ULDXIndex and MWDXerDB V22.03

Paul Blundell

I would not think so, I have found that the time of day is a bigger factor.


On Fri, Mar 11, 2022 at 2:24 PM James Rohrer <Jim.rohrer1955@...> wrote:
Do you expect the ULI scores to be lower during the spring and summer?

On Thu, Mar 10, 2022 at 9:20 PM Paul Blundell <tanger32au@...> wrote:

The latest version is now online:


The change log includes all the changes since 22.02.


Gary DeBock

On Thu, Mar 10, 2022 at 07:24 PM, James Rohrer wrote:
Do you expect the ULI scores to be lower during the spring and summer?
I think it's time for a reality check here.

Long range DX is very dependent on seasonal changes, especially transoceanic DX on medium wave. For example, here in the USA I can routinely receive transoceanic DX from Asia in the fall, and from Australia in the spring and summer.

What Paul is doing is receiving the same eastern Australian stations over and over, which can be routinely received by anyone with a radio at night in his location. Everyone is free to choose the style of DXing they prefer, of course, but if you are interested in long range and/ or transoceanic DX on medium wave, you will need to learn the seasonal propagation changes in order to have much chance of success.

Gary DeBock (in Puyallup, WA, USA)

Jorge Garzón <iberiaDX@...>

When I introduced back in april 2021 the ULDX Index I wanted to get a math value (an Index) easy to be recognized internationally, obtained in a quantitative way, as always numbers show. Under these premises, experienced DXers face the challenge: distance and power of a given station. To achieve a difficult DX we experiment, design antennae or choose a vantage spot to hear weak signals. How difficult is DXing a station with an UL receiver? That's the value shown by the Index: the higher the score, the most difficult challenge to face! 

The way to calculate is easy: D (distance, km) / W (power, watts). 

Thee is also a world recognized code to show a signal quality: the SIO and SINPO codes. Scored from 1 to 5 gives an idea of the listening conditions:

S: Signal strenght, I: Interference (QRM), N: Noise (QRN), P: Fading, and O: Overall quality. 

Signal strenght can be accurate with a signal meter, but a few ULR have implemented them, and those with give erratic readings. 

Interference can vary in very short distances or depends on electronic devices around. 

Noise increases or decreased according to regional conditios or meteo conditions. 

Fading is related to surroundings, combination of waves and propagation itself. 

Overall signal is a combination of the former ones and includes the subjective sensation of listening comfortability. 

Quality of the signal values have then more to see with QTH conditions, meteo, or qualitative aspects. Use them as ULDX index modifiers would distort a quantitative math index. That's why they are not included as a part of the index score itself and that's why SIO/SINPO was implemented by DXers many years ago. 

Of course DXers can achieve the challenge as they prefer, but in my opinion the way to calculate the index should be kept in a quantitative method as this is a global way to compare by numbers the challenge to get that wanted DX with an ULR. 


Paul Blundell

Fair point and clearly I have misread the feeling of how this should work.