The mini-mob:
 
 
The history
The idea for the MINI-mob aerial came out of the wish to be on SW driving-mobile qrv, without too much
"to strike". After I was quite for years successfully with the "Hustler" qrv, something "small" had to go,
but at least as efficient as before.
 
 
The idea
After I had made at the portabel operation with the Micro-vert aerials by DL7PE very good experiences ,
 the operation with this aerial draught had to go in my opinion also directly on the carriage roof
be possible without resonant counterbalance.
 
The aerial
The function the mini-mob is to be seen in general as a serial resonance circuit. The capacity "ON TOP" is
the emitter and "AT THE BOTTOM" the coil brings the whole to the standard resonance. Now the difficulty
was to understand the corelations between slimness degree of the emitter and L / C of relation on the efficiency
of the aerial. After many experiments I have arrived nowadays with the "efficiency" of the Hustler Antennas,
without now still to have to take for a drive "monsters" on the carriage roof. How one from this description
absolutely immediately can recognise, the MINI-mob is a mono band aerial.
 
The execution
In 2000 I had carried out the first attempts and measurements in the home garden and, besides basic
experiences accumulated. Enclosed two pictures from this time.
( Picture 1 and Picture 2 )
In the following now some data and pictures from the aerials. At the moment these are following
aerials: three for 40m, four for 20m and one for each band from 17m to 10m that I have built up to now.
Anyway they show the present state of my knowledge. Whether the efficiency of the aerials
can be still increased clearly wide without increasing the length, if I want to get out by other attempts and
measurements in summer. The aerials are fed at the bottom of the coil over a 1:6 UnUn with 50 ohms, because
the aerials have in the feeding point approx. 8 - 9 ohms amounts. The tuning to the precise resonance frequency
takes place through a tuning stick with 10 mms of diameter and 20 cm of length at the top point of the aerial.
In the meantimeI have collected some experiences, also with the adaptation. The first adaptation were 9 turns with
Cul wire 1.5 mm of diameter. The conection was at 3.5 turns. The VSWR was so fairly satisfactory and the QSO's were
inspiring. Then the disillusionment came when I had concrete data with my FA-network tester: A W F U L!!! Now after
many experiments and measurements I have found an adaptation which promises something, the practise will show it!
The new data are 5 turns with 2x2,5mm ˛ wire, conection at 2 turns. Details are evident below and the measuring data
are inserted into an Exelsheet.
The new field strength measurements are made in march 2012 at the beach of Andalucia (see the picture down left).
Who now like to get more informations can download a PDF-File with all the results of the tests.
 

 

Dimensions of the
20 m aerial
 Emitter: ...aluminium pipe
Diameter: ............. 22 mm
Length: ................... 36 cm
Coil : ................ PVC pipe
Diameter: ........... 25 mms
Length: ............... 23,5 cm
Turns: ............................ 75
Wire: ............ 1.5 mms Cul

Dimensions of the
40 m aerial
Emitter: .... aluminium pipe
Diameter: ............ 30 mms
Length: ..................... 80 cm
Coil: ................... PVC pipe
Diameter: ............. 30 mms
Length: ..................... 31 cm
Turns: ............................ 117
Wire: .............. 1.5 mms Cul

The matching
Un-Un as a savings transformer
Ferrite: ........... FT 140-43
Turns: .............................. 5
Connection at :............... 2
Wire: ................ 2x2,5 mm²
in addition, alu-foil under the rubber
stuck and with foot connected.

The measurements
The comparative fieldmeasurements were carried out from 20 m of distance at 5 m height with a logarithmic field strength meter 100mV/db. The SWVmeasurements were made directly on top of the car with the FA-networktester and 30cm of RG 223 cable.

Who has got now desire to build the aerial independently, and perhaps them also wants to
calculate and build for other bands, here for that I make available an EXCEL-Sheet
and a construction-sheet for the download.

MINI-mob.xls

Construction

Now a lot of fun and a lot of successful results while copying.
73 es 55 and gd dx with "Driving-mobile"!
de Harald DL2MHW