Project in Progress - Updated 15/01/2021

After installing the OCFD, it was quite apparent that whilst it was getting out very well according to the Reverse Beacon Network, Hearing stations was still a bit of a struggle so with that in mind, a dedicated receive antenna was researched and whilst attending the DX Engineering Virtual Hamfest during lockdown, a discussion was had about Beverage Antennas and the BevFlex was mentioned as an alternative for those with small "Lots" who wanted a receive antenna at around 200ft.  The ability to switch between directions will also allow NW/ SE directivity for my station.

The beauty of the Bevflex, is two-fold. It has the ability to support smaller lengths, and can site the control point at any point in it's length, both areas that traditional beverage antennas don't have. It also uses inexpensive RG-6 75-Ohm coax as the element and shack feed with a last run of 50 Ohm into the receiver. For the FT-2000, that is straight into the RX socket, for the FT-847 it's more equipment to source for TX/RX switchover, a later task.

A SV1AFN J310 Pre-Amp is described below ;

Parts

Unified Microsystems Bevflex-4X Kit

250m Drum - RG6 (From CPC) - 

8 x F-Type Coaxial Connectors and Boots (From CPC)

2 x 4ft Copper Earth Rods (From Screwfix)

Earth Connections (From Screwfix)

20 x Gallahger Multi-point Electric Fence Posts (From Mole Valley Farmers)

UHF to BNC Adaptor

BNC Patch Cable - 50Ohm

BNC to F-Type Adaptor

F-Type Barrel Connector

Assorted cable, Cable ties and sundries
 

The cable run is as detailed in my M1VPN Shack page, but essentially is curved and not straight. It's the longest I can go within the confines of the property, until I can speak nicely to the person who owns the woods ! I'm hoping the Gain Pattern is not too far from that direction as it's nicely NW / SE. I'm thinking the Reverse Beacon Network will also be quite helpful in testing this too.

 

The Build

After being sat on the shack table since it arrived, box opened a few times to look at the units and understand the manual, I just wanted it outside ! A basic install that needed to be completed by the end of the day, so required an initial install to get up and running but ready to experiment with once more time becomes available.

I ran out the element RG6U from one end to the other, pushing my way through brambles and bushes for about 264ft. I then laid out the Feed Box to Shack lines, which are partially underground in conduit, with some other conduit to lay in the spring. A final jiggle and the coax feeds were through the hole in wall to the controller.

Next, RG6U to F-Type connectors, except the ones I bought from CPC were slightly too small for the RG6U, also from CPC to putting them on was painful, and not particularly great. These will be replaced with Crimp Outdoor F Types at the end of the experiment. CPC have been told ! Short runs of solid core Electrical cable then used as the earth, just pushed into the damp ground.

Connecting up to the FT-2000, and nothing... I spent about an hour metering out the coax runs mainly because the connectors were so poor, it had to be them except it wasn't. I had in my mind that the BNC on the back of the radio was RX in, but it's not, its RX out. RX In is the SO-239 beside it. A quick find of a PL-259 to SMA to BNC and it was connected.

A quick test with Medium Wave Radio stations demonstrated the directions, Forward and Reverse was working well with only 264 ft length that is not straight ! In the evening, onto 40m and the ability to knock out the whole of Europe brought up the US/Canada well. Interference from Euro/Russia was also able to be nulled out.

What's left to do ;

  • Replace control box to Radio connections with a F-Type Adaptor to BNC, BNC Patch Cable to the Radio to BNC Adaptor to PL-259.
  • Install the Copper Earth Rods
  • Experiment with the height of what is a BOG at the moment, looking at 4 inch raised using the fence posts placed every 12 ft.
  • Look at RX/TX options for Other radios - DX Engineering RTR-2, with Preamp is potentially the unit but the NCC-2 also looks functional too
  • Speak to the owner of the Woods to ask to continue the BevFlex into the trees for another 50m to make a 350ft overall run.

 

Performance

 Excellent directionality, quiet and functional. Requires a Pre-Amp for 40m upwards as described in the manual, with a SV1AFN J310 PCB


 

Modelled Orbital Plot for BevFlex 4x

 

SV1AFN J310 Pre-Amp

The additional component required for the 40m and higher bands is a Pre-amp. Whilst the IPO two stage pre-amp in the FT-2000 works well with a +20db gain, the ideal was to add an external pre-amp. With many HF low noise designs, the SV1AFN looked the most interesting and capable with a pair of J310 MOSFETs in Push-Pull to provide preamplification of a 0 - 30 Mhz RF signal.

Initially, this pre-amp is going to be always powered from the FT-2000 accessory voltage from the rear of the radio, although I have a DC Coaxial relay that could add to have the ability to switch the module in and out should I need the facility.

 


SV1AFN J310 Pre-amp in test

Joomla templates by a4joomla