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 Post subject: am transmitter
PostPosted: Jun Wed 19, 2019 8:31 pm 
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not sure if this is the right location but i am looking for opinions on am transmitters. i want relatively high quality audio. would an am transmitter do what i want or would i be better off wiring aux inputs. the am radio stations around here sound pretty bad even on a new decent quality radio. is that the best am can do or are the stations forced to limit quality to fit in the band allocation. if i can get decent quality sound will something like the hand built lil 117 work or is that more of a project that wont sound that great. any other suggestions. looking for something that sounds good but wont destroy my wallet.


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 Post subject: Re: am transmitter
PostPosted: Jun Wed 19, 2019 8:58 pm 
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Most will say to build your own from a kit, which is the most inexpensive way to go. I believe they're easy to find on the Net. I bought a solid state pre-built unit many years ago, but built units are kind of pricey. Somewhere around $200. Check eBay. I paid that much, but have enjoyed it for almost 20 years! Honestly, I hate the sound of a vintage set with direct input. It's just too clean and pure - if that makes any sense! The transmitted signal is more "natural", often with just hints of some background noise as AM should sound.


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 Post subject: Re: am transmitter
PostPosted: Jun Wed 19, 2019 9:05 pm 
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Joined: Feb Thu 28, 2019 7:48 pm
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Location: Lawrenceville, Illinois 62439
How do the local stations sound on your car radio? You may have interference from something in your house. My AM radios sound pretty good in my home (with the flat screen off, CFL's off, one room away from the kitchen appliances, furnace, A/C, no modem or router), but they don't sound nearly as good in my store.
No use building a transmitter if you don't like the sound quality.
Dan


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 Post subject: Re: am transmitter
PostPosted: Jun Wed 19, 2019 9:19 pm 
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mustagcoupe wrote:
i want relatively high quality audio.

Everyone does, but the determination is completely subjective. What passes for me may not for you. Your only option is to build a circuit, or buy a completed one (illegal to sell in the U.S., but there are sellers that still do). If you don't like the audio, you can always sell it.
I doubt however that any OTA signal will sound as clean as a direct connection from the source to the radio. Remember also, that even if you connect a stereo input, the AM radio or transmitter will only produce mono.

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 Post subject: Re: am transmitter
PostPosted: Jun Wed 19, 2019 9:20 pm 
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One good thing is you can boost up the transmitter to where it will drown out most interference. It's true though, if the interference is severe, then a direct input is the only answer.


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 Post subject: Re: am transmitter
PostPosted: Jun Wed 19, 2019 9:32 pm 
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I have tried the radio in my car too. 3 different radios. They all sound slightly fuzzy with very little bass or high end. Any recommendations on a kit. Would prefer tube but solid state is ok. Is the lil 117 any good. It's cheap and simple. Uses 1 tube with a 117 volt filiment


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 Post subject: Re: am transmitter
PostPosted: Jun Wed 19, 2019 9:42 pm 
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I can accept the quality of that's the best am can do. I don't dislike it just wondering if it can be better. It just seems like a waste to put an aux in on everything and not use most of the radio


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 Post subject: Re: am transmitter
PostPosted: Jun Wed 19, 2019 11:04 pm 
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The transmitter you mention does not work well at all and is a waste of time and money to build.

Go in the ARF homebrew section and look at some of the tube transmitter designs, there is one using a 6GY6 that works really well, also the 6888 one is good. Either of those is many times better than the one using a 117 volt tube.

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 Post subject: Re: am transmitter
PostPosted: Jun Wed 19, 2019 11:09 pm 
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Consider that everything is a trade-off. For the convenience of being able to transmit to all your sets, the audio quality probably won't be as good as a direct connection to any one of them.

There's a British company that puts out a transmitter called the Spitfire; you might Google it if you don't want to home-brew.

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 Post subject: Re: am transmitter
PostPosted: Jun Wed 19, 2019 11:10 pm 
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Location: Long Island, N.Y.
mustagcoupe wrote:
I can accept the quality of that's the best am can do. I don't dislike it just wondering if it can be better. It just seems like a waste to put an aux in on everything and not use most of the radio

Exactly - go with a transmitter even if you get a little interference. Direct input really sounds like your using your radio as an amp. It's just too pure to sound "right" for an old set.
By the way, I find if I turn on certain lights in my apartment I can eliminate interference. Even grounding the transmitter sometimes helps. I built a kit transmitter years ago, but must say that I have no regrets buying a good pre-built unit. If you really enjoy listening to your vintage sets, it's well worth the investment. I can't even estimate the amount hours on the one I bought 20 years ago!!


