Type Acceptance / Type Certification

Discuss FCC rules, regulations, news, and information!
Post Reply
User avatar
Dale H. Cook
Posts: 747
Joined: Thu Dec 20, 2007 9:08 am
Location: Roanoke/Lynchburg, VA
Contact:

Type Acceptance / Type Certification

Post by Dale H. Cook » Wed Aug 20, 2014 5:52 am

I would like to pick your brains about type acceptance and type certification.

One of the drawbacks to the LPB low power AM transmitters (AM-100 et alia) is that they are rockbound. The frequency is controlled by a crystal that produces a square wave at six times the carrier frequency. The difference between an AM-100 and an AM-100P is that the crystal in the latter is more stable, resulting in a carrier frequency that meets the frequency requirements for the AM broadcast band. An AM-100 (without the P suffix) cannot be used for AM broadcast, only for applications such as carrier current stations

I own an example of an AM-100 whose frequency was changed at the LPB factory, including an AM-100P crystal, and that was used for broadcast, but which does not bear a type acceptance ID label and shows no signs of having borne one.

I have developed a synthesized oscillator upgrade for the LPB transmitters along with a system allowing field exchange of the elliptical harmonic filter networks, making it possible for an engineer in the field to change the frequency of an LPB transmitter. In theory this upgrade (involving a TCXO synthesizer reference oscillator) would transform an AM-100 into an AM-100P. My questions are about what I would need to do to make the modified transmitter legal for AM broadcast use. The 1998 revision of type acceptance / type certification requirements makes it appear that this could be done as long as I have acceptable and properly calibrated instrumentation so that in my application I can certify to the Commission that the modified transmitter meets Part 73. Would I need to get a broadcast attorney involved? That would probably push the cost beyond what I would be willing to invest, given the relatively low number of conversions that I could expect to do. As it is the certification would not be cheap as, in addition to the application fee, I would need to run a bunch of my instrumentation through a local calibration laboratory.

A frequency agile AM-100P would make a useful emergency transmitter for clusters or chains with multiple AMs, as well as being usable for a long wire STA. As a side note, does anyone know what LPB charged for a frequency change, or have any idea what kind of price a cluster or (more likely) a chain might be willing to pay for a frequency agile conversion?

What prompted this are three factors. One is that I recently acquired a non-functioning but repairable AM-100. The second is that, now that I am once again a contract engineer, I have two clients with an LPB used at night and a third who would like to change the frequency of an LPB for night time backup and emergency use. The third is that I would like to have a frequency agile LPB that I could loan to a client with a damaged LPB so that I could repair the latter in my shop instead of repairing it in the field.
Dale H. Cook, Contract Engineer, Roanoke/Lynchburg, VA
http://plymouthcolony.net/starcityeng/index.html

User avatar
Deep Thought
Posts: 3167
Joined: Thu Mar 20, 2008 9:23 am
Location: La Grange, IL
Contact:

Re: Type Acceptance / Type Certification

Post by Deep Thought » Wed Aug 20, 2014 7:58 am

Contrary to popular belief, you don't have to use a "type accepted" transmitter. It just relieves you from submitting the measurements specified in §73.44 to the FCC prior to using it on the air. Almost every construction permit has something similar to the following as a condition:
Permittee shall install a type accepted transmitter, or submit
application (FCC Form 301) along with data prescribed in Section
73.1660(b) should non-type accepted transmitter be proposed.
§73.1660(b) references §73.1690 :
(e) Any electrical and mechanical modification to authorized transmitting equipment that is not otherwise restricted by the preceding provisions of this section, may be made without FCC notification or authorization. Equipment performance measurements must be made within ten days after completing the modifications (See §73.1590). An informal statement, diagram, etc., describing the modification must be retained at the transmitter site for as long as the equipment is in use.
§73.1590 then requires equipment performance measurements specified at §73.44, which every AM station is supposed to be doing every year anyway. For AM transmitters the frequency stability and spurious emission/NRSC mask requirements are about all that is needed. I am not sure it is worth the $$$$ required to get it type accepted due to the very small market for such a modification. It would require you to sell the kit for over $1000 to have any chance of making your money back.
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

User avatar
Dale H. Cook
Posts: 747
Joined: Thu Dec 20, 2007 9:08 am
Location: Roanoke/Lynchburg, VA
Contact:

Re: Type Acceptance / Type Certification

Post by Dale H. Cook » Wed Aug 20, 2014 9:47 am

Mark -

Thanks for the advice. I would not "sell a kit" per se. I would only modify LPB transmitters as a contract engineer for stations who own them and would measure and certify that the modified transmitters meet requirements for frequency stability (hence the TCXO reference oscillator for the synthesizer), spectral purity and power output. I have no desire to sell modified LPBs. If a station wants a modified LPB they can buy an unmodified one and contract with me to modify and measure it. Fortunately the LPB crystal oscillator is a square wave oscillator operating at six times the carrier frequency so the transmitter was already designed to create a spectrally pure output from a very impure oscillator input. Meeting the NRSC spectral mask would require that the licensee own an NRSC processor anyway, as the LPB design predates NRSC. I have an Inovonics 222 in-house and so could document that the modified transmitter meets the mask when used with an NRSC processor.

