Ian Jackson wrote:
My immediate lateral-thinking guess is that the OP has acquired some
RG6Q, and is wondering whether he can use it as antenna drop cable for
UHF TV (which, in the UK, includes HD). He has specifically said that
it's for use at less than 1GHz. His main concern is probably that
quad-shield might be a more lossy than RG6 (which indeed it could be as
a smaller diameter dielectric would require a smaller diameter inner in
order to maintain a Zo of 75 ohms, and this would increase the
attenuation). Of course, he could also be concerned about some of the
many other parameters - but I suspect not. If it's not attenuation
that's concerning him, I'm sure he will tell us.

This was my understanding as well. But he reverted to shouting and
indicated that we have all misunderstood him.

He asked about the performance. As he was pointing to loss, I would
guess he would like to know the performance w.r.t. loss. But as he
also indicated a use case, I think he wants (or needs) to know if the
loss is not too high for the use case he has.

That cannot be determined given the info there is. We need to know
what margin he has on the signal and how long his cable run is.
The margin is determined by the type of signal (terrestrial, cable,
satellite, we can rule out satellite because he said 1GHz). When
terrestrial, we need to know how close he is to the transmitter.

Even with all such general information, it probably is not possible
to close in enough on the calculation to know if a couple of dB or
so of extra loss per 100m is going to affect the performance of the
system.