Antennas April 2019
The April 2019 meeting was dedicated to the topic of antennas.
The ARRL annually dedicated their QST issue to antennas and we thought why not do the same for our meeting. The topics presented were very well received and several people have asked for information on the antennas presented.
Antenna topics which were highlighted:
- Commerical antennas
- Off Center Feed and Vertical antennas
- NVIS Antennas
- Hexbeam Antennas
- Detecting RFI with a Handheld Antenna
Mike Cook VE3ZMC presented on a number of antennas he has for portable and QRP work. He has used these antennas for operating on both summer and winter Field day. The units described were DX Engineering TW Antennas, (review of the antenna), and the Hfp vertical.
Off Center Feed and Vertical Antennas.
Richard Finn, VE3PNK presented information provided by Dave MCCarter, VE3GSO on a two band vertical and Multiband H.F. Centre Loaded, Off Centre Fed Dipole. The presentation material can be found here.
Mike Watts, VE3ACW presented on the theory of NVIS and the type of antennas which would be used. Resources such as W2EDP can be reviewed at this Document.
The G0FAM antenna does not appear to be on line so here it is described:
Think of a G5RV but use 94ft of top wire fed in the centre by 41ft of 450 ladder line to a 1:1 balun.
Run wire around the house/appt either high up or on the floor using every room to make the biggest loop you can. Feed this loop with balanced line 450 ladder or 300 TV line to a tuner, preferably a manual one with a balanced line input.
The lowest freq you will be able to operate on will be the freq for which the loop is a wavelength, so make it long!!
The highest will what the tuner can do.
When I ran an 80m loop I could do 3-30 MHz and by switching tuners run 50-450 MHz (20-30 dB gain up there)
Members shouldl search on NVIS to get the general idea of what it is.
Practically any HF dipole you erect is an NVIS antenna 'coz we can't get the bloody things any higher.
But !! to really explore NVIS try running out an 80/40/30 m dipole on traffic cones 1m off ground and work 100-300 Km. Use FT8 to convince yourself then try SSB.
Hexbeam and other antennas.
John Pedersen, VE3MGR showed the group the center conductor mast used in the hexbeam . He also explained in more detail the concept of the hexbeam. A previous presentation document is here
. Also presentated was information a J-Pole construction, with details here
and ground plane antennas with details here
Detecting RFI with a Handheld Antenna
Pat Ross,VE3CNX, presnted an antenna he uses to detect RFI, An example can be found here
. An ARRL article on RFI is here
These topics were very well received and club members learnt alot and it brought forward questions adn new ideas. The excutive have discussed that every April will be an Antenna presentation session, if you have an idea or antenna to discuss please contact a executive member to discuss.