AM MW.

** ROTFL !!!

You took the words out of my mouth - Jan !!!!!!!!!!!!


Did that when I was just 7 years old, then a one transistor ( Ge ) radio
with headphones, then a simple valve ( TRF) AM radio then ....

I figured " radio " was far too tough for the slight rewards available.

The idea of becoming a " radio ham" simply held no appeal at all to me.

Soon, I discovered that hi-fi audio offered almost immediate reward and
generally in proportion to effort.

That seemed to me like a much better game to play.

Youth has such naive dreams .....



..... Phil

 

[brent]

Hello there,

I am a digital engineer by education and practice. However, something possessed me lately and I have a new found love for RF. I would like to start designing radios and have amassed a good number of RF books.

1) Is it doable?

2) Can I work up the knowledge just by reading books and experimenting. I'm interested in designing RF circuits not just home-brewing stuff from magazines or buying ready made equipment.

3) Any suggestions for RF/Radio beginner newsgroups and forums.

I appreciate any information / encouragement / reality checks etc.

Thanks

1.) Of course it is doable. It is much easier if you work for a
company which has a network analyzer, signal generators and a spectrum
analyzer... Having access to those items is almost a necessity.
Another question to ask is do you want to design low level RF circuits
or are you more interested in RF systems?

2.) Well, I guess I see that you are interested in RF circuits....The
thing about RF is that the circuits and systems kind of go hand - in -
hand, especially if you are interested in radio. For, instance, Noise
Figure management is more of a system issue, but you need to know it
if you design a front end filter/amplifier. If you work for a company
which has RF needs then find some way to shoehorn into this.

3.)I have a website which teaches smith chart / reflection / and the
principles of noise using interactive flash programs (It also has
other topics) It is here:

www.fourier-series.com

 

[M. Hamed]

Thanks everyone for all the responses.

Jan Panteltje wrote:
Start by building a simple crystal receiver for AM MW.

I actually built a number of them. This is what actually got me hooked. I also bought an superheterodyne AM kit that I soldered. That sealed the deal for me, I wanted to design those things and play with them not just solder them.

brent wrote:

It is much easier if you work for a
company which has a network analyzer, signal generators and a spectrum
analyzer... Having access to those items is almost a necessity.

I do have access to signal generators and a high end oscilloscope, and somewhat limited access to a spectrum analyzer, but no access to a network analyzer. I'm sure my company has one or more somewhere. I just don't think there is any
good reason they would give me access to it.

Another question to ask is do you want to design low level RF circuits
or are you more interested in RF systems?

both actually. Whole receivers and transmitters. Not necessarily with the greatest performance, but functional enough.

3.)I have a website which teaches smith chart / reflection / and the

Thanks much. I'll check it.

John Larkin wrote:
If you don't know that stuff already, you should give yourself the equivalent of
a "Signals and Systems" course: Fourier transforms, spectra, modulation, impulse
response, filtering, convolution, I/Q processing, detection. And learn some
about noise. And digital filtering.
A little theory along these lines is very helpful, even if it mostly builds
qualitative instincts.
Maybe somebody here can suggest some books that cover this basic theory. If
you're a digital guy, you may not have been forced to learn this stuff.

I have studied some of that in school, and self studied some of the rest. But not with enough rigor or application.

Tim Wescott wrote:
Are you wanting to change careers, or to build radios as a hobby?

Just a hobby. I still love digital work and I thinks it fits better with mybrain and current experience. But the idea of transmitting and receiving voice and data over a distance is very fascinating to me. I always loved radios and analog electronics just didn't have the right mentorship at the time to take it as a career. Neither did I have the very early kickstart that most analog and RF guys will tell you stories about. I still managed to getmyself a bit more educated about analog and now about RF. I built a few oscillators and amplifiers, designed and built an OpAmp out of discreet transistors, and have played a lot with LTSpice.

Either way, get a copy of the "ARRL Handbook" (and if you end up using
it, plan on getting a new copy every five or ten years). It's filled to
the gills with practical information. It shies away from theory, so if
you need theoretical underpinnings then you need to pull out your
circuits & systems books from college.
Wes Hayward's books on RF design are useful, too.

I do have both books and I'm struggling so much through them but I'm learning. It takes several readings sometimes.

 

[Edward Lee]

Just a hobby. I still love digital work and I thinks it fits better with my brain and current experience. But the idea of transmitting and receiving voice and data over a distance is very fascinating to me.

