Monday, March 9, 2009

R8 HF Vertical

(http://www.lairdtech.com/)

Recentl
y I picked up a second hand Cushcraft R8 vertical.

I had the folliwing goals in mind
  1. Vertical
  2. Multiband
  3. No radials
  4. Low take off angle
  5. WARC bands included
  6. Possibility of field day operation
  • Vertical
Given the layout of the my house's lot, a second antenna would be easier to install if it were a vertical. Also my existing antenna is a 80M to 6M Windom Buxcomm model 802136 and I am intersted in having a vertical to compare. I'll likely never setup a beam so this second antenna will be it.
  • Multiband
Multiband is tablestakes, because I need to able to get as much out of an antenna as I can. The R8 is one among very few 8-banders covering from 40 to 6m, WARC included.
  • No radials
I like the idea of no radials, mainly because of the ease of installation and flexibility of installation lacation. R8 uses 7 49in stainless radial rods at the base of the antenna.
  • Gain and Low take off angle
DX, DX, DX, Low take off angle is important for DX work. With its low radiation angle R-8 vertical should have distinct advantages compared to my windom. The 360 degree coverage should be nice as well.
  • Power Handling
The R8 supports 1500W which is plenty for my FT2000D which is a 200W rig.
  • WARC bands included
I enjoy digital operation and I often find that the WARC bands have activity, but the Windom antenna does not tune up on 30m for example.
  • Possibility of field day operation
The R8 could be used in field day operations but due to its weight it is not easy to get it down without help. Once installed, I think its up there for the long run.

Considerations
  • Guying
I did guy the antenna down to three points.
  • Grounding
I have grounded the mast to a single 8ft ground rod with a run 10ft run of #6 ground wire.

Specifications

Model R8
Gain, dBi 3

Height, m. 8.7

Horizontal rad, deg 360

Power Rating, Watts CW 1500

Vertical Radiation Angle, deg. 16

Band / Bandwidth (kHz) 10m >1500

Band / Bandwidth (kHz) 12m >100

Band / Bandwidth (kHz) 15m >450

Band / Bandwidth (kHz) 17m >100

Band / Bandwidth (kHz) 20m >350

Band / Bandwidth (kHz) 30m >50

Band / Bandwidth (kHz) 40m >150

Band / Bandwidth (kHz) 6m >1500

VSWR at resonance (typical) 1.3:1

Weight, kg. 10.5

Wind Survival kph. 120


The Cleanup

Since the antenna was second hand I had quite a time cleaning up the antenna and setting all the element lengths to the specification.
  • I cleaned up external surfaces with a combination of steel wool and lots of work. With this I was able to restore the antenna to showroom look, shine and all.
  • The short 6" terminal tuning stubs rods were oxidized such that it was impossible to remove these from the longer stub tubes. I did confirm that all stubs were all stuck in place at the right lengths.
  • I opened the R8 matching network box and confirmed that there were no mechanical failures of the components inside. A mechanical inspection was complete.
  • I completely assembled the antenna indoors to see the antenna fit together and confirmed nothing was mechanically broken or missing.
Installation Preparation
  • I decided to install the vertical on the corner of my backyard shed. A 2 in pipe was installed up through the roof of the shed.
  • I decided to guy the antenna from the initial start
  • I placed a 1:1 choke at (near) the antenna.
  • Grounding, 8ft copper clad steel rod at base of mast
  • Feed line, was 100ft RG/8
  • Lightning arresor, was placed at the house
Operation
  • All bands tune up and better than 1.5:1 on all but the high end of 40m.
  • Have not tried to see how it tunes on 6m.

1 comment:

VE3MPG - Bob Baillargeon said...

It will be interesting to hear how the R8 works for you Adrien. Have the R6000 and it's a real DX chaser. Have a 3 point guy on it at this location and it barely moves in the turbulent winds we get here near Vernon. Got mine used too and completely refurbished it last year - quite a job getting all that aluminum polished up. I used a conductive grease on each section after polishing to assure a good electrical fit and to prevent oxidation. Used black bumper paint on the match box to get it back to showroom condition.

Bob VE3MPG