VLF/LF/HF Active Vertical Antenna Base Unit

Mark Lucas

Good afternoon Chris.

I have your VLF/LF/HF Active Vertical Antenna and noticed of late the base unit red LED showing connection to the amplifier doesn't immediately light when the unit is powered up.  There are times of up to 10 seconds of delay.  This happens more often than not and usually occurs if the unit has been powered down for a while.  The green LED does immediately light upon power being applied.  This is recent as the unit didn't exhibit this issue until the last couple of months.  No apparent change in performance except it doesn't appear the amplifier is working until the red LED comes on.

I also have the Broadband Active Antenna and both base unit LEDs light immediately upon power up.

All the 12V DC equipment is powered with a 35A Samlex power supply with only a total load of 5A or so when everything is turned on.  It ramps up almost immediately to full voltage.  My transceiver is on a separate power supply.

Any cause for concern ?  I'm closer to moving all my equipment to a new rack mount desk and will no longer be able to see the LEDs as they will be in the rear inside the cabinet.



Chris Moulding

Hi Mark,

Thanks for letting me know about the problem.

It's a curious one.

In the Base units for the range of active antennas we manufactured before Covid there was a series resistor in the DC power feed that powered the red LED from the voltage drop across the resistor.  The resistor value was selected so that the red LED glowed at half brightness in normal use and at full brightness when shorted out. The series resistor also limited the fault current to a safe value.

There is nothing in the head amplifier that should act as a timing circuit. The amplifier should immediately turn on when powered up.

All I can suggest is that you check the cable connections between the Base unit and the head amplifier. Maybe an initial poor connection is clearing up as DC current starts to flow through it.

Some transceivers used to pass a small DC current through the antenna changeover relay on receive to clear bad contacts in the relay. What you are experiencing sounds similar.



Mark Lucas

Ok.  Will do.  When I first received the antenna I had to replace the cable going through the lower element as it had been crushed against the aluminum tube during shipping.  I'll check the BNCs as one of the crimps may not be up to par.  I'll be replacing the coax run to the outside when I finally move the equipment.

Thanks much.

Mark Lucas

Following up on the antenna, both the feeder cable as well as the cable from the choke to the amp check good.  I did test for a few days with a new cable going directly to the amp.  Has the same issue but still intermittent.  I did clean the BNC sockets with small amount of contact cleaner.  The base unit goes immediately every time tested to around 11.18 volts and there is 11.17 or so measured at the amp end of the cable.  I'm now wondering if the problem could be in the amp.  Being as it doesn't occur every power cycle, it's been frustrating trying to pinpoint.   I'll keep a watch to see if the issue becomes more frequent.  Thanks much for your help.  Now on to looking at your new loop antenna...