If you are interested in RF voice and data, it's mostly digital
anyway. For voice, it's probably bluetooth. For data, 802.15.4
(packet radio) might be more suitable, especially for point to multi-
point network. BT is lossy, where you don't care about dropping some
bits. 802.15.4 can deliver reliable data packet, but unreliable
latency.

 

[[email protected]]

I do have access to signal generators and a high end oscilloscope, and somewhat limited access to a spectrum analyzer, but no access to a network analyzer. I'm sure my company has one or more somewhere. I just don't think there is any
good reason they would give me access to it.

Most companies are enthusiastic about engineers learning more. I
would find out if your company has a network analyser and get to know
the people that use it. They are the ones that will either help you
or claim you may damage an expensive piece of gear.


Dan

 

[M. Hamed]

I'm glad I have all the books recommended so far. I have Ron Quan's book and I like it a lot. I hope he will have a new version for FM. I also got Experimental methods and I'm learning slowly from it but I think it's still goes over my head. I personally think Wes Hayward is a great RF engineer but not a very good teacher, but this is just my impression that could be premature. I used to hate the Art of Electronics style of writing and explanation until it grew on me and I gained some more knowledge and experience (which is still little).

Tim Wescott wrote:

Learning the stuff _is_ an uphill battle -- but the view from the top is
great. You might want to get an amateur radio license -- then you'll be
able to legally work at frequencies that'll let you get around the world
with a five watt transmitter.

(I've got an amateur license -- KG7LI -- but I've kind of lost interest
in radio these days. The primary attractor was building my own radios,
and now that's too much like work. So I compete in model airplane
contests for fun instead).

Would I be able to build receivers without a license? How about low power transmitters? As for model airplanes I always tell my friends that model airplanes will be my retirement hobby. There's so much fun to have with Digital, Analog, and RF but it seems like a lot of fun too I'll save it for retirement.

If you have the love for it, and the talent, and are willing to invest
the time required to climb the learning curve, it's eminently doable.

Thanks for encouragement. Maybe I should have better phrased the question as, is it doable when you're not having it as a career? I am willing to invest the time, but if that means years and years of study without much financial gain then may be I will reconsider. It's a hobby but I don't expect to put as much time as I'd put in my real job or if I'm getting a degree in RF.. A hobby is a fun side activity.

Yes, but that can take a long time and a lot of money and can be
frustrating to the point where it makes you want to quit learning.
The approach you've taken - asking for advice/mentoring from this
group - is, I believe, ideal in that some of us have already been down
the road you're starting on and can help you avoid the pitfalls we've
experienced.

I'm glad I'm in the right place. I thought the community here is more focused on Analog design but it seems there are enough radio and RF gurus here.

I'm interested in designing and building AM and FM radios out of discreet components with acceptable performance. Then may be I could move to transmitters and receivers for sending voice over small distances or remotely controlling electronics. I would then try transmitting and receiving over the ham bands to maybe talk to other people (or a friend that I will loan my equipment). Somewhere along this line I'd like to experiment with Software Defined Radio and DSPs and perhaps eventually move digital functionality to an FPGA. On this note I have to say I was inspired by SDR project built by theself-taught Jeri Ellsworth that she posted on youtube.

My ambition throughout all this is to home brew everything or most of it, and make things out of discreet components rather than ICs. Possibly build things in modules as I move along and hook up modules to perform the functions I'm looking for and work on optimizing them.

 

[M. Hamed]

Most companies are enthusiastic about engineers learning more. I
would find out if your company has a network analyser and get to know
the people that use it. They are the ones that will either help you
or claim you may damage an expensive piece of gear.

Some companies have no budget for training. They expect you to learn everything on the job. They have very tight schedule that any extra-curricular activities outside your narrow focus are considered a waste of time. They have very little inter-departmental communication and hostility some times. Mycompany is one of them. I don't know any of the RF guys at my company, andjust can't imagine walking over to them asking to borrow their network analyzer!

 

[brent]

Some companies have no budget for training. They expect you to learn everything on the job. They have very tight schedule that any extra-curricular activities outside your narrow focus are considered a waste of time. They have very little inter-departmental communication and hostility some times. My company is one of them. I don't know any of the RF guys at my company, and just can't imagine walking over to them asking to borrow their network analyzer!

