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 Post subject: Re: First time crystal radio build
PostPosted: Apr Sat 24, 2021 12:47 pm 
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Location: New Hampshire
Chas- yes it very well might be hooked up to a plastic pipe I will check later.
macrohenry- my antenna is 3 feet, it's in my basement with the rest of my setup, and it's 3 feet higher than the radio itself.
wayne- good to know, so my understanding is not enough power is coming through the antenna and onto the coil? I also need a longer antenna right?


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Sat 24, 2021 4:16 pm 
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whfh99 wrote:
Chas- yes it very well might be hooked up to a plastic pipe I will check later.
macrohenry- my antenna is 3 feet, it's in my basement with the rest of my setup, and it's 3 feet higher than the radio itself.
wayne- good to know, so my understanding is not enough power is coming through the antenna and onto the coil? I also need a longer antenna right?
Antenna, longer, higher and as much in the open and away from other electrical services as practical The concept is to introduce circulating RF currents using the antenna and ground. "tapping into" those currents and detecting the modulation as audio. All that "power" derived from that antenna/ground system.

For the inductance tuned crystal radio the antenna is a major portion of the tuning element and is essentially fixed. That "system" determines the range of frequencies (broadcast) the radio can tune to generate enough RF to be detected. There is such a "thing" as an antenna that is too long and overload the radio.

Your antenna/ground experiments are as much of a learning curve as is the actual radio... chas

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 Post subject: Re: First time crystal radio build
PostPosted: Apr Sat 24, 2021 4:24 pm 
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ok thank you


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Sat 24, 2021 5:31 pm 
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whfh99 wrote:
macrohenry- my antenna is 3 feet


Henry, 5 pages of good suggestions and you still expect 3 feet of wire to be sufficient?


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Sun 25, 2021 4:55 am 
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whfh99 wrote:
macrohenry- my antenna is 3 feet

I see. That alone is enough to doom this project. Being only in the basement where transmitted medium waves are attenuated so as to practically border on the non-existent, there just isn't enough signal to grab and overcome the inherent losses in a passive circuit.

It's like trying to look at a faint astronomical object with a small aperture telescope. They call large aperture telescopes "light buckets" because they collect a lot of light. That's what you want your antenna to do: Collect a lot of signal.

I have one of the most "powerful" single tuned crystal radios, in fact designed by crystal radio guru Ben Tongue. With passive circuits, "powerful" essentially means very low loss. It has a contra wound 660/46 litz coil and uses special high-sensitivity diodes and a low loss headphone matching circuit with a "Benny" and genuine Deck Talker sound powered phones. Even with all that, to pick up a close strong station just 11 miles away it needs at least a 25-foot antenna at first floor ceiling level or higher.

I think you just identified the weakest link in your system. In my opinion at this juncture, there's not much sense in trying to improve anything else in your system until you get an antenna that is functional.

Another way of looking at it is that antenna functions are generally reciprocal, that is that a good transmitting antenna can make a good receiving antenna. As stated a couple of posts above, a longer antenna has more inductance and capacitance with it, which have a tendency to lower the operating frequency. This is necessary to get into the range of medium waves. If you look at the 10-foot maximum length part 15 transmitting antennas they require a huge loading coil of somewhere around 1,000 to 1,500 microhenries. Your coil is nowhere near that. So with a 3 foot antenna your tuning is way off.

Fortunately you can keep plugging because putting up a good antenna is not really that hard.


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Sun 25, 2021 4:53 pm 
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I don't have enough electric fence wire left for a suitable antenna but I do have 16 feet of standard insulated wire with clips on both ends. that I will experiment with later.
also turns out that my copper wire ground went to more copper wire pipes not PVC pipes however I hooked up to a different pipe ground just in case.
found a diode on a scrap board that I had and I am using it instead of the transistor, who knew germanium diodes came in black...


henry


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Sun 25, 2021 6:39 pm 
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Location: Monroe, NC 28112 USA
Yesterday I was experimenting with a 35mm diameter piezo disc. e-Bay has them for about a dollar each. I had a broken maple bar stool leg found on the side of the road. I cut off a wafer and machined it to take the disc. Some sticky-back aluminum foil tape attaches the disc. The small end is just the right size to snap into the throat of my 1924 Bristol horn speaker bell. I hooked this up to my Heathkit CR-1 crystal set and tuned it to a strong station. This kluge piezo horn driver could easily be heard throughout my 16' x 24' shop. (If the next door neighbors caged dogs are not barking their brains out.)

