Transmitter management is an interesting way to do the part 15 hobby.

I have mapped out a number of AM & FM frequencies, as well as a shortwave and longwave frequency, and am building transmitter/antenna setups for each frequency, backup transmitter/antennas for each frequency, and of course the programming feeds to each transmitter.

The next time I get married there will be one pre-nuptial condition... she gets the kids, dogs, furniture and dishes, but I keep the transmitters!

When listening to my stations on the collection of radios I feel quite privileged to be hearing the smartest programs selected by the only man capable of such good taste, which is me.

In some ways I no longer need the rest of the world, except maybe to borrow their roads and postal service.

Anyone reading this who yearns for a boost in self-confidence, get yourself a part 15 radio transmitter and start building your vast network of personal radio stations. Before long you will look down on others for their pitiful lack of decent radio.

Why do it alone? Join the ALPB.

Is anyone here familiar with the Hawks AM Broadcaster?

It was a Part 15 transmitter until the maker dissolved in the 1990s.

I am seeking a schematic, manual and picture of the Hawks AM Broadcaster.

A web search gets buried in the hundreds of "hawks" sports teams and their affiliate stations.

Perhaps the FCC used the following reason for setting the Part 15 AM power cap at 100 mW to the final stage.

This amount of power with a 10-foot length of wire antenna provides a useful signal to an AM radio located in close proximity to the transmitter. Any more power causes some nearby radios to become overloaded and thus distorted.

The "close proximity" purpose of Part 15 AM has origins in the phonograph oscillator, the original form of Part 15 transmitter, intended to inexpensively input an audio signal to the superior amplifier, loudspeaker and wood cabinet of an upright AM console radio.

I have proven the liklihood of this theory by use of an AMT5000 from SStran.com, which has the convenience of a fine-tuning adjustment for the power output.

When set to the lowest power 0f 36 mW to the RF input, the AMT5000 rides the background noise on the AM dial at night, resulting in other stations creeping in and mixing with the audio.

When set high, 275 mW to the final RF stage, a radio 10-feet away distorts due to overload.

But the mid-setting, 100 mW, presents a solid undistorted signal to radios near and far within the same building.

A further use of Part 15 AM transmitters is a matter of clever invention by users, who have discovered that by placing the transmitter/antenna outdoors with excellent ground radials, a 100 mW signal can cover a distance exceeding a mile, according to many reports.

My Case for 100 mW has not been refuted, proving its truth.

Audio All Pass Filter/Phase Rotator

http://vi.raptor.ebaydesc.com/ws/eBayISAPI.dll?ViewItemDescV4&item=13068...

very interesting. wonder how it would help part 15 am operations? also can you pair them into stereo and use them on part 15 fm and what good (if any) would they do there?

A little more on the circuit and what it does...

http://www.w3am.com/8poleapf.html

Back over on that other site (you know, the one that claims to be the 'authoratative radio reference') they're preparing to release several new radio reviews.

I hope they do a better job on the individual reviews than on the transmitter shootout they did.  Don't get me wrong, overall the effort was impressive, but there were several errors and shortcuts taken that reduced the rigour of that particular exercise.

Such as, not understanding how to appropriately tune the AMT5000, and blaming the documentation, rather than actually getting the information.  It is valid to criticize the documentation if it is found lacking - it is NOT valid to just go ahead with testing without having all the facts at hand.

Such as repeatibility, particularly with a kit transmitter such as the AMT5000 - the results are highly dependent on the quality of the build.  [In a recent post 'over there', a highly praised reference was made to a blog site that reviewed shortwave radios.  One of the major factors in that particular review was repeatibility, but I guess they didn't see the relevance to their own reviews.]

It has become apparent after much discussion on the results of that shootout challenge that the relatively poor grounding played a significant role in the performance of the AMT5000 - it was affected more than the other transmitters (which does appear to match up with theory).  That's a valid result.  What is NOT valid is to continue to test the AMT5000 in an individual review with a poor ground - a better ground needs to be used to see if that particular transmitter lives up to the promise of its efficiency.  And then ideally (perhaps in Shootout V2), matched up against those other transmitters with all using that better ground.