While I am at it let me pick your brain about one other thing. Would a series of spectrum analyzer measurements be needed or do you think it would suffice to use 100% pink noise modulation through an NRSC processor and document it using a spectrum analyzer with the necessary options for NRSC measurements? It would essentially be the same as an annual NRSC measurement but with pink noise substituting for normal program material. Offhand I don't know how good that measurement would look, as I am accustomed to making NRSC measurements with program material and pink noise might make for a more severe circumstance.
Dale H. Cook, Contract Engineer, Roanoke/Lynchburg, VA
http://plymouthcolony.net/starcityeng/index.html

TPT
Posts: 636
Joined: Mon Dec 03, 2007 3:18 pm
Location: St. Marys, WV

Re: Type Acceptance / Type Certification

Post by TPT » Wed Aug 20, 2014 4:09 pm

Suspect that an annual NRSC measurement would still be required, whether the transmitter was "modified" or "original equipment."

That being said, with your example of a modified LPB, having your tests on file would probably be sufficient, for two reasons:

1. Don't think there is any AM station still on licensed at 100 watts on a primary basis. Lots of daytimers using LPB's for nighttime flea power operations on a secondary basis, but don't believe annual NRSC measurements of these stations on night power has ever become an issue;

2. If the LPB was used on a temporary basis (e.g.--under an STA to drive a long wire) AND interference became an issue, the record of spectrum measurements would be a good defense. Especially where the "interference" resulted from some kind of external mixing.

User avatar
Deep Thought
Posts: 3167
Joined: Thu Mar 20, 2008 9:23 am
Location: La Grange, IL
Contact:

Re: Type Acceptance / Type Certification

Post by Deep Thought » Wed Aug 20, 2014 5:16 pm

Dale H. Cook wrote:While I am at it let me pick your brain about one other thing. Would a series of spectrum analyzer measurements be needed or do you think it would suffice to use 100% pink noise modulation through an NRSC processor and document it using a spectrum analyzer with the necessary options for NRSC measurements? It would essentially be the same as an annual NRSC measurement but with pink noise substituting for normal program material. Offhand I don't know how good that measurement would look, as I am accustomed to making NRSC measurements with program material and pink noise might make for a more severe circumstance.
As long as it meets the occupied bandwidth and harmonic/spurs requirements "under normal program conditions" (you get to define that) as well as the +/- 20 Hz frequency stability you should be good to go. For these transmitters that means -65 dBc for anything outside of the NRSC mask range.

This falls into a sort of grey area since the rules speak of modifying previously accepted equipment, which this isn't. However, as long as you provide complete documentation in the form of test sheets and a certification that the transmitter meets the requirements of 73.44 when used with a compliant audio processor I don't see any reason to expect any issues with the Commission.
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

User avatar
Deep Thought
Posts: 3167
Joined: Thu Mar 20, 2008 9:23 am
Location: La Grange, IL
Contact:

Re: Type Acceptance / Type Certification

Post by Deep Thought » Wed Aug 20, 2014 5:18 pm

TPT wrote:Lots of daytimers using LPB's for nighttime flea power operations on a secondary basis, but don't believe annual NRSC measurements of these stations on night power has ever become an issue
Most are now memorialized on their licence on a primary basis if the station has nighttime authority (more than PSRA/PSSA hours) which makes it important to make sure the equipment passes muster.
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

User avatar
Dale H. Cook
Posts: 747
Joined: Thu Dec 20, 2007 9:08 am
Location: Roanoke/Lynchburg, VA
Contact:

