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 Post subject: Working on a AM transmitter prototype
PostPosted: Oct Wed 09, 2019 9:56 am 
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Joined: Sep Mon 30, 2019 8:07 am
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Location: Cheney Washington
Hello All,
As I was working on my Crosley Model 51 restoration I came up with a unique idea for a mini AM transmitter. I love to restore these antique radio and put them into operation. The only drawback is that you are stuck listening to modern broadcasts thru a radio that is almost 100 years old. So here is my idea: I have purchased all of the components to build mini AM transmitters plus a few MP3 music players. What I will do is build the transmitter and attach the mp3 player to it. The MP3 players are pre-loaded with 12 hours of vintage radio broadcasts and music. All of this will be stored in a vintage case that would not look out of place next to your radio. Imagine turning on your antique RCA Radiola Model 20 and tuning in Glen Miller or Amos and Andy. My wife says I should pre-load ours with some old time Christmas Broadcasts for the holiday season. I will let you know how well they work when I am done. I plan on selling these units for $25.00 with my restored radios. I would like to hear your comments or ideas to see if this is worth pursuing.


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 Post subject: Re: Working on a AM transmitter prototype
PostPosted: Oct Wed 09, 2019 10:24 am 
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Location: Long Island, N.Y.
Sounds like it would be a nice unit. I've actually used AM transmitters for many, many years. I have a good solid state unit that I've used daily for at least 15 years. I usually input my laptop and have anything imaginable to listen to on my old sets.
The biggest problem about taking time to find something on the dial is that I just don't have the time.
Good luck with your idea.


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 Post subject: Re: Working on a AM transmitter prototype
PostPosted: Oct Wed 09, 2019 10:31 am 
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Location: 13 Critchley Avenue, PO Box 36, Monteith Ont, P0K 1P0
MonkeyPaws wrote:
I plan on selling these units for $25.00 with my restored radios. I would like to hear your comments or ideas to see if this is worth pursuing.


What do you mean by "worth"?

If you mean "financial worth", then no it's not worth it. In a tiny niche market, your margin has to be huge or your product incredibly expensive to be worth doing especially given the startup costs.


If you mean "personally satisfying", then the only person who can answer that is you.

If you mean "will it sell"?, then, only speaking for myself ... no. I would spend the extra to buy a commercially made xmitter and feed it from a preloaded tablet or a web feed, something that would reach farther than just a few feet.


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 Post subject: Re: Working on a AM transmitter prototype
PostPosted: Oct Wed 09, 2019 12:53 pm 
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Sounds like a nice project. As far as who will be interested on here... A few will want one hands down, a few more will tell you how useless it is and the rest will argue how illegal it is and 4 pages later the thread will get locked. That's kinda how these projects tend to go. Personally I'd try to sell it on a maker site where people do these projects. If you want to capture a younger audience just include "steampunk" in the project name.

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 Post subject: Re: Working on a AM transmitter prototype
PostPosted: Oct Wed 09, 2019 1:45 pm 
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Location: Suburban Chicago
If you can really sell them for $25 then I might be interested. I'd like to see what you are actually making before I commit. You might have to offer the transmitter part as a collection of parts (or perhaps a BOM from someplace like Digikey) for the buyer to build to make them qualify as "home built" under FCC regulations. I guess the question for you is how many do you have to sell to make the project worth it to you? If it is strictly a labor of love then it is worth doing as long as you love it!


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 Post subject: Re: Working on a AM transmitter prototype
PostPosted: Oct Wed 09, 2019 2:11 pm 
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I myself am in the process of getting ready to modify a pretty small auto FM converter for old radios. Planning to run on 12V wall wart. connect directly to the radio screw terminals and use the 10 foot wire for FM and then back to AM in the bypass mode. The only issue there is that I only know of one FM station that plays stuff like big band, and not constantly. But there is lots of hip hop etc. Yippee. Or stale old rock. Well it will be nice and quiet and presumably no RFI in the house issues but as for a great program improvement, well. I do have the converter lashed to a communications receiver to test it and so far so good.

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 Post subject: Re: Working on a AM transmitter prototype
PostPosted: Oct Wed 09, 2019 2:30 pm 
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If you're planning on listening to Glenn Miller and other vintage radio programs, I might suggest the 6AB4 & 6888 two tube AM transmitter. In fact, I think that the parts to that kit are still available.


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 Post subject: Re: Working on a AM transmitter prototype
PostPosted: Oct Wed 09, 2019 4:18 pm 
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Sounds like a worthwhile project if it works well, you can sell for $25 and still make a bit off of it.

When I was in school, one of the electronic projects was to make an AM modulated wave. It was part of the Heath/Zenith course and I was surprised how well the two transistor circuit worked!

I tried using it as a transmitter with good results. I'll have to dig up the notes on it. It is no SSTRAN, but still useful. :D

-Steve

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 Post subject: Re: Working on a AM transmitter prototype
PostPosted: Oct Wed 09, 2019 4:46 pm 
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Location: Vancouver Island, Canada
Right, a cheap power supply for your transmitter needs to be tested for AM interference, and many wall warts fail in that regard. Battery operated should be fine.

Since you are putting the MP3 player next to the Crosley, it could be hardwired to the volume control, but then you are bypassing the AM front end.

Definitely do searches here for designs and discussions galore, and keep us posted.

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 Post subject: Re: Working on a AM transmitter prototype
PostPosted: Oct Wed 09, 2019 5:09 pm 
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Joined: Aug Wed 24, 2011 4:35 am
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Location: Sunnyvale CA
MonkeyPaws wrote:
I will let you know how well they work when I am done. I plan on selling these units for $25.00 with my restored radios. I would like to hear your comments or ideas to see if this is worth pursuing.