I guess we'll have to wait and see.

Hello. I don't know where else to post (I mean, where else on the entire Internet). I was hoping that maybe some folks here could help me out. I apologize for the length, but I come to you tired and disappointed, after doing as much homework as I possibly could before simply begging answers off smart people without doing the work.

I have always been interested in radio, but never really good with electronics. With my dad's help I built a Ramsey FM-10 when I was in high school and marveled that I could "broadcast" my CD player 10 feet away. As the years went on I became less interested in having my own "radio station" and more interested in, well, the best comparison would be wireless in-ear monitors that musicians now use on stage. I have since learned a bunch about electronics, and gotten into the Arduino scene too. But I'm finding two things to be true: First; I learned electronics way too late to ever be an effective "hacker" or "maker," and secondly, if something's not popular, all the Googling in the world won't get you anywhere.

I have several problems currently that I could solve with wireless IEMs, and it doesn't so much matter what they are, but I can't take on the cost right now (a good transmitter and receiver pair is about $800, and I could use at least three). Low latency is important so Bluetooth is not an option. I much prefer the speed of light in this circumstance. I live in a really rural area, so I'm not at risk if I radiate 251mV/m at 3m, but on the other hand I'd rather not be broadcasting in a public band anyway just for a little privacy-through-obscurity.

I'm asking here because I don't know where else to go. I will be more than happy to take suggestions on broadcast-band solutions so that I'm not scolded for being off-topic, but I'd love to start playing with, say, FM MPX in the ISM/license free UHF bands (500-900MHz). But I have been Googling literally for months and I can't find anything except unconfirmed GIFs on schematic websites of "UHF RF transmitters" without stereo encoding circuity, or widely-available low-bandwidth ASK/FSK transmitter ICs that are unable to carry audio. The other thing that seems to be dominating search results is "audio/video transmitters," the wireless packs you see on video cameras at live events. It's like nothing I need exists and Shure, Sennheiser, and Nady are custom-designing every IC and circuit they sell, which I know is not the case. I have no problem with hand-soldering TSSOP, QFP, though I'd rather not, and I long for the days when you couldn't get stuff in anything but DIP.

I have been playing with the Silicon Labs Si4703 (FM receiver) and Si4713 (FM Transmitter) chips which are available on breadboard-friendly breakout boards through Sparkfun and Adafruit, but they're made to sit 2" from a car radio and transmit your MP3 player to it. I've made the right length monopoles and dipoles, and I've run random-wire the length of the house and they still fade and multipath behind interior walls. It's ridiculous, honestly, all the technology we have and I can't throw an FM signal through a couple of pieces of drywall without static and fading. There's also a low-mid-size media market about 30 miles from my home and I'm sure part of the problem is there are no unused FM frequencies anymore. There's even a high power Christian network on 87.7 there, which of course splatters into 87.5 and 87.9.

It seems like every lead is a dead end. For example, the holy grail: Texas Instruments makes a line of "PurePath" wireless audio link tranceivers that auto-frequency-hop and coexist in 2.4GHz with wifi and everything, and the chips are less than $4 on Digikey and require a minimum of external circutry to function. Feature set is excellent, and it can be used with or without a microcontroller. Has automatic handling of frequency congestion and just seems to be the perfect chip for the job. It's only available in a 40QFP package, and it has a ground pad. So, essentially, since I don't/can't afford a wave solder machine, I am unable to use this chip, even if I could get a board fabbed for it. TI makes a "development kit" which is two fully-built transcievers on PCBs for $150, and I personally don't think $75 for a breakout board housing $12 worth of ICs is a good investment.

Are we at the end of the DIY age? The "makers" would say no, except I'm sick of making yet another project that just makes LEDs blink at the expense of a 16MHz microcontroller. Did I just learn electronics too late in life? Or am I missing something obvious? I totally accept the concept of integrated circuits and I have no issue using them. But as far as I can tell, there are NO chips that will do what I want, that are available unless I'm a big business with a fabrication department and a large R&D budget.

