Railfan Technology > MFJ-1866 outdoor discone antenna review.

The MFJ-1866 is a discone antenna.  Such antennas are vertically polarized and
are noted for wide bandwidth.
These antennas have essentially no gain over a 1/4 wavelength whip but the
nominal gain they do have is about the same over a wide range of frequencies.

For strictly railfan use, a discone offers no advantage over a 1/4 wavelength whip.

For a scanner enthusiast or amateur radio operator - railfan, this antenna is
a viable option.

The antenna is imported from Taiwan and the hardware is metric. 
Construction is aluminum top plane and skirt rods into a cast, bright metal plated
holder.  The connector is a standard SO-239 "UHF" socket.

VSWR measurements to 450 MHz. 

450 MHz.......2.8:1 VSWR
440 MHz.......2.4:1 VSWR  ham radio
420 MHz.......2.0:1 VSWR
220 MHz.......1.7:1 VSWR  ham radio
200 MHz.......1.7:1 VSWR
180 MHz.......1.5:1 VSWR
160.89 MHz....1.5:1 VSWR  center of US railroad frequencies
162.55 MHz....1.7:1 VSWR  NOAA weather broadcasts
144 MHz.......1.7:1 VSWR  ham radio
120 MHz.......1.3:1 VSWR
110 MHz.......1.7:1 VSWR
080 MHz and lower very high VSWR


Notes:  The claim of transmit operation down to 50 MHz is "optimistic."  My measurements
indicate the antenna becomes poor for transmit below 110 MHz.  It will receive some signal
down to the claimed 25 MHz low end.  So will a straightened wire coathanger. 

Construction is quite robust as the design uses 8 plane and 8 skirt elements.  Usually, consumer
level discones "get by" with 4 or 6 elements.  The popular "Hustler" discone uses 3 elements.

Elements are aluminum, not stainless steel as claimed on the package. The interface between the
element end and cast metal holder are press-fitted, threaded, bright- plated steel.

The mast clamp u-bolt is stainless steel and requires a 10mm wrench to tighten.  The clamp will not
fit typical 1.25" "TV mast."  Slip a stainless-steel 5/16" nut over each threaded end to act as a
spacer and the clamp will grip 1.25" tubing.

Assembly tips:  You will need a 10 mm wrench for the U-bolt nuts and the holder to tube screw, an
8 mm wrench for the clamp to tube screws and a 6 mm open end wrench for the element to holder interface.
You may also need a 10mm nutdriver or socket.
One of the skirt elements blocks easy access to the tube-to-element holder screw.  It is a simple
matter to remove the element, tighten the screw with a 10mm nut driver or socket and replace the
skirt element.
Do not overtighten the elements or other hardware. 
Tip: Before assembly, wipe down the elements, tube and clamp with 91% isopropyl alcohol to remove
dirt and grease and spray  these parts with gloss clear paint.  Wait until the antenna is assembled
and coax connected before cleaning and painting the element holder.
 
Be sure to follow all electrical code requirements in your area.

Operation:  It works OK for both railfan and amateur radio use and in my view represents a good
value for the @$50 price.
Be Well,

Tim Colbert  K3HX
 



Edited 4 time(s). Last edit at 03/09/17 06:09 by K3HX.

Good review Tim.

For railfans, a standard whip or ground plain would probable be as good or a better antenna, but if you spend time listening to other services (aircraft, police, military, etc...), this would make a great antenna.  It would also work great for ATCS.  This would be an antenna to consider for you home location.

John

One thing to keep in mind about discones is you get no band selection off noise. If you are in the boonies they work fine and are quite handy, but in a metropolitin area, all sorts of strong signals and inter-mod will blast through your receiver because the discone receives them all equally. We took them off our emergency ham stations for that reason here in LA.

Do what works for you.
73's
Scott, AB6YS

Scott Schifer
Torrance, CA
TinyTrains Website

re ATCS.....unless you have very short low loss coax, the signal loss over a stub antenna will be great.

Finding an affordable discone that's effective on 6 meters is not easy.