Starting a Part-15 AM Station

What you do next is say what your goals are. Makes a big difference in what you can or can't do, especially if you want your TH station to remain certified.

You won't get much range straight out of the box. If you set the unit by a window and hang the wire antenna outside, you might expect a maximum of about 200' ... but probably less.

You can purchase an ATU and whip antenna for it to extend the range. It's AM radio and only 100mw, so it's going to be different in every locality.

I have a TH but it's producing a great deal of hum I can't get rid of. Probably a power Supply problem. One of these days I'll order a new PS for it and see if it will work.

Did you buy yours via the year-end sale? Is that still going on?

A stream, a blog, a podcast, something in print, a youtube video - audiences now are becoming much more comfortable with the multiplatform approach and it takes some of the burden off of the limited range of the Part 15 compliant transmitter.

I'm a happy TH user, too - though I just moved for the fourth time in five years so I'm down again briefly, but I stream and blog like crazy, and I'm definitely considering podcasts, too.

There are services out there to host your streaming (as I've been informed). However, in my opinion, the fun part is hosting your own streaming, i.e., running a server with the appropriate software. You can register a domain name for next to nothing, and use one of many companies providing DNS services for dynamic IP's (so you don't need a static IP).

You don't need tons of bandwidth for the streaming, either. 40kpbs (bits per second, not bytes) streaming mp3 provides good quality in MONO - since we play mostly old jazz, old time radio and doowop (50's and 60's), using mono is appropriate (and more authentic than simulated stereo). Your mileage may vary, depending on your programming format.

Another often overlooked aspect of Part 15 is license-exempt wireless networking. You're allowed 1 watt output power and a 6db gain omnidirectional antenna, which can give you a 1/2 mile to 1 mile usable range - probably more than getting a listenable signal on the AM band with Part 15. And if you're transmitting point to point, i.e. directional, you're allowed an effective output power of 4 watts - you can use this capability to set up a bridge between multiple wireless networks (unlike multiple AM transmitters, which may or may not be considered legal by the FCC, and certainly not by Industry Canada - there are specific regulations here prohibiting the use of multiple AM or FM transmitters rebroadcasting the same source). Plus certified transmitters, amplifiers and antennas are readily available and relatively inexpensive.

There have been discussions on both the negative and positive aspects of creating your own radio wireless hotspot, and its usability, here in the past, but there's no disputing the fact that it is just as much Part 15 radio as AM or FM. And it just might be the ticket for someone who is located in a densely populated area. At the very least, it's a lot of fun to experiment with!

I just picked up a Talking House and also experienced a terrible hum problem. After a lot of experimentation I was able to solve the hum problem by replacing the factory power pack, relocating the transmitter to the garage (away from all the electrical interference in the house), and attaching a separate ground wire to the transmitter case.

To get the audio from the computer to the transmitter in the garage, I ran it over CAT3 cable (available at Home Depot). The setup is hum free, sounds pretty good, and getting about a mile plus for range.

Hope this info helps.

Sagle47,

where did you get the new power pack from? got any suggestions? The Hum is not that bad when there is music going but when the music is in a low point, stand back, a bit strong. Also, did you buy the antenna that is made for the Talking House or did you make it?

Yes, I did buy one of the Talking Houses that is on the New Year sale.

Right now I am using the wire antenna that came with the unit. I do have the ATU, that will be installed when it gets warmer and I can get on the roof.

The power adapter came from my "junk" box. As a tip, I buy power adapters for $2.00 ea. at the local Animal Shelter thrift store.

With a little placement experimentation I think you will be quite happy with the Talking House.

I did have an impedance mismatch from the computer sound card to the line level input on the TH transmitter (sound was distorted) which I resolved with an impedance matching device from Radio Shack.

Nice feature of the TH is you are able to hear what is going into the transmitter via a built in speaker in the transmitter. Makes it handy for an installation like mine where the transmitter is located some distance from the computer.

Hope this helps.

Again, good luck.

You're right about the PS. I plugged the one I'm using for the Spitfire into the TH, and the hum totally disappeared. The Spitfire PS is rated at 15v. The TH input says 18v, but the measured voltage of the TH PS is 15v. I haven't measured the actual voltage of the Spitfire PS yet.

I adjusted the antenna length up as far as it would go and broadcast on 1700kHz. The signal got out further than the Spitfire on the same frequency, but the audio is awful (Spitfire audio is much better). Sounds over-modulated, even with the sound output turned down a notch from my iMac.

I'm using a Griffin iMic, which works perfectly with the Spitfire. If your computer sound card has a real line-level output, not a jack for a headset, it should work. Why would there be an impedance mismatch? Anyway, now I'm wondering if I'm having the same problem.

What is the Radio Shack part no. for the impedance matching device you got.

Well, since 'Clearwire' became 'Clear', policies have changed somewhat. I.e., they are now virtually all consumer-based. They say that now I can't stream continuously, and nothing unattended, so I guess that means I can't continuously access Shoutcast servers using that connection. I don't see what their beef would be if I only have one upload 'listener' ... myself, the rest of my listeners are handled by Shoutcast servers, but it's their business. If they lose me it will likely affect their sales here.

So if I save Clear for out-of-town (e.g., high school 'away' games on the mainland), and provide several line-of-sight repeaters from my own server base in town, plus feeding a couple Part 15 AM TX' and also perhaps a few FM TX', I should be able to have enough coverage to stay alive.

