Ian is more interested in differences between the two systems across the whole day. I am more interested in long path, especially morning LP propagation, when very low angles are likely to be more important.
 |
| Beach set-up on an earlier outing. Hint: use a Raspberry Pi system for WSPR, not a laptop! |
Indeed, this is what the results show. Across the whole day, the two systems typically return about 1dB or less difference in signal (in favour of the low angle, VK3QN system).
But, at morning long path (Wales), the difference in favour of VK3QN becomes more like 3dB, as it did this morning.
But, of course, this does not allow for the fact that VK3QN has eight fewer elements in operation than VK3MO. To my mind, that means the smaller array of VK3QN is, regardless of time of day, doing very significantly better than VK3MO (noting that 'smaller' is huge by most people's standards - a 2 x 6 element 14MHz array!)
With Ian's consent here's the fabulous VK3QN, fixed long-path system:
Anyhow, here are the latest results, probably the last for a while now. Coast data are the two strongest curves (labelled (C)), and my slightly inland delta loop the lowest two curves (labelled 'I'). Note the enormous difference between coast and the delta back home, peaking at 19dB (power factor of nearly 80 times) stronger at the coast! Because the delta has a measured 6dB more gain than a 1/4 wave vertical (a delta is essentially a close-spaced, phased pair of verticals), the real difference is more like 25dB! Note that this kind of gain is probably only available for this path, at this time; it's likely to be significantly lower for other DX outside of long-path time.
 | |
| Are you blighted by RFI back home? Why worry? Even a quiet rural area is rubbish, compared to the coast! |
 |
| Same (inland) site comparison of 1/4 wave vertical and full-wave delta loop at 14MHz for the reception of long path signals from VK3QN. |
The propagation that leads to all this is revealed, probably quite accurately, by Proppy HF, but is a little different to what one would imagine. If you compare this with a plot of the antipodean point from VK3MO, which is not far from the Azores, then the propagation is seen to centre there; no doubt, there are complex paths, including antipodean focussing, present.
 |
| Proppy HF prediction of propagation at 07:00UT today. |
 |
| Antipodean point to VK3MO/VK3QN |
For the record, here's a plot of all the main stations heard (V51 heard only once, hence no line):
4 comments:
Wow, a huge difference John. The question is....is it not a difference between different computers/radios? If both were identical... might be a stupid thing to think... I really want to do this comparisation myself sometime. Although I don't have identical radio/computer as well. Food for thought....73, Bas
Hi Bas. It's a very important point. The two RX stations are not the same in many ways: (1) The 1/4 vertical has 2-3dB less 'design' gain than the delta loop. That makes the results even more astounding. (2) The RX at coast is Raspberry Pi running WSJT-X, but at home it's a Win10 laptop running the same software (there is no difference in reported SNR between that and JTDX, however). (3) The RX rig at coast is a Kenwood TS480, and at home, a Yaesu FT-450. I do now have another Raspberry Pi, but that is a model 4B, whereas my coast unit is a 3B+. The theory of ground losses and conductive grounds means little or none of the difference in SNR is due to system differences. Unfortunately, I am not a millionaire private researcher, so I cannot accommodate all these possible avenues of difference!
John, just for the record... Could you do a test again at your home QTH. With your mobile setup at your home QTH as well. Just to see if there is much difference between the 2 systems. "Design" gain doesn't say anything in real world experiments. This way you can extract the differences from the tests you do on 2 locations. 73, Bas
Already done. More data to make it more robust later - very tired!
Post a Comment