Coax loss on Ham frequencies

  

Below on the coax loss chart you will get a very nice representation on coaxial loss on the ham bands depending on which one you are using or plan to use.

  

In this table, you will notice that anything above 5dB has been left aside. As a matter of fact, at 3dB loss, you are loosing 50% on your incoming signal and also of your transmitting power. At a 5dB loss, you are around 70% attenuation! For this reason it is not at all practical to use these coaxial lines for anything above 3 dB on any selected band. I for one, want to keep things below 1.8dB if at all possible and cost efficient! That is my goal on all bands even if my current setup is giving me higher rates at this time, when all is finished, i should see a clean improvement. It's clear to me that investing in low loss transmission lines, good connectors and good antennas can make a 10W setup much better than a 100W rig with an amplifier hooked up to a wire! Think about it! 

  

**Less loss = better receive and transmit. It works both ways. Many operators bother with BIG amps, but have no receive ability thus they can be heard but cannot hear!

  

Here is a Chart I made to help compare coaxial loss in function of the frequency used. This helped me select the appropriate coaxial cable to use in regards to loss but i also had it crossreferenced to cost. From there you can find out what is the best value for your money. In this chart i removed the $$ cost because of a big price increase in the last few years and it is no longer properly representing the real cost. 

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

After analysing all the factors, sometimes for a few tenth of a dB, costs explodes! You might want to think about stacking instead of spending so much on the coax, as you will gain more dB and more value for the money. Simply adding an extra stacked antenna you should gain from 2dB - 3dB if stacked properly. So yes coax is very important, it's just that sometimes for more gain, it's better to stack dollar for dollar! It's all about best performance to price ratio you can get! If money ain't a problem, Stack and get yourself the best possible coax + a preamp!   :-) For the rest of us, do the math!

  

Something to think about also is the use of mast mount preamps. These will come in handy to bring down loss to 0dB and also bring down overall noise figure in your setup as the weak signal is preamplified before travelling down the coax. The amplified signal is sometimes as high as 20dB Gain! The smaller the coax length between the antenna feed point and preamp, the better, as this prevents loss and added noise. Some have noise figures of <1dB on 144 and other LNA's are down to <0.4dB! These are great figures and really can help you hear a lot better as the signal arriving at your radio is stronger and cleaner. Don't forget though that this only works on RX! Hummm......stacking.... did you say stacking?? Maybe for the price, that is better but keep in mind you are still introducing noise in the line with coax length down to the shack.

  

© 2015 VE2NRG Sean Magowan

VE2NRG's Amateur radio station

Created with the QTH.com SiteBuilder.