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captainron19

FM Transmitter Antennae

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All,



DIY christmas forum has had quite a lot of users that have made a easy homebrew version of the ramsey jpole. here is the link:

http://www.doityourselfchristmas.com/wiki/images/a/a7/How_to_make_a_dipole_antenna.pdf

Pretty simple and cheap as all get out to make, it doesnt have the choke that the ramsey has, dont know how much that affects the performance tho.

As far as FCC goes, If we stay under the wattage limits.... :cool:

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bretk wrote:

All,



DIY christmas forum has had quite a lot of users that have made a easy homebrew version of the ramsey jpole. here is the link:

http://www.doityourselfchristmas.com/wiki/images/a/a7/How_to_make_a_dipole_antenna.pdf

Pretty simple and cheap as all get out to make, it doesnt have the choke that the ramsey has, dont know how much that affects the performance tho.

As far as FCC goes, If we stay under the wattage limits.... :cool:

field strength..not wattage/ERP...

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DonFL wrote:

bretk wrote:
All,



DIY christmas forum has had quite a lot of users that have made a easy homebrew version of the ramsey jpole. here is the link:

http://www.doityourselfchristmas.com/wiki/images/a/a7/How_to_make_a_dipole_antenna.pdf

Pretty simple and cheap as all get out to make, it doesnt have the choke that the ramsey has, dont know how much that affects the performance tho.

As far as FCC goes, If we stay under the wattage limits.... :cool:

field strength..not wattage/ERP...

AAAAHHH that makes sense, those sneaky government devils:P

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DonFL wrote:

Orville wrote:


Most often today, car antenna are built into the rear window or the windshield, but some still have external antenna. And none of these external antenna rust because they are made of aluminium in most cases.

Geez Orv, how old are your cars? Windshield antennas went away years ago..I haven't seen one in the last 4 cars I've bought, ranging from 1999 or so up to a week ago. Its all external, and has been for a long time.



1997 and 1998, but they don't have the internal window antenna either.

But they were both still made before 1999 models that quit doing that!:(

And of which I did not know they had stopped doing it. Especially since at one time I had a 2001 that had one of those internal antenna, built right into the back windshied glass.

So that's why I figure they were still doing it.

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In radio telecommunications, effective radiated power or equivalent radiated power (ERP) is a standardized theoretical measurement of radio frequency (RF) energy[1][2] using the SI unit watts, and is determined by subtracting system losses and adding system gains. ERP takes into consideration transmitter power output (TPO), transmission line attenuation (electrical resistance and RF radiation), RF connector insertion losses, and antenna directivity, but not height above average terrain (HAAT). ERP is typically applied to antenna systems.
For a simplified example, if an antenna system has 9 dB gain and 6 dB loss, its ERP is 3 dB over (equal to double) the TPO. The use of circular polarization, or otherwise splitting between horizontal and vertical linear polarization, causes a "loss" of 3dB, cutting the reported ERP in half. If full-wavelength spacing is used between antenna elements in an array, the ERP is increased multiplicatively with the number of elements. For half-wave-spaced elements (used to limit RF radiation hazard beneath the radio tower), only half of the elements count. Null fill also detracts from the ERP by increasing the power in the nulls that form between side lobes. Stations with beam tilt often have two ERPs listed: one at the angle of tilt (the main lobe), and another in the standard horizontal plane. When only one ERP is listed, this is usually referring to the power in the main lobe.

Per Wikipedia :cool:

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+ 1 dB Bretk, : )
----------------------------------------------------------------------------------------------------------
I'm not going down that road with the 100 watt transmitter, but with my 32 years of being a broadcast engineer all I have to say is, good luck

But, I like the Slim-Jim antenna myself, if your going to get inspected anyhow, do it with style. And the FCC will talk about your system for years when they train the new employees they will be hiring with the fines you will be paying

Or better yet get a 4-bay rototiller antenna, you will get more gain in dB and your light show will be picked up in a 30 mile contour,

you might as well apply with the FCC for a LPFM license, heres what you need to know.

73.811 - LPFM power and antenna height requirements.

(a) LP100 stations: (1) Maximum facilities. LP100 stations will be authorized to operate with maximum facilities of 100 watts effective radiated power (ERP) at 30 meters antenna height above average terrain (HAAT). An LP100 station with a HAAT that exceeds 30 meters will not be permitted to operate with an ERP greater than that which would result in a 60 dBu contour of 5.6 kilometers. In no event will an ERP less than one watt be authorized. No facility will be authorized in excess of one watt ERP at 450 meters HAAT.


