I so much wish there could be a affordable hand held field strength meter tuneable to a given frequency and measurable down to at least .1mV/M. To measure the 100uV/M for BETS and include the 250uV/M for the FCC measurement.
That Tenmars I showed a while ago would work if it was frequency selective.
A big +1. For AM, we don't have to be concerned with field strength. If we take care of the DC input to the final, and the length of ground lead + antenna, we're covered. Using a certified transmitter for FM is most likely enough to ensure compliance, as the power from such a unit is highly unlikely to be orders of magnitude out of adjustment. I'm thinking that it is only signals that are orders of magnitude greater than BETS-1 and Part 15 levels which draw unwanted attention. (I recognize that in Canada, a certified transmitter has to be used.)
Nevertheless, for those of us who like measuring things, it sure would be nice to own an accurate field strength meter. Our BETS-1 and Part 15 FM signals are highly unlikely ever to draw attention from the authorities, but I'd like the extra feeling of security that would come from going out in the field and verifying that my signal is within the allowed field strength limits.
You can get a used Potomac FIM-71 VHF Field Strength Meter for ~$500-1000 depending on condition, and currency (US or CDN). Tektronix provide a calibration service. I don't know how much they charge, but you could probably kit yourself out with a calibrated meter for around US$1000, give or take. It's not chump change, but neither is it unattainable for the enthusiastic hobbyist with a budget.
One day, one day.........
I'm hesitant to ask this because I may have missed a significant point in reading this discussion.. but why is that little adjustment access hole such a big deal and why the fuss over on the best way to cover it up?
Is it just because it could make it easier for someone to operate in a non-compliant manner? Is that the big deal about that ant size hole? - or are you worried about ants getting in there?
But seriously, why has the hole there gotten so much attention that it managed to spark this three three page thread discussion?
By the way, theres a hole in my sock too.
@richpowers Wow 3 pages! didn't think that much but here's the thing..... you actually answered your own question as it is about a potential violation when the consumer can easily access RF power from outside. A mean agent could say that voids certification. More in Canada as certification is everything here.
.....it is about a potential violation when the consumer can easily access RF power from outside. A mean agent could say that voids certification. ..
Ok, That's what I thought the hubbub was about.. but isn't that extreamly unlikely? In fact, doesn't that hole have no possibility whatsoever of ever being a certification issue at all?
I stare in awe.
@richpowers And the thread goes on and on!
I had mentioned I was at the lab here near Toronto last year and any way for the user to easily access and change the RF or, have the capability to have the RF adjusted without taking it apart and changing components would never pass certification. And the lab mentioned that the Decade the way it is with one version for both countries and RF adjustable would never get a pass today. You need two transmitters, one for each country.
The Hamilton Rangemaster with it's ability to operate above 100mW by the user adjustable power would not pass either. At least in Canada if the lab is going by the book.
For peace of mind, I filled the hole with epoxy putty from the inside and on the outside never know the hole was there.
What I would do is patch the hole, take the cover off, up the power, put the cover back on, wipe the finger prints.
@richpowers And the thread goes on and on!
I had mentioned I was at the lab here near Toronto last year and any way for the user to easily access and change the RF or, have the capability to have the RF adjusted without taking it apart and changing components would never pass certification. And the lab mentioned that the Decade the way it is with one version for both countries and RF adjustable would never get a pass today. You need two transmitters, one for each country.
The Hamilton Rangemaster with it's ability to operate above 100mW by the user adjustable power would not pass either. At least in Canada if the lab is going by the book.
For peace of mind, I filled the hole with epoxy putty from the inside and on the outside never know the hole was there.
Technically the rangemaster is not capable of more than 100mW due to components used in the design and the design itself. as you go above 100mW you lose asymmetrical modulation plus the audio transformers in the rangemaster are not designed to handle the audio power required to bring an above 100mW power setting to 100% modulation. the transformers will eventually fry. so even though the power is adjustable to over 100mW there is two big technical reasons (legal issues aside) to not do it. you want the audio input setting about halfway and the input set as close to 100mW as you can get it and use either a scope with demodulation probe or a schlockwood sw300 mod monitor to set modulation to 100%.
