Coax Upgrading

[Secret Squirrel]

I posted a thread yesterday asking about the coax length to use with an amp. I wanted to thank everyone for his/her comments. I am using a 1/2 wave GP that was NIB from the 80's, kinda likes like a Starduster without the support rods, with 50 feet of RG8/U also NIB from the 80's. The antenna is set 15 feet on an 2 inch black iron pipe. It is grounded with #4 unshielded copper wire from the antenna mount to an 8 fight grounding rod at the mast base. Total cost in this setup was 70.00. 15.00 was into getting new ends on the coax and 24.00 was for the #4 copper wire. I get zero noise from my house. The SWR was 1.3 on 1, 1.1 on 19, 1.2 on 40. If I disconnect the copper ground wire I will get static across the band and SWR goes to 1.6. After reading the comments from my previous thread I decided to tune the coax to the correct length for the Velocity Factor of RG8/U which is 0.80. I calculated that 58 feet is two full wavelengths for channel 19. I did not have an 8 foot jumper, but I hooked up my SWR meter using a 9 foot jumper RG8X and the SWR was between 1.1 and 1.2 across the band. The longest base to base contact I have made barefoot is about 27 miles. All the locals run IMAX 2000's. My question is what real world experience has anyone had upgrading coax. I had sent an small amp, Palomar Elite 300, away to Clay's to be tuned with a Uniden PC66XL, Philippines made, & an Astatic 636L. My coax and antenna should be able to handle 1000 watts, but to be conservative I was not planning on trying to run more than 500 watts through this setup. What improvements can I expect by upgrading the coax to a modern type coax with a foil shield and non-PVC coating?

[drdx]

Coax length, other than the more you use, the more the loss, can be any length and work fine.

Upgrading coax may help minimize the loss and if your old coax is very low quality, you may see a slight increase in performance, and better shielding for TVI, etc.

27 miles is not bad. I'm assuming that antenna is 1/4 wave from the feed to the tip. The Imax is a 5/8 wave with, in theory 3db gain, or in plain terms, it effectively doubles transmit power over a 1/4 wave design. You said 1/2 wave, is that from tip top to the bottom of the sloping radials, or just the radiator. A starduster was only 1/4 wave (9 ft or so) from feed to tip. Also note, the drooping radials can be a TV interference factor.

-drdx

[209 first class]

i would say the better coax (lmr 400 has 100% shield, whereas 213/rg8u only have 95%) will give you a tiny tiny less bit of signal loss, but with that short length, you probably will not notice it. i have read the 100% shield will help with tvi / interference, but this doesnt make total sense to me since the tvi ect travels on the outside of the shield. so the jury is still out on that one... if you have no interference the benefit is with the less signal loss. tip for your setup: if possible, get the base of your antenna over 18 feet. this is a half wave of the operating frequency, being so close to the ground, the earth soaks some of the radiowaves up before they get out of the antenna in a complete wave. 18 ft is the bare minimum. most antenna radiate near the base. 36 feet will definitly give better performance. (one wavelength) i bet at 36 feet, you will do 40 miles with the same coax. 2zero9