Hi.
So recently I’m losing adsb signals on some aircraft that are close by and low (up to say 2,000ft) it has most recently done it this afternoon on Great North Air Ambulance helicopter G-NHAE ICAO 401141 it was tracking fine until it got east of my location then it just drops out but anything in the same area on mlat is fine
Does anyone have any suggestions what I can do, as I’m picking tracks up fine in the same area when they mlat
The signal is probably strong enough to overload your receiver.
The fix is to drop your gain but the price may be that your maximum range is reduced.
A lot depends on how often this occurs and how important it is for you to maintain track on low, nearby aircraft. If the occurence is rare, you could just keep the gain as is and live with the brief dropouts. If you want to follow the helicopters, then you will need to drop the gain.
As @geckoVN said there is a trade off with modifying the gain. I live smack under the approach for a secondary airport, so when in use I get waves of pretty strong signals hitting my receiver. There is a compromise in setting the gain to get some range, but also make a good fist of tracking aircraft overhesd.
Helicopters are difficult as they can loiter and are usually pretty low. When the local miscreants in my area kick off and the police helo is overhead, the gain to track it is 10-12 db down from what I normally use which would really crimp my range. I just wait it out and hope for a swift arrest.
I have dropped my gain and will monitor over the coming days to see how it goes.
Same issue again today it appears that piaware thinks an aircraft is tracking on mlat whereas it’s actually on adsb no idea why this issue has appeared
Not sure I completely understand the question, but I will try 
If I look at tracks for the helo you referenced (G-NHAE) most are a mix of ADS-B and MLAT. I guess the combination of relatively low flying aircraft and the challenging geography you have in the north of England (a number of flights cross the Pennines) makes getting consistent ADS-B positions difficult so Flightaware reverts to MLAT when necessary. FA staff are probably best suited to answer when/how/why they switch between ADS-B and MLAT.
I have had a play around and added some adaptive commands through putty, pretty easy to spot the time I had a local issue after the command kicked in it resolved.
This typically means a transponder or GNSS problem. We’ll only fall back to mlat if there is no ADS-B position data. mlat requires the same sort of reception as receiving ADS-B, so it’s likely to be a transmit-side problem.
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