Topband: DX Engineering RX 4-square - what we found out - a bit long

[Carsten Esch]

...

First: We (DL4LAM - Peter, DL6LAU - Carsten, SM6CNN - Anders, SM6CMU -
Ingemar, SM6DOI - Staffan,) are not connected to DX-Engineering in anyway -
in fact it was the first time I 'went shopping' at DXE ...
But: As both SM6DOI and me are selling amateur radio products here in
Europe, we are always looking for products to distribute ;-) ...

As early adopters, DL4LAM and I were very interested in the RX 4-square from
DXE. Somewhere (on the Internet?) there was the claim it will work like 240m
long Beverages but will 'only' need a 41m x 41m footprint for optimum
performance on 160m.
Unfortunately there were not many 'real-life' reports found.

2 weeks ago DL4LAM and I placed the order for an

- DXE-RFS-1P Receive Four Square with Controller
- DXE-ARAV-4P Active Receive Antenna, vertical configuration, pack of 4
- DXE-RPA-1 (optional preamp)
- some small stuff like connectors and the like ...

Than the big question for me (living on a 30mx30m lot) was were to put them
to try ... To make it short ... I decided to visit Staffan, SM6DOI close to
Gothenburg. Staffan is well known for his 160m expertise, he has a 50m tall
vertical to transmit (very close to the Baltic Sea (Swedish West coast) and
8 Beverages for RX.

In detail these are

0°	    180m long
60°       180m long
120°      240m long
180°      200m long
240°      240m long
300°      200m long

All up 1,5 meters, 9:1 ferrite balun, terminated with 460 ohms, Ground rods
are one meter at the terminated side and three metres at the feed point. All
coax is RG58. Ground under the antennas is wet blue clay.

Uli, DJ2YA was kind enough to measure the exact velocity factor of the used
RG-6 coax (0.84 in our case) so I could cut the delay lines as explained in
the manual (you can download these from DXE if you need more details) and
installed the so called 'Snap n Seal' connectors - btw - these connectors
are great an so easy and quick to assemble, never saw them b4 in Europe ...

Thursday morning I loaded the car and drove about 700km to meet Staffan. He
and SM6CMU had already prepared some wooden pallets (still a lot of snow on
the frozen ground in SM) with a short aluminium tubing for the active
vertical elements. They also had positioned the palettes that the side
length of the 4-square was 135ft (41.15m) and that 2 of the elements were
pointing to 310° (resulting in 40°, 130°, 220°for the other directions).

A 1m ground rod was used at each vertical. When I took out the 102in (2.6m)
'long' whips Staffan and Ingemar were looking rather amazed. This should
work like a 240m long Beverage - hard to believe ...

The RX4SQ was positioned about 100m from the shack and about 200m from the
TX antenna. One of the Beverages was close to one element of the RX4SQ
(within 3m or so) and an unused 10m tower was about 20m away. Other than
that the 4SQ was on an open field ...

The installation went very quick. Back in the shack we had an ORION I and a
box were the Beverages could be selected. The same box had another RX input
and we connected the 4 position switch for the RX4SQ to this input. This
allowed us to instantly switch between the 2 antenna systems for A - B
comparison.

As it was still daylight we checked the performance on the OK beacon on
1854kHz. The result was amazing. The F/B of the RX4SQ  was very good
(25-30dB) with a very clear forward lobe. Ok, it was still daylight,
probably it will only work nice at day ;-) ...

But also when dawn came, we had the same results ... The signal output of
the RX4SQ was lower than the Beverages but there was not a single case were
the RX4SQ would have lost a QSO compared to the Beverages. We than tried the
optional preamp from DXE and signals got stronger (with more or less the
same SNR). It was more a personal taste ... I liked the 'stronger signal',
some others from the test crew didn't ...
We only made a handful of contacts during the first day of the contest
spending hour after hour comparing the Beverages against the RX4SQ.
We compared the antennas quite some time on signals from NP4A, PY7ZY, 6O0N,
VP9I, KG4SB, 9N7JO, PJ2T, HA7TM/HI9, HS0ZDJ, W's, JA's and the result was
ALWAYS the same ... The difference was VERY SMALL in most cases, sometimes
the Beverage was 'a little bit' better, sometimes the other way round. Very
often there was really no difference.
The second contest night brought the same results. After sunrise we
disassembled the RX4SQ and I took another 8 hour drive back home where I am
just typing this as the contest will last another 3 hours ....

So talking about the comparison at the SM6DOI QTH, the RX4SQ worked like
advertised and MUCH BETTER than we all thought. One might say that maybe
Staffans Beverages do not work well but looking at his results on 160m I
think they work (quite) good (on his very good ground). Maybe it was an
advantage to have the RX4SQ on very good ground also ...

There would have many more tests possible but a long weekend is just too
short ... We thought about reducing the side length in the second night to
70 feet and see how the system works with this spacing but this would have
caused some more work in cutting the delay lines to the new length. 'Social
commitments' did not make this happen - maybe next time ....

We did some listening on 80m and 40m too and 80m seemed to perform very well
with the spacing we used too. On 40m the directivity was very low but the
array was still very good on receive (always compared to the above mentioned
Beverages)

For us, the performance was truly outstanding for 4 phased 2.6m long whips.

Hope that all the details did not bore you, we wanted to give you some more
insight about the installation rather than saying

"THE DX Engineering RX 4-SQUARE WORKS GREAT" ... (although this would have
said it all)

Well done Tom and DXE ... Maybe I will add some more thoughts later ...

We enjoyed listening to your signals (no VK, ZL, W6 heard here)! I will
gladly answer questions about 'our installation' and the like if you have
some ...

Regards,

Carsten, DL6LAU (and DL4LAM, SM6CNN, SM6CMU, SM6DOI)