Artisan Radio's go to transmitter is the Decade MS-100, BETS certified, and it sits on the top of a wooden cabinet by a window, close to the PC that generates its audio.
Recently, I've been experimenting with a Whole House 3 transmitter, RSS-210 certified. I figured that since I'm the only known listener, and I don't advertise, there should be no problem in using it (RSS-210 is basically intended for self use and not broadcasting to others, but the allowed FM field strength is identical to BETS, at least it was when the WH3 was certified).
In the past, the WH3 got about the same range as the Decade, which is to be expected. But when I fired it up this time, range was quite a bit more, and it's a bit of a mystery. Maybe someone can help me explain it.
I placed the WH3 in front of the powered off Decade, which sat in its usual place on top of the cabinet, antenna still extended. And I noted the increased range.
I then moved the Decade off the cabinet, and range fell back to normal on the WH3 (again, about the same as the MS-100). I thought it might have been the audio or power cable to the WH3 increasing the signal strength, but disproved that theory - moving and extending both did little to the range. Moving the transmitter around on the cabinet didn't do much either.
The only thing I can think of is that somehow the signal from the WH3 got coupled to the MS-100 antenna (which is much longer than the 6 inch wire of the WH3, and is resonant). Does that make any sense?
Or am I missing something?
Issue #7 is the last RSS-210 issue that still had the BETS strength in the text. The wholehouse 3 was certified after that you will see if you look the number up.
The older Broadcastvision I got from Ebay is the only one available certified back when issue 7 was in force that is available. The number, and it's in the REL look up page, is 7212A-0819ID.
The wholehouse is 8728A-WHFM3 with issue #8 in 2013. Issue 8 did not have the choice of BETS strength anymore. It was then it got harmonized with FCC
How are you measuring the range, and seeing the difference?
I think yes the only explanation is with close coupling of the WH3 to the longer antenna is enchancing it's signal strength. Try the same thing with no audio cables on the WH3 if you can check range with the carrier.
I have this Broadcastvision here and would rather use it as more convenient but afraid of the broadcasting thing. I don't just do it to myself and advertise I'm there.
Well, if I ever got a visit I could just tell the agent this was more convenient but I have 2 Decades that are BETS so I won't use this anymore. It goes about the same as the Decade even though RSS-210. I wonder if using it from indoors would still be considered broadcasting as if I was told I can't use it it would be like it's certified legal but can't be used. Does that make sense? But the BETS certification just gives me more peace of mind.
Next to the Decade the BVE is the second best one there is quality wise.
The difference in range sitting in front of the Decade was quite noticeable. While my range tests were not scientific by any means, the signal from the Decade faded out at a certain point, whereas the WH3 continued for at least several hundred more meters. Almost double.
And yet, when the Decade was moved, the WH3 went back to its normal range.
Guess I'll continue on with the Decade.
@artisan-radio Several hundred meters! Not feet? That's amazing. Regular operation, no "secret" power boost? Wow! Has to be inductive coupling going on but that's really quite something.
You may have hit on something here. How to increase range without any modification at all.
@mark Yeah, the range was effectively doubled from the MS-100. Of course, the fact that even without that, the ranges are pretty much the same means that the WH3 is operating at more than Part 15 and RSS-210 Issue 8 levels (as the Decade is BETS).
I'm still not fully convinced that that was what was happening, but I can't think of anything else. Without the setup I described, I can't get the WH3 to obtain that range. As I said, I've moved it around, I've made sure that the audio and power cables are in roughly the same positions. It makes no difference.
I'm putting the Decade back into operation, so I'll try the WH3 again operating in front of it (powered down) to see what happens.
Just for experimental reasons, if you have another Decade try the second one the same way you did with the wholehouse 3. See what happens. One off but antenna extended for wave length of frequency and the second operating with antenna at frequency length beside the off one.
I second Mark's request to try the antenna experiment he describes. I can envision that a passive antenna (not directly driven by active RF) acting as a transformer when located near an actively driven antenna. If so, the principal might also be applied to AM RF boost.
I will do that. First, later today, I'm retrying the WH3 experiment. I also note that the Decade is in a metal case, and the antenna (i.e., wire) of the WH3 overhangs the Decade, as I have it at a 45 degree angle (it won't stand vertical as the plastic encasing it is broken). Perhaps the Decade is also acting as a mini ground plane.
