I'm not sure exactly what Dave had in mind when he asked the question, but I can't think of any situation where 15.209 would be better than 15.219.
Ermi I was thinking that a 209 spec rig would have more range in the near field than the 219 rig at say 530kc and therefore be better for say in house type of use. It was more of a question following along this threads comments. I take it I got the wrong impression?
Great refrences scwis! There should be a part 15 hall of fame and Phil B. ought to be the first inductee for his great transmitter, great customer service, and great posts.
hamilton need to be at the top followed by talking house, then phill b, then chez radio.
sorry guys, but from a pure transmitter design standpoint hamilton and talking house came up with some very unique rf output stage / atu designs for their transmitters.
the sstran is a great little tx in it's class, but did not really offer anything unique to the hobby design wise.
the same for the chez procaster.
but i will admit phil b. is very intelligent and active on these forums and very willing to go into technical details of his transmitter something the designers of certified transmitters seem to not care enough about their potential customer base to do.
and for that phil gets a cudos.
just thought i would add my two cents.
from a personality standpoint phil takes first prize. from a design standpoint it unfortunately has to be hamilton and talking house.
This thread began with an in depth description of the early wireless discoveries including induction and modulated broadcast, and I add to the list of inventors the name of Nathan B. Stubblefield, a Kentucky farmer and inventor who, according to an article I read In High Fidelity Magazine back in the 1970s, demonstrated wireless transmission of harmonica music in 1892 with a St. Louis Post Dispatch reporter in attendance and a followup article in print. See this Wikipedia link:
http://en.wikipedia.org/wiki/Nathan_B._Stubblefield
Yea I was going by the forum participation and the making part 15 affordable. I bet if the sstran was $1000 + it would be pretty advanced also but would not be available to those of us where this is just spending a few fun hours fiddling. I was in business long enough to know about different markets and it's probably not fair to compare the transmitters let alone the people but I personally have had great experiences with Phil and his rig and when I saw his comments on a thread scwis mentioned I made my hall of fame comment. Anyway all mentioned and many more would belong there I'm sure. Dave
Ermi could I ask for clarification.. 209 doesn't have more range in the near field at 530 kc than 219?? Just talking nearfield like those folks who are just using part 15 for their homes, OTR and the like and want for whatever reason to be at the low end of the band. Dave
i would love to see phil incorporate a toroid output and class e final section in his next transmitter revision. also be nice to see 600 ohm balanced input.
i think users would pay for the little extra that these mods would add to the cost of the kit.
and if you use solid state balanced (instead of transformer) then it's easy to use either balanced or unbalanced.
The field strength limit of Section 15.209 is so low that it can't even be measured with a standard field strength meter at the specified measurement distance of 30 meters. The background noise in an urban area is much higher than the field strength limit.
This is a near field topic: To determine if the 15.209 field strength limit is met, it is necessary to bring the FSM closer than 30 meters to the antenna (like 15 - 20 feet) and make the measurement in the near field. The increased antenna gain in the near field gets the signal above the background noise level. Then, it is necessary to make the appropriate corrections to the reading to determine if the the limit is met. This is a very complex calculation, primarily because MW FSMs measure the magnetic field strength, and not the electric field strengt, but read the electric field strengt. This is fine for far field measurements, because the electic and magnetic field strengths are proportional to each other in the far field. But, in the near field, there is no such proportionality.
I'll take it that your original statement stands that 219 always beats 209 regardless of frequency. This leads me to other questions like how do the certified 209 rigs get any coverage at all? Me thinks it has something to do with 20' masts/"grounds" Ahem dare I say dipoles 🙂 Dave
I am not aware of any Part 15 AM transmitters certified to 15.209. The ones I know about are certified to 15.219.
I have forgotton the rule section. Maybe I have it backwards. I'll try to re-educate myself tonight. Sorry.. Dave
part 15.219 = antenna and power limits
part 15.209 = general radiated emissions limits
I for some reason thought that the 100mw input was only for homebuilt units where it was felt by the FCC to difficult to require testing for field strength. I thought certified transmitters were always tested to 209 (fs=24000/freq.) . I spent the last hour trying to find where I got that idea and couldn't find it.? I always wondered how any certified transmitter could beat or equal a homebuilt. Next question: why would anyone build to 209 spec? 🙂 Dave