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 Post subject: Re: am transmitter
PostPosted: Jun Thu 20, 2019 1:32 am 
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Is this one any good. Making an order from them and I saw this. https://www.tubesandmore.com/products/k ... ransmitter


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 Post subject: Re: am transmitter
PostPosted: Jun Thu 20, 2019 5:26 am 
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Might want to verify what the range on that is. As a copy of a wireless record player transmitter, may not go beyond one room.

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 Post subject: Re: am transmitter
PostPosted: Jun Thu 20, 2019 2:50 pm 
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mustagcoupe wrote:
Is this one any good. Making an order from them and I saw this. https://www.tubesandmore.com/products/k ... ransmitter

Basically same league as the Lil'7. Waste of time.

Using cast off XP computer, the SA stereo tool program and programming stored on same computer, my homebrew tube transmitter(offshoot of 6888, 6GY6 mentioned) is better than most OTA and as good as 97% of the the better stations. Without audio processing, other than the SS trans(built in processing) no transmitter is going to sound really good. I keep a scope connected so I can check modulation envelope & demodulated audio, these things do require an occasional tweaking. For the not as technical minded, a set and forget solid state LM386 is probably best choice. Fairly decent without audio processing.

Note I recently modulated a Knight Broadcaster with same computer setup and it still sounded weak & tinny. Of course the Knight Broadcaster is mostly for old farts trying to relive their youth.

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 Post subject: Re: am transmitter
PostPosted: Jun Thu 20, 2019 3:40 pm 
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I would suggest the 6888-6AB4 AM transmitter as it is an exceptionally good performer.


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 Post subject: Re: am transmitter
PostPosted: Jun Sat 22, 2019 3:14 am 
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Location: Phoenix, Arizona
I use an AM transmitter made around a 6888 tube for a modulator. It sounds decent on my Mcmurdo Silver M-5.

I started with a pentagrid converter tube kit and it sounded ugly.

I tried a computer with processing and it sounded ugly.

I feed my Xmitter with an FM tuner and they all have good processing and it works fine for me.

Its on a timer and comes on Saturday morning and goes off Sunday afternoon.

It is a little tricky to set the modulation for low distortion but it is stable once set up.

I have four tubes in my Tx, a 6C4 for the oscillator a 6888 for modulator, a 6V6 for PA, and some octal triode for audio gain.

I listen on a variety of sets scattered around the house.

Jim


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 Post subject: Re: am transmitter
PostPosted: Jun Sun 23, 2019 9:36 pm 
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Keep an eye out for an AMT-3000 transmitter, or an AMT-5000. I don't know where or if you'll find one, but if you do -- snap it up!

Some years ago we had someone here offer an AM transmitter as a kit. His business was called SSTRAN, the transmitter was the AMT-3000. He later improved on it with the AMT-5000. Lucky me, I've got two 3000's and one 5000, and have no desire to part with any of them!

Here's the deal: you cannot sell any transmitter unless it's FCC approved. These models would certainly pass, but the approval process is so dadblamed expensive that a small business could never afford such a thing. BUT -- there is no law that forbids one from selling a bag of parts and an instruction sheet, so these were sold as kits. The kit included a precut PCB with a surface-mount IC already attached, a case with custom faceplate, and all the other components needed to make your dream come true. The audio quality outperformed everything else out there by a mile -- it was great.

What happened? Orders came in by the truckload, and orders got backed up to the point where many were questioning integrity, making chargebacks, and cancelling orders. A victim of their own success, SSTRAN shut down operations.

Are there used ones out there? You bet! But many are hesitant to put them on eBay or other sources for fear of the FCC coming after them for selling a non-certified transmitter. Actually I think you can sell a homebrew without complications, as long as one sells no more than 5 units total. Regardless, if you see one of these, snap it up -- there's no law against buying it.

