Who cares if you know the exact field strength. That wasn't the test. The test was simply referrenced to the strongest field strength.
So you measure all the transmitter field strengths, assign the strongest as the reference point and based on ratio state how far below each other transmitter is.
And besides, you only need an accurate field strength measurement for Part 15.209 like when you plug a Talking House transmitter into an AC ground and nullify its Part 15.219 certification. Rich will corroborate this.
Calibration is moot unless you are testing for compliance.
Over at that so-called neutral Forum, the discussion is still going on. The tester is still taking umbrage over any criticism of the Shootout (with the assistance of another like-minded individual). Amazing.
They still refuse to see any faults in the testing process, instead telling anyone and everyone to do it themselves if they don't like what they did. While taking personal shots at various people in the process. So much for science (and engineering, for that matter).
They refuse to acknowledge that testing multiple examples of each transmitter would have been more rigorous (in the event that there could have been problems with the ones they used - and in particular, the AMT5000, which was built from a kit). They refuse to acknowledge that testing each transmitter with an identical antenna (and not just the one supplied by the manufacturer) would be more accurate (particularly since the AMT5000 does NOT come with an antenna). And they refuse to acknowledge that there might have been user error in tuning up the AMT5000 (they're blaming the manufacturer for not providing better documentation, as opposed to worrying about obtaining the most correct result).
In short, THEY are absolutely right. Everyone else is absolutely wrong. It couldn't have been done any better (a favorite saying of my mother-in-law).
Methinks they protest far too much for people who claim they're not hiding anything.
After I wrote my previous post, I realized that the broadcast engineers that are involved with the discussion just might not understand how simple the objections to their testing really are. Sometimes engineers (and others, to be fair) get so close to a problem, and what you've done in relation to that problem, that you can't step back and see the forest for the trees.
Now, I really don't care about the verbiage as to their objectives in this test. The reality is that by measuring the relative field strengths of the signals produced by the transmitters, they are stating that there is a 'winner' (which they name) and 'runner-up's, and they are also implying that the winner is the best. At least, it will appear that way to the casual reader (probably about 90% of all readers).
Field strength is certainly the major determining factor of transmitter range. But there are other factors as well. And sometimes it's not quantity (i.e., range) but quality (as in sound) that has an impact on which transmitter is the 'best'. But certainly, comparing field strengths FAIRLY is an experiment that is well worth the time and effort.
The test should have been very simple. First of all, you need to ensure that you have perfectly working examples of each transmitter, and that you have the knowledge to tune them up to work perfectly within the 100 mw limits of Part 15. More on that later.
If that is the case, then you need to 1) test each one against the same ground and 2) test each one with the same antenna. If you can meet all of these criteria, then the results will reflect one and only one thing - the efficiency of each transmitter getting its signal to the antenna. And the testing will be impartial and objective. Scientific. One variable.
So here are the problems with the testing as described. At first, I was going to say that that at least the same ground was used for each transmitter. But that was not the case - the Talking House was grounded through its power plug to the same ground rod, but it's not clear if the length of the power cord was taken into consideration (even though the Talking House is FCC certified in that configuration). The other transmitters used identical ground configurations so there was no problem there.
The same antenna was NOT used for each transmitter - the manufacturer supplied ones were used. In doing so, you're not going to get an objective comparison of the efficiency of the transmitters (as the antenna plays a major role - you're just muddying the waters and introducing other variables). And in actual fact, the AMT5000 does NOT come with a manufacturer supplied antenna other than a simple wire. And talk about being put at a disadvantage here - the Talking House transmitter with a wire performed much more poorly than the SAME transmitter with the ATU/whip antenna and it's obvious that the antenna was the ONLY reason for the differences. So it appears that the worst performing antenna was used to test the AMT5000 with. Very few people who take the time and effort to build this kit would use that kind of antenna, but rather, probably build one, such as a whip with a base loaded coil. What if, for example, the AMT5000 had been tested with that kind of antenna? My reasoned guess is that it would have performed the best of all the transmitters, and then others would have complained about the unfair advantage of using THAT antenna.
Now, back to my first point. It is not known whether ALL of the transmitters obtained were working correctly, particularly the AMT5000, which was built from a kit. It was stated that it was donated by one of their Forum members, but the build quality and details are unknown. It IS known that several were obtained from dealers and they likely were well gone over before they went out. Now, this issue has been glossed over by the testers, and they blamed several manufacturers for not supplying demo units. But that is a red herring. Who cares why they didn't have the appropriate material to do their experiment? At the end of the day, it could not be guaranteed that each transmitter was tested and guaranteed to be working correctly. Another variable is introduced.
