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 Post subject: Re: Antique Wireless Assoc. AM tx board
PostPosted: Jan Fri 15, 2021 4:02 am 
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Location: Scotia, NY 12302
fifties wrote:
So is the oscillator a fixed crystal, or what type of component(s)? I wouldn't be able to use any of those three frequencies.


The oscillators are self contained circuits in surface mount or 14 pin dip metal can. There are other frequencies available but I'm not sure
of them all. I corrected one in my last post, it is 1024. In my location 1000 and 1544 are now unused. Here is a link to a data sheet. (If I
copied it correctly )

https://www.mouser.com/datasheet/2/96/C ... 665263.pdf

Al

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 Post subject: Re: Antique Wireless Assoc. AM tx board
PostPosted: Jan Fri 15, 2021 6:01 am 
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Thx. It looks like 1mHz is the lowest frequency, which is fine, but I'm wondering what circuitry is needed
to select a particular frequency.

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 Post subject: Re: Antique Wireless Assoc. AM tx board
PostPosted: Jan Fri 15, 2021 6:47 am 
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 Post subject: Re: Antique Wireless Assoc. AM tx board
PostPosted: Jan Fri 15, 2021 1:27 pm 
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Joined: Jan Fri 27, 2017 8:41 pm
Posts: 335
Location: Springwater, NY
fifties wrote:
Thx. It looks like 1mHz is the lowest frequency, which is fine, but I'm wondering what circuitry is needed
to select a particular frequency.


While the example datasheet linked above has a defined frequency range, 1 MHz is not the lowest frequency of operation of the AWA circuit. The PCB accepts a crystal oscillator and frequency of your choosing; there are a multitude of choices for oscillators and manufacturers. There are four frequency-dependent components, two caps and two inductors. It's a matter of choosing values and all values are readily available.


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 Post subject: Re: Antique Wireless Assoc. AM tx board
PostPosted: Jan Fri 15, 2021 3:57 pm 
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NW2K wrote:
fifties wrote:
Thx. It looks like 1mHz is the lowest frequency, which is fine, but I'm wondering what circuitry is needed
to select a particular frequency.

There are four frequency-dependent components, two caps and two inductors. It's a matter of choosing values and all values are readily available.


The most frequency-sensitive component is L2, the antenna tuning inductor. If you choose a frequency other than what is on the datasheet, you will probably have to tweak L2 to find the optimum value.


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 Post subject: Re: Antique Wireless Assoc. AM tx board
PostPosted: Mar Thu 18, 2021 5:41 am 
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Joined: Jul Sat 11, 2020 6:58 am
Posts: 202
Location: Ventura, CA
If the parts are available from Digikey AND you mail in your order with a check, Digikey will ship you your order for free to a US destination. No minimums either. I've been using that perk from them for years. The only gotcha these days are tariffs. So make your order as though you're going to purchase online, start checking out and when you finally get a grand total list including all tariffs - print it out and mail it in with a check.

For those that built this, where did you find the schematic? I see they sell the board but is the schematic and parts list posted somewhere? If not, what are the values for the two inductors on the board? And is the oscillator CMOS or TTL output?

Thanks,

Dave


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 Post subject: Re: Antique Wireless Assoc. AM tx board
PostPosted: Mar Thu 18, 2021 5:50 am 
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Joined: Jan Sat 25, 2020 5:23 am
Posts: 545
Location: Colorado Springs, CO 80917
Quote:
And is the oscillator CMOS or TTL output?


All the oscillators I have, the data sheets I found for them talked about the outputs driving TTL inputs,
so I assume TTL output designs.


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 Post subject: Re: Antique Wireless Assoc. AM tx board
PostPosted: Mar Thu 18, 2021 4:07 pm 
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Location: Yukon, OK USA
Several of the members on this board worked out a functional LM386 / 3904 design that worked and could be built on a protoboard. It was just above beginner level project.

https://www.antiqueradios.com/forums/viewtopic.php?f=12&t=335976&start=0

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 Post subject: Re: Antique Wireless Assoc. AM tx board
PostPosted: Mar Thu 18, 2021 5:22 pm 
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Joined: Jul Sat 11, 2020 6:58 am
Posts: 202
Location: Ventura, CA
black85vette wrote:
Several of the members on this board worked out a functional LM386 / 3904 design that worked and could be built on a protoboard. It was just above beginner level project.

https://www.antiqueradios.com/forums/viewtopic.php?f=12&t=335976&start=0

Excellent! Thanks!

Dave


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 Post subject: Re: Antique Wireless Assoc. AM tx board
PostPosted: Mar Thu 18, 2021 6:15 pm 
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Joined: Dec Wed 30, 2020 5:01 pm
Posts: 111
Location: Columbia, SC USA
I would like to try to build this, and I have a couple of newbie questions. I've recapped a couple of AA5s, and I'm still trying to learn my way around circuits. I want to understand what I'm doing.

One of you said "adding a ground" cleared up some noise. How do you go about doing this?

Also wondering if this could be powered off a usb power pack, or battery.

Thanks for your patience.

D


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 Post subject: Re: Antique Wireless Assoc. AM tx board
PostPosted: Mar Thu 18, 2021 7:24 pm 
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Joined: Jan Sat 12, 2008 12:25 am
Posts: 265
Location: Kingwood, Texas
ai6vx wrote:
For those that built this, where did you find the schematic? I see they sell the board but is the schematic and parts list posted somewhere?


A schematic and parts list is included with the board.

