[Thursday] Suggested Radio-Related Interactive Exhibits

Sat Aug 24 05:43:42 MDT 2019

 We also need to have an active exhibit showing "how a radio works" in the simplest form. If we already have this then "My Bad" or OOPS! 
To most of us that know "how a radio works" it is easy. However "if you don't know it isn't easy"
This is something I taught for years related to automotive electronics and interference. However my subject matter can be easily tweaked to show how a radio works and not how to keep stray electromagnetic force out of the vehicle, or make it transparent. 
I think we have pictures and diagrams showing zig zag lines from a transmitter antenna and then those same type of lines going into a receiving antenna. But what are those lines and how do they get from one antenna to another so you only hear the station you want. 

I can do a presentation for one of our Wed nite events and someone else at the museum can take it from there if this is a good idea.
1 emf (radio waves) in the atmosphere, background and intentionally transmitted at a specific frequency.
2 converting that to audio
3 tuning to make it selective so you only hear one station.
Initially it needs to be kept this simple. 
To do the above you need an antenna wire several feet ling a Digital meter and a crystal radio. 
To set it up for a possibly larger group you can feed the crystal radio in to a simple amplifier with speaker. 

HUH Wireless stuff from a steam guy ???
Hope this is helpful
Ernie
     On Friday, August 23, 2019, 11:20:07 PM EDT, Ken Carr via Thursday <thursday at newsm.org> wrote:  

 This post is mostly directed at the NESWM hams.Suggestions and comments are welcome from all.
Randy has asked for some suggestions for additional interactive (engaging)
radio-related displays at the museum.We already have an excellent start with the interactive displays in thewireless building. I believe Craig and several other people were responsiblefor that (my favorite is the little tubes that light up ... can't recall their name).
Below I have a list of some suggested exhibits. One of them, the scanningdisk TV, was suggested by Chris Prata last Wednesday night as we weretouring the museum with some guests.
The list I came up with is short on particulars and I'm not sure what isworkable. It is just a bunch of quick ideas.It would be good if everyone could come up with a list and we could alldiscuss particulars.----------------------------------------------------------------------------------------

Interactive Radio Displays

Operating anold radio

Computerstation displays photos of a sampling of old radios from NEWS collection...Clicking on any radio brings up 3-minute video of that radio being operated.Show a little about what was done to revive radio, feature period ads fromcatalogs or museums for this radio, and finally show how to operate it. Periodaccessories should be used (headphones, speaker, meter to monitor filamentvoltage, radio premiums of period, etc.)

Can you playthis radio?

Complex lookingradio receiver is on small desk with table. Sign no. 1 with instructions (i.e.1-5) guide patron to tuning in local broadcast station or our own transmissionon BC band. Sign no. 2 is “Expert Challenge” which steps through process oftuning in live ham radio QSO in single side band (SSB). Demonstration includesantique headphones and antiseptic wipes.

Build a CrystalRadio in 5 Minutes or Less

Groupchallenge. Museum guide seats 5 patrons at radio construction booths (cubicles)arranged in semicircle. Booths and walls feature photos of crystal radios andaccessories from our collection along with period advertising. Docent gives 5-8minute talk about crystal radios and specifically fox hole radio. Each cubiclehas instructions (displayed on placard) for constructing radio. Docent passesout parts kit to patrons and tells them to begin making a radio. Docentprovides guidance if needed. Each person’s first name is put on scoreboard withtime they took to make functional radio. As patrons leave they are givenhandout that illustrates how to make 3 different crystal radios at home:simple, intermediate, advanced. Learn More: Web and book references provided atend of handout.

Morse CodeChallenge

1 Watch shortvideo or read simple instructions on placard on how to operate code key.

2 Patronfollows instructions and sends message with straight key. Message is ‘received’on computer screen (old iPad running audio to code interpretation app). Patronencouraged to persist at keying until message is ‘properly received’ (displayreflects what patron intended to send).

3 AdvancedChallenge no. 1: Perform as above with sidewinder key.

4 AdvancedChallenge no. 2: Perform as above using antique wireless age key and sounder.

Antennas : Make an antenna. Docent demonstrates how radio withoutantenna receives nothing. Then constructs dipole. Next switch in dipole that isoutside and tune same spot on radio.

Or: Station consistsof radio and labeled antenna switch (A, No antenna; B. 10 foot wire; C, Outsidedipole). Patron switches antennas to demonstrate difference.

Match The Tubes:Patron presented with 5 different vacuum tubes from different eras (tubes arein a basket or wood block with hollowed out areas to receive tubes). Below arefive descriptions of each tube in chronological order.  Patron must place proper  tube in the slot with the matchingdescription.  This encourages  them to read about the different tubes andrecognize features.

Bonus: If they get the tubes in the correct order they willlight up and radio station will be heard. To make this work each tube has astiff pin/wire or dowel attached to its central indexing tab. Pins vary in length. If all pins are placed correctly each one will activate a relay in a string of relays which collectively will turn on theradio.

