How much rf can I cram into RG8U?

[captbob92]

I've got a project in which there is a 75 foot run of RG8U transmitter to antenna. Not the cheap stuff, this has foil, brad etc. I'm running 300 continuious watts through it at 98.1mhz . From day one it runs very warm to the touch. I'm seeing only a slight reflected power. I always thought RG8U would handle up to a kilowatt continuious and have in fact used it for temporary AM transmission with little heat.

So here's the question, is this heat normal at that frequency and power level? If not I can probably squeeze a half inch line in place of the RG8. Could you reccomend a 1/2 inch relatively flaxable cable as a substitute? There is a relatively sharp 90 degree turn in the run ( 2 feet radius tops)so it would have to be bendable.

Thanks in avance for any suggestions

[Deep Thought]

It works fine at AM frequencies "up to a kilowatt" because the losses are a lot lower (2%, or around 0.15 dB/100 ft). At FM frequencies you are losing around 30% of the input power in the coax (1.9 dB/100 ft), and that power is converted to the heat you are feeling.

The real question is what "project" would run 300 watts at 98.1 without using the proper cable (1/2" Heliax type)?

[captbob92]

Its a translator. I had originally hoped for a short run of coax but construction issues and the landlord extended it obviously too far. So any particular type of coax do you reccomend?

[Deep Thought]

Considering that you can get RFS LCF12-50J 1/2" Foam Coax for about a buck thirty per foot I have a hard time believing that there is not enough money in the budget to do this right.