There is also some question on the tuning of the transmitters. It appears, at least as stated by the manufacturer of the AMT5000, that the testers did not know how to tune that transmitter properly. Their response - blame the manufacturer about the lack of documentation (this, when they got the transmitter via other avenues). But again, if what you want is an accurate measurement of the efficiency of each transmitter, then who cares about whose fault it is? Another variable is introduced, and you WILL not have the CORRECT results.
But you'll have a real snazzy looking magazine article.
You make some valid and insightful points, but note, that none of the transmitters actually come supplied with an antenna from the manufactures, with exception to than the Iam and SStran with their wire antennas. However both the Rangemaster and the Grain transmitters do call for a Radio Shack part number 21-903, or similar 102 inch whip antenna.
In regard to the use of the ATU with the Iam.. I never liked the idea of his including it's use in the challenge, primarily because the external ATU is no longer an available product, and even rather difficult to acquire a used one.. I had questioned this matter on the hobbybroadcaster forum before the results were even publicized.. I don't recall what the response to this concern was.
So it appears that the worst performing antenna was used to test the AMT5000 with. Very few people who take the time and effort to build this kit would use that kind of antenna, but rather, probably build one, such as a whip with a base loaded coil. What if, for example, the AMT5000 had been tested with that kind of antenna?
This is what I thought, but in another thread here, somebody on this forum stated to me that the 5000 does not use such an attenna since it already has the loading coil built in, and that it actually can use a standard whip like the Rangemaster or Grain transmitters do.. Is this not correct?
There is also some question on the tuning of the transmitters. It appears, at least as stated by the manufacturer of the AMT5000, that the testers did not know how to tune that transmitter properly. Their response - blame the manufacturer about the lack of documentation ...
I've read the debate(s) (as it were) concerning the accuracy of the tuning instructions.. I posses no knowledge enabling me to even speculate a technical weigh in on that, I can only ponder.. but your point shines through when you say: But again, if what you want is an accurate measurement of the efficiency of each transmitter, then who cares about whose fault it is? Another variable is introduced, and you WILL not have the CORRECT results.
My view concerning your opening statement:..
The reality is that by measuring the relative field strengths of the signals produced by the transmitters, they are stating that there is a 'winner' (which they name) and 'runner-up's, and they are also implying that the winner is the best. At least, it will appear that way to the casual reader (probably about 90% of all readers)
I really think Phil should submit some form of statements to be published to CQ magazine (which the challenge was published in) in response to the result of the Transmitter Challenge, otherwise the perception of those "90% of all readers" may very well accept it as truth that the AMT5000 is a weak contender.
I personally still don't believe that testing for the Challenge was somehow rigged as some suggest - To me, that idea doesn't make sense, it just doesn't add up. However, at the same time, neither does the AMT5000 results.. Something was wrong, whether it be improper tuning instructions, or a improperly built unit, or something else which hasn't even been fathomed.. It needs to be addressed in publication, in the same limelight in which the challenge was published.
Otherwise the AM5000 will appear... to the casual reader (probably about 90% of all readers as a less than optimal transmitter.
Ther Procaster which I purchased last summer came with an antenna from the manufacturer, made of three sections (maybe it was two) of aluminum tubing.
I also noted earlier (I think) that the Procaster included in the photographs of the test is NOT a current model. It's an older model and I know there had been some changes to the unit since that one was built (According to Chezradio anyway)
And again, the ability to modulate has a huge factor on range. There should have been some sort of standard audio test included. I know that's more work and another variable, but it's a huge factor in how far you can be heard.
Tim in Bovey
I thought there was mention of a 'tone" that was used on all transmitters?
Ah.. excuse me, somehow the Procaster had slipped my mind during my last post. And as you point out, the fact of using varying versions of current and non current versions of transmitters (as well as no longer available accessories) adds yet another variable into the equality of the transmitter test..
To be sure, there were underlying problems with the competition.. But really the way to put all transmitters on a more equal ground (pun not intended) would have required that all the manufacturers had agreed to involve themselves (most did not) by providing current models, being verified as properly constructed and properly operating.. or at least that only brand new current models were purchased and undoubtable verified as properly assembled (in the case of the kits) units to utilize during the test.. But of course this would of had to been accomplish at the expense of the testers..
No, everything wasn't perfect with the challenge, nevertheless, it was still the only apparent manifested effort of a challenge to occur that even tried to provide any kind of active comparison between numerous xmtrs..
Flaws and all, the challenge event still remains to be the only, and thus the best. Potential inaccuracies can be complained about, but talk generally comes second to action. At least a nobel and active effort took place.
Part 15 radio is a a technical culture, like music, medicine, books, earth sciences, and other cultural subjects. Part 15 radio is not a sport.
Treating the transmitter comparisons like a competitive sport was not a good idea, and that fact alone might explain why some manufacturers preferred to stay out of it.
But, and here is where I side with Rich Powers, the transmitter event was good promotion for the Part 15 pastime.
