FWIW here's my follow up to John's "So Far"
1. Agree completely the transmitter belongs where the antenna is. Be it ground mounted or elevated. This eliminates any issues with the legalities of a long feed line to the antenna, and eliminates any signal loss through this lead. Although presently there is no legal way to ground it when elevated. Which is working fine for me.
2. There aren't that many controls. However using a better quality power supply is always a good idea, although I've not found any noise or issues with that supplied with my Procaster, but there are indeed much better ones available. As for rack mounting it would be a piece o' cake to add a volt meter to the power supply output and rack mount it. You could certainly mount the supply and on/off switch to a rack mount if desired.
3. There are many perfectly wonderful rack mounted processors that are dandy for Part 15 AM. You could choose to use one with just about any respectable Part 15 transmitter. If you were to use the built in at no additional cost processing in the Procaster you could, if you were so inclined, wire up your own remote panel for the controls for the built in processing. The controls are all in the small studio interface box that remains in the studio. Controls are all either PC mounted potentiometers, or small pin jumpers to set up compression, input gain, modulation, and turning processing on and off. Of course with a Rangemaster and many others, if you're using processing you've purchased a separate unit and it's probably rack mounted anyway.
4. I too like meters. I've never felt a need to monitor the power supply voltage to the transmitter, but again this is easy and you could choose from a wide variety of great looking panel meters for this. VU metering would best be on the audio source, be it a vintage control board or computer (there are some fun VU meters for computer screens). In my case I purchased a very inexpensive rack mounted LED VU meter device where the LED VU lights run the full span of the unit. In my case I have them monitoring the final part of my audio chain which I won't explain in detail, but it's the audio level into the cable TV system that also carries my programming. If those lights are blinking and the levels are right, they're correct on the air and to the cable TV. As for signal strength, it's really easy to build a very basic field strength meter - doesn't have to even be tunable that at close range would easily indicate your signal on a panel meter. It would completely not provide any actual field intensity, but it would show signal present. you could even calibrate it so that, say, 100% on the meter would be your typical signal strength, and should there be any drop in signal the meter would drop accordingly. You'd get nice, useful, relative field strength. And it could be made to look great. The circuit is pretty basic and can be build right on the back of a two space rack panel. You could easily build it on a one rack space panel but that wouldn't leave room for a really neat meter.
5. These two transmitters are generally considered to be the cream of the crop. I'm not a C-Quam fan, simply because it will never see a comeback. Never. AM will go all digital before C-Quam makes a comeback. That said, if there were a top quality C-Quam Part 15 transmitter made -- on the same quality level of the Procaster or Rangemaster, with similar construction and features, I'd consider it -- just because there are no real disadvantages and some minor advantages. There are simply no readily available C-Quam receivers available to the general public that are quality units.
6. Obviously the most efficient transmitter design is desired. I like to think that the makers of the top units available today have done the best they can, and not simply said "that's good enough" when designing their transmitters. But as technology and parts availability changes, so do possibilities. It would also have to be affordable. If a transmitter cost $800 and was 85% efficient, would you spend $1500 to have one that was 91% efficient? Would this make a noticeable difference in coverage area? I have no idea what the efficiency of the top units are, but I like to think they're the best they could do taking all the variables into consideration.
TIB
Thanks for the comments. They sound about right to me. Here are a few things I might throw in, be them right or wrong:
1. Regarding processing, I do have an ART Pro MPA II 2-channel Tube Microphone Preamp and the matching Pro-VLA II 2-channel Opto Tube Leveling Amplifier. I'm not even sure what all these things do, but I got them for virtually nothing. Do you think they would have any application here?
2. About grounding, what do we really need? I remember someone complaining that the TH transmitters ground through the power supply. Wouldn't they all? Then there is that ground wire from the transmitter to earth. Do we indeed need them both? It doesn't sound like your set up has the latter of the two. I'd thought about building a ground lead tuner connected at the transmitter and having the insulated output wire from the GT run down inside one of the tubular legs of the tower. I've heard doing something like that helps a bit.
3. On the other hand, could we put the power supply at the tower base in a weather proof enclosure and then ground that with a short lead to the earth and radials?
4. Not that I think such grounding shenanigans are really necessary as the legal definitions of ground and ground lead are not necessarily the same thing.
5. Well, I kind of hate to admit, but given the choice of 85% efficient for $800 or 91% efficient for $1500, I'm afraid I'd go for the 91%.
Here's to putting together the best Part 15 stations as we can.
All comments are welcome and encouraged...