Re: Type Acceptance / Type Certification

Post by Dale H. Cook » Wed Aug 20, 2014 7:20 pm

Deep Thought wrote:[As long as it meets the occupied bandwidth and harmonic/spurs requirements "under normal program conditions" (you get to define that) ...
I will have to play around with that. I have at least some CDs to fit about any popular music format that an LPB might be used for, and I can go to a client station here in town and record some of their talk programming. It would be interesting to compare NRSC measurements of various formats with pink noise measurements. Of course, for anything other than pink noise I need a full-blown NRSC-compliant AM processor, so I will need to get back to work on the Inovonics 235 that I recently picked up cheap in non-working condition and fix that.
Deep Thought wrote:... as well as the +/- 20 Hz frequency stability ...
Witha TCXO that should be no problem - the one I have in mind is a Crystek with a frequency stability of +- 1 ppm.
Dale H. Cook, Contract Engineer, Roanoke/Lynchburg, VA
http://plymouthcolony.net/starcityeng/index.html

BigRed
Posts: 85
Joined: Tue Mar 27, 2012 8:59 am

Re: Type Acceptance / Type Certification

Post by BigRed » Thu Aug 21, 2014 12:31 pm

Why couldn't you start with an easier question to answer, like how to solve the problems in the Middle East, then work up to this one . . . (just kidding, kinda . . . )

The old system of Notification, Certification, Acceptance and Approval (OET 61) has been replaced for new equipment (happened back in the early to mid 90's, I think). There now appears to be three options: Verification - Section 2.902 is a procedure where the manufacturer makes measurements or takes the necessary steps to ensure that the equipment complies with the appropriate technical standards. Declaration of Conformity - Section 2.906 is a procedure where the responsible party makes measurements or takes other necessary steps to ensure that the equipment complies with the appropriate technical standards. Certification - Section 2.907 is an equipment authorization issued by the Commission, or on behalf of the Commission, based on representations and test data submitted by an applicant. Specific guidance for filing an application for authorization under the certification procedure may be found Section 2.1033.

Almost ALL broadcast transmitter installations require Verification as per CFR47§73.1660 Acceptability of broadcast transmitters.
(a)(1) An AM, FM, or TV transmitter shall be verified for compliance with the requirements of this part following the procedures described in part 2 of this chapter.

So if equipment is Certificated, that documentation will also serve as Verification, but the Certification process is NOT required in order to meet the licensing requirements of the Rules. (Type Accepted transmitters appear to be "grandfathered" if just installing them and turning them on was OK at one time, don't remember specifically.) There would seem to be two notable exceptions: most Part 74 LPTV transmitters and all Part 73 LPFM transmitters are required to be Certified. I'm guessing that's because the Commish expects those to be "cheap and dirty" and wants to be certain that the manufacturer actually took the time to sit down and fudge, I mean make the necessary measurements.

So, for changing the reference oscillator in an AM transmitter it appears that you will simply have to Verify each transmitter after making the modification (and I'm guessing that for the sake of this discussion you become the manufacturer of the new transmitter using the old transmitter as a major part in the new one?). Certification would be a waste of time and money as it appears to have no additional benefit for AM broadcast licenses. [The Certification process is not difficult, just tedious. It's done on-line at the Commission's OET WEB site, no lawyer is required, and you don't even have to be the party that actually made the transmitter. Just cough up the filing fee and supporting documentation that demonstrate that the equipment complies with ALL applicable sections of the Rules (wait, maybe you DO need a lawyer?) and you're off to the races.]

But, there's the tiny little reference to "part 2" . . . most of us don't have the equipment available to actually do some of those measurements; I suspect they're seldom completed for Verifications.
For example, for the oscillator testing you might need an environmental test chamber to demonstrate that the oscillator can stay on frequency in a given temperature range. Have a look at CFR47§2.1055 Measurements required: Frequency stability. (3) From 0° to +50° centigrade for equipment to be licensed for use in the Radio Broadcast Services under part 73 of this chapter.

And don't forget that you're supposed to do radiated emissions measurements, Part 15 compliance. See CFR47§2.1053. That's stuff coming out of the cabinet and from the AC and signal wiring; makes the conducted measurements look like childsplay. (Although not necessary, this is where a 10-meter anechoic chamber comes in real handy, or even a 3-meter chamber would be nice.)

And both the radiated and conducted spurs and harmonics need to be "investigated" from DC to the 10th harmonic . . . . CFR47§2.1057.

But wait, there's more; (and I SWEAR I'm not making this stuff up). Here's a link to Part 2: http://www.ecfr.gov/cgi-bin/text-idx?SI ... ain_02.tpl

On the other hand I have a sometimes radio client who's one AM rig was running at 23 Hz above carrier for what was probably years. It was noticed by one person and posted on a WEB site (before I got involved with the station), and still no one of import (the FCC) noticed. (Yes, it's fixed now, but because it bothered ME, not anyone else . . .)

