AMATEUR RADIO STATION  W7ACP
Return to SnellsNotebook

Palomar 95.375' Zeppelin Antenna

    Antennas On The Switch

    • Palomar 95 (P95) - August - September 2021: Tested remaining configurations of antenna length, UNUN mounting height and counterpoise use, configuration and length.  Settled on a wire 95.375 ft in length with the UNUN at the top of the 30 foot  flag pole, and no counterpoise.  Modeled this configuration in 4NEC2 and compared it's predicted performance to observed performance in PSK Reporter while making hundreds of FT8 QSO's.  For my location with it's restrictions this antenna length is ideal.  In a less restricted location I think I would investigate the 200-300 foot antenna length.  The MFJ 993b Antenna Tuner has made this configuration really shine!

    ZEP Antenna Configurations

    The Palomar Bullet 9:1 UNUN connects the 50 ohm coax to a psudo-random length of antenna wire.  I say psudo-random because there are specific requirements for the length that this wire should not, and can not be.  That would be any lenght that is resonant on any band the antenna will be used on.  Picking a practical wire length is non-trivial to operate on 80-40-30-20-17-15-12-10 Meters.  In my case where I am severely constrained, I believe I can get away with about a 60' horizontal run combined with the 30' height of the tall flag pole.  An 84' foot wire probably is the longest I can expect to use at this location.  136', 140.5', 117.5' and anything over 295' are options, but too long (maybe).

    NOTE: Fall of 2021 - After testing many lengths and UNUN mounting heights, I have settled on a 95.375 foot wire length with the UNUN at 30 feet AGL.  This will be know as Config 12 and is likely the final configuration of this HWEF antenna.

Config 1


      In the first configuation, I put the UNUN at the top of the pole and ran the wire out terminating with a 10' nylon rope to keep the end of the antenna out of reach of passers by.  

      Config 2
      Moved the Bullet UNUN to 72" AGL.

      I discovered through reading various antenna manufactures descriptions of working antenna installations, that the UNUN doesn't have to be especially far above ground, and that the antenna wire doesn't have to be especially straight in any plane.

      So for this configuration I mounted the UNUN at about 5' AGL, ran the antenna wire (55') to the top of the pole, 30' AGL and then down to 7'.  This shortened my horizontal run 20'.

      Config 3
      Installed 17' counterpoise 'under the antenna' at 0' AGL.

      In this configration I added a 17' counterpoise to the UNUN, mounted it at 2' AGL, and ran the 55' antenna wire up and out as before.  Horizontal run about 17'.

      During testing of this configuration, I tried an AM Broadcast "Brick Wall" filter to reduce the effects of KCID on my receiver.  The filter did EXACTLY what it advertised.  Input signals at AM Broadcast frequencies were attenuated 40dB.  It was here that I recognized the QRM was coming from common mode current on the outside of the coax braid (which was grounded - and that makes zero difference to RF on a 50' run).  The Brick Wall was returned, and a Palomar Engineers CMFN-500-50GB filter was installed to decouple RF on the braid and drain static on the braid.  This made a substantial reduction in KCID interference at lower HF frequencies, but there is still more than I want, particularly as the frequency goes up.  By 10M it's 'nasty'. 

      Config 4
      Moved Bullet UNUN to 24" AGL, added CMNF.

      Since I have about 60' horizontal I wanted to increase antenna wire length, to increase 'intercepted RF' - eg: increase sensitivity, so shortly I will install an 84' #14 THHN wire.  The UNUN will be at 2' AGL and the horizontal run will be 64'.

      Config 5
      The big change in Config 5 is the coax is looped in a CCW single loop on the side of the shack about 12' x 6'.  This made significant changes to the SWR.