Friday 29th June, 2012 20:10
FAMPARC 7 Band (VKS-737)
HF Antenna Tuning Review
The whip was mounted on a Terlin Mobile Whip base which was attached to the bull bar of my 4WD vehicle. The base was connected to the RigExpert AA-54 via a short length of RG-214 double shielded coax.
The antenna was first checked with the jumper wire not connected. The 3995 KHz frequency was a little out so the tuning tip was adjusted to tune the antenna to the appropriate resonance point for that frequency and another sweep performed. The jumper wire was then moved to the respective tap for each of the other frequencies and a sweep of the antenna performed over a 1000 KHz bandwidth.
The following Analyser traces speak for themselves:
A friend of mine, Robert, recently purchased a 'FAMPARC 7 Band HF Whip Antenna' at a local Hamfest and decided to drop by so that we could test the antenna using my RigExpert AA-54 Antenna Analyser.
The FAMPARC club is currently constructing the following models of HF mobile whips:
Further information on the Franskston and Mornington Peninsula Radio Club (FAMPARC) HF Whips can be found on their web site at http://www.vk3frc.org.au/?page_id=24
Further information on VKS-737 can be found on their web site at http://www.vks737.on.net/
5 band Model (80, 40, 20, 15 & 10 Metre)
8 Band Model (80, 40, 30, 20, 17, 15, 12 & 10 Metre)
13 Band Model (80, 40, 30, 20, 17, 15, 12 & 10 Metre) + VKS-737 Australian National 4WD Radio Network frequencies of 3995Khz, 5455Khz, 8022Khz, 11612Khz and 14977Khz
7 Band VKS-737 Australian 4WD Frequencies Model (3995Khz, 5455Khz, 8022Khz, 11612Khz, 14977Khz and 27 MHz)
The antenna tuned up perfectly without any issues at all, and needless to say we were impressed. Once the 3995 Khz frequency was adjusted, there was no requirement to retune the antenna for any of the other frequency tap points.
The Terlin base was not earth strapped to the frame of the vehicle and I suspect that if it had been, the dips would probably have been slightly deeper and the VSWR slightly better at each tuning point, but that hasn't been validated.
Time will tell regarding how well the antenna performs on air and how it physically survives in the field. When Rob reports back to me, I'll update this page with his findings.