John
W9LWA
1. Your ART Pro units are quite useful. The Mic pre-amp is just that. Is used to bring mic level up to line level to input to a mixer, etc. Most mixers have some mic inputs already with built in pre-amps that are perfectly functional for broadcast use. But, musicians especially, and those who record them, will go crazy trying different mic pre-amps for the perfect sound, minimal noise, perfect gain, etc. Mic pre-amps can cost from about 50 bucks to many thousands. I do use a dbx 286S mic pre-amp for some of my voice over work, most clients want dry, unprocessed voice if they're project is for broadcast use. Every station I've worked at in over 45 years has never used an outboard mic pre-amp -- what was built into the console was fine. But that's a nice unit and could probably be used to get a nicer sound than a built in, but if that's necessary for broadcast is up to debate. I tend to go with the theory that if you're processing your audio on it's way to the transmitter you're better off to NOT be applying any additional processing before that in the audio chain.
Your leveling amp is most often used in a recording setting, but could easily be used for compression/limiting in a radio audio chain. But won't have the ability to give you asymmetrical modulation or any of the other features specific to broadcasting. But it's the sort of thing I'd use in a back up situation should a stations main processor bit the dust, and I needed a quick substitute while repairs were completed. It would be set up to give solid loudness while preventing over modulation.
2-3. What we really need for grounding is debatable for eternity. And what is legal is equally debated. FCC says ground lead and antenna can max at 3 meters combined, total. Clearly there are various interpretations, various oddball scenarios that have somehow been certified, and those who have their own beliefs. Best, most common case is a ground mounted transmitter with a 3 meter antenna. Transmitter is grounded at the Earth. In my case I have an elevated transmitter and have attached no ground lead at all. The only wires to it are audio and 12V from the supplied wall-wart. I get the coverage I need. I may do better with a ground. I would certainly do better with a 30 foot ground lead going from the transmitter to the earth, but that would clearly not be legal. Some say I must have some radiation from my power/audio cables, or a ground through them, or some such. I don't really know. I know it was certified with this audio/power cable in use. And I know that even if it were ground mounted the same 50 feet of cable would be between the transmitter and the studio, so it wouldn't really make any difference. I've never worried about grounding the transmitter case, the circuit itself, or anything else. I suppose it would be wise, legal and possible to mount a spark gap at the antenna so if it was hit by lightning it would jump to ground (this is how commercial AM towers are set up) but I haven't bothered. The wall-wart is plugged into an APC UPS to protect it from power surges, etc and it also has enough back up power in it to keep the station on the air for a day (at least) during a power outage. It a power supply is grounded (say you opt for a separate 12V supply, something high quality like one would use for a ham transmitter) with a 3 prong plug, does that ground carry through on the 12V wires to the transmitter? Methinks not. I opted for an elevated transmitter because ground mounted it would be under 6 feet of snow 6 or more months out of the year.
5. I'd have to do the math and see what the actual gain would be for the cost.
TIB
I think we may be losing the forest for the trees.
What makes Part 15 broadcasting unique? Playing the Top 40 hits along with all the other thousands of stations (no matter what genre you're in)? Reaching massive numbers of people like the much more powerful, licensed stations?
I think it's being unique. Unique programming. A unique sound (such as AM stereo). I applaud Thelegacy for his work with C-QUAM, regardless of whether it will take over the world or not. It's caring about the few users that you might actually have in your tiny listening area. Caring about the community which you serve. THAT'S how we can make a difference, however small.
I understand that this is a technical discussion, but the technical aspects of Part 15 are some of the least important, imho.
Why approach the problem of the 'perfect' Part 15 transmitter with the same sort of eyes as the big boys?
I think the issue is first deciding what you want your station to do, or be. Then, and only then, drill down on what is needed to produce those results. It may be (and I certainly believe it) that for most people, transmitters already exist that entirely fill their needs.
If you don't solve the problem in this fashion, you risk having a wish list a mile long, most of which isn't really necessary or even important.
For me, as I've stated earlier, sound quality and following from that, AM stereo, would be the two things I'd most like to see on a transmitter (one that is certified).
I can go across the AM dial in my area and hear exactly one licensed station that has decent sound, as listened to on my car radio. All are talk stations but even then, I find it difficult to listen to muddy and/or tinny audio. The one station that has my ear cares about how it sounds, and even when it plays musical interludes, it sounds great. The rest of the stations obviously don't care how they sound. No wonder AM radio is losing listeners by the droves.
