I read somewhere that the a reasonable power level for a twinlead J-pole is 5W, and several claimed to have run 25-30W without problems. The twinlead might be the limiting factor, although I'm not really sure why it would be. Intuitively, I would not expect it to be a problem for over 100W.
RG-174 is a crappy choice for a feedline. We use it at work quite extensively for internal module connections, even up to 1 GHz, but these runs are typically low power and very short (usually <1 foot). It does have good shielding properties.
Power handling capacity is around 60W @ 400 MHz. Perhaps I could just use a piece of RG-8X (mini8) or RG-58 instead? After all, I'd be using that for the feedline anyway.
And you might be right. Why would I build more than one of the same? When I was building some antennas for the 1.2 GHz band, I built one 1/4 wave whip, two dipoles, and one bi-quad, just so I could measure the relative gain of each pair used in a somewhat controlled setup (a spec. analyzer and transmitter ~20 feet apart in an open room). From that, I measured ~9 dBd gain for the bi-quad.
RG-174 is a crappy choice for a feedline. We use it at work quite extensively for internal module connections, even up to 1 GHz, but these runs are typically low power and very short (usually <1 foot). It does have good shielding properties.
Power handling capacity is around 60W @ 400 MHz. Perhaps I could just use a piece of RG-8X (mini8) or RG-58 instead? After all, I'd be using that for the feedline anyway.
And you might be right. Why would I build more than one of the same? When I was building some antennas for the 1.2 GHz band, I built one 1/4 wave whip, two dipoles, and one bi-quad, just so I could measure the relative gain of each pair used in a somewhat controlled setup (a spec. analyzer and transmitter ~20 feet apart in an open room). From that, I measured ~9 dBd gain for the bi-quad.