Comet cha-250b better near ground vs up at 25' on house??

[M0GVZ]

Folks,

I was doing some testing of a CHA-250B.

Initially I had it about 30' from the house near the ground attached to a metal fence post. I had it this way because I was testing it in comparison with a fan dipole with an A/B switch to compare the two.

The fan dipole was mounted on a mast on the top of the house roof at around 25' high. At the top of the mast is a dual band 2m/70cm vertical. The fan dipole was mounted offset a few feet from the mast with a non-conductive mount.

Interestingly, the CHA-250B vertical was getting better signal reports than the dipole. Weird, but this was on the receive also - I noticed several S units difference.

I took down the fan dipole yesterday and placed the CHA-250B on the mast feeding it with LMR240.

Now, I'm seeing a lot of noise. On 20m I've got S7 of noise and my signal does not seem as good as before, such as when listening for the beacon stations.

Makes perfect sense. The lower to the ground it gets the more NVIS the antenna becomes so you hear closer stations stronger. Raise the height and it starts hearing more distant stations stronger and closer ones weaker.

Also nearer the ground you get more ground loss which results in weaker signals but it also attenuates noise as well. One of the best receive antennas is a beverage antenna which is several hundred feet long only several feet above the ground and actually has the end of it put in the ground. The losses atennuate the unwanted noise more than the wanted signals.