The fact that the outcome of the competition is inconclusive and subject to question is also a good thing, because it preserves the mystery of whether one transmitter might be better than the others or perhaps things like antenna and grounding might tilt the balance. This mystery is at the heart of keeping the transmitters on the market, allowing customers to decide independently which product they prefer.
"Sometimes engineers (and others, to be fair) get so close to a problem, and what you've done in relation to that problem, that you can't step back and see the forest for the trees."
At my day job, I refer to this as "worshipping at the altar of complexity."
I still think we need to physically gather with our toys somewhere, and test them the way we want.
The Rangemaster and the Grain transmitters are designed to be used with a whip. The ProCaster comes with it's own whip (you can argue that it's a small pipe and so not identical, but for all intents & purposes it's the same). The AMT5000 could have been mounted in a weatherproof box and configured with a whip. And to make the testing consistent, the Talking House should really only have been tested with a whip (in place of the built-in wire so that it's internal tuner could have been used) or, better yet, not tested at all - using the ATU plus whip is really using a base loaded coil antenna.
The point has been made about modulation. That is certainly a factor in determining the effective listening range of the transmitter (along with compression) but I don't believe that your field strength will be affected - these are some of those 'other factors' I mentioned that determine how your signal sounds and thus it's range.
But the biggest kicker in the entire mix is the argument that somehow it's the manufacturer's fault that the testers did not know how to tune the AMT5000 correctly. That's like saying, in an astronomy experiment, that you couldn't properly measure the differences in light from an object's transit across a star because you didn't know how to properly focus the telescope. But it's not YOUR fault (since you're an astronomer with over 40 years experience)! Really. Why bother doing the experiment in the first place if you don't know how to properly operate the equipment, or there is some question about it. You need to get the information, period. Or that 40+ years of experience really doesn't say all that much about you at all (I've worked with many people who claim that type of experience, but without knowing the details, it's difficult to judge exactly what that means - there's a difference between a true 40 years of varied and interesting experience, and having 1 year of experience 40 times, for example).
'Worshipping at the altar of complexity'. Lol. I like that.
My euphanism is a bit more crude, but probably just as accurate. In my day job I call it 'Baffle them with B*llSh*t'. There are some that just see the world in minute detail, but miss the overall picture (such as using the same antenna). Others do it deliberately. Those that employ this latter technique hope, of course, that you will be so awed by their technical and experiential prowess that you won't probe deeper into what they really were doing (one of the corollaries of using this technique is personally attacking and disparaging anyone who attempts to do so, because, of course, they don't have the same level of experience and knowledge and intelligence that you do). I learned very quickly as a Manager that if someone couldn't step back and summarize, clearly and succinctly, what they had done, and why, without any of the crap or ego, then you had better start worrying and asking pointed questions.
Like I'm doing now. Because they're likely hiding something (even if it's only their mistakes).
Artisan is absolutely right about the irony that years of experience may not be years of knowledge.
I operated a financially succesful audio recording service for years while being mystified about how unbalanced audio and balanced audio could be converted.
It's only been during the recent decade that I finally grasped how electric system ground figures as a safety factor, and about one year since I woke up to how ground radials contribute to transmitter efficiency.
I'va had forty years of experience. Worship me.
This dead horse could use a beating.
As a man of the idle class I frequent the negative part 15 site as a way of knowing what the other class discloses by way of ruminative behavior, and see that our own Socratic dialogue here at part15.us continues to attract ad hominem attacks from their side, while ignoring our sincere participation in meeting the Challenge.
Just now I note that Artisan, Rich(F) and PhilB have each been subjected to the knockout game, consisting of a verbal punch sufficient to disqualify them while at the same time establishing the glorious righteousness of the punchers.
What most disappoints me is that I can't identify any attacks intended for me.
I've said things, been critical, found fault, made fun of, yet for some reason I am not good enough to ridicule?
That means one of two things: either they agree with me and what I've said about the Challenge, or they are not up to a real challenge.
Tell you what. Let's merge these two websites. Just like Time Warner and Comcast. Just sign right here, the world will have one cohesive part 15 website, and you'll be forever removed from embarrassment and disgrace.
Do we have a deal?
You must have missed a few posts there, Carl.
You've been called, amongst other things, the head of the cabal of PhilB. And not in a flattering way.
To tell the truth, I've lost interest in both of the sites in which discussions have gone on. Those involved directly in the Challenge aren't interested in any criticism, and are taking it personally. I've been involved with people like that before, and they just aren't going to listen. They're so focused on themselves that they just can't believe that they've done anything wrong.
Read other posts by them elsewhere. Any time they refer to others who disagree with them on any issue (or to whom they disagree with), they attack the credibility and the individuals personally - and not what they're saying. That, to me, says more about the attackers than anything else.