I do have a 2nd Decade, and I will replace the WH3 with that Decade in a 2nd experiment, which will likely be completed tomorrow.
I can think of a few more things I can try. Putting the 2 Decades on top of each other, both powered off (which was actually the original configuration when I noted the increased range) with the WH3 in front (it brings the antenna closer to the case metal). And powering off the WH3 in that latter configuration, running one of the Decades.
We'll get to the bottom of this.
There definitely is some sort of effect in the setup I described. The range of the WH3 definitely increased; it wasn't as much as previously but then, the setup wasn't identical. The next step is to put 2 Decades on top of each other, one with antenna extended, in front of the WH3. That will duplicate my original setup exactly, and I'll test that out.
The final test will be to use 2 Decades, one in front of the other, both with antennas extended and the back one powered off.
I'm hoping to do both tests tomorrow.
I'll be doing antenna tests later today, but my suspicion is that I've accidently invented a variant of the Yagi antenna. It consists of a driven element, and a number of resonant radiators (1+) that are not electrically connected to that element.
If that is the case, and right now it appears to me to the best answer, unfortunately it would be difficult to apply it to the AM broadcast band. The radiator elements would have to be huge.
I think this is somewhat of what you are doing. https://en.wikipedia.org/wiki/Monopole_antenna .. Somehow the other antenna near the transmit one in a certain position acts as a ground plane....an artificial one and is giving you more gain. You can also try this....operate the Wholehouse 3 sitting on the shelf and check range. Then put the wholehouse on a large piece of aluminum foil and now see what happens. May be the same thing that is happening by a monopole that is attached to the Decade. The decade is not on so it is not affecting anything. You could remove the antenna from the Decade(unscrew it) and it would do the same thing as the Decade is just a paper weight holding the antenna if turned off.
Try this with the Decade, put the Decade on a large sheet of foil and see if you get gain and more range than without.
Then you will know what you are doing. But the antenna near the transmit one is reacting with the electromagnetic field either adding antenna or a simulated ground plane.
The results of using a driven Decade, with another Decade close by with the antenna extended yielded no useful range extension.
Further investigation indicates that the lengths of the driven and reflector elements if this was acting as a yagi antenna are way off, and so that is unlikely to be the case.
I suspect that the extended Decade antenna is acting like a counterpoise or ground to the WH3, much like Mark is saying, even though they're not electrically connected. I think I will go to the next step, and place the WH3 on a metal sheet of some sort (without the Decade around). That should narrow things down even further.
But all this goes to show that there are many things that can affect a low power FM signal, some of which are out of your control, and others you wouldn't even think of. It's one of the issues surrounding Part 15 FM broadcasting - unless you have expensive test equipment, even if you use certified transmitters, you really have no idea what your field strength ends up being. And lets face it, most, even if they have that test equipment, aren't going to check the field strength every time they turn the transmitter on.
Really, Part FM broadcasting should have rules that more closely align to Part 15 AM, which doesn't restrict field strength as long as you restrict input power and antenna/ground length.
@artisan-radio said:
Really, Part 15 FM broadcasting should have rules that more closely align to Part 15 AM, which doesn't restrict field strength as long as you restrict input power and antenna/ground length.
I agree. The rule could be 2 mW max(FM) output into a 1/4 wave antenna(monopole) like Decade no field strength rule. FM doesn't have an input power or ground length.
I don't understand the AM and the input part? Why can't it be the output at the antenna, say 100mW max? The input thing doesn't make sense to me.
Well, we all think this and that and we should have New Zealand's way but unless one of us runs for office and gets elected it will never be.
Interesting to see what a large piece of foil or metal surface does to the range of the Wholehouse and the Decade. I may try it myself here with a large sheet of foil under the Decade and see what happens. I do know that Decade even with the plastic case has a conductive coating on the inside and the ground lead of the antenna is connected to the cabinet as is the ones in the metal case. I'll report back as to any result.
I find it interesting that the WH3 range was increased, while the Decade's wasn't. Perhaps the Decade is better grounded than the WH3.
The WH3 managed to get certified by making its antenna a piece of 6 inch wire, obviously non resonant. The Decade was certified with a resonant telescopic antenna.
If things go as they have been, you won't see much of a difference with the Decade over top of a metal plate, at least a small one. You'll probably see range extension to the WH3.