The Antenna Farm

(according to the XYL...)

 

 

The tower top is readily visible standing out amongst the houses in my suburban estate. This picture was taken in late 2000 after tower and antenna repairs.

 

 

The picture with clearer skies was taken March 2002. The multi-frequency wire dipole/ inv-V is visible in the lower image, with a balun at the centre and feeder dropping clear of the tower and its cables. By the way, the bird on the boom of the 6 metre beam is a crow, one of many local varieties who make use of the 'bird perch'. 

(More often it is kookaburras with maximum number counted on the array of aluminium at any one time : 13)

 

Oct 2007 : Apart from replacing the inverted-V with the Diamond W-8010 multiband dipole (3.5/7/14/21/28) and the support ropes, nothing much else has changed !

 

Nov 2007 : Created coaxial traps for 18 & 24 MHz and made the W-8010 into a dipole array that now covers all HF bands: 3.5/7/10/14/18/21/24/28 MHz !

 

 

31 Dec 2007 : 10 el 2m "OzGear" yagi (Y10EL144H) added at a height of 8m on a separate mounting pipe. 

(Note - the OzGear yagi was originally built by me for sale through our business and was a 'left-over' when we ceased manufacturing antennas at our shopfront premises back in mid 2007.)

 

 

 

29 March 2008 : 

 

VHF /UHF yagi antennas updated -

 

  • 2m yagi replaced by a new 11 element version (approx gain: 12.3dBd) 
  • 24 el for 70cm added (approx gain: 16 dBd) 
  • both booms approx 5.3m long, based on DL6WU
  • T-matched feeds with 1/2 wave coax baluns
  • BF988 MESFET masthead preamps added for each band 
  • 2 x 15m LDF4-50 feeders installed, N female at the top, N male at bottom of the runs. 

 

 

  • Original plans were to feed the preamp supply DC up each coax - until the extra RF losses were measured (about 3dB total), caused by the DC feed RF choke in the amp unit plus the RF choke in the DC power feed at the bottom - no thanks ! 
  • A quick change of plans and a separate multicore power cable was installed and split between the two preamps. 
  • The "flyleads" are short lengths of low loss RFI 9006 Cellfoil coax with BNC and N connectors on respective ends. 
  • The aluminium bracing tubes were added to each yagi provide long term mechanical stability. 
  • The two masthead preamps can be seen in the larger image - with the 2m one above the 70cm one - mounted on the vertical support pipe between the two arrays.
  • Raw VSWR of each yagi: 1.05:1 on 144.175 and 1.1:1 on 432.175 (at the yagis, not the bottom end).

 

 

Note - the yagi array was being raised on 26th March but the mounting pipe bent where the 32mm upper tube telescoped into the 38mm lower tube as the array was raised to about a 45 degree angle. The result was a damaged 2m yagi boom - which had to be replaced.

 

A "gin pole" was added to a replacement masting pipe to take the load today (29/3) - and up it went - no worries. When/if it comes down again, the gin pole will have to be re-fitted to avoid the mounting pipe bending. Note that the tubes were/are "galv steel masting pipe" and not water or fencing pipe. 

 

 

December 2008 :

 

The Ham-2 rotator head unit on the main telescopic tower was replaced with another second hand unit, RG213 feeders on the 50 MHz yagi and the Icom AH7000 discone replaced with LDF4-50 heliax, flexible flyleads replaced with CNT-400 /(LMR-400) to just below rotator (start of the LDF4-50). All maintenance was done from the basket of a 12 metre cherry picker, hired for a 1/2 day (for $240, Kennards Hire). 

 

Subsequent examination of the old rotator showed that the grooves for the brake wedge in the bell housing had been ground away - allowing the antenna array to rotate/move easily in even a light wind - and never in the desired direction ! Helpers : Roy VK4ZQ, Neil VK4FHYH, son-in-law Brad Gilliam.

 

Mid-December 2008 : 

The 2 metre and 70cm yagis were finally re-erected after 6 months of them leaning against the end of the house ! They had been brought down for rotator maintenance on the Thursday before Queen's Birthday weekend (early June 2008) - and were to be re-erected on the Saturday a couple of days later. However family issues on the Saturday, then 4 broken metatarsils in my left foot on the Sunday put everything on hold for about 6 months- while the plaster cast was on as the foot healed and I had to learn to walk again ! This time, when erected, the rotator was at the bottom on a hinged plate and the whole mast tube section now rotates - via a Yaesu GS-050 thrust bearing mounted just below the lower yagi. 

 

 

MY FIELD DAY ANTENNAS ARE DESCRIBED ON SEVERAL DIFFERENT PAGES ON THIS WEBSITE

 

 

October 2010 : 

It's a cloudy day here in Brisbane but the absence of direct sunlight may make the wires of the W8010 inverted-V and the yagis stand out a little better than some other times. Note that there is no longer a rotator visible on the 2m / 70cm yagi arrangement - because it is now at the bottom of the rotating pipe - at ground level - with a thrust bearing up the pipe.. 

 

{Mouse over images to see in more detail }

 


This is the view from East-South-East of the top of the tower with the Wilson HF tri-band yagi very obvious below the 6m yagi. The 2m & 70cm yagis are seen at the RHS over the rooftop.

Alternate view of the tower top from the East.

Clearer view of just the VHF & UHF yagis, as visible over the tile roof from the back yard. 

This view is at a slightly different angle and shows the discone on the top and the tails drooping from the W8010 traps.

This view shows the balun for the W8010 multi-band antenna set up as an inverted-V at top RHS of the image, traps below.

Yet another view....
   
VK4ADC