December 22, 2015

CWTD Episode #77

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

Podcast

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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 ... < http://www.w1pid.com/>

- Somewhat unpredictable results

- Variant is EARCHI 6_40 antenna

                http://earchi.org/92011endfedfiles/Endfed6_40.pdf

                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 ...< http://www.aa5tb.com/efha.html>

 

 

 

    N2CX Halfer ... < http://www.njqrp.org/n2cxantennas/halfer/index.html>

   

 

   

 

-Performance approaches center fed resonant dipole

-Requires tuner or matching device

 

Commercially available

 

   Par EndFedZ ...< http://www.lnrprecision.com/endfedz/>

 

SOTAbeams .... < http://www.sotabeams.co.uk/half-wave-end-fed-antennas/>

 

 

 

Vertical antennas

- Inefficient if too short

- Requires substantial ground system

- Commercially available

 

The Buddistik ...< http://www.buddipole.com/buddistick.html>

 

QRP Kits ... < http://www.qrpkits.com/pac12.html>

 

 

-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 ...< http://www.alexloop.com/instructions2.html>

 

Alpha Antennas ... < http://www.alphaantenna.com/>

 

 

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

SOTA BEAMS ... http://www.sotabeams.co.uk/antennas-hf/

  

 

“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 www.reversebeacon.net  
• "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!

 

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2)  CWTD PROJECT UPDATES

GPS-DO ...  http://www.cwtd.org/CWTD_GPSDO/index.html

- 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)