So what section do you file for a minor change in?

[Radio Bob]

Sounds good. About the Jampro, I am imagining it is side mounted on a pole with an overall height of less than 20 feet above the building, as opposed to a larger pole or monopole. Presumably if you go vertical polarization you are thinking of a top mounted vertical element with radials. This could change antenna height, but you could account for this on the application. One thing is the typical vertical antenna will not have a grounded element, while the Jampro is grounded.

You might be happier with a top mounted vertical polarization antenna. However, the translator may not be experiencing circular polarization at its best, because the design type of the JLCP is an early implementation of circular polarization. More recent designs (including one Jampro makes) could provide higher quality circular polarization. That could be the crossed or bent dipoles or the helical.

Just want to make it clear I am not criticizing Jampro. It is the design type, not the company.

Is there a transmitter sizing or transmission line loss situation?

I'm going to use a OMB vertical with the pole side toward the ocean ( we are located along the gulf ) . I'll calculate the RF at the antenna required by the antenna then place a Bird meter at the antenna input and set the exact feed level allowed by the license right at the antenna input so there will not be any question of the exact erp. Then I'll work the math back word to determine the actual loss in the line and required TPO. Since I can easily reach the antenna this is more accurate than calculating it based on manufacturer line loss

 

[Kelly A]

I'm going to use a OMB vertical with the pole side toward the ocean ( we are located along the gulf ) . I'll calculate the RF at the antenna required by the antenna then place a Bird meter at the antenna input and set the exact feed level allowed by the license right at the antenna input so there will not be any question of the exact erp. Then I'll work the math back word to determine the actual loss in the line and required TPO. Since I can easily reach the antenna this is more accurate than calculating it based on manufacturer line loss

Not the way it's supposed to be done. The antenna gain at frequency should be a published specification. The transmission line manufacturer publishes the specs for velocity factor and loss. When you prepare the application, you use those specifications and calculate the ERP and associated TPO for the application based on those specs. That's what the FCC accepts, because you'll need to include those specs anyway, including antenna make and model. Most times using manufacturer specs actually create a real world advantage anyway.
This isn't the same as base current or impedance reading an AM. Measuring TPO at the antenna input doesn't give you useful information, certainly not as a way of determining antenna gain. Ultimately TX line, connectors, and all the associated impedance transformation is in play.

 

[Radio Bob]

Not the way it's supposed to be done. The antenna gain at frequency should be a published specification. The transmission line manufacturer publishes the specs for velocity factor and loss. When you prepare the application, you use those specifications and calculate the ERP and associated TPO for the application based on those specs. That's what the FCC accepts, because you'll need to include those specs anyway, including antenna make and model. Most times using manufacturer specs actually create a real world advantage anyway.
This isn't the same as base current or impedance reading an AM. Measuring TPO at the antenna input doesn't give you useful information, certainly not as a way of determining antenna gain. Ultimately TX line, connectors, and all the associated impedance transformation is in play.

So your saying use the specs provided by the manufacturer for the transmission line at the proscribed length and the specs provided by the antenna manufacturer for gain as opposed to actually measuring them? Sure, why not, less work

 

[Radio Bob]

So your saying use the specs provided by the manufacturer for the transmission line at the proscribed length and the specs provided by the antenna manufacturer for gain as opposed to actually measuring them? Sure, why not, less work. BTW of course we are talking FM here not AM

 

[Kelly A]

So your saying use the specs provided by the manufacturer for the transmission line at the proscribed length and the specs provided by the antenna manufacturer for gain as opposed to actually measuring them? Sure, why not, less work

Manufacturers specs are usually based on losses and velocity factor at 10 or 100ft lengths at that frequency. There's usually a table or chart showing the frequency, velocity factor, and loss depending on length. The Commission will accept those published specs in an application, as it relates to your proposed installation.
My comment that you don't measure input power, let alone in an attempt to determine line loss or antenna gain for FM at the antenna input. It isn't the same as measuring base current at the feed point of an AM antenna.