Two of these would make great High impedance earphones for crystal set work... Considerably more sensitive than the Brandes Superior headset I had handy to try along with my quickie driver. Would need more testing to see if the sensitivity is greater than Baldwin phones or Navy type sound power phones.

I think it would be pretty easy to use a hobby type 3D printer to make a housing for these piezo discs...

Plan to use this same disc to find out how much power it can take.

I'll try to remember to report back.

Robert


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Sun 25, 2021 7:25 pm 
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Location: Colorado Springs, CO 80917
Quote:
experimenting with a 35mm diameter piezo disc


That experimentation deserves its own thread! It'll be a lot less seen buried inside a "first time crystal radio build" thread. Kudos for doing the work. I've seen a video in which one of those discs was used as a kludged-together record player tone arm & it actually worked.


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Sun 25, 2021 7:44 pm 
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Oh my gosh!!! Just got out a little class D amplifier board and hooked its output in reverse (8 Ohm to 1k Ohm) of a transformer salvaged from a 50s AA5 junker radio. The piezo ROCKS! on that same Bristol bell. Almost to the point of pain right in front of the horn. The fidelity is easily better than any Radiola UZ-1325 horn. I'll start a separate thread.

But now really interested in using these for crystal sets... Glad I came across this thread.

Robert


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Sun 25, 2021 8:14 pm 
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Post a picture Robert.


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Sun 25, 2021 8:58 pm 
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thanks for sharing Robert!
I would be very interested in changing/modifying some of the components in my radio once it is built.

Speaking of which how long should my antenna be for my radio? remember I am using 30 ft of scrap insulated wire on the thin side, sadly don't have any way of getting 30 feet onto a tree to make a large antenna.


-henry


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Sun 25, 2021 9:54 pm 
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Location: Colorado Springs, CO 80917
Quote:
I am using 30 ft of scrap insulated wire on the thin side, sadly don't have any way of getting 30 feet onto a tree to make a large antenna.


Wire thickness isn't much of an issue right now, since you're just trying to get something to work right & receive strong local stations. If you want to go DX-ing (listening for weak, far-off stations) then antenna details become a lot more important. For now, as much wire as possible, as high as possible is important. I've unwound old relays & motors for long lengths of wire to make temporary antennas.
Would you be cool with sharing your postal code (zip code) so we might see what radio stations are near you & whether getting one on your set may be as easy as in some large cities with several big stations, etc.?


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Sun 25, 2021 10:58 pm 
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hwhall wrote:
Quote:
I am using 30 ft of scrap insulated wire on the thin side, sadly don't have any way of getting 30 feet onto a tree to make a large antenna.


Wire thickness isn't much of an issue right now, since you're just trying to get something to work right & receive strong local stations. If you want to go DX-ing (listening for weak, far-off stations) then antenna details become a lot more important. For now, as much wire as possible, as high as possible is important. I've unwound old relays & motors for long lengths of wire to make temporary antennas.
Would you be cool with sharing your postal code (zip code) so we might see what radio stations are near you & whether getting one on your set may be as easy as in some large cities with several big stations, etc.?



is close it. there should be some fairly close stations and Boston is not too far. there is a good list of stations nearby on Wikipedia.
how close would I have to be to receive a local station? not planning on going dxing anytime soon on this set but it sounds fun :D


henry


Last edited by whfh99 on Sep Thu 02, 2021 12:50 am, edited 3 times in total.

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 Post subject: Re: First time crystal radio build
PostPosted: Apr Sun 25, 2021 11:04 pm 
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Henry, here's a list of nearby stations;

https://radio-locator.com/cgi-bin/locat ... 301&state=

It looks like WKXL/1450 at 2 miles distant, and WGIR/610 at 14 miles would be your best bets.

