[KYHAM] Radio Theory and Construction workshop

[Bill Fuqua]

Notice: We will not meet July 12,2003 due to Indianapolis Hamfest.

The Radio Theory and Construction workshop will meet Saturday, July 19, 
2003 in the basement of the Red Cross Building at 1450 Newtown Pike, 
Lexington, KY. The Workshop will begin at 1:00PM and continue until 3:00PM. 
Sometimes we stay longer.

This workshop is for anyone interested in the subject of radio theory or 
construction. Anyone may join in the workshop at any time. This workshop 
does not really have a beginning or an end. It is a continuing effort to 
help those that are interested in knowing more about the internal workings 
of radios (receivers, transmitters and antennas) and/or building them. A 
ham license is not required and there are no age restrictions. I encourage 
young students to participate.
Participants will have to obtain their own tools and they will need to 
purchase a beginner's radio kit (AM-550K).

I have some kits in stock just now so you will not have to wait. Just pay 
me for the kit and I'll order another to replace it in stock. That way we 
will have some always available for new participants.

This kit cost about $20 and it is perfect for learning soldering, component 
identification and basic radio theory. Sources for these kits are:
Edlie Electronics http://www.edlieelectronics.com/
Electronics express http://www.elexp.com/.
There are two styles of kits. One has an integrated circuit audio amplifier 
(AM-550K) and the other has a transistor audio amplifier (AM-550KT). We 
prefer the one with the integrated circuit Amplifier but you can use the 
other if you like or if the preferred one is not available. Also, a very 
basic portable cassette tape player will be needed. These are less than $10 
at many department stores or can be found in garage sales for a $1 or so. 
It has been reported that WalMart has them for about $5. The cassette 
player will be modified to become a sensitive audio amplifier for future 
experiments and trouble shooting. I try to encourage participants to be 
resourceful and use common items found around the home. The tape player is 
a good example.
If you wish to join our workshop please e-mail me so that I can add you to 
our list. I have a short questionnaire to get some information about your 
interest, experience and knowledge level. If you cannot be contacted by 
e-mail call me in the evening at (859) 272-9523 and I will add you to a 
phone list. This is necessary because we do not hold the workshop every 
weekend due to other obligations, vacation, hamfest and license exam sessions.
Please let me know if you are coming and what you have to bring or would 
like to discuss at the workshop so I can have some time to prepare and 
gather any materials that will be helpful. Even if you are not coming to 
the workshop I would appreciate an email. I like to stay informed of your 
project's progress and I am always happy to answer any questions you may 
have. If anyone is interested in starting the beginning basic workshop or 
if you know of someone please contact me.

The Bluegrass Amateur Radio Society's Youth Education Program (Y.E.P.) can 
provide kits, tools and parts students up thru the 12th grade.

Some students have completed their kits and will begin working on their 
individual projects soon.

We discussed some possible projects during the July 5th workshop. But 
mostly discussed third order products caused by non-linearity in receiver 
amplifiers and in power amplifiers used in transmitters. There are two 
effects caused by third order distortion in amplifiers.  One is Cross 
Modulation such as you have when you are receiving a weak signal and there 
is a very strong signal that  may be out of band. This causes you to hear 
the modulation on the strong unwanted signal as well as the signal the 
desired signal.
The second effect is Intermodulation Distortion. This is the apparently 
broadening of a signal that is sometimes called "splatter".  A very common 
problem in linear power amplifiers. And all have it to some degree but some 
have worse intermodulation distortion than others.  We went thru the math 
and proofs of these effects and discussed the two-tone method of measuring 
this type of distortion.
All those present had a handle of the math necessary to understand the proof.
         We also reviewed frequency mixing and why non-linear devices 
perform this function.  Every once and a while I'll cover more mathematical 
topics like this but only when all the those present have the appropriate 
background. And to many it may be boring as  well.  Due to the holiday 
weekend the younger students were away with their parents.
         There are some more practical aspects of this discussion 
(non-math) that we may discuss later.

73
Bill wa4lav


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