Topband: New 160M high performance receiving antenna at W3LPL

[donovanf at starpower.net]

Hi Larry,

Your 160 meter CW skimmer is working extremely well, it spotted T6LG last night.  No other U.S. skimmer spotted him!  I couldn't hear any trace of T6LG, I guess I need to move my BSEF receiving array to Maine!

I use exactly the implementation described at:

http://pvrc.org/bsef/bsef.html

Each vertical is 25 feet of aluminum tubing with four 25 foot umbrella wires and eight 70 foot radials (inexpensive 16 AWG speaker wire) laid on the ground.  The verticals are low impedance at the base, so there are absolutely no issues with handling very high impedances like in the Hi-Z array.  My insulators are phenolic, but any insulator -- even wood -- will work fine with low-Z verticals.  

The strong advantage of the low-z BSEF array is that there is no need to adjust the phasing, the only adjustments are is inductors and resistors at the base of each vertical.  Adjusting them takes five minutes or less.  If you want to steer the sidelobes, you could eliminate the fixed phasing line in the center of the array and run two RG-6 feedlines to a DX Engineering NCC-1 Receive Antenna Variable Phasing Controller in your shack.   

The low-Z BSEF receiving array has important disadvantages too:
  - it is physically large (300 x 130 ft), 
  - it needs radials, and 
  - its strictly a monoband antenna.

Each vertical is base loaded with a resistor and inductor, adjusted to resonance (75 + x0) at 1840 kHz.  Each base loading enclosure has a BNC connector that I use only with my MFJ-259 to set the impedance to exactly 50 ohms resistive and zero ohms reactive at 1840 kHz.  A 25 ohm resistor (measured with a digital ohm meter) runs from the BNC connector to the 75 ohm F-connector.  The RG-6 must be disconnected when connecting the MFJ-259 to the BNC connector.

The F-connector connects to a half wavelength (225 feet) of RG-6 that goes to the RF combiner near the center of the array.

The RF combiner uses three Minicircuits Labs 75 ohm splitters used as simple RF combiners.  The only phasing line is a 68 foot length of RG-6 and a phase inversion transformer that sets the relative phase of the rear two broadside verticals relative to the front two broadside verticals.  This phasing provides minimum sidelobe levels.

I highly recommend the low-Z BSEF array since you obviously have the space.  You should reduce your broadside spacing to 300 feet rather than 320 feet, your sidelobes will be minimized as a result.  Although 320 feet is a good choice for a transmitting BSEF array (maximum gain), 300 feet is a better choice for a receiving BSEF array (minimum sidelobes).

I'll be pleased to answer any specific questions about my BSEF receiving array implementation.  The three photos pretty well cover everything I could possibly tell you.

73
Frank
W3LPL





---- Original message ----
>Date: Sat, 2 Feb 2013 10:51:52 -0500
>From: "Larry - K1UO" <k1uo at uninet.net>  
>Subject: BSEF  
>To: <donovanf at starpower.net>
>
>   Hi Frank,
>
>     I read with interest your comments on the new BSEF array
>   there.   My experiments with a 70X320 BS/EF array with 20ft
>   Hi-Z type verticals was short lived since strong winds toppled
>   trees directly on top of 2 of the verticals!!  The direction I
>   am aimed is favoring Africa one way and the North Pacific the
>   other (switchable).
>   I will be rebuilding them to 24ft verticals with fiberglass
>   rod insulated bases (less pf) and trying it once againSmile
>   Initial results were comparable to a small broadside phased
>   Beverage array here but that was without any tweaking of the
>   phasing and of course directions were not exactly the same.
>   What phasing arrangement did you employ?
>
>   73 and congratulations
>
>   Larry  K1UO