Again, I understand I'm not talking exclusively about unlicensed operation in the FM/AM broadcast bands, but I'm starting to believe that doing so at a legal power level is useless. I'd honestly rather roll my own solutions, so I learn and can add features, than buy a commercial LPFM transmitter, and as I said I'd like to be in license-free bands anyway. Is there someone here with knowledge and experience in this area that can take pity on me? Even the $900 Sennheisers are essentially 1930s-era FM tech but in a different band. That simply cannot cost $900 to do in the iPhone era.

Thank you,

ej

http://www.ebay.com/itm/AM-Stereo-C-QUAM-Transmitter-/141633790669?pt=LH...

Thought this may be of interest to someone.

Mark

Every spring at this time I like to summarize the standard viewpoint held by KDX Worldround Radio regarding Part 15 AM radio transmitters.

Most persons contemplating to build a low power AM station begin to wonder which transmitter will give the most range. But two other questions should come first:

1.)  What is the available budget?

2.)  How much engineering experience do you have?

The trick to getting the most on a small budget is to build your own transmitter from sstran.com, the AMT3000 or AMT5000.

But without the skill to solder and build a kit part by part, a larger budget is required to obtain a ready-built transmitter from several suppliers in this category. In essence, one is paying for his own lack of skill; that is, paying someone else for having built and marketed a complete package.

For those having the choice of going either way the question of range depends of such factors as RF output efficiency of the transmitter and antenna design with good radial ground system.

The AMT5000 operates in the Class E mode achieving 98% output efficiency (manual p.26), well above the norm of other transmitter designs which more typically achieve perhaps 50% output efficiency.

Arguments abound regarding output efficiencies of the costly prebuilt transmitters, but their output efficiencies are only claimed but undisclosed, resulting thus far in mere sports-like "challenges" regarding range.

Even the least costly AMT3000 from sstran.com, designed for in-home use, can be upgraded to a serious contender in the range category by following the free instructions for improving the output/antenna system.

Here at KDX Worldround Radio we operate an AMT3000 with our own self-built loading coil/antenna, and an AMT5000 according to the manual instructions, and our only concern regarding range of either transmitter is to pull back so as not to trigger an "inspection" for excess field strength.

What's in your wallet?

i got a 2004 model sstran, and the PLL is not functioning correctly. i get a carrier on 1410, and just a little fluttering on the freq i actually want it to be on. i've tried changing dipswitch settings and it doesnt work on other freqs either, just 1410. has there been any revisions since this early model? this thing has been on and off the back burner since 2007. all joints got re-flowed with solder and continuity checked for shorts. IC's have been replaced. i've done kits and homebrews that have been more successful and i wouldn't be suprised to find a break in the connection somewhere on a PCB trace, since im out of ideas otherwise. not into dropping more money for a factory repair, since 98 bucks is more than enough to pay for milliwatts and im a polak bastard farmer with not a lot of money to throw at things like this. starting to think i have a lemon

http://makezine.com/projects/super-simple-fm-transmitter/

On another site I found a link to a page that will plot coverage prediction using Longley Rice. http://lrcov.crc.ca/main/index.php (requires free registration). (If this has been covered before, I am sorry. I searched the forum for “lrcov.crc.ca”, and did not find anything so I think this may be a new topic).

The tool is pretty slick, you can use the map to select the transmitter location and the area to model reception in.

I tried putting in the tiny power used by Part 15 compliant FM transmitters, and the coverage prediction tool complained and failed to run. Then I worked through orders of magnitude until I found the lowest power it would accept, 0.00001W.
I used the first formula on page 29 from the FCC’s oet63rev.pdf to figure out the required antenna gain to get a field strength of 250 uV/m at 3m with a power of 0.00001W. I got a power gain of 0.001875 or -27.3dBi.

So if I did my math right, using the generator linked above, a power of 0.00001W and an antenna gain of -27.3dB with the polarization set to vertical should model a part 15 transmitter, assuming it is putting out the maximum allowed 250 uV/m at 3m using a vertical antenna.

