Inconsistent bearings, often 180 degrees off

1

I have a 5 element Arrow antenna about 8 meters above ground and 1+ meter above the highest side of the roof.

Some days, I see near perfect results across 6 known, fixed location transmitter sites, mostly DMR sites sending beacons every 70 seconds or so.

Today, I see the DOA display fluctate a lot during the brief beacons, frequently ending on an about 180 degree in the wrong direction.

I have previously had a dual band 2m/70cm colinear antenna on a second fiber glass mast about 2 meters from the Kraken mast - and at the same height. Suspecting this, I have now lowered the dual band antenna to a point where the top is about 1,5 meters below the bottom of the Kraken antenna.

Today is windy, both mast waving a bit, but not excessively.

Could the second mast still cause interferrence due to the proximity to the Kraken antenna ? -and is motion of the antenna a serious factor - guessing, that it should not have a great influence, as all 5 elements move together - and the waving of the antenna is quite a bit below the speed of light :slight_smile:

Any hints on improvements ?

Regards

Michael

2

How long is the signal burst duration? It could be that it’s locking on to noise or some other signal if the burst is very fast.

But yes the second mast could be interfering, but I wouldn’t expect it to cause a bearing a full 180 degrees off. If you’re running on a fast device like a Pi 5, you could try increase the FIR order on the VFO to better filter out other nearby signals.

3

Burst is pretty long - actually a beacon of about 5 seconds every 70 seconds.

Plan is:

  1. Raise antenna about 2 meters higher, getting clear of other metal objects
  2. Upgrade to Pi5 if needed - currently I use a 4

Apears that windy days with both masts waving can introduce errors too

Regards
Michael

4

DMR has two time slots. If the TX is only using one slot the transmission will be 30 ms on and 30ms off.

5

Agree, but the Kraken device do not demodulate DMR as far as I know, so it is likely received as one long transmission of close 60 ms bursts.