Help a Fellow Out

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Sean Lemieux
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Help a Fellow Out

Post by Sean Lemieux » Wed Apr 08, 2020 9:15 am

Hey Everyone, we received a question via letter that maybe someone here could help out with or at least point in the right direction for some further information. Here is the question (this is the exact format of how the question was written):

"If you have any information that will turn a Battery Held Transistor Radio into a weather, channel Radio (NOAA)?
Sony Product is being sold in the facility. I know they share similar function, Between one and two Batteries.
I also have a one battery weather Band that has no AM station. FM works fine when DC/DC converter is covered.
I am working on a Sony 2 Battery that has AM only and no FM station, just air or -Hiss- aka sh, sh, sh, sh sound."


Any assistance is greatly appreciated!
-Sean

dyarker
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Re: Help a Fellow Out

Post by dyarker » Wed Apr 08, 2020 11:04 am

https://en.wikipedia.org/wiki/NOAA_Weather_Radio

Going to need a working FM section that can be "hacked" to higher frequency than FM broadcast band. Skill level suggests $20 to $30 and trip to Best Buy (?) so he can listen to NOAA while trying to convert an old radio. (Which may not be possible if it has LSI IC guts.)

Cheers,
Dale Y

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Janitor Tzap
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Re: Help a Fellow Out

Post by Janitor Tzap » Wed Apr 08, 2020 11:37 am

I agree with dyarker,

It will be hard, too impossible to hack a FM radio that has LSI IC in side.
You would need a AM/FM Radio from the late 60's to 70's that you can still find a schematic for.

Back in the 60's and in to the 70's there were kit's for High frequency Receivers for Air traffic, Police,
and Weather that you could connect up to AM/FM Radios.


If he is just needing a Weather Radio.
Just check online at Ebay, Amazon, Etc....
The last one's I saw, were only like $20, and ones that have the Weather Alert were going for $30 to $40.


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CeaSaR
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Re: Help a Fellow Out

Post by CeaSaR » Wed Apr 08, 2020 3:19 pm

And on the current sales front, Radio Shack still has a web presence that sells the weather radios. They aren't cheap, but they are guaranteed to work (at least for a little while, it is the vestige of Radio Shack, after all). https://www.radioshack.com/collections/ ... d-scanners
Hey, what do I know?

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jwax
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Re: Help a Fellow Out

Post by jwax » Wed Apr 08, 2020 7:20 pm

Got a smart phone?

Sean Lemieux
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Re: Help a Fellow Out

Post by Sean Lemieux » Thu Apr 09, 2020 9:10 am

Thanks for the input everyone! I'll pass along your comments in the return letter.

jwax - From what I can tell, his options are limited. I don't believe he has access to a phone or computer.

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CeaSaR
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Re: Help a Fellow Out

Post by CeaSaR » Thu Apr 09, 2020 12:12 pm

Like they said, if it's an older radio with discrete oscillator circuits, then you have the option of modding it to a degree. If it is a "radio on a chip" design, then you are pretty much SOL.

To the actual receiver, it needs to be FM and able to pick up the range of 162.400 to 162.550 MHz. You can find those numbers on https://www.weather.gov/nwr/ here in the States. If you want to hold off for a day, or make a second mail, I'll look up some simple schematics that can be adapted.
Hey, what do I know?

Sean Lemieux
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Re: Help a Fellow Out

Post by Sean Lemieux » Thu Apr 09, 2020 1:09 pm

Awesome, thank you CeaSaR! I will be writing him back on Monday so anything by then will be helpful.

-Sean

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Janitor Tzap
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Re: Help a Fellow Out

Post by Janitor Tzap » Thu Apr 09, 2020 5:02 pm

Sean,

I found this circuit on Sparkfun.
https://learn.sparkfun.com/tutorials/si ... -guide/all
They have discontinued the kit, but the schematic is listed there, with a parts listing.

Hope that helps.