I've typed enough on this. But here's what I am doing

My FM transmitter is FCC Part 15 compliant and if you want to hear what my "broadcast" sounds like just watch this video. the audio was recorded off of my portable FM radio jacked right into my camcorder. And look how far I am from the house and no static

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PMC wrote:

+ 1 dB Bretk, : )
----------------------------------------------------------------------------------------------------------
I'm not going down that road with the 100 watt transmitter, but with my 32 years of being a broadcast engineer all I have to say is, good luck

But, I like the Slim-Jim antenna myself, if your going to get inspected anyhow, do it with style. And the FCC will talk about your system for years when they train the new employees they will be hiring with the fines you will be paying

Or better yet get a 4-bay rototiller antenna, you will get more gain in dB and your light show will be picked up in a 30 mile contour,

you might as well apply with the FCC for a LPFM license, heres what you need to know.

73.811 - LPFM power and antenna height requirements.

(a) LP100 stations: (1) Maximum facilities. LP100 stations will be authorized to operate with maximum facilities of 100 watts effective radiated power (ERP) at 30 meters antenna height above average terrain (HAAT). An LP100 station with a HAAT that exceeds 30 meters will not be permitted to operate with an ERP greater than that which would result in a 60 dBu contour of 5.6 kilometers. In no event will an ERP less than one watt be authorized. No facility will be authorized in excess of one watt ERP at 450 meters HAAT.


I've typed enough on this.
8< snip >8

So what transmitter are you using?

And did you buy it as a part 15 FCC compliant unit or was there something you did to it to make it FCC Part 15 compliant? If the latter, what and how did you get it to be part 15 compliant?

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PMC wrote:

+ 1 dB Bretk, : )
----------------------------------------------------------------------------------------------------------
I'm not going down that road with the 100 watt transmitter, but with my 32 years of being a broadcast engineer all I have to say is, good luck

But, I like the Slim-Jim antenna myself, if your going to get inspected anyhow, do it with style. And the FCC will talk about your system for years when they train the new employees they will be hiring with the fines you will be paying

Or better yet get a 4-bay rototiller antenna, you will get more gain in dB and your light show will be picked up in a 30 mile contour,

you might as well apply with the FCC for a LPFM license, heres what you need to know.

73.811 - LPFM power and antenna height requirements.

(a) LP100 stations: (1) Maximum facilities. LP100 stations will be authorized to operate with maximum facilities of 100 watts effective radiated power (ERP) at 30 meters antenna height above average terrain (HAAT). An LP100 station with a HAAT that exceeds 30 meters will not be permitted to operate with an ERP greater than that which would result in a 60 dBu contour of 5.6 kilometers. In no event will an ERP less than one watt be authorized. No facility will be authorized in excess of one watt ERP at 450 meters HAAT.


I've typed enough on this. But here's what I am doing

My FM transmitter is FCC Part 15 compliant and if you want to hear what my "broadcast" sounds like just watch this video. the audio was recorded off of my portable FM radio jacked right into my camcorder. And look how far I am from the house and no static



Before anyone jumps on the LPFM bandwagon, it should be noted that an LPFM license cannot be issued to an individual or commercial entity.

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Orville wrote:

PMC wrote:
+ 1 dB Bretk, : )
----------------------------------------------------------------------------------------------------------
I'm not going down that road with the 100 watt transmitter, but with my 32 years of being a broadcast engineer all I have to say is, good luck

But, I like the Slim-Jim antenna myself, if your going to get inspected anyhow, do it with style. And the FCC will talk about your system for years when they train the new employees they will be hiring with the fines you will be paying

Or better yet get a 4-bay rototiller antenna, you will get more gain in dB and your light show will be picked up in a 30 mile contour,

you might as well apply with the FCC for a LPFM license, heres what you need to know.

73.811 - LPFM power and antenna height requirements.

(a) LP100 stations: (1) Maximum facilities. LP100 stations will be authorized to operate with maximum facilities of 100 watts effective radiated power (ERP) at 30 meters antenna height above average terrain (HAAT). An LP100 station with a HAAT that exceeds 30 meters will not be permitted to operate with an ERP greater than that which would result in a 60 dBu contour of 5.6 kilometers. In no event will an ERP less than one watt be authorized. No facility will be authorized in excess of one watt ERP at 450 meters HAAT.


I've typed enough on this.
8< snip >8

So what transmitter are you using?

And did you buy it as a part 15 FCC compliant unit or was there something you did to it to make it FCC Part 15 compliant? If the latter, what and how did you get it to be part 15 compliant?


