December 22, 2015

CWTD Episode #77

Portable Antennas
Excellent ways to get on the air while in the field ... and at home!


1)  Portable QRP Antennas

Portable hamming is a popular activity particularly during Spring, Summer and Fall


Different types dictate antenna used

- Short impromptu outings need quick up skywires


- Camping, SOTA and IOTA ops or events can be more elaborate

Types of portable antennas


    Random length wire

- Non-resonant wires thrown over convenient tree or ??

- Example is 24 to 30 foot wire and similar ground counterpoise

- Quick to put up/take down

- OK for casual operation

- Needs tuner


     W1PID is great enthusiast ... <>

- Somewhat unpredictable results

- Variant is EARCHI 6_40 antenna


                easy to duplicate, uses 30 ft wire and coax for counterpoise





 The End Fed Half Wave Antenna

- L(ft) = 468/F(MHz)

- Also works on harmonics


A number of proponents ...


 Steve Yates AA5TB ...<>




    N2CX Halfer ... <>





-Performance approaches center fed resonant dipole

-Requires tuner or matching device


Commercially available


   Par EndFedZ ...<>


SOTAbeams .... <>




Vertical antennas

- Inefficient if too short

- Requires substantial ground system

- Commercially available


The Buddistik ...<>


QRP Kits ... <>



-Full size verticals are cumbersome for casual portable use


 Magnetic loops


-Convenient for limited space or crowded public areas


-Many SOTA ops like portability and band-hopping characteristics


-Common 3 foot loops

    -Convenient size

    -Fast, easy setup

    -Mount on camera tripod

    -Inefficient on 40 meters, good on 20 and higher

    -Narrowband – needs retuning for QSY


-Commercially available from ham distributors


Alex Loop ...<>


Alpha Antennas ... <>



Dipoles and doublets


-Center fed half wave dipole


-Dependable, repeatable performance, particularly with balun


-Somewhat more effort than end fed wires

    - but not much if inverted vee configuration

    - Center at least 20 ft up, ends above head level


-Can be mulitbanded

    -Leapfrog segmented dipole

    -40/20/15 tri-bander

        -Doublet uses open wire line for multibanding


Dipoles commercially available




“Fixed mobile” operation


-Use ordinary HF mobile antenna on vehicle


    -Extra ground system helps effectiveness


    -Good when no antenna supports


    -Convenient for inclement weather


    -Superb for spur of the moment operation

        -While wife is shopping at the mall

        -While vacationing and can’t set up portable station


N2CX mobile operations ...

                 N2CX vehicle parked at Whitestone Brewing Company ... not QRV after this stop!



               K400 mounted on edge-lip of rear hatch                           Ground wire brought to bolt to ensure solid ground to vehicle 


Is my antenna working?

  • Use Reverse Beacon Network to check it out  
  • "Skimmers" monitor CW portions of ham bands
  • They log signals received and post on web page
  • The see CQ’s and TEST signals
  • E.g. "TEST TEST de N2CX N2CX K"
  • Screenshot from N2CX home antenna with 3W


  • Handy check but…

- Depends on propagation, antenna pattern, available skimmers, QRM

- Less than 10 dB SNR – weak signal

- 10 dB to 20 dB – reasonable signal

- Above 20 dB SNR – you’re golden!




GPS-DO ...

- Motherboard layout is complete.  Going to fab this week

- Motherboard Kit available in January
   - Price target: ___
   - Holds the VCXO and Oven boards, and contains the NEO-7M GPS receiver (not included), Disciplining and Temperature Display circuits
   - All fits into the GPS-DO Enclosure

ELMER 101 and the SW30+ Kit

- Parts nearly received
- Price target: ___ (ballpark estimate)
- AA0ZZ Enclosure design in fab
- Orders to be accepted starting with January CWTD episode (January 12)