@carl-blare Even I am stuck between a rock and a hard place. To seal the hole I have to take the cover off...which I'm not supposed to do, but have the hole to access the RF, not supposed to either. But maybe we were(Rugster and I) over reacting. If it was done by the manufacturer who said it doesn't void certification than any unlikely issues if they come up e.g. a visit, I just refer the agent to the manufacturer and keep the email response.
I emailed Michel over at Decade on Thursday morning, to ask about the lack of sealant on the power adjustment pot and, as of Saturday evening, have not heard back. I'm beginning to think that I may not hear back from him on this.
One of my new-to-me MS-100's has been on the air for a few days now. I'm very happy with both of them. Am planning to do a write-up at some point, when the inspiration hits.
I had mentioned I was at the lab here near Toronto last year and any way for the user to easily access and change the RF or, have the capability to have the RF adjusted without taking it apart and changing components would never pass certification. And the lab mentioned that the Decade the way it is with one version for both countries and RF adjustable would never get a pass today. You need two transmitters, one for each country.
Reading this reminds me of the MS-100 review on HB, where the unit that Decade sent for review was one that had the power set for the Canadian market. HB had a local engineer readjust the power level down to the correct level for compliance with FCC 15.239 before proceeding with their review.
Incidentally, the HB review of this transmitter has a picture of it with the top cover removed. Their unit had the same thing - sealant on the over-modulation adjustment pot, but no sealant on the power level adjustment pot. The power adjustment pot on theirs was a top adjust one, so I assume their top cover had no hole for easy access to the power adjustment.
Interestingly, their review unit was the stereo version. The stereo generator board had 3 multi-turn pots, which all had sealant on. Their unit had a total of 5 multi-turn pots. All of them had sealant on, except for the power adjustment pot.
There's always been a controversy over the Decades FM compliance. To this day I still dont understand how it achieved certification. The topic is more controversial than the Talking House variable lengths ground lead and its range extenders additional 10ft feed line.
I received a reply from Decade today. Basically, it said that yes, it was indeed possible that there was no sealant on the power level adjustment pot but that, based on my description of the transmitter range, it sounded as if the power level was OK.
Here's something I don't think ever got mentioned in this thread that might ruffle your feathers. The story is a couple years old, but still relevant:
https://www.radioworld.com/news-and-business/headlines/fcc-cites-bsw-over-transmitter-certifications
Excerpts:
"The FCC has cited Broadcast Supply Worldwide for marketing several low-power FM transmitter models that it says didn’t comply with commission rules... ... Decade MS-100, MS-100M and MS-100S models unlawfully... ...Michel Carrier, president and owner of Decade Transmitters Inc., contacted Radio World after this story originally appeared. He disputed the FCC’s account.
“I really wonder why the FCC inspector came to that conclusion, especially when the MS-100 and the MS-100S have been Part 15 certified by the FCC in 1997. You can look in the FCC certification database and you will find it there. They also stated that the MS-100 lack a proper labeling and manual disclosure, which is also not correct.”
He said no one had contacted him and believes it was a misunderstanding. “We have been manufacturing quality FM transmitters since 1991 and have always complied to FCC and Industry Canada rules. All transmitters use discrete, military grade components, not a ‘full-FM-transmitter-in-a-single-chip’ like the cheap Chinese transmitters that you can find an Amazon and other online stores. The FCC should not waste its time on legal transmitters like ours, but should check out the thousands of illegal Chinese transmitters sold online.”
I remember this story! Misinformation! I contacted Decade about this when I saw it and Michel at Decade contacted radioworld and was going to sue for damages and the story was corrected and an apology made. Michel told me that some stupid agents at ISED Canada along with some FCC agents don't know "dick all" The decade is a valid certification in the USA and Canada and the label is there. It can be used anywhere in the two countries and for broadcasting in Canada.
It's like the spokes person that said that an AM legal transmitter goes only 200ft.
This is a big problem as if you get a visit by an ill informed or ignorant agent you are best to have all info with you to show, including the rules in each country. And I wish I could stop hearing distance limits all the time....no such limits exist, AM or FM in the USA and Canada.
Artisan and I have been posting about this many times.
.. Michel at Decade contacted radioworld and was going to sue for damages and the story was corrected and an apology made...
But Mark, the above link IS the updated follow-up story: "..Michel Carrier, president and owner of Decade Transmitters Inc., contacted Radio World after this story originally appeared. He disputed the FCC’s account..." but there's no correction or apology, nor any updates about it, it only states Decades response.