If it is only $25, at least a few dozen will buy one (me included), because that is just pocket change. I am certainly not going to quibble over the performance for that kind of money.

Brett


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 Post subject: Re: Working on a AM transmitter prototype
PostPosted: Oct Wed 09, 2019 6:15 pm 
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Joined: Sep Mon 30, 2019 8:07 am
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Location: Cheney Washington
The whole unit will be approx the size of a pack of cigarettes. The signal will have very short range (about 10ft) and must be close to the radio to function. Hence the vintage tin sitting next to the radio


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 Post subject: Re: Working on a AM transmitter prototype
PostPosted: Oct Wed 09, 2019 10:26 pm 
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Joined: Feb Thu 17, 2011 11:27 pm
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Location: Long Island, N.Y.
MonkeyPaws wrote:
The whole unit will be approx the size of a pack of cigarettes. The signal will have very short range (about 10ft) and must be close to the radio to function. Hence the vintage tin sitting next to the radio

That's sounds really cool. I'd be tempted to get one myself. Count me in! :)


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 Post subject: Re: Working on a AM transmitter prototype
PostPosted: Oct Fri 18, 2019 6:04 am 
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Joined: Sep Mon 30, 2019 8:07 am
Posts: 22
Location: Cheney Washington
Hello All,
I built some of the mini AM transmitters and tested them with one of my old radios. The red and black leads are the antenna and ground. The other connector is for the 9V battery. The unit will only transmit a few inches, so it has to be very close to the radio. After trying this I decided to attach the Ant/Gnd leads directly to the radio binding posts to see what happens. Low and behold I was able to listen to the 1938 broadcast of "War of the Worlds" clearly. What this tells me is that I can set up one of my old sets and hook this rig to the radio and play old time radio broadcasts with an MP3 player. I can preload days worth of broadcasts on a single 16GB card. When I receive the MP3 players I will load them with 70hrs of broadcasts. I will them send them to three of our group members free of charge to test them.

Attachment:
Mini AMT.jpg
Mini AMT.jpg [ 537.73 KiB | Viewed 1760 times ]


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 Post subject: Re: Working on a AM transmitter prototype
PostPosted: Oct Fri 18, 2019 11:00 am 
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Joined: Feb Thu 17, 2011 11:27 pm
Posts: 13603
Location: Long Island, N.Y.
MonkeyPaws wrote:
Hello All,
I built some of the mini AM transmitters and tested them with one of my old radios. The red and black leads are the antenna and ground. The other connector is for the 9V battery. The unit will only transmit a few inches, so it has to be very close to the radio. After trying this I decided to attach the Ant/Gnd leads directly to the radio binding posts to see what happens. Low and behold I was able to listen to the 1938 broadcast of "War of the Worlds" clearly. What this tells me is that I can set up one of my old sets and hook this rig to the radio and play old time radio broadcasts with an MP3 player. I can preload days worth of broadcasts on a single 16GB card. When I receive the MP3 players I will load them with 70hrs of broadcasts. I will them send them to three of our group members free of charge to test them.

Attachment:
Mini AMT.jpg

That is so cool! Congrats on a very clever unit. Looking forward to having one!


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 Post subject: Re: Working on a AM transmitter prototype
PostPosted: Oct Fri 18, 2019 11:55 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 20750
Location: Warner Robins, GA
Is this going to be a kit or a fully assembled unit?

Also I'm not so sure about operating the transmitter on 9Vdc unless the audio transformer drops the voltage enough to where the maximum voltage for the TCXO is not exceeded.


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 Post subject: Re: Working on a AM transmitter prototype
PostPosted: Oct Fri 18, 2019 5:31 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Beautiful Downtown Burbank CA
'Paws, try .1 cap on your ant/gnd connections. I get several feet of transmission range on the same setup.


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Ant cap.JPG
Ant cap.JPG [ 647.23 KiB | Viewed 1660 times ]
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 Post subject: Re: Working on a AM transmitter prototype
PostPosted: Oct Fri 18, 2019 5:54 pm 
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Mike Toon wrote:
'Paws, try .01 cap on your ant/gnd connections. I get several feet of transmission range on the same setup.


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01 cap.JPG
01 cap.JPG [ 508.56 KiB | Viewed 1654 times ]
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 Post subject: Re: Working on a AM transmitter prototype
PostPosted: Oct Fri 18, 2019 6:03 pm 
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Joined: Sep Mon 30, 2019 8:07 am
Posts: 22
Location: Cheney Washington
Mike Toon wrote:
'Paws, try .1 cap on your ant/gnd connections. I get several feet of transmission range on the same setup.


Thanks for the info. I would have never thought of that. I will try that ASAP and let you know how it worked


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 Post subject: Re: Working on a AM transmitter prototype
PostPosted: Oct Fri 18, 2019 6:12 pm 
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Location: Beautiful Downtown Burbank CA
I had to check. The .01 cap seems better but try several sizes.


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 Post subject: Re: Working on a AM transmitter prototype
PostPosted: Oct Fri 18, 2019 6:16 pm 
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Location: S. Dartmouth MA 02748-1225 USA
Interfacing one of these with a Blue-Tooth transceiver would allow wireless connection to a so equipped computer/iPhone. That would further increase the distance and allow streaming content from YouTube etc. If not B-T then USB which possible could power the unit, but limit to computer only...

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