As mentioned previously, part 15 compliance is not just about "adding a part" to make it compliant. It requires samples to be submitted to a certified test lab, submissions to the FCC, etc. Its not something an individual would do; it would be an effort the manufacturer would undertake.

Having a transmitter that might possibly meet part 15 compliance is simply that: a transmitter that might meet all the spec requirements to be compliant. Its a big difference, especially to the FCC.

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DonFL wrote:

Before anyone jumps on the LPFM bandwagon, it should be noted that an LPFM license cannot be issued to an individual or commercial entity.


I'm not asking for an license {but understand why you posted it}, just if they bought it already FCC certified (which he did not say certified, he said compliant), which do not mean anywhere near the same thing, so to me "compliant" means it may not be FCC Certified out of the box, but that he did something to make it more in-line with the FCC Part 15 rules and regulations so that it complies with them, but the unit may not be "officially certified".

So I asked my questions to get clarification to their meaning as to whether the unit is actually FCC certified or what was done to bring the transmitter to bring it into closer compliance with those FCC Part 15 rules, than to assume something incorrectly.

I would say my transmitter is compliant, but just can't say how compliant because I have no way of testing the antenna output that they appear to go by, and I doubt that the majority of home decorators have the tools/equipment to verify, or test that compliance either.

I brought mine into compliance by adding an 10dB/50-ohm pass-through attenuator between the transmitter antenna connector and the antenna itself. But I still can't really say for certain just how "compliant" to the FCC Part 15 rules are WITHOUT having the tools/equipment to verify it.

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Orville wrote:

DonFL wrote:
Before anyone jumps on the LPFM bandwagon, it should be noted that an LPFM license cannot be issued to an individual or commercial entity.


I'm not asking for an license {but understand why you posted it}, just if they bought it already FCC certified (which he did not say certified, he said compliant), which do not mean anywhere near the same thing, so to me "compliant" means it may not be FCC Certified out of the box, but that he did something to make it more in-line with the FCC Part 15 rules and regulations so that it complies with them, but the unit may not be "officially certified".

So I asked my questions to get clarification to their meaning as to whether the unit is actually FCC certified or what was done to bring the transmitter to bring it into closer compliance with those FCC Part 15 rules, than to assume something incorrectly.

I would say my transmitter is compliant, but just can't say how compliant because I have no way of testing the antenna output that they appear to go by, and I doubt that the majority of home decorators have the tools/equipment to verify, or test that compliance either.

I brought mine into compliance by adding an 10dB/50-ohm pass-through attenuator between the transmitter antenna connector and the antenna itself. But I still can't really say for certain just how "compliant" to the FCC Part 15 rules are WITHOUT having the tools/equipment to verify it.







My bad, not enough coffee yet this morning...or a typo on PMC's part...compliant..or certified? It may be one, or both, (or neither :shock:).

Compliant would mean operating the unit per the part 15 regs (i.e., field strength limit). And you are correct, it can be difficult to confirm for the typical user.

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DonFL wrote:

Orville wrote:
PMC wrote:
+ 1 dB Bretk, : )
----------------------------------------------------------------------------------------------------------
I'm not going down that road with the 100 watt transmitter, but with my 32 years of being a broadcast engineer all I have to say is, good luck

But, I like the Slim-Jim antenna myself, if your going to get inspected anyhow, do it with style. And the FCC will talk about your system for years when they train the new employees they will be hiring with the fines you will be paying

Or better yet get a 4-bay rototiller antenna, you will get more gain in dB and your light show will be picked up in a 30 mile contour,

you might as well apply with the FCC for a LPFM license, heres what you need to know.

73.811 - LPFM power and antenna height requirements.

(a) LP100 stations: (1) Maximum facilities. LP100 stations will be authorized to operate with maximum facilities of 100 watts effective radiated power (ERP) at 30 meters antenna height above average terrain (HAAT). An LP100 station with a HAAT that exceeds 30 meters will not be permitted to operate with an ERP greater than that which would result in a 60 dBu contour of 5.6 kilometers. In no event will an ERP less than one watt be authorized. No facility will be authorized in excess of one watt ERP at 450 meters HAAT.


I've typed enough on this.
8< snip >8

So what transmitter are you using?

And did you buy it as a part 15 FCC compliant unit or was there something you did to it to make it FCC Part 15 compliant? If the latter, what and how did you get it to be part 15 compliant?


As mentioned previously, part 15 compliance is not just about "adding a part" to make it compliant. It requires samples to be submitted to a certified test lab, submissions to the FCC, etc. Its not something an individual would do; it would be an effort the manufacturer would undertake.

