Datalink signal and low altitudes

[bop1701]

Afternoon - 

      When flying low altitude in mountainous areas (terrain masking) datalink symbology often dissappears from the HSD.  I'm assuming terrain is blocking the signal.

     Is there an indication on the HSD or elsewhere when the datalink signal is lost?

Thanks in advance again!

[silverdevil]

3 hours ago, bop1701 said:

Afternoon - 

      When flying low altitude in mountainous areas (terrain masking) datalink symbology often dissappears from the HSD.  I'm assuming terrain is blocking the signal.

     Is there an indication on the HSD or elsewhere when the datalink signal is lost?

Thanks in advance again!

i do not know if it is modelled in DCS. but as an example, TACAN in DCS and real life the AC has to have LOS to the transmitter. so i am guessing LOS is also the issue in your case.

[darkman222]

How is datalink transmitted in real life? Radio signals bend around mountains and objects depending on wave length. Its not a laser that needs line of sight.

[silverdevil]

3 hours ago, darkman222 said:

How is datalink transmitted in real life? Radio signals bend around mountains and objects depending on wave length. Its not a laser that needs line of sight.

https://www.wbdg.org/FFC/AF/AFMAN/134465_TACAN_Air_Navigation_Station.pdf

https://en.wikipedia.org/wiki/Ultra_high_frequency

"Radio waves in the UHF band travel almost entirely by line-of-sight propagation (LOS) and ground reflection; unlike in the HF band there is little to no reflection from the ionosphere (skywave propagation), or ground wave."

[Dragon1-1]

Yeah, longwave radio bends around mountains, UHF and VHF (so pretty much all aircraft comms) does not. If you ever tried to listen to the car radio while driving through mountains, you might have noticed terrible reception in some spots (unless you were listening to an oldtimey AM station, which doesn't have this problem). 

[bop1701]

Yes, it's line of sight.  But is there something on the HSD or elsewhere that indicates when datalink signal is lost?

[Raptor9]

1 hour ago, bop1701 said:

But is there something on the HSD or elsewhere that indicates when datalink signal is lost?

The "datalink signal" is not a continuous, singular signal; like when your phone indicates signal reception from a cellphone tower. The datalink is composed of discreet radio microbursts of data that are periodically transmitted from various units in the battlespace, which are then processed and displayed in the cockpit based on the data contained within those radio microbursts.

There is no indication in the cockpit when the radio signal from Air Traffic Control is lost because there is no continuous signal being broadcast from a single ATC tower. In similar fashion, there is no indication in the cockpit when datalink is lost because there is no continuous datalink radio signal being broadcast from a single unit in the battlespace. If line of sight is lost between your aircraft and a unit transmitting information across the datalink channel, the information received from that particular unit is simply no longer received, just as if you can no longer hear the voice radio transmissions from that unit while still hearing all others on the same frequency.