Tuesday, 26 July 2016

VK7 & ZL2 from Castell de Montgri at dawn

I hiked to Castell de Montgri with the radio gear and accompanied by our nephews and some friends early this morning for some sunrise pics and a bit of radio.

Castell de Montgri
Castell del Montgri WCA EA-06968 / CGI-339
locator: JN12nb, coordinates: 42.051816, 3.13178  315m a.s.l.

10Mhz inv V dipole
The 30m dipole went up and I started calling CQ at 5.25z whilst I was putting the WCA reference in the cluster. First DX call via long path was VK7CW in Tasmania with a 579.  There is a great take off towards the west from the castle entrance. A bit later I logged ZL2AP [264deg LP bearing] and VK7BC [280deg LP]. 

/P gear 

73 Angel
EA/M0HDF/P [from EA3 land]

Sunday, 17 July 2016

Raca summit @ EA5 - free ground gain

On my last visit to the Raca summit in EA5 near Castellon, I worked USA, TX on QRP with an inv V dipole at low height on 21MHz. I was curious to see how much ground gain I got from up there...

I downloaded the terrain profile data from the K6TU web page after registering.
HFTA shows a good 3-6dBi gain at low angles and a 4-5dB improvement vs. the low dipole in flat terrrain.

location: 40.049806, -0.015337
Raca - USA - 4-5dB of free ground gain
73 Angel

Thursday, 14 July 2016

Low band RX antennas... next project

Been thinking about my next project for a while. The last CQ WPX CW SOSB 40m suited me and the effort was more competitive than previous given the antenna space constrains / garden orientation and local QRN.

Improving the RX performance seem a logical next step...

Plenty of good info about low band RX antennas [presentation and videos] in the Contest Uni web

A couple of simple antennas to build and experiment:
  -BOG - beverage on the ground - 
  -small RX loop

The small loop should significantly null the local VDSL noise in the street [overhead cables]

Given the proximity of the TX - I am planning to build an additional isolation relay box for the RX antenna. I do not want to risk damaging the TS-590S receiver.

or the G3BJ 

Sunday, 3 July 2016

Doublet analysis (II) - 4nec2 & Voacap

4NEC2 integrates VOACAP engine. So it is easy to simulate your antenna and run point to point predictions and coverage maps.
Below is an example of my Inv-V doublet

Inv- V Doublet - 4nec2 - 14Mhz, max gain 6.84dBi @ ~30 deg elevation

Birmingham - New York path example
I have worked plenty of contest stations over the last few months with the doublet
DX bearing from here is 286deg
Antenna max gain [beam] bearing is 330 deg N/NW - Delta = 44deg [dictated by small garden]
4NEC2 generates a type 14 model for the antenna at the specified azimuth for [1-30MHz]
This is what the elevation gain plot looks like for 14Mhz towards the DX bearing
Gain @ 10deg elevation is -2.8dBi
It is useful to run VOACAP method 13 to check that the TX antenna gain pattern is correct
For RX antenna I use a 3dBi isotrope

Inv-V doublet Gain at 14Mhz - bearing 286deg

Below is the generated SNR plots for the path, also showing the MUF & FOT for the specified reliability [70%]

VOACAP -  Bham -> NY path, SSN 43,  rel 70%, 

It is also possible to run area coverage simulations
4NEC2 generates a type 13 model of the inv V antenna for a given freq [14Mhz in example below]

VOACAP coverage - 500W - 14Mhz, 21UTC, SSN 43, TX antenna = inv V doublet
73 Angel