As to some of the other features being talked about, there are a lot of 'nice to haves', but nothing that would further my objectives in doing Part 15 broadcasting. Maybe someone else's, but not mine.
I don't even care about transmitter efficiency. I've found there are too many other factors that affect range to focus on that one particular thing. Locate your installation in the right place and you'll get great range. Locate it in a bad place, and your range will suck. It doesn't matter whether you're using a Rangemaster/ProCaster or a Talking House (with large differences in efficiency between the two), or even a 'perfect' transmitter. When I was on Bowen Island, my Rangemaster was lucky to be heard 1/4 mile away on a car radio, because of the poor ground conductivity. That same Rangemaster, in a similar installation in Pitt Meadows could be heard at least a mile away in all directions, and much more in some, because of the good ground conductivity (and other factors that some have debunked here).
In the Pitt Meadows installation, even my Talking Sign and Talking House transmitters were getting a mile and more range. Noisier in the fringe areas than the Rangemaster, to be sure, and not as far for any given direction, but still comparable.
My 2 cents, anyway.
I especially agree with Artisan's perfect transmitter with two ways to power. Household A/C with the transformer and filtering on board just needing an A/C cord or a second power input for using D/C like a battery. The onboard power supply would be much better than wallwarts which degrade the sound quality except for the block style computer ones.
Yes range is as much dependent on location and the radio but it should be the max. power allowed.
And importantly Certified for Canada also as Industry Canada read me the riot act about using transmitters with FCC approval only.....no good here.
The Decade has all the features of the perfect transmitter except for not being able to work with D/C but the design to need a plus and negative D/C voltage, needing an A/C supply is how the excellent sound quality is achieved as I was told by Decade.
As for us being unique, if I was to sound just like commercial stations what would be the point of doing my own. I would just listen to them.
Well, I do agree that the transmitter should sound really good. Not just kind of good, but really good. I don't think that's mutually exclusive with having the highest possible output in pursuit of the best range. I'm ok with stereo, although I suppose that rules out the Rangemaster and Procaster which everyone seems to tell me are otherwise the two best transmitters on the market presently.
I'd mostly been thinking in terms of add-ons to current transmitters and I'm not sure what it might cost to have an engineer or some other competent person design our dream transmitter. If it's affordable enough, perhaps those of us interested could then build our own or get them from China. Some things like power supplies and processor boards are already so available that there seems little need to reinvent the wheel for those.
I don't know if we can foster enough improvement over current products to make this worthwhile, but I'm good to look into it further.
I wonder if those Greek processor boards are any good?
John
W9LWA
What do you think we'd have to do to get your transmitter and antenna designs on a tower? Is C-Quam an option? It seems important to some folks here.
Either way, I think you're onto something here...
John
W9LWA
Bluetooth Audio receiving at the transmitter will END the issue with long audio cable acting as a raiding element and thus making a transmitter non compliant (Geez problem solved there.
Less power loss at the final does not mean the FCC will change the rules because your making the most out of 100 mW
Some folks really need to read Michelle Bradley's forum on Facebook because she is part of RECNet and I popped the question about the old ATU and the new ATU for the Talking House as well as Procaster and Range. Honest Engine answer a gentleman on that very forum said his range to a Pocket Radio was still listenable at 4 miles No Terk AM Advantage Loop to receive better and at 2 miles the signal was still Very Clear. So again many I know have been vague about Range because of Fear after a certain individual pressed the issue with ground. Don't worry about your certified unit getting out even the FCC knows all about this issue.
Back to transmitter design I think it should be able to run on solar power so when power goes out you can announce emergency information to your listeners. Its very important to be able to stay on air if there may be a long period of no power. If your station gets in good with officials you can give updates on the progress and maybe where one can take shelter from extreme cold or hear or severe weather.
Thanks for the comments, Legacy.
Wouldn't any transmitter work with a solar array? I wonder how much an array would cost to power a 100 mw transmitter? It couldn't be that much, could it? I wouldn't mind using solar power just for the novelty of it.
I'm not concerned about audio cables radiating. Or anything else that isn't a ground lead, antenna or transmission line for that matter. If the FCC cared about audio cable they'd have included it in the regulation...
John
W9LWA
Random comments before I head for work:
"Wall Wart" does not immediately mean crappy. There's a big difference between a good quality supply and a cheap Chinese one. People see a 12V supply for $50 and have a cow at the price, and pop on Amazon or eBay and grab one for $3 then bitch because they're crap. We have racks of professional broadcast equipment at work that run on quality "wall warts" some of which have been in service 25+ years with no issues.
