Efficiencies in Radio Amateur (2)

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#1
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Hai

 

Back in the past,there's crystal radio which was common for every families(i.e Kids gadget).

I'm starting with crystal radio as my first radio entry.

 

There's numberous schematics right now.

 

I'm tried to builts as "product" to listen in HF/SW bands.

 

If there're any comment will consider well

 

THank

Jeck

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Last Edited: Sat. Feb 8, 2020 - 01:57 PM
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The big problem with "crystal set" radio receiver is the very poor sensitivity. The second problem is bandwidth - that is, tuning is very broad and it  does not separate signals that are very close to each other in frequency. 

 

Above the AM broadcast band, you need much more sensitivity and a crystal set will simply not respond.

 

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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The crystal radio is very interesting.  It does not use any power like a battery or wall outlet.  The energy needed to drive the tiny earphone speaker comes from the AM radio signal itself.

 

Crystal radio is how many young people learned about the world back in the 1910s and 1920s.  But in the 2020s, a crystal radio compared to the world-wide internet is like a  toy sailboat compared to an ocean liner cruise ship.

 

If you are interested in radio and have an Arduino, then I suggest trying these FM receiver ICs: https://www.ebay.com/itm/5pcs-FM...

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The problem is that the  OP lives in a remote location in SE Asia (Indonesia, perhaps) and such things are very difficult and expensive for him to obtain. His primary interest is Short Wave, not FM.

 

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

Last Edited: Sat. Feb 8, 2020 - 08:28 PM
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Is there much AM in the SW band?

#1 This forum helps those that help themselves

#2 All grounds are not created equal

#3 How have you proved that your chip is running at xxMHz?

#4 "If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand." - Heater's ex-boss

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As far as I know, most SW broadcast is still AM.

 

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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I had a couple of crystal sets as a boy -- they sold them as toys at the time. We had a local station with their antenna about 10 miles from the house -- picked them up well -- and almost nothing else! But it was fun to see what might work as an antenna. The little clip on the dial of a rotary phone was good, my bedsprings were so so and I think that the ground from an outlet was good too.

 

Jeckson, as Jim has pointed out, crystal sets are not very good -- but maybe you can make one work.

 

Things to consider

 1. Get a germanium diode for the detector. 1N34s are still available. They will be more sensitive

2. Find some high impedance headphones. Single earphomes used to be commonly available -- https://www.amazon.com/Crystal-Radio-Earphone-Impedance-3-5mm/dp/B0052EE0AU

 

The link is to an Amazon part -- don't know if that works for you, but that's the part that you want.

3. Figure out what frequencies you want and look for information on values for the coil and tining tuning capacitor that will work.

4. You might get lucky hooking to a ground (electrical or something like a metal pipe). If it's electrical -- MAKE SURE THAT IT'S A GROUND!!! The screws on outlet boxes will work.

5. If that doesn't work, hook your set up to  the longest wire that you can install outside of your house.

 

In the end, if you are lucky, you will here hear some faint signals from here and there -- unless there is a fairly strong broadcast station in the area.

 

Google can probably give you a great deal more info on this.

 

Good Luck,

hj

 

 

Last Edited: Sun. Feb 9, 2020 - 01:13 PM
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ford2go wrote:
I had a couple of crystal sets as a boy
similiar with but just one and others AM,FM receiver with power.

 

ford2go wrote:

The link is to an Amazon part -- don't know if that works for you, but that's the part that you want.

3. Figure out what frequencies you want and look for information on values for the coil and tining tuning capacitor that will work.

4. You might get lucky hooking to a ground (electrical or something like a metal pipe). If it's electrical -- MAKE SURE THAT IT'S A GROUND!!! The screws on outlet boxes will work.

5. If that doesn't work, hook your set up to  the longest wire that you can install outside of your house.

 

Yes, with tap the coils and tuning capacitors will made all SW band could coverage.

 

Jeck

 

 

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Jeckson -

 

Could you tell us what you are trying to do? Maybe there is another way? What is important about the two frequency radio?

 

Best wishes,

 

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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Hai

 

ka7ehk wrote:
Could you tell us what you are trying to do? Maybe there is another way? What is important about the two frequency radio?

 

I trying to built SW radio...Built cheap.

 

the two frecuencies radio SW simultaniously   https://www.avrfreaks.net/forum/efficiency-amateur1

 

Regards

Jeck

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Then try a simple regenerative receiver. Just a couple of very standard transistors will do. 2N3904 are just a few US pennies each. Pretty sure there are equivalents in European and Asian transistor numbers.

 

There are quite a few designs on the internet for short wave receivers that use just a few transistors. I am building one that uses plug-in coils for different bands. No need for multiple receivers.

 

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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 It's well worth your while to learn morse code also. Transceiver are much simpler and cheaper to build. And there are a lot of keyer projects on the net using the AVR. Have fun !!