TheRadioBoard

I have to admit my head is swimming from reading/seeing the various designs...some say design A is great, others say it has issues which design B fixes, still more say neither A nor B is all that good compared to designs C....Z.

So, what is the (a?) best/good design for a relative newcomer to build..a person who is focused on the actual performance and use of the radio?

I built xtal sets when I was a kid, so I've had that experience. Now, I'd like to try something that has good capabilities and can be expanded on.

I thank you for pointing me to plans or information.

t

Any of the contest sets are top notch. be sure to look at other years entries in the left column.
The Lyonodyne probably has the most information and variations in design on the web and on the forums. (next to the simple Mystery set)
http://crystalradio.us/crystalradios/2010-1.htm#haydon
Your best route is to build a simple set and maximize your antenna and ground before building a contest set.
If fidelity outweighs DX considerations then a high Q Miller set is the way to go.

Hey Thumper,

Good to see you over here.

Re the "best" design, it simply depends on how many parts you have on hand (or are willing to buy), etc.

As you probably know, ANY crystal radio will get the most benefit from the best antenna and ground you can build as we discussed before. One option is to take the radio "on the road" and set it up on a long wire/good ground.

Personally I would suggest an easy STRAIGHTFORWARD "Tuggle " type circuit as a fairly simple but good performing SOLID wire coil design for the A.M. broadcast band.

A Tuggle has an "optional" series antenna or ground var cap, a tuned antenna coil w/ var cap,a tuned detector coil w/ var cap and an optional trap coil w/ var cap ( if you have strong local stations you need to tame).Each coil has the capability to move closer or further away from the coil next to it.

The ability to tune the antenna circuit REALLY boosts reception a LOT.

The series antenna or ground var cap is sort of "optional" but nice to have.

Not only is the DESIGN important, the TYPE of parts USED in a design is also a BIG factor.

K

thanks, K and homebrew..

good to see you here, too, krystallo...

I take it that "solid" wire is in contrast to "stranded," correct? I have seen photos where builders appeared to have used silver jewelry-grade wire - uninsulated - to form the links between components.. Looks cool, not sure how well it performs.

are you suggesting that there is a trade-off between sound quality and ability to grab and select from among many stations?

I may need to buy some components as I don't have ready access to old parts or "junk" radios and even radio shack appears no longer to sell all the parts...maybe they offer fixed capacitors and resistors..

I will look at the radios you recommend...the tuggle, competition designs..

do I need to get comfy with any formulae? I'm thinking "yes" based on comments here and elsewhere...I have a couple of stout cardboard tubes I set aside for my coils...they're mailer tubes, and diff. diameter and thickness than toilet or paper towel tubes. I would assume that would alter coil performance, number of windings, etc.

thanks for any additional information...now, I'm off to reading at your suggested spots.

t

You will end up with a better set using plastic household containers. I like the type two recycle ones. They have a 2 inside a triangle usually on the bottom.
I've just started using some of the silver plated teflon coated military surplus wire that has recently flooded the ebay market. Coil Q's are around 2X the copper solid wire. Mine ran around 2 cents a foot. It appears to be the biggest bang for the buck right now.
A small Litz (175/46) wire coil will run 6 to 7 times the Q of a equivalent solid wire coil.
You can breadboard the set with plug in coils and upgrade to more expensive coils or different styles anytime. One of the thrills of the hobby is improving the set and pulling in a unexpected long DX.
The current version of the Lyonodyne is pushing number 20. I have a clone of I think number two using solid wire cylinder coils that is a excellent set.

Let me make sure I'm reading you correctly, homebrew...

are you saying that it's better to use plastic household containers (and/or discarded plastic bottles,etc) than to use a cardboard mailer tube?

I know what you mean about the 2 inside the triangle...refers to a certain type(s) of plastic material...

Sounds like you're saying that silver or silver-plated wire produces higher-Q coils than solid copper...


Now, the basket-style coil doesn't look complex to make, but perhaps harder in the doing than in the looking at it?

and your "clone of number 2" refers to some version of a Lyonodyne set?


thanks!


t

are you saying that it's better to use plastic household containers (and/or discarded plastic bottles,etc) than to use a cardboard mailer tube?
yes
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Sounds like you're saying that silver or silver-plated wire produces higher-Q coils than solid copper...
yes - here's a good primer on coil design using different types of wire:
http://theradioboard.com/rb/viewtopic.p ... 26&start=0
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Now, the basket-style coil doesn't look complex to make, but perhaps harder in the doing than in the looking at it?
They take me longer to make but are easy enough once you build the jig.
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and your "clone of number 2" refers to some version of a Lyonodyne set?
Yes, a very early version I built around 1978. I'm not sure if the curent one is actually number 17 but the set has evolved over the years.
Here's a Lyonodyne built from less expensive parts and the DX log:
http://www.antiqueradio.com/Jan04_Dougl ... Fever.html

I assume you're in the U.S. As you know, our AM broadcast stations are separated by 10 kHz. This channelization works fine if all you care about are local stations. If you want to hear anything more than 50 miles away, you have to contend with interference from adjacent stations, especially at night.