Make the Radio Work;  Circuit diagram of radio is drawn on woodeneasel. The drawing has actual binding posts and tube sockets. Hidden below is areal radio. At each position where a tube belongs there is a real tube socket.Flip chart explains how to ‘activate’ the radio:

1 attach the indoor antenna (patron ties in antenna withalligator clip and lead … 10 foot wire antenna)

2 Insert mixer / converter tube, no. ****** (text brieflyexplains what this does)

3 Insert First IF tube, no. ******* (text briefly explainswhat this does)

4 Insert 2nd IF / detector tube no. ******* (textbriefly explains what this does)

5 Insert audio amplifier tube no. no. ******* (text brieflyexplains what this does)

6 Turn on radio (volume/on switch attached to board)

7 Adjust station with tuner control

8 Unhook antenna lead and attach to bigger antenna (antennano. 2, up 25 feet outside)

Tune a Radio:

1.     Presented with a 1920’s regenerative radio.Instructions show how to turn on and tune. Patron does so. Warned aboutexcessive feedback and howling. Turn off and go to second radio.

2.     Presented with a 1920’s 3-dialer (Tuned RadioFrequency) radio. Proceed as above

3.     Presented with a 1940’s superheterodyne consoleradio. Instructions show how to turn on, tune station, and turn off. 

At each stage patron is informed about merits and faults ofeach design.

Do You Cohere?

Station has several coherers that work on differentprinciples.

Patron is briefly informed of function of coherer and isthen encouraged to make each one work.

1.     Patron dials up power on rheostat and thenpresses code key (massive) and sends ‘spark wireless radio transmission’(actually a nearby but hidden transmitter is activated).

Audio creates sound of sparktransmission. As rheostat voltage is increased more of the coherers activate ,thus demonstrating the relative sensitivity of each design.

Coherers begin to cohere and asthey do a sounder next to each is activated just once.

2.     Next the theory of the decoherer is explainedand patron performs same task as above but with set of coherers that includedecoherers. Constant buzz with interruptions (long and short Morse codecharacters) is heard. Communication is now possible.

Amplify This !

Patron ispresented with working crystal radio. It is explained that since they work onvery little current (whatever is present in the radio wave itself) it is notenough to make loud noise. How might they make it louder (amplify)?

Solution no. 1  Attach two sets of earphones to one crystalradio so more than one person can listen in. Unfortunately with the addition ofeach earphone the volume in each is reduced.

Solution no. 2Make the output of the earphone reverberate against the walls of an expandinghorn. Connect earphone to the end of a horn speaker. (Randy's idea)

Solution no. 3Attach output of crystal radio to a crude amplifier. We may build one or betterstill attach the crystal receiver to the kind of amplifier that was sold as anaccessory to the Radiola III (we have at least one of these on display in themuseum. I suspect more are squirreled away somewhere). Other solutions areoffered in various crystal radio enthusiast books. We can also provide tube andtransistor-based amplifiers that can be switched in from a control panel.

Create Electronic Components From Scratch

Patronpresented with samples of production electronic / radio components. Each isexplained and its operation in a circuit is demonstrated (connect to circuit,push button to activate, effect seen on attached meter, lamp, speaker, etc.)

Next patron isgiven material to ‘make’ their own components. They then test them by insertinginto circuits. Resistors and capacitors may be taken home. Printed labelsprovided for outside of capacitors and resistors.

Everything isrun on battery power, no high voltage danger.

Components:Resistor, Capacitor, transformer

Mechanical Television Camera

Mechanicaltelevision camera is activated by patron and image of patron is seen on vintageTV (round porthole style) CRT. (Chris Prata)

Library

Open thelibrary for study by anyone. Although we will not lend publications, patronsare free to purchase photocopies of select pages of old publications. We makethe copies and charge 50 cents per page (or whatever fee schedule that gives ussome revenue and keeps the patrons happy). The library can have rotating themedisplays that feature such items as: original patents, advertisingillustrations, collections that address one particular field, etc.

Posters thatare reproductions of illustrations might be on sale in the library.

Radio Drama Room (Old Time Radio)

Small groups(5-20 at a time) enter our ‘living room’ which is set up like a living roomfrom 1939. There is a large console radio with a tuning eye, a rug on thefloor, upholstered couches and chairs, etc. Make it look just like 1939 … realcomfy. When everyone is seated the radio comes on (a child patron is asked todo the honors). The lights dim and the only bright light in the room comes fromthe radio. An announcer comes on and does the intro for today’s show.

It may be TheShadow, Buns and Allen, Johnny Dollar, Jack Benny, etc. Choose titles that areappropriate to the season (horror during the fall, Christmas shows in December,etc.). The show will run for about 20-30 minutes. The room should be wellventilated (AC) and sound proof.

