So its that time of month again ;) Yes the intense radio/puter/geek meeting weeks =) Adelaide Hills Amatuer Radio Society -
VK5BAR are having their monthly meeting on Thursday the 15th, May. I joined up as a member at the AGM in January. I finally received my certificate for my foundation licence last week, so I'm all good to go =)
I have a 10watt radio on loan from Jacqui and I've manged to listen to the WIA broadcast on Sunday morning. Only just mind, there was so much noise it was barely readable. Thats probably a task for this weekend is to get an antenna sorted for the 80 meter band. That was the clearest of all the available repeaters. The 40 meter band seemed pretty empty. The 10 meter band had the faintest of signals and the only thing I could pick up on 80 meters was the WIA broadcast. I had a 40 meter half wave length dipole strung across the front yard, well maybe more like a inverted vee, still need to build a decent balun too. Maybe HAMs don't get out of bed before 10am like other sane people? Maybe they've all been up late working the radio until the wee hours? ;) I need to get a better space for the radio and get an antenna up more permanently.
HF antennas
Kim, the 80 metre antenna needs to be up as high as possible as with the 40 mtr but while 40 may seem quiet if you tune around slowly you will find signals
if the vswr is ok on the antenna you should be able to call local adelaide guys during the daytime, a CQ will get a response often. 80mtrs is usually around S9 noise day or night but signals at night will be much stronger and from further away.
frequencies to check are 3.600mhz , 3640mhz, 3618mhz in the mornings and evenings up to about 930pm usually a few groups have Nets on those frequencies. the 80m broadcast relay is even low here competing with the noise, an old 27MHz CB antenna will work ok for 10 metres up high with a groundplane it will work well for local stuff up to 30 miles(at 20 feet high) not so good for getting over the Lofty ranges though :(
a good compromise antenna would be a quarter wave of wire with half of it wound onto a 50 MM PVC pipe with 12mm spacing and the rest strung up to a pole or tree to get height, connect he coax inner to the bottom of the coil, very close by drive an earth stake into the ground and connect the coax shield to that and there you go an 80 meter "almost" Vertical
exact dimensions are about right if you use the ARRL hand book formula 1/4 wave= 246/Freq Mhz= feet then add 7% to allow for the inductance of the coil. go to http://www.spirat.com.au/vk5zvs/pic9.htm. this link shows the 160mtr ( 1.8mhz version) importantly however the earth has to be a very good, low impedance RF ground, SWR can be adjusted by folding back the end of the long length on itself and taping when the swr is at its best
you can use a fancy connector for the coax connection at the base of the antenna or a simple screw type power block, at 80M it doesn't matter too much. I have found the 160m version is very low noise and gets out very well, I am about to knock up a 40mtr version to see how that performs
cheers
Jacqui
HF Antenna
Well the call book says 160meter band is for advanced licences only. So I'll try an 80meter version of that I recon. It certainly doesn't look hard to build. Perhaps only measuring the length of wire accurately being hard. Its a tad wet at the moment to be playing on the shed roof today, but I'll try to get the 40meter dipole up somwhere today before tomorrows broadcast. Perhaps build a 1:1 balun also.
correction
Yes Kim your correct but this type of antenna can be built for any of the lower bands
Note the correction to my first post its a quarter wave not half wave as originally stated I have edited the original post also to show the correct calculation.
I will listen on the 80M tomorrow and 40M
the network team are supposed to be here in the morning to do the fulham upgrades but I doubt the weather will cooperate enough to get anything done.
cheers
Jacqui