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 Post subject: Re: am transmitter
PostPosted: Jun Mon 24, 2019 4:49 pm 
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Location: Phoenix, Arizona
I remember SSTRAN and I thought the problem was an FCC issue. One of these transmitter makers got fined by the FCC as I recall for about $7,000.

To broadcast on AM or any other licensed frequency you have tp comply with FCC Part 15 rules which require the transmitter to be built by the user, the output power and antenna size is limited.

I believe the "Talking House" deal caused some trouble at the FCC although I still see those around.

My goal was to provide my own music and tune it in on the Mcmurdo Silver console. First I tied the kit with a pentagrid converter tube which had too much FM content and sounded generally bad on the broadband HiFi M-Silver.

I also was planning to use a computer to play the MP3 music into the transmitter and that never worked very well. I tried several processing app's and none really ever worked well enough. The AGC/limiter was way to flakey.

Now I run a decent FM tuner tuned to vintage Rock and I teave the transmitter on for the weekend, (I hogged it out using posts on this very web site). The 6888 was the best modulator. Modrn FM stations have the very best processing.

I use all tubes and the entire thing hangs out on a shelf in my garage.

I spend a little time in my "radio Room" and the current toy is a Grebe CR-9 I bought recently on eBay playing into a Magnavox horn speaker. Yesterday I had the M-Silver M-5 on most of the afternoon and evening and it sounded just perfect with its thympy juke box bass.

Jim


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 Post subject: Re: am transmitter
PostPosted: Jun Mon 24, 2019 5:44 pm 
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Location: Sandusky, OH usa
Has anyone had any dealings with the transmitters made in Turkey sold on eBay? I see them advertised but really no info other than that it covers three frequencies on the AM band. Kinda scary to order from Turkey I think. Still they are only $69.

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 Post subject: Re: am transmitter
PostPosted: Jun Mon 24, 2019 6:04 pm 
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Location: Sarasota, Florida
Quote:
I remember SSTRAN and I thought the problem was an FCC issue. One of these transmitter makers got fined by the FCC as I recall for about $7,000.


As I recall, not naming any names here, there was somebody offering "completed" SSTRAN kits for sale at swap meets. Not sure if they were being sold off the shelf, or if he was simply offering the service of building your kit, but there was somebody else -- who offered "certified" transmitters for sale, that turned him in. I've also heard that Ramsey was fined; I have one of their FM Stereo transmitters (kit-built) that somewhat exceeds the legal range; I limit it by shortening the antenna to keep things in line. There's a variation of the kit, with a different power transistor, that'll give you a full-fledged pirate station. Kinda cool in a way, but illegal is just that, and even a kit with instructions is pushing things a bit. In fact, I could buy a couple components, follow the instruction sheet, and away we go.

As I understand things, you can build and use a non-certified transmitter, provided you keep your signal within legal limits, and even sell it, but don't sell more than five of them. Plus, you're not supposed to HAVE more than five of them, although they generally have no way of knowing unless they raid the place. If you're going to build and sell transmitters, they want certification -- meaning they want to test it themselves and be assured that it operates within legal limits. The Talking House is indeed certified, and is sold the Real Estate agents who want to transmit data to cars passing by a house for sale. It's the only decent-priced certified transmitter around, remembering you can buy them for sale on eBay and other places cheap. Audio is not as good as SSTRAN, and really requires external audio processing (volume level, etc.) but if done right it's not bad.

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 Post subject: Re: am transmitter
PostPosted: Jun Tue 25, 2019 3:26 pm 
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SSTRAN was never in any trouble with the FFC. Their products were perfectly legal to sell in the US, and the firm had absolutely no way to control what people did with the kits once they were sold. The fact that one vendor attempted to sell assembled kits and got fined is not at all related to SSTRAN's own operations.

SSTRAN was a one person operation, and for various reasons the owner could no longer sustain the business. I don't think anyone here knows the exact reasons, but running a business is hard, making money running a business is even harder, as especially as a sole proprietor.

Buying the kits, assembling them, and turning around and reselling the assembled kits was a clear violation. Assembling a kit as a favor to a friend or family member that just bought one is OK. Doing so as a regular service is a bit of a grey area, but it's probably not worth the trouble; people do seem to get over sensitive on this issue.


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