Are there comprehensive diagrams of how Part 15 networks function? Equipment lists?

http://www.radioshack.com/product/index.jsp?productId=2062443

As I live in a small town this is the only thing I could find locally that could be adapted to do the job. I picked up a couple of items (jacks, etc) while at Radio Shack that made connecting it pretty easy.

I believe there are other impedence matching units being sold on the internet that make the installation more straightforward, which would bypass the fabrication aspect of the project.

I don't know what the impedence of the line out on the sound card is, but this device resolved all the distortion problems. I am listening to the TH5 now with an old radio and it sounds pretty good.

There are some very knowledgeable folk on this forum that can advise you better than I. I'm just passing along what worked for me.

Good Luck.

Thanks for the RE ...
http://www.radioshack.com/product/index.jsp?productId=2062443

As I live in a small town this is the only thing I could find locally that could be adapted to do the job. I picked up a couple of items (jacks, etc) while at Radio Shack that made connecting it pretty easy.

Hmm ... pretty strange. But, hey, whatever works 😉 That's a standard XLR microphone adapter. It's a transformer for connecting an XLR loZ mic to a 1/4" hiZ mic jack. Being a sound guy, I always have one or more of those in my travel kit ... and of course, I have tons of adapters in the same kit. So, no problem there. Not sure it will work in my case, could make it worse. More in a moment.

I guess I was thinking about a variable impedance box of some kind, such as a speaker impedance matching box.

May I ask please what the sound was doing before you did the fix? Did it sound like over-modulation (clipping and distortion) or under-modulation (weak, not loud enough, some background noise)? Exactly where was the sound card's output level (computer's volume control or separate control for the sound card)?

I partially cured my situation by attenuating the computer's audio output level. But in the process, the volume got weaker at the receiver. I'm thinking about giving it some outboard compression to alleviate the distortion and level the signal and see what happens.

BTW, I live in a small town as well. Friday Harbor, WA. There were only three newspapers and one more online local news service in the county. One of the papers went down, and one is basically for another island. Therefore we have very limited venues for advertising local business, hence the need for a radio station.

Good Morning:

Before playing with the impedence matching I had to keep the output volume of the sound card very, very low. Even at such a low level the sound from the TH was so distorted it was unpleasant listening to it. Sounds like a variable impedence device would be ideal.

My home brew fix works very well (probably just luck), now I have the output from the sound card set at mid-level with the signal from the TH being nice clean audio.

Good Luck.

I've found that a lot of ISP's are restricting the use of servers (i.e., streaming or uploading, even with only one connection) on residential accounts. I (Artisan Radio) had to go to a business account at a great deal more cost. You don't require static IP's, however, as a lot of DNS providers give you tools to automatically change your IP address on DNS servers over the Internet if it does change.

I haven't found any comprehensive diagrams for complex networks (that I understand, at any rate). That's why I'm experimenting, which is a lot more fun anyway.

I currently have a wireless network, with the router providing a DHCP service to my LAN. I'm also running a short range bridge to another local wired network. To the devices that are wired to the bridge, it appears like they're talking directly to the wireless router/DHCP server. I also have just recently purchased a Trango, point to point long-range bridge that I will be experimenting with; I would imagine that I would require another wireless router, not running DHCP, in the remote location, to provide wireless services for listeners.

If you're interested, I can report on my findings once I get things going, as it appears you are now going to have to do what I want to do as well.

I just got what appears to be an earlier model TH. Instead of the 1/8 line-in jack like my other one has, it has a mono RCA plug. The sound isn't quite the same. It has an onboard speaker, but with no volume control, and it only outputs a weird pulsing sound ... I think it only works with the message recorder, because you can't hear it in the broadcast (thank God).

The sound has some distortion, so I'm thinking there is an impedance mismatch.

So ... just to be sure, which way did you connect your Radio Shack transformer? IOW which end is connected to the sound source and which end is connected to the TH transmitter?

Many thanks ...

"-it only outputs a weird pulsing sound ..." is very likely the result of of RF getting into the audio input circuit. The sound you here is called "motor-boating'. It is common when audio circuits try to deal with radio frequency energy. The sound you hear is an amplifier semiconductor and a coupling capacitor discharging making the noise; the amp or preamp has turned into an oscillator.

The fix is to feed the audio through shielded audio cable, sometimes with the addition of ferrite beads to knock down the common mode current on the audio input wires. On rare occasions the RF energy can cause the audio interface transistors to fail (short out). This failure has resulted in motor-boating and audio distortion in the past. BTW, most computer audio cards have a very low output impedance.

Oddly enough, one other culprit is poor decoupling in the power supply filter on early models of some transmitters. If you have access to an O-scope you would be able to take a look at the wave forms to determine where the box is failing.

The audio input to the TH transmitter is un-balanced mono regardless of the plug size. The input impedance of this transmitter (~several k-ohms) could be low which could be caused by a blown (shorted) capacitor or buffer transistor. Again, these would cause the behavior you are experiencing.

Additionally, combining stereo into mono can cause too much signal for the mono input. Try combining the left and right channels through a resistive network. Remember to feed the transmitter with an unbalanced audio output. Make sure the audio device feeding audio to the transmitter is "unbalanced" or wired so that the input appears to be. On balanced outputs, connect only the plus side and the ground to the transmitter input; do not connector the minus side at all at the input plug.

If the units internal recorder circuit works OK, then the audio input is not operating properly. That's why you should start there. You will need to eliminate each possibility one at a time; component failure, input level impedance matching, input shielding and decoupling, and power supply decoupling.

One other thought, some consumer electronics have an internal jumper to change the normal audio input level between -10 db and +4 db. Just a thought to consider. I hope this isn't too confusing.