Selectivity is the ability to separate the desired station from those on adjacent channels. With the LC (inductive-capacitive) circuits used in crystal sets, you don't get squared-off selectivity. The curve is more bell-shaped. So, while you may have good selectivity at the "nose," the "skirts" are wide enough to allow interfering stations to be annoyingly strong.

The bandwidth required by an AM broadcast station is proportional to the highest audio frequency transmitted. If the station limited its audio response to 5000 Hz/5 kHz, their signal would extend 5 kHz either side of center. That frequency range is good enough for speech, but not for music. So a station on 900 kHz is always going to have some signal component at 890 and 910 kHz. You just do the best you can.

Fidelity is almost the opposite of selectivity. Where a selective circuit will by design cut off the high-frequency components of the desired station, a hi-fi circuit lets them pass through. At the outer extremes of the desired signal's audio-frequency range, though, you're going to run into the high-frequency components of stations on either side of it.

I won't beat the horse further by talking about the horrible crud some stations are doing to their signals in the name of progress, that makes their signals broader and full of distortion as well. Sadly, audio fidelity rarely exists in modern AM broadcasting. So I'd go for selectivity. If you need a little better fidelity to understand the station (that's a great tuned circuit!), you can always tune off to one side a kHz or two, assuming you aren't tuning toward a blasting flamethrower station.

73,

_________________

http://kr1s.kearman.com/
http://qrp.kearman.com/

I am in the US..and the 10khz spacing sounds familiar...more of this is coming back to me.

could you elaborate on what some stations are doing to their signals in the name of progress?

I see the merits of your suggestion to go with selectivity over fidelity...

Now, do the same/similar principles apply when trying to build a SW crystal set?

SW is AM, correct? simply different wavelengths and frequencies, but method of propagation still the same?

thanks!

T

The industry term is "IBOC." It supposedly stands for "in-band, on-channel." In reality, it's all over the band, and AM DXers hate it. There's more at Wikipedia: http://en.wikipedia.org/wiki/HD_Radio


SW is AM, and both frequency ranges use ionospheric propagation. Don't know how long it's been since you listened to SWBC, but it sure isn't what it was before the Berlin Wall came down etc.

For SW, almost all of the signals will be much weaker than most of what you'll hear on the BC band, so you have to be more concerned with efficiency. Mike Tuggle has had some experience with SW crystal sets. A good starting point: http://www.antiquewireless.org/otb/dxxtal.htm

Just to be transparent, I haven't built a crystal set since the 1950s, only regens and superhets. I follow the discussions here with great interest, and thought I could fill in on a few questions you asked. There are many RadioBoard regulars with vast crystal-set experience and theoretical knowledge, including Mike Tuggle himself. I hope he'll be drawn into the discussion!

73,

_________________

http://kr1s.kearman.com/
http://qrp.kearman.com/

I greatly appreciate yours and others' responses...they are of great help. I have listened a bit to SW since the wall came down, but I don't have enough experience either before OR after to say what's different.

My goal in trying to capture SW signals is partly bcs AM is such a vast wasteland of dreck...the AM DX-ing I did years ago (on decent, amplified store-bought sets) revealed stations which were unique and special...now any station is about like any other station. like McDonald's. A big mac in New York will be just like a big mac in duluth, MN.

I was/am concerned that AM/FM would go the way that TV did in 2009, going to all-digital broadcasts, which to me would be a shame....

any danger of that happening?

uh....reading the wiki, that answer is revealed...sorry...

I hope that most station owners find it too expensive to go that round...one reason would be that crystal set building would be obviated, and that's almost too sad to even think about.


t

Amen to that. The menus at European McDs are much more interesting. The reduction in local broadcasting makes it harder to ID a station, too. I've often been tempted to send reception reports saying, "I heard your station at such-and-such a time and date, using a radio I built myself for $15.00. Sure glad I didn't pay more than that!" Got to where all I wanted to listen for were stations outside the U.S. Living near the ocean in Florida helps with that.

For the radio experimenter, there's still the challenge of building the best-possible set. New discoveries are still being made in crystal-set and regenerative-receiver designs. IMO, AM broadcasting died years ago, and IBOC is just a futile effort to reanimate the corpse.

73,

_________________

http://kr1s.kearman.com/
http://qrp.kearman.com/

sums it up nicely....but, if domestic AM is dreck, and broadcasts are going digital, what's the point of building crystal sets? Aside from the fun of building a great set, there's the listening WITH the set that's the other half of the fun...

should I focus only on SW crystal receivers?

t

Use plug in coil designs. That leaves band options and coil upgrades pretty well open.

how so? are you saying, build 1 basic radio, but swap out just the coils to change what type of radio you receive?

t