OPEK HVT-600 Multi-Band Mobile Antenna 40-Meters Mod Hack - David VK4ICE
Having Trouble Tuning Your OPEK HVT-600 to 40-Meters?
By David, VK4ICE
Some users have noted when tuning these whips on 40m, the SWR dip seems to be below the 40m band (about 6.900 MHz according
to my Analyser).
Before you set about cutting the whip to bring to dip into the 40m band, STOP! You are going to need the length is you want to use 80m (around 3.600 MHz), so DON'T CUT THE WHIP.
A little trick to reduce the inductance of a coil is to introduce a shorted turn into the field of the original inductor. For many of you, your eyes just glazed over and you are now asking, "Say What?!?
Easy... A small stainless hose clamp (this is a loop or shorted turn) fitted just above the 40m tap will move the dip up around 7.100MHz, then you can lengthen the whip to get you down to 7.060 MHz. Don’t tighten the hell out of it, just snug works fine. You can leave the hose clamp in place for all bands above 40m as the wander lead bypasses this area on the inductor. You will need to remove the clamp for 80m operation as this part of the inductor is in use.
Credit: David - VK4ICE