At 30 MHz, you're right at the border between HF and VHF. Below about 30
MHz, atmospheric noise dominates, and reducing the coax loss will make
no difference at all in your ability to hear signals. Above about 30
MHz, receiver noise dominates, and reducing the coax loss 2.5 dB will
make an improvement, the amount depending on the relationship between
the receiver noise figure and the atmospheric noise. But the boundary is
fuzzy, so right at 30 MHz it's probably a toss.

But here's a very simple test you can do which will give you a
definitive answer: Tune the receiver to a frequency where there's no
signal, and disable the squelch if it has one so you can hear the noise.
Then disconnect the antenna from the receiver. (With some receivers you
might have to replace the antenna with a dummy load rather than just
disconnecting it, but that isn't usually necessary.) If the noise level
drops when you disconnect the antenna, reducing coax loss or otherwise
improving antenna efficiency won't make any difference in your ability
to hear signals. If the noise doesn't drop, then efficiency improvements
will improve your ability to hear signals.

Roy Lewallen, W7EL

Robert11 wrote:
Hello:

Don't have a good feeling for the significance of this:

For a receive only application, using coax from the Balun of a simple
outside antenna to the receiver,
is a loss of, e.g., 2.5 db "meaningful" ?

Specifics would be 100 feet of RG 58 at 30 MHz

Or is it worth the extra $ to go to a less lossy coax (application would
always be for receive only)

BTW: R/S Coax a decent quality ?

Thanks,
B.