Friday, 22 April 2016

EP2A in the log - ATNO

100W CW - 19:30 UTC - S9 (no preamp) - great signal on my doublet here and not that busy.
4.5up ... 4th call in the log. Happy days!

This makes my 158th DXCC [most QRP/LP and wire antennas]

Update: Easy to work on 40m on Sat night at 23:50z

clublog Expedition status

Monday, 4 April 2016

Juan de Nova in the log - ATNO

I visited my friend and experienced DXer Chris on Sunday to "have a shot" at FT4JA with his beam at 17m above the ground and legal power [400W here].

The propagation on Friday and Sat was great - they were coming pretty well on my 40m band vertical buried in the garden.  But on Sunday what a difference... K=3 and a solar storm meant low signals up here [52deg N latitude].
At 10z FT4JA signals on 15m were peaking S4 with the high gain preamp and lots of QSB, 17&12m were not better. I could hear a lot Southern-Eastern EU /  AS / JA / SA stations getting in the log but no G stations or very few northern EU.
The cluster was showing no DX to EU, apart than a very weak 4S that I managed to bag for another ATNO by beaming 60 deg N/NE. No signs of VK0EK at all.

IC-756 PROIII - FT4JA split - 7up

After a round of unsuccessful calls we decided to measure the line impedance of his aerials with my antenna analyser as planned. When I got back to it the signals had improve to S7 / S8. Around 12z I heard the first G station getting through the wide pile up and a few calls later I was on the log. Great operator on the other end - pace and precision. I was relieved and pleased to have worked them.
Great ham spirit from Chris to allow me to work from his DXer station.

Sunday, 3 April 2016

Design Notes on my Doublet

This is the design / measurements work I did on the doublet I have been using recently. I did not want to loose/forget this. It is more an exercise of understanding the homebrew open wire line line characteristics, the impedance seen by the tuner than anything else.

Inv V Doublet
Doublet centre at 11m above ground  [using Spiderbeam HD 12m fibreglass pole]
Doublet ends at 7.2m above ground [Tecadi mast / house end]
1:1 200W Gwhip choke balun
0.6m of RG8x between balun and tuner
LDG RT-100 remote tuner
Wire Spec 7/0.2 rapid  - diameter = 0.6mm [copper w/o insulator]
Length per arm = 8.25m

Open Wire Line design/construction
  - built with  SOTAbeams spacers
  - space between wires = 27.5mm
  - wire 7/0.2 spec / 0.6mm diameter  [copper w/o insulator]
  - length 16m

Open Wire line simulated impedance Zo = 540 ohm

Open Wire measurements [with antenna analyser]

   - Velocity factor measured  VF = 0.93
             VF=L*F /492 with  Zi = Zo @ 1/2 WL,
              {1/2 wl measurement with 100 Ohm resistor - F = 8.87Mhz, L=16m }

   - Line impedance - Zo [Ohm] = 570ohm
             Zi = Zo^2/Zl @ 1/4 WL { with Zl = 2.23k resistor /  Zi = 146Ohm}

 Dipole3.exe @ G4FGQ Simulation 
The G4FGQ dipole3 is a useful tool as allows to change parameters and see their impact as well as it gives an estimate for the overall efficiency of the system.

The table below compares the simulated values and measured values with my antenna analyser at the input of the line [balun end].

m - measurements
s - simulated

                          Rs [Ohm]  Xs [Ohm]  SWRs       Rm [Ohm]  Xm[Ohm]  SWRm
F = 8.6 Mhz      84.1           0                1.7            83                 0               1.7            *resonance
F = 3.5 Mhz      7.6             2                6.6            8                   16              6.7          
F = 7 Mhz         328            -1358         115                                                                  *out of range
F = 10.1 Mhz    361             948            58                                                                   *out of range
F = 14 Mhz       55              22              1.5            63                 38             2
F = 18.1Mhz     530            -1561         101                                                                 *out of range
F=  21 Mhz       56              39              2.1            45                 61             3.3
F=  24.9 Mhz    218            -594           37                                                                   *out of range    
F = 28 Mhz       1212          1193          48                                                                    *out of range

With the 16m length of open wire line the remote tuner and 1:1 balun are able to tune/match the aerial on all bands and the simulated efficiency is reasonable apart from 80m as one would expect.

more to follow on 4NEC2 simulations & loading coils for 80m

73 Angel M0HDF