But enough of my whining about the FCC's practices and procedures . . . If I were doing what you're proposing, I'd do the modification then measure the carrier frequency against a "traceable" standard, then measure as many of the Part 2 requirements and all the Part 73 requirements that I could; do a proof on it just like you would on a new transmitter installation [transmitter output power, bandwidth occupancy, conducted harmonics and spurs into a DL to the 10th harmonic, the NRSC measurement into the station's antenna if the opportunity presents itself, maybe even an old fashioned audio proof if you charge for your reports by the pound and have the time (or at least a frequency response and distortion "spot-check" )]. If the oscillator's supplier has a temperature stability test that shows compliance with CFR47§2.1055(3) I'd include that too. Write it all up with pretty graphics and add a page that attests to the accuracy of the measurements and the measuring engineer's qualifications, I'm sure that you know the drill better than I. Put that documentation into the station's files and call it a day. And I think it needs to be kept for at least two years (I'd keep it forever), just like any other "official" transmitter measurements . . . But I seriously doubt it ever comes up during an inspection. (Last AM inspection I was around the Inspectors had no clue as to how to measure AM power!)

Good luck, and now I'm going to go eat a handful of Excedrin for this bloody headache that suddenly came up for some reason . . . :)

kcbooboo
Posts: 446
Joined: Sat Dec 10, 2011 4:53 pm
Location: East of the Mississippi

Re: Type Acceptance / Type Certification

Post by kcbooboo » Sat Aug 23, 2014 12:39 pm

I don't mean to throw a monkey wrench into the works, but it seems to me that if you want to show that the transmitter, after you've made some modifications, meets the various FCC emission rules, shouldn't it do that on its own, without requiring an external audio processor to do the NRSC filtering? At some point down the road someone could easily and innocently replace the audio processor with one that doesn't necessarily have NRSC filters. Maybe an NRSC filter would cost more than the LPB transmitter it would be installed in, but that's the final point where you can make an audio connection, so it should do all the work to pass muster.

Didn't the Harris MW-1/1A need several additional components to make it NRSC-compliant? How hard could it be to add those to any other transmitter?

Bob M.

User avatar
Dale H. Cook
Posts: 747
Joined: Thu Dec 20, 2007 9:08 am
Location: Roanoke/Lynchburg, VA
Contact:

Re: Type Acceptance / Type Certification

Post by Dale H. Cook » Sat Aug 23, 2014 2:32 pm

kcbooboo wrote:... shouldn't it do that on its own, without requiring an external audio processor to do the NRSC filtering?
The LPB transmitters as built did not have to meet the NRSC mask as they predated NRSC. My intent is not to modify them to meet the NRSC mask, it is only to make them frequency agile.

Correct me if I am wrong (Jeff?), but IIRC even current AM transmitters in and of themselves do not have to meet the NRSC mask.

In use an LPB is almost certainly going to be fed by the same NRSC-compliant processing that feeds the main transmitter. That is certainly the case at my three client stations that use LPBs at night. Another client station for a time ran an LPB into a long wire under an STA after they lost their transmitter site. That one had pretty simple processing but I put an Inovonics 222 in front of the LPB.
Dale H. Cook, Contract Engineer, Roanoke/Lynchburg, VA
http://plymouthcolony.net/starcityeng/index.html

TPT
Posts: 636
Joined: Mon Dec 03, 2007 3:18 pm
Location: St. Marys, WV

Re: Type Acceptance / Type Certification

Post by TPT » Sat Aug 23, 2014 3:00 pm

Don't know about new AM transmitters, but I would venture that most transmitters over, say, a dozen years old, only meet the NRSC mask with the filtering in the processor.

User avatar
Deep Thought
Posts: 3167
Joined: Thu Mar 20, 2008 9:23 am
Location: La Grange, IL
Contact:

Re: Type Acceptance / Type Certification

Post by Deep Thought » Sat Aug 23, 2014 10:59 pm

You need that with any AM transmitter. Some (Nautel) have low pass filters built in but generally don't follow the NRSC curve by themselves. Nautel ships theirs set to 16 KHz by default.
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

User avatar
Dale H. Cook
Posts: 747
Joined: Thu Dec 20, 2007 9:08 am
Location: Roanoke/Lynchburg, VA
Contact:

Re: Type Acceptance / Type Certification

Post by Dale H. Cook » Sun Aug 24, 2014 6:06 am

Thank you, Mark. If a new transmitter needs an NRSC processor I see no reason to modify old transmitters so that they don't.
Dale H. Cook, Contract Engineer, Roanoke/Lynchburg, VA
http://plymouthcolony.net/starcityeng/index.html

Post Reply