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 Post subject: Re: First time crystal radio build
PostPosted: Apr Sun 25, 2021 11:24 pm 
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Location: Colorado Springs, CO 80917
Quote:
It looks like WKXL/1450 at 2 miles distant, and WGIR/610 at 14 miles would be your best bets.


Seems to have numerous likely stations. Those two are likely to be loud enough.
WKXL 1,000W day/night
WGIR 5,000W day, 1,000W night
And there's these three, as well:
WGAM 1250kHz, also 14miles 5,000W day/night
WFTN 1240kHz, 17 miles 1,000 watts day/night
WEZS 1350kHz, 20 miles 5,000W day but only 112 watts night.


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Mon 26, 2021 12:42 am 
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thanks, guys
glad there are some local stations that my radio could pick up.
now the question is how long should the antenna be?
also, I have a decent amount of copper wire left, do you think I could do a simpler version of something like this? -http://makearadio.com/loops/index.php
the only reason I asked was that-A stringing wire on a tree is not that practical for me. B this would make it a bit more portable. C I probably have all the materials unless the tuning cap is needed, I was thinking of just using the copper wire and wooden base part. though the more I think about the more it sounds like it wouldn't work...give me your thoughts.

henry


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Mon 26, 2021 1:45 am 
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Well, going back to page two of this epic thread, LOL;

Quote:
Here's a set I had always planned on building but never got around to it. You might give it a try.

https://worldradiohistory.com/hd2/IDX-C ... l%20set%22

The antenna winding is 23 turns on a 5 x 9 inch box.


If you don't have a tuning cap, post a WTB in the classified forum here, with the maximum amount you can pay.

Alternatively, an external antenna for a crystal radio would need to be a dozen to twenty feet long minimum, but doesn't have to be outside. You can string it across the ceiling if necessary.

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 Post subject: Re: First time crystal radio build
PostPosted: Apr Mon 26, 2021 4:19 am 
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Posts: 705
Location: Colorado Springs, CO 80917
Quote:
do you think I could do a simpler version of something like this?


I'm going to say that it'd be better than the wire that was in your earlier photo (like 18 inches or something) but it may not be better (and is for sure a lot more work) than hanging a lot of wire as you've been advised before.

You really, really need to get your basic circuit working before messing about with other experiments like that antenna. Until you have something that detects stations in your earphone, you won't know for sure what isn't working (still). Adding more to it just adds more variables that might not be right.

I've started putting together something close to your setup. Wound 100 turns of #28 magnet wire onto 2 inch diameter cardboard tube. Kept the turns close together vs your loose windings, because closer spacing makes the coil have more inductance (micro-Henries). I can just barely hear two stations with just the coil, a diode, an earphone (appears to be a piezo type) and a ground wire clipped to my heater vent. Had to pick through several salvaged diodes to find one that worked.

This is in a 3/4 underground basement, sitting on a wood workbench. It's too dark to go hang some wire outside but maybe tomorrow I'll see if that improves it much.


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Mon 26, 2021 1:01 pm 
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I think I am just confusing myself now...
Forget the loop antenna for now.
If you can get 2 stations with just a ground I must be doing something wrong...
Unless I have it hooked up to my ground and "antenna" it does not make any noise.
All I have ever heard on this radio is a lot of humming, Would you mind posting a picture of your setup? I think I might have to redo My Copper wire coil Again.


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Mon 26, 2021 4:27 pm 
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whfh99 wrote:
I think I am just confusing myself now...Forget the loop antenna for now. If you can get 2 stations with just a ground I must be doing something wrong... Unless I have it hooked up to my ground and "antenna" it does not make any noise. All I have ever heard on this radio is a lot of humming, Would you mind posting a picture of your setup? I think I might have to redo My Copper wire coil Again.
IMHO: You need a one on one person to guide you through.

Try reaching out to:

http://www.nearc.net/

There is a meet coming up in about 3 weeks. But email someone in the club who may live near to you.

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