Darrell


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 Post subject: Re: Antique Wireless Assoc. AM tx board
PostPosted: Mar Thu 18, 2021 7:29 pm 
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Joined: Jan Sat 12, 2008 12:25 am
Posts: 265
Location: Kingwood, Texas
tgr131 wrote:
Also wondering if this could be powered off a usb power pack, or battery.


It requires 9 volts DC. It will work off of a battery, but I suspect a typical 9 volt battery would die after a few hours. I wouldn't suggest more than 9 volts. I went as high as 12 volts, but the modulation density dropped noticeably. If you are looking for portability, a 12 volts gel cell reduced to 9 volts would be fine.

Darrell


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 Post subject: Re: Antique Wireless Assoc. AM tx board
PostPosted: Mar Fri 19, 2021 11:44 pm 
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Joined: Jul Sat 11, 2020 6:58 am
Posts: 202
Location: Ventura, CA
Thanks all! I went ahead and placed an order for the board from AWA

Dave


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 Post subject: Re: Antique Wireless Assoc. AM tx board
PostPosted: Mar Tue 23, 2021 5:52 am 
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Joined: Jul Sat 11, 2020 6:58 am
Posts: 202
Location: Ventura, CA
ai6vx wrote:
Thanks all! I went ahead and placed an order for the board from AWA

Dave

Got my board today, including schematic and parts list. Interesting that the supply to the oscillator is not regulated. Wall wart specified isn't regulated either.

Time to start ordering parts.


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 Post subject: Re: Antique Wireless Assoc. AM tx board
PostPosted: Mar Tue 23, 2021 4:51 pm 
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Joined: Dec Wed 30, 2020 5:01 pm
Posts: 111
Location: Columbia, SC USA
The parts list calls for "Carbon Film" 1/4 watt resistors. Last December I had ordered kit of "Metal Film" 1/4 watt resistors. Are they interchangeable for this type of project?

If not, can I use the 1/2 watt Carbon Film resistors I got from Sal in his kit?

Thanks!

D


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 Post subject: Re: Antique Wireless Assoc. AM tx board
PostPosted: Mar Tue 23, 2021 5:03 pm 
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Joined: Jul Sat 11, 2020 6:58 am
Posts: 202
Location: Ventura, CA
tgr131 wrote:
The parts list calls for "Carbon Film" 1/4 watt resistors. Last December I had ordered kit of "Metal Film" 1/4 watt resistors. Are they interchangeable for this type of project?

If not, can I use the 1/2 watt Carbon Film resistors I got from Sal in his kit?

Thanks!

D

I've read that metal film are better in every way. I'd use what you have.

Dave


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 Post subject: Re: Antique Wireless Assoc. AM tx board
PostPosted: Mar Wed 24, 2021 3:34 pm 
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Joined: Jan Sat 12, 2008 12:25 am
Posts: 265
Location: Kingwood, Texas
tgr131 wrote:
The parts list calls for "Carbon Film" 1/4 watt resistors. Last December I had ordered kit of "Metal Film" 1/4 watt resistors. Are they interchangeable for this type of project?

If not, can I use the 1/2 watt Carbon Film resistors I got from Sal in his kit?

Thanks!

D


Nothing critical about these resistors. Use whatever you’ve got.

Darrell


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 Post subject: Re: Antique Wireless Assoc. AM tx board
PostPosted: Mar Tue 30, 2021 5:54 am 
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Joined: Jul Sat 11, 2020 6:58 am
Posts: 202
Location: Ventura, CA
Built the AWA TX board tonight. Not real happy with the performance. Distance isn't great, gets static-y just a few feet away, and the modulation is low. Increasing the audio levels on my MP3 player, or other audio source and the audio become distorted, yet overall still much lower volume than commercial stations.

Double checked my work and everything looks correct. I even bought the recommended wall adapter (9V 100mA, linear) and find that the oscillator is being fed 7.96V as there's not enough load to drop the adapter output (9V adapter is measuring 11V). I was hoping I didn't have to fiddle with the circuit, but looks like I might have to if I don't find an assembly mistake.


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 Post subject: Re: Antique Wireless Assoc. AM tx board
PostPosted: Mar Tue 30, 2021 1:23 pm 
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Joined: May Sun 16, 2010 3:22 am
Posts: 304
Location: Scotia, NY 12302
ai6vx wrote:
Built the AWA TX board tonight. Not real happy with the performance. Distance isn't great, gets static-y just a few feet away, and the modulation is low. Increasing the audio levels on my MP3 player, or other audio source and the audio become distorted, yet overall still much lower volume than commercial stations.

Double checked my work and everything looks correct. I even bought the recommended wall adapter (9V 100mA, linear) and find that the oscillator is being fed 7.96V as there's not enough load to drop the adapter output (9V adapter is measuring 11V). I was hoping I didn't have to fiddle with the circuit, but looks like I might have to if I don't find an assembly mistake.


The one I built works very good. For my first test, I had the Tx on my bench in the basement and fed it with a portable CD player. I walked upstairs carrying a radio
and went all through the house including the split level over the garage. The Rx audio got weak in a couple spots but just moving a little one way or another brought
it back. I brought it with me to our local antique radio meeting and hooked it up in the back of my car. Another member listening in his car drove away and lost the
signal at least 100 feet or so away. I am also using the wall wart in the parts list. I also built it with the variable inductor but hear no difference in changing it.

Al

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 Post subject: Re: Antique Wireless Assoc. AM tx board
PostPosted: Mar Tue 30, 2021 3:08 pm 
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Joined: Jan Sat 12, 2008 12:25 am
Posts: 265
Location: Kingwood, Texas
Mine also works well. The audio is clean and I can receive it throughout the house and into the outer reaches of my yard. It appears you have something wrong.

Darrell


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