radio building books.

[K9ase]

I've been watching various you tube videos on making crystal sets.
most of the books that get mentioned are out of production and/or close to $100
Are there any cheaper books for good radio projects?

[KD8DEY]

I've been watching various you tube videos on making crystal sets.
most of the books that get mentioned are out of production and/or close to $100
Are there any cheaper books for good radio projects?

There are PDF copies of old books available online, BUT you have to look around for them...

[KD8DEY]

If you wanna be creative....There have been people that made variable capacitors using coke cans, sauce pans, or even a couple pieces of single sided PCB with a hinge...Razor blades or even copper oxide scraped off wire & shoved into a Bic pen tube sealed with wax on the ends with a piece of wire as a detector..wax paper and aluminum foil as the capacitor for the headphones....More than one way to skin a cat...

The L/C can be determined using an online calculator to figure out what you need to cover the frequencies of interest
There is one called Professor Coyle....

Inductance is preferred over capacitance for a performance set, and I have read that the coil being close to "Square" (Length & diameter appx the same) is also preferred, but not an absolute.
If you go past 5" diameter, the coil starts to become Directional...

660/46 Litz is considered the ultimate for a typical radio (Look at a chart on litz wire and frequency being covered. (Maybe I can Find it)
As far as Magnet wire, There is consensus that there is not much to gain going larger than #18Awg. (Incidentally, they both have the same number of turns per inch)

If you decide to use a single coil, some people like to add taps every so many turns. Where you connect the diode and antenna effects sensitivity and selectivity....
For a single coil, there is debate on which type offers the best "Q"..
Basket Weave, Spider Weave etc...

The quality of the capacitor, silver plated with ceramic insulators are considered the "Holy Grail"
Fo-215 Diodes are considered top notch as far as diodes, But are hard to find. Russian D18 diodes are a very close 2nd, and
available on E-Bay..Genuine 1N34A are hard to find...

Then there is the debate on design for multi coil sets such as the Mystery set, Mystery set+,....

For a "Performance" set, stay away from wood/paper as the coil form, they add "Q" losses..Plastic or even no coil form seem to be preferred..
I remember reading in an Amp builder /Antenna coil thread to check the suitability for RF by placing the material in a Microwave, If it got warm, don't use it...The same advice could probably be applied to crystal sets...
Does this help??!!

[K9ase]

Thanks for the tip on the calculator. I came up with some diodes.
But now I'm wondering what will happen if I had an air cap in the circuit and if so how big.
I was thinking of taking one from some old parts radios I have laying around.

[KD8DEY]

Thanks for the tip on the calculator. I came up with some diodes.
But now I'm wondering what will happen if I had an air cap in the circuit and if so how big.
I was thinking of taking one from some old parts radios I have laying around.

A variable capacitor out of an old radio should work fine, and is a good source of cheap/free parts. (Dont forget to grab the Diodes)
The only thing is that you have no idea if it is a "365" pf, or it's range unless it came out of an AM BCB radio...

I dont have any radio corpses around, so I ordered one from RF Parts (15-410 pf ), which should cover from below the 630m band to above the 160m band using around a 300uH coil... I also grabbed one of those reduction drive knobs. Between the 2 parts I could have probably picked up a nice battery powered SW radio... (Wouldnt be as much fun, YMMV)

Peebles originals (Mike Peebles also has them along with kits ets.
E-Bay can come up with some Gems if they dont want to try to Ass rape you.

if you know the range of capacitance, you can figure out what frequencies you can tune using what inductance...
I grabbed one of these a while back


Handy Dandy tool for playing with Radio
they measure the tiny values used in radio unlike typical commercial models.

I came across it looking around for a meter, when I found out that the ham that did the AADE meter went SK
there is also a kit out of Australia, but around $100

My big problem is my eyes are going bad, and I have trouble seeing to do what I want...

I have several files that would be of interest, but unfortunately I discovered the other day that my hosting plan doesnt allow file sharing.
If the board picks up, it may be viable to upgrade, but not just for a few people. Better off sending them to somebody if interested by E-Mail...