Solar transmitter power. Wouldn't take much. What do you plan on feeding that transmitter with? Have a mixer? Where's your music and other programming coming from? A computer? Running a processor? All that stuff is going to need power. The transmitter itself uses a tiny amount of juice. It's the other stuff that takes all the juice. I have a APC UPS supply. It runs the station for 3 days with no AC. At least that's the longest it's had to run the station. It would probably run longer. Faster, easier, more power than solar. Solar up here isn't too handy. It's only daylight from about 8 AM - 4 PM up here in the winter. And you'd have to go clean snow off it every couple days.
I can't say that I've EVER heard of someone having an issue with a radiating audio feed or DC power feed. I can't find a NOUO that cites that. That only seems to come up here when I mention I get about 1.3 miles with NO ground lead attached to my Procaster. There's always someone who pipes up and says "then you're getting ground from your audio / power leads". If that's the case so is the owner of every Procaster or other transmitter ever put on the air. We all have power and audio going to our transmitters. And every certified transmitter was certified with power and audio leads attached. At least the Procaster was. It's all there in the lab photos that were submitted for certification. I assume that other certified units were powered up for their certification tests.
Bluetooth to the transmitter? If it's close enough. And if you have the power at the transmitter. And it creates another link that can have issues. If you need to, fine. Nothing beats the simplicity and durability of wire.
Don't dig the concept of AC operation with an onboard power supply. Who wants to run 110 volts out to their transmitter? Further, introducing high A/C voltage into the same case brings a huge potential for noise, heat and other issues into the transmitter box. There's nothing wrong with an outboard power supply. Not to mention one of the most prone failure components are electrolytic capacitors. No need to put filter caps inside the transmitter box for power. Keep that stuff out of there. You wanna pull your transmitter down every few years to change the caps that failed because they've been running 24/7 and roasting in the summer sun? These are reasons why so much professional gear has an outboard supply these days. Keep the noise, heat and extra components out of the area of the audio or other sensitive circuits.
Off to work.
TIB
Hi John,
I bought a 100 watt solar array from Harbor Freight for 149 bucks. Comes with a controller and all interconnects. 100 watts is overkill for a Part 15 transmitter but it can certainly be done for a few bucks. This setup kept my 12 volt battery topped off for all of Field Day using a 100 watt PEP transceiver.
Tim, to change the subject just for a minute, you said you have this....."I have a APC UPS supply. It runs the station for 3 days with no AC. At least that’s the longest it’s had to run the station".
My station consists of a small 11" laptop running with screen off and flash, not hard drive, small mini compressor, and the Decade MS-100 transmitter. That's it. What model of APC back up do you have?
I always thought that these things would only work for 1/2 an hour or so.
Well, that sounds easy enough. I was thinking solar because I think the best place for my tower would be at the back of the property and I wouldn't have to run a power line back there. Indeed, with a good battery, something like you have should work fine.
Thanks for telling us about it.
John
W9LWA
I'm not where I can take a look at the backup UPS right now, but it's a bug sucker. UPS units come in a million different sizes and capacities -- and prices! Mine runs an older iMac (screen off) and the Procaster for quite some time. Longest was three days. The typical ones you get at a big box store or computer store will only run a typical computer for a few minutes -- 15 - 30 minutes is common. They're designed to keep your devices running and safe, not really work as back up power. They give you time to do a proper shut down before they conk out.
At work (commercial broadcast stations) we have three air studios, with a myriad of equipment and all together we have 8 UPS units. Although these only keep us running for about three hours, they're running several computers, microwave STL transmitters, satellite receivers, control boards, etc.
These units come in sizes from a couple hundred watts to several thousand. Naturally the more back up power available, and the more features, the more they cost. I *think* the one I have in the studio is 5000 watts. (I'm abbreviating specs here, there are more details that go into it). it's an older model with no bells and whistles. Nowadays you can buy ones with digital readout that tell you present current load, how much available run time you have in minutes, and when power events happened, etc. They can even connect to your computer to do an auto shutdown before back up power fails, email you to let you know what's going on, etc.
Do a quick search on choosing a back up power supply, etc. and look at the various models available at online retailers and suppliers. Price, features and capability is very varied.
And of course they all protect your gear against power surges, brownouts, and all sorts of other evils.
Hope that's helpful.
TIB
It wouldn't have to run the laptop..the battery will do that for about 8 hours, just the little compressor and the Decade, not to much power between the two things...maybe 30 watts if that. But 3 days!, for one of these back ups, with all that running from it!
I'll check it out.
Now back to the subject.