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gerty
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Re: Help a Fellow Out

Post by gerty » Fri Apr 10, 2020 1:21 am

You can buy one of these for $22. They're a cheap ham radio that can be programmed for the weather freqs. They also have a FM radio in them.. You would program it to receive only and could also be used as a scanner for local Police, Fire, EMS Providing they areUHF/VHF analog
https://www.ebay.com/itm/Baofeng-UV-5R- ... e74525046c

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CeaSaR
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Re: Help a Fellow Out

Post by CeaSaR » Sun Apr 12, 2020 10:58 am

I've found a few that are very simple, but I won't share them unless I can get them to work. I have several commitments today, but am going to hit the breadboard again tonight. Hopefully what I have works and is doable for someone who is looking to mod an existing radio.
Hey, what do I know?

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CeaSaR
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Re: Help a Fellow Out

Post by CeaSaR » Sun Apr 12, 2020 10:30 pm

Well, I've tried, but my stock is not up to snuff for this and I'm out of time.

Again, if the radio he is looking at is a modern radio, then it is almost certainly a "radio on a chip". If it is an older unit, say from the 60's or earlier 70's, then they would be mostly discrete components with coils, etc. And even then, the FM section is harder to hack. If he follows the antenna onto the board and finds an actual coil, and the actual tuner is an air-gap variable cap or a small plastic encased variable cap (old transistor radio type), then it's possible. See the coil I specify below.

Here are 2 very useful links for calculating the needs of the coil and variable cap:
Put in 2 values and it calcs the 3rd - https://www.omnicalculator.com/physics/ ... equency-LC
Plug in the dimensions and details and it calcs the value of the coil - https://www.electricaltechnology.org/20 ... lator.html

That being said, there are some possibilities that are unvetted. You may or may not wish to include them in your letter.

To start off, if the person can get a relative or friend to order the Baofeng listed above or another similar type, then that would be the best outcome.
I looked at a few stores:
Kohls has one for $20, regularly $25: https://www.kohls.com/product/prd-40132 ... d=60381826
Home Depot had one for $25: https://www.homedepot.com/p/Eton-Americ ... /310199899

There are still companies that accept real snail mail orders, so that might be an option too, but most want a lot more for their radios, the least expensive one I saw at Newark was around $80. Probably out of reach.

Now to the scratch builds. The requirements are pretty steep for this, using just 3 volts, and the fact that there is a shortage of small enough variable caps out there for the picking.

The first 2 are tutorials on how to make variable caps at home.
This uses cardboard forms: https://crystalradio.net/beginners3/cap.shtml
This one uses a screw and enameled wire: https://www.electronicproducts.com/Pass ... citor.aspx#

Schematics - here's 2 that can be modded - a different coil should do the trick:
Just the receiver, it will need very high impedance earphone/earpiece (think crystal - good luck finding one) or an external amplifier: http://electronicseveryday.blogspot.com ... eiver.html - replace the coil with 1/4"D x 5/8"L x 7 turns. That should get you in the ballpark with the specified tuning cap. For the BF199 transistor, possible substitutes would be 2N5109, BC547 or 2SC945.

Complete radio and amplifier with volume control but runs on 6 - 9 volts: https://electronicsprojectshub.com/fm-receiver-circuit/ - replace the coil with 1/4"D x 5/8"L x 7 turns, same as above. replacement for the BF494/BF495 is 2N3707, though a 2N3904 or 2N2222 might work.

Checking All Electronics, they have a lot of what is needed here, including variable cap, wire other components and protoboard. (1-800-826-5432) 14928 Oxnard St. Van Nuys CA, 91411-2610
Digikey, Mouser and Newark are other places that have even more than All Electronics, but I'll leave their info up to you.

Wish him good luck for us!
Hey, what do I know?

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Lenp
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Re: Help a Fellow Out

Post by Lenp » Mon Apr 20, 2020 4:46 pm

A quick E-bay look shows many weather band radios new and used, for around $20.
Ordering bit piece parts could cost that much in shipping if ordered from several vendors, and, who carries 'radio' parts any more anyway?
And at the risk of destroying a working radio, is this really a sensible DIY project for someone without a solid background and experience?

Don't reinvent the wheel. Just get four, stick them on some boards and go for a ride! :grin:
Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)

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