Then I got stuck at the coverage display.
What is a dBµV/m, and how does it relate to dBu used by the FCC for service contours?

In dBµV/m, what would correspond to what a car radio can receive, what a portable radio can receive, a 60dBu service contour, and a 57dBu service contour?

At last an excellent review on the difference between C.Crane's FM Transmitter 2 and the original FM Transmitter 1:

http://radiojayallen.com/c-crane-fm-transmitter-2/

We don't have a forum category for "Time Machine" but someday we'll be able to go back and add one.

For now the category "Transmitters" will do, since time travel requires transmission of a sort.

This week's Mischke Road Show visits Professor Ronald Mallett, PhD, a theoretical physicist who is working on a time machine.

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

im getting a signal on 1640 where i want it, but theres a stronger spur present on 1240. unsure of what i can do to clean that up. hopefully my chips aren't junk. 

Hi there,

I was hoping someone might be able to help.  I've recently come into possesion of a derelect Panaxis FME-250 that I'd like to get up and running again.  Does any one have or know where I might locate a schematic?  I'm particularly intrested in the audio input section.

I've been able to locate the plans for the FME-500, but the inputs are considerably different.  Any help would be great.

Thanks!

As we know, a "transmission line" is a cable to deliver RF output from a transmitter to an antenna.

Part 15.219 limits the length of any transmission line as part of the 3-meter limit also including ground lead and antenna, and my question is:

Why does the FCC place a limit on the length of an AM transmission line in 15.219?

As an academic question, if a transmission line was to be used to deliver RF output from an indoor AM part 15 transmitter to an outdoor 3-meter vertical antenna,

What would be a practical limit in length of the transmission line to achieve good performance?

Part 15 AM outdoor installations tend to utilize bottom loading of the 3-meter vertical antenna for a number of practical reasons, such as listed here:

1.) the Part 15.219 3-meter rule can best be met by mounting the transmitter near the ground and close to the antenna;

2.) being close to the ground the power and audio connections can be conveniently brought to the transmitter.

But we hear stories of security, resulting in stolen or damaged transmitters due to their easy access by intruders. To increase security for an outdoor installation a transmitter mounted 10-feet in the air at the top of the antenna would be more difficult for vandals.

Difficulties of top-mounting/loading a part 15 system are listed here:

1.) getting power and audio up to the transmitter;

2.) grounding.

?

Hi folks.

We have a hamilton rangemaster that we use at a school for parents waiting in the parking lot.

I sent it back in to be serviced and somewhere between the company and my office the crystal was removed and is now missing. I wrote to Keith and he explained that he cant get the crystals anymore and wanted 100 dollars or so for an agile one. In the education world, thats a LOT of money. Do I have any other options?

I've got an idea to solve the problem of folks who may not be educated about micro broadcasting and calling the police or any other law enforcement or haggling you about your FM transmitter that may go a hundread and 50 feet (or more) outside your yard.  At the Top of the hour you have a station ID something like this:

Your listening to The Legacy playing Progressive Rock, Classic Rock.  We are a part 15 FM station using the Whole House FM Transmitter 3.0 certification ID XXX-XXX-XXXX (fill in the X's with the real numbers on the back of your certified unit.  This Meets part 15.239 rules that states we must not cause harmful interference to licensed stations nor other communications services.  If you are receiving interference on any other frequency other than 96.3 (fill in your frequency here) please don't hesitate to call (fill in your google voice number) yes you should use google voice to forward to your cell phone or real phone.  You can also send an Email to (fill in your Email) this way you solve any possibility of your station interfering with something caused by a defective transmitter or maybe your using a frequency too close to someone's favorite station.  Maybe if your transmitter is causing harmonics they'll tell you what other frequency they heard you on so you can try and correct any issues.  At least it lets the public know your willing to play nice on the dial.  Just a thought since I use NextKast and its capable of doing this at the TOH just like a real station.

https://scontent-mia1-1.xx.fbcdn.net/hphotos-xtp1/v/t1.0-9/10996949_1020...