DXCC #196 on 6m: FJ

With quite a bit of luck (just checking the band between dinner and bringing the kids to bed) I was able to work FJ5DX, St. Barthelemy, for my 196th country on 6 meters. Wow ! That was a long time ago I could add a new one to the log … Heard him for about 10 mins with 55 signals.

Sporadic E season finally started at full steam

After a really slow start, the 2008 sporadic E season took off last week with some nice openings. Also yesterday and today (24/25 May) the band was wide open. Over the last week the following countries made it into the log: SV, E7, LZ, CT, EA, UR, YO, YL, HA, YU, F, OH, SM, SP, ES, GM, G, GW, EA6, EI, UA, 4L, LY and OJ0.

My antenna performs well so we just have to wait for some long haul Carib openings now in order to try and hit the 200 mark (5 to go). With JW, CY0, FJ, V3 and HK0/S expedition by the end of June + maybe VP9 or another Carib new one (J3 or VP2M) it is theoretically possible to do that …

1.2 WL 6m Antenna – part 3: it’s up !

Today (blue sky, record temperature for the day of the year: 28 deg C) I have put the antenna in the mast. Quite a job because the D3040 combi dipole had to be removed first. That antenna will be deployed again in September or so when the 6m season is over.

The boom-to-mast clamp for the 6m beam is a PIA35JXX cast aluminium piece made by I0JXX. However, the casting appeared to be of very bad quality. It broke and the fracture clearly showed an air inclusion in the cast explaining the clamp weakness.

So a quick replacement was made with a piece of stock angle aluminium and a muffler clamp saddle. Probably a lot safer anyway …
(Meanwhile I0JXX confirmed the air bubble issue and promised to send a replacement: good service !).

So there it is, my shiny new 6m yagi …

Now, where is that sporadic E ??

1.2 WL 6m Antenna – part 2

Yesterday I fine-tuned my 6m antenna. The YO PROGRAM predicted that elongating the driver would increase the resonance frequency (contrary to normal dipole behavior …). So 2mm extra on both sides of the driver yielded the following SWR plot with the miniVNA.

Nice to see that theory coincides with practice ! Here is the SWR prediction of YO (hor. scale: 48.6 to 50.5 MHz, vert. scale: SWR 1 to 2).

Here is the YO file of this antenna:

PF5X 6-el 50 MHz yagi
Height 20500.000
50.000 50.150 50.300 MHz
6 elements, millimeters
12.0000 10.000
0.0000 1475.0000 0
800.0000 1390.0000 50.000
1645.0000 1385.0000 0
3290.0000 1350.0000 0
5385.0000 1335.0000 0
7150.0000 1330.0000 0

It is basically a DK7ZB design with the position of the driver slightly modified in order to tune the antenna to 28 ohm. WIth a quarter wave stub (2 x 75 ohm coax in parallel) the impedance is transformed to 50 ohms.

The max. gain is predicted to be 18.2 dBi @ 20.5 m above ground level and 4 deg radiation angle. Here are some radiation plots.

(plots generated by 4NEC2 v5.7.2 by Arie Voors)

Tomorrow the yagi will be put in the mast. Let’s hope there is some sporadic E propagation then to test drive this antenna.

1.2 WL 6m antenna – part 1: test set-up

My slightly modified DK7ZB 6 element 6 meter Yagi design is almost ready for use. Today I have put it on a small mast about 4.5m above the ground. Using a miniVNA (see screenshot of measurement result below) it seems the antenna is close to being spot-on. The SWR is 1.05 at best around 50.105 MHz, whereas the design target was best SWR at 50.150 MHz. YO showed SWR 1 when correctly matched to 28 ohm. So bit of tweaking should do the trick; a matter of a few millimeters …