Re: DGRD
From: John G4SWX
Date: Sat, 20 Jul 2024 20:53:09 UTC

On Fri, Jul 19, 2024 at 05:06 PM, Earl Shaffer wrote:

    I normally see a significant difference between the VK3UM EME planner vs WSJTX. I'm not sure which one is more correct for me.

It all depends upon how the antenna noise temperatures are calculated.
ON 144MHz, WSJT-X and MAP65 agree as you might expect, however, they disagree with WSJT9 & 10. I guess Joe reworked the algorithm.
I seem to remember that it is currently calculted in 15 x 15 degree sectors. (I keep wondering if using the algorithm that Joe uses for the background would give more realistic G/T calculations than the 'pick two numbers' method.)
They both disagree with VK3UM planner but Doug(SK) wrote this a very long time ago and the 400 > 144MHz conversion algorithm is a little problematical.
 
On 144Mhz the sky temperature is by far the most important factor but many do not realise this number because of their antenna sidelobes are seeing something far more noisy, eg. ground, sun or the galactic centre. 
These simple calculations do not include ionospheric depolarisation and this loss can be significant, particularly at low elevations during the daytime in the summer months.
 
DGRD is a very broad yardstick: on 144MHz if it looks low you will probably do a bit better than when it is high. Less than 5db seems good to me.
 
John G4SWX