Having a transmitter that might possibly meet part 15 compliance is simply that: a transmitter that might meet all the spec requirements to be compliant. Its a big difference, especially to the FCC.

correcting my typo: replace "compliance" with "certified/certification". Big big difference between the two terms in this context.

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certified, should have been the term. I noticed that when I submitted.

Also it was a joke about the LPFM, if you seriously think you need 100watts after all the people on this forum scream about this topic.

I have asked the powers the be that control this forum to give me a sticky thread just to post a simple things to remember chart, but it never happened. Sooo,

what do I use?

Teknique ICBM-136

I love this thing, I been using this unit since I started, but its been discontinued because this was a 40 channel, now they sell a 8 channel
I bought 2 more of the 40 channels when they were discontinued, look around on the net they might be available, or look the the 8 channel

ICBM136

check the frequencies it covers, you might get lucky

Also check this out if your looking to make your broadcast sound great.

Breakaway Audio Enhancer it costs $29.00, this is what I use

my whole FM "power plant" including processing was under $75.00

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PMC wrote:

My FM transmitter is FCC Part 15 compliant

Part 15 says that an FM transmitter must not exceed 150 μV/m measured at 3 meters [from the antenna]. How did you ensure that your system meets those requirements?

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Steven wrote:

PMC wrote:
My FM transmitter is FCC Part 15 compliant

Part 15 says that an FM transmitter must not exceed 150 μV/m measured at 3 meters [from the antenna]. How did you ensure that your system meets those requirements?

Its actually 250 uV/m but whats 100 uV/m among friends...:cool:

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DonFL wrote:

Its actually 250 uV/m but whats 100 uV/m among friends...:cool:

That's interesting. I found the 150 μV/m figure at GPOAccess.GOV. Could it have changed?

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Been 250 as long as I recall. Would have to go back and do some digging thru old files to get to the exact subsection.

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Surfing4Dough wrote:

Page 18:

http://transition.fcc.gov/Bureaus/Engineering_Technology/Documents/bulletins/oet63/oet63rev.pdf

What is the "periodic" transmission listed just above ours? I only transmit periodically (suspect it means something different though).


I guess this is what disqualifies us from "periodic" transmission:

§ 15.231 Periodic operation in the band 40.66–40.70 MHz and above 70 MHz. (a) The provisions of this section are restricted to periodic operation within the band 40.66–40.70 MHz and above 70 MHz. Except as shown in paragraph (e) of this section, the intentional radiator is restricted to the transmission of a control signal such as those used with alarm systems, door openers, remote switches, etc. Continuous transmissions, voice, video and the radio control of toys are not permitted. Data is permitted to be sent with a control signal. The following conditions shall be met to comply with the provisions for this periodic operation:
(1) A manually operated transmitter shall employ a switch that will automatically deactivate the transmitter within not more than 5 seconds of being released.
(2) A transmitter activated automatically shall cease transmission within 5 seconds after activation.
§ 15.231 Periodic operation in the band 40.66–40.70 MHz and above 70 MHz.

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Steven wrote:

PMC wrote:
My FM transmitter is FCC Part 15 compliant

Part 15 says that an FM transmitter must not exceed 150 μV/m measured at 3 meters [from the antenna]. How did you ensure that your system meets those requirements?

If you look at the attached pic you will see my transmitter on the left side and coming out of that box is a white wire, that's the antenna for that Part 15 transmitter, if you attach any other antenna to that white wire you are no longer compliant, so I wrapped the wire around a dipole (not attached to it) as long as you don't modify its FCC legal


Attached files 307610=16851-Box+Antenna.JPG

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so what you're saying, i think, is..you have a part 15 certified transmitter, have not modified it, so it remains certified, and so are assuming you are compliant, meaning, not exceeding the 250 uV/m limit.

But, you have not actually conducted field strength measurements to confirm?

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DonFL wrote:

so what you're saying, i think, is..you have a part 15 certified transmitter, have not modified it, so it remains certified, and so are assuming you are compliant, meaning, not exceeding the 250 uV/m limit.

But, you have not actually conducted field strength measurements to confirm?
there is a sticker on the back of my transmitter that says the FCC ID, which is good enough for me. (picture attached) you can see the yellowing of the paper to see how old this unit it is, this FCC certification ID sticker is equal to the UL sticker on electrical devices, which means it was tested by a company that approved it was Part 15

If you FM Transmitter doesn't have or provide a FCC ID number, chances are its not compliant, but if your willing to pay......

the Potomac Instrument needed to calculate the the field strength cost more than I'm willing to pay and that's the one that the FCC uses.

here's one for $300 (I never used it, probably never will)



Attached files 307644=16855-FCCID.JPG

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