Go over there with something like a whip antenna with a bnc connector
on it and tell them that you have wanted to see how the VSWR behaves
over frequency and ask them to make a quick measurement. They will
likely do it for you , it will take ten minutes and they will probably
enjoy showing you. then you can get the conversation going. If you
have some other commercial item that already has connectors on it ,
like a filter, that will work too.

 

[[email protected]]

Some companies have no budget for training. They expect you to learn everything on the job. They have very tight schedule that any extra-curricular activities outside your narrow focus are considered a waste of time. They have very little inter-departmental communication and hostility some times. My company is one of them. I don't know any of the RF guys at my company, and just can't imagine walking over to them asking to borrow their network analyzer!

Find a new employer. That place will kill you, if you have a brain.

 

[[email protected]]

Start by building a simple crystal receiver for AM MW.

Assuming of course that there is still some local AM BC service in the
country in which the original poster lives in.

But in reality, what do you learn by building a crystal receiver ?
That the loaded Q and hence varies depending of the loading of the
resonant circuit ?

A direct conversion HF receiver would be much more rewarding, one
could experiment various frequency sources, such as VFO, PLL and DDS,
especially since the OP has background with digital electronics.

The same principles apply for I/Q receivers common in WLAN devices.

 

[John S]

Assuming of course that there is still some local AM BC service in the
country in which the original poster lives in.

But in reality, what do you learn by building a crystal receiver ?
That the loaded Q and hence varies depending of the loading of the
resonant circuit ?

Well, there is some thrill to listening to a radio station with no
external power.

 

[Phil Allison]

But in reality, what do you learn by building a crystal receiver ?

**You can learn a lot and very inexpensively.

It's the first step towards gaining a feel for what RF is all about.

The OP is clueless enough to need it.



.... Phil

 

[M. Hamed]

My first crystal radio is what got me hooked on radio. I learned a lot by doing it and there is a lot to be learned still...but I got too anxious and wanted to move up quickly. I have an article lying next to my bed titled "AGreat Teacher: The Crystal Set" by Phil Anderson WØXI.

I'd like to think of myself as a bit older than a 2 year old with radio andelectronics. I have poured so many hours over electronics and radio books (beside school work but that was almost worthless). But maybe so in comparison with people who have been building and learning and experimenting for decades.

I'm having fun so far, even with the heavy study. I'm not sure if it's worth it on the long run, since it's probably too late to be a career, but I'llkeep doing it while I'm having fun and learning. And who knows maybe it will serve me in the future.

Thanks for the inspiration.

 

[Phil Allison]

"M. Hamed"

My first crystal radio is what got me hooked on radio.

** Its a lot like illegal drugs really.

Crystal sets regularly lead on to the much harder stuff.

Transistors, valves, ICs...




.... Phil

 

[Phil Allison]

"dave"

My MFJ-956 (multipurpose VSWR bridge, counter, sig generator) uses a 1N34A
germanium diode in the "front end". I used the same diode model in 1961
when I built a crystal radio per Alfred Morgan's "Boy's First Book of
Radio and Electronics".

** You and I must be close to the same age.

My very first crystal set used a Galena crystal plus cat's whisker.

That was not too successful so the next one used an OA91, IIRC.



.... Phil

 

[M. Hamed]

The 1977 ARRL Solid State Design book was good, but is out of print.

I see one copy on Ebay.


<http://www.ebay.com/itm/SOLID-STATE...3?pt=US_Manuals_Magazines&hash=item1c3134ade7>


Politicians should only get paid if the budget is balanced, and there is

enough left over to pay them.

Thanks for the pointer. I ended up picking a copy off Amazon for double the eBay price. It's the 1994 print and claimed to be in a better condition. That's how desperate I am. Now I need 80 hours a day to indulge.

 

[M. Hamed]

I do have experimental methods. I am still not convinced it's a good replacement for Solid State Design. But I'm still a beginner.

 

[M. Hamed]

It covers solid state analog, power supplies, classes of amplification,

feedback, superheterodyne, regeneration, etc. Plus DSP, direct

conversion receivers. It still tells you about Dead Bug and Manhattan

Style construction. I don't remember a dim bulb tester, but nobody's

perfect.

I opened the Mixers chapter today and I take back what I said In any case I own both books now and I plan to read them both.

 

[[email protected]]

Found 1n34a very cheap at http://www.bgmicro.com/1n34a-germanium-diode.aspx