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The Part 15 FM transmitters pose a challenge for the ambitious engineer hoping to improve them with modifications.
A modification might be, for example, adding a switch to turn off the stereo generator.
Looking at five transmitters on hand, it’s mostly the IC chips, the integrated circuits, which raise the greatest obstacle for the most part because some of them are unmarked and can’t be traced to a data sheet which would aid in their reverse engineering.
It would also be nice to add a control to calibrate the stereo injection level, many transmitters are found to have stereo pilots or subcarriers set above professional levels.
I’ll sit back while someone makes the meaningless claim that modifying some of these devices negates their certification. Then I’ll come back and explain why that’s a non-issue.
Total posts : 45366Only the operators of unlicensed transmit systems (and in a few cases their landlords) have been been given NOUOs by the FCC, where FCC Part 15 applies.
BTW, FCC Part 15 does not define/limit the relative amplitude of either the 19 kHz pilot carrier OR the L-R subcarrier components of analog FM stereo transmitted and compliant with §15.239.
Total posts : 45366Rich posted: “Only the operators of unlicensed transmit systems (and in a few cases their landlords) have been been given NOUOs by the FCC, where FCC Part 15 applies.”
I don’t understand what you mean. Please explain.
Total posts : 45366That certification does not even come close to guaranteeing a legal device.
We also know that you can get a NOUO using a transmitter that was purchased as a certified device.
We also know that as long as you’re not building them to sell, it’s perfectly legal to design and build your own AM or FM Part 15 transmitter. As long as it meets the appropriate rules when in operation.
I see no legal issue with making modifications to your purchased certified transmitter. However that you’d need to be able to test and demonstrate that it meets the applicable rules. Tougher for FM than AM.
If I were of a mind to modify a purchased, certified FM transmitter I’d want to complete careful testing first to insure that it was legal in the first place. My experience has shown me that odds would be that your certified transmitter probably wasn’t legal in the first place.
If your device WAS over the limit, and you HAPPENED to get an FCC visit, and it’s been clearly modified, you’d have a lot of ‘splainin’ to do.
In the end it’s the OPERATOR who must be able to demonstrate his device is legal, modified or not. Certification does not relieve the operator of being ultimately for the legal operation of the transmitter. Right or wrong, that’s the way it is.
TIB
Total posts : 45366“I don’t understand what you mean.”
__________
Hopefully others will.
Total posts : 45366At one time Part15(dot)us was a healthy site for discussion of technical projects relating to the Part 15 hobby, but of late all threads lead to NOUO threats and warnings.
At least Tim’s response above had context in which my opening inquiry was acknowledged before it was snuffed by bridging it to Rich’s NOUO advisory.
But Rich’s “Negativity” lived up to its title by having no context at all and serving as an agenda thread to generally warn about the coming NOUO holocaust.
Then we have #5 with Ebenezer Scourge being snotty.
Total posts : 45366Mr Blare:
If you deny the literal accuracy of my previous posts in this thread, then please post your proof thereof.
Total posts : 45366The current transmitter I am using now….the Broadcastvision, like the Decade MS100, didn’t have an on off switch so I did a “mod” to wire in a small mini switch at the power jack and making a small hole in the case and mounting it so now the transmitter can be switched on and off. This in no way should affect the certification because nothing was altered as to the operation of the transmitter. It may void a warranty but that’s all.
Mark
Total posts : 45366You’re right, Mark, an on/off switch won’t stand out as being a mod unless you mention it to someone.
And to Tim’s thought that mods will require explaining, I would say that a well maintained file folder neatly showing the mods and giving technical explanation should serve to demonstrate technical competence in the eyes of inspectors and would not be counted as a mark against Mark. (except that Mark is in Canada and should really worry if the FCC comes calling)
Hey Rich… non sequitur.
Total posts : 45366Your mods will only require explaining if the FCC man shows up, and you’re over the limits. If the man shows up and your transmitter is completely butchered with mods covering an entire table, it doesn’t matter as long as you signal is legal. On the other hand, if your transmitter is completely 100% factory fresh stock, and you’re over the limits, it’s still your butt he’s after.
In case of the modded unit he’s gonna want to know what you’ve been doing. Either way, if you’re over you’re illegal, mods or no mods.
The crux of my comment was that mods are completely legal, certified transmitter or not. It may or may not cancel the certification. However, since certification neither promises you a legal transmitter, nor shields you from a violation, mods don’t make any difference. Unless of course they take a legal transmitter and make it illegal.
All certification does is allow the transmitter to be sold in the US.
TIB
Total posts : 45366Thank you Tim and good morning everyone. I’m in recovery from daylight time, a full hour has been taken away and the impact on the brain will be felt for awhile.
I agree, Tim, with your take on the question of modifying part 15 FM transmitters… the real issue is the field strength and/or the interference factors.
As for Mr. Scourge, and he has earned his unbecoming names and criticisms, he wants “proof” for undefined reasons, without which his latest ludicrous topic shifts are believed to stand, in his own mind, that is.
Regular readers have come to know that all attempts to carry out a full and rational conversation with Scourge are circular… they always lead back to the same conversation.
We are about due for the resurrection of “long ground leads” and reminders of “KENC”, and always the accompanying threats and warnings of NOUOs everywhere.
Yet, and this should be all the “proof” we need to shut his yap for the last time, NO MEMBER OF PART15(DOT)US HAS EVER RECEIVED A NOUO (Notice of Unauthorized Operation).
Scourge’s unfounded intimations of rampant violation are baseless and terroristic. Proof positive.
Total posts : 45366… As for Mr. Scourge, and he has earned his unbecoming names and criticisms, he wants “proof” for undefined reasons, …
Does Mr Blare believe that whatever people say or post with no proof is accurate?
without which his latest ludicrous topic shifts are believed to stand, in his own mind, that is. …
My posts have been exactly on point in this thread. Mr Blare is the person introducing other subjects, opinions, and personal attacks here in his continuing attempts to control this board by intimidation.
And with that I expect not to respond further to the posts of Mr Blare.
Total posts : 45366Another soiled thread.
Total posts : 45366I wanted to modify my C Crane
stereo FM transmitter to mono.
I think it was Carl that actually found
me the schematic.
Many people have lifted off one side of
the 38 kHz crystal and put an on/off switch
in there. Take the crystal out of line, and
it’s mono.
I couldn’t do that. My vision is messed up.
Heck, 20 years ago I started to pick up the
wrong kid from daycare. Somebody helped
me, and I took my son home. My wife drove
the car. The other kid, little Mortly, got a ride
home later. I know that because I talked to his
mother, Mrs. Portly the next day and she verified
that.
OK NOW HERE’S THE IMPORTANT PART
So I wanted to make the C Crane FM transmitter
mono. I couldn’t put a switch in. So I took a
big pair of pliers to the 38 kHz crystal.
CRUNCH
Total posts : 45366In #2 Rich added: “BTW, FCC Part 15 does not define/limit the relative amplitude of either the 19 kHz pilot carrier OR the L-R subcarrier components of analog FM stereo transmitted and compliant with §15.239.”
That statement is misleading and incorrect. The FCC has set strict standards for stereo and other sub-carriers. A Part 15 FM transmitter is a scaled-down version of a professional transmitter.
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