Make a radio transmitter in 5 seconds

Display radiois tuned to portion of the band that does not have a station playing. Thepatron is given several items with which they may create electric dischargesthrough the rubbing together of dissimilar materials. If the humidity iscorrect (low humidity, dry weather; AC will help) they will hear the dischargeon the radio. Placard explains that this was the basis for early sparktransmitters. Note that the emission can be heard anywhere on the band. Thiswould never work for broadcast radio. Eventually radio transmitters that usedvacuum tubes and finely ‘tuned’ circuits were able to create distinct ‘radiostations’ on specific frequencies.

How is your Radio Eyesight?

Present patronwith an operating radio that has a tuning eye (magic eye, miniature cathode raytube). Explain the theory of how it works. Encourage patron to ‘tune’ the radioto various stations using the tuning eye for accuracy.  If possible lighting should be subdued atthis exhibit. Point out how the eye opening varies with signal strength.

How do you put a value on an antique radio?

Display6—10  antique radios and speakers. Theyare in various states of repair and completeness. Provide overall guide as towhat features determine the value of a particular radio. This can be text thatis displayed above the radios or it may be audio that can be accessed withearphones (disinfected earphones like those in airplanes are given to allpatrons with admission ticket).

Afterlistening to the audio discussion on radio values the patron uses a  ‘score card’ that is keyed to the displayradios. They must grade each radio on certain characteristics and finally put adollar value on the radio (pencils available). When they have completed thescore card they press an ‘answer’ button that reveals the values and explainswhy each radio has a particular value to collectors.

Radios of Rhode Island

Specialexhibit put together by Len A.

How is a radio restored?

Static exhibitof about 5 models of the same radio, each showing the progression of stepsinvolved in restoring that radio.

Interactive Analogue Demonstration ofStages of Superheterodyne Radio Receiver

Mostexplanations of how a simple superheterodyne radio works are too complex orvague to keep a person’s interest or to convey understanding. If eachelectronic stage of the superheterodyne radio is displayed alongside a workingmechanical (not electronic) analogue of the separate stages it may be possibleto illustrate how a radio works in an intelligible manner.

The setup:

Front andcenter (controllable and accessible to the patron) are 6 working devices thatconvey each successive stage of a radio receiver. None of these devices areelectronic or necessarily electric. They demonstrate physical properties orobserved mechanical phenomena that are similar (analogous) to the electrical orelectromagnetic functions of each stage of a radio receiver. Some examples (notnecessarily accurate):

Tuning forksand multiple piano strings: fan dipole antenna as a medium that electronicvibrations (radio waves)  pass throughand vibrate within, some better than others, due to ratio of antenna length towaveform length. (Represent antenna by fan dipole).

Structureconsisting of mass suspended by springs and set in motion by eccentric drivewhich reaches maximum amplitude when spring-capacitor and mass-inductor are inphase or what would be called resonance in radio circuit. (p. 444, Sutton,Electrical Oscillations). This mimics the local oscillator of the radio.

Competingwaveforms may when they collide result in addition and new (sum) waveform isproduced as demonstrated in rod model (p. 139, S-28, Sutton (1937). This isanalogous to the mixer stage of radio although in a radio sum and subtractionof RF is produced. The difference is the frequency that is selected out. Thismimics the mixer section of the radio. (Note: the mixer and local oscillatorare usually combined in one vacuum tube and together referred to as theconverter stage.

The output ofthe converter / mixer is fed to the Intermediate Frequency stage which is acircuit tuned to a particular frequency. It has an amplifier (tube) that isoptimized to amplify only that one frequency, the intermediate frequency, whichis allowed to pass through this stage and pass to the vacuum tube foramplification. Analogue representation of this stage: 4 different tuning forksare tapped. In front of them is one piano wire. It only responds (vibrates/oscillates) in response to one of the four tuning forks since its length allowsit to vibrate optimally at just one frequency.

And so onthrough the remaining stages of the radio. 

Behind theMechanical models is a large labeled and color coded block diagram of a radio. 

Rather than ablock diagram you might use actual radio parts within the blocks.

Activating anyphysical model will cause the analogous radio stage to light up. Whereappropriate actual radio tubes (with clear designations in front of each) canbe used. Safe DC battery power would be applied to filaments only as each stageis selected.

Finally patronwill be encouraged to turn on the ‘radio’ and tune in a station. 5-part fandipole has numerous colors (frequencies along its length). Only one color at atime appears in ‘glow’ of the converter stage. Local oscillator (LO) withinconverter stage has a different color. The color that emerges from this stageand goes to IF amplifier is always the same color as the LO (others arefiltered out). As tuning dial is rotated you see that the color entering the converterstage change, one color for each station frequency.

And morestages follow …….

This displaycould have several things that the patron could control. A lot of planningwould need to go into this. It would be good for an electrical engineer tosupervise the design.
Comments and additional ideas welcome.

Ken Carr ...  KE1RI, A New England HamWesterly-Pawcatuck AACAN.E. Steam & Wireless Museum

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