Friday, August 22, 2014

Single knob Travelloop 6.5 - 31 MHz

This small loop can handle 20 Watts from 45-10m . Loop circumference is 2.5 m with a Faraday coupling loop of 50 cm . Sticks are 6 mm glass fibre ( kiteshop).The 2 vertical sticks are 41cm and the suports are 34cm long.  A 2 x 500 Pf tuning capacitor with the sections put in series is used for tuning. Because of the high Q  a 1:3 reduction is convenient but not mandatory . The loop is made of RG-213 with the shield and centre soldered together. Highest SWR is 1:1.5 .  Despite of bad conditions, first contacts were made troughout Europ with 10 Watts SSB. Meanwhile contacts were made with 5 Watts SSB over the Atlantic including the Caribic , Brasil , USA ands. See the list below.  The Faraday coupling loop is made of RG-58 and is bend to a slightly horizontal oval, reducing the space between the loops that leads to a drastic improvement of the swr / return loss.
40m PLOT

Plot 14.200MHz after coupling loop modification.

Improved coupling by reducing the space between the loops . I used a piece of U-shaped plastic for the looprest.
Although fast tuning is a big plus with this loop, the overall efficiency is less than the twin capacitor Travelloop further down on this blog. The broadband coupling loop makes a perfect match impossible. A perfect match can only be made with a 2 capacitor coupling . The efficiency on 40m. is only about 5% but enough for cw. The fun realy starts at 30m. and up. On 20m.the performance is verry acceptable . On 10m.efficiency equals a full size 10m. band dipole and amazing contacts can be made with a verry low noiselevel.
Some september 2014 holiday QSO's made with my FT-817 and 5 Watts PEP ssb mainly on the 10m band :

HB9AYR made a verry nice copy of the Travelloop Mono . Enter his call at to get more info:
HB9AYR Travelloop Mono

Tuesday, February 04, 2014

Mini Travelloop for receivers

Portable shortwave receivers are normally equiped with short telescopic whip antennas producing  a poor  reception. This option has more selectivity and a better impedance (low Z) over the 6.8-31 MHz range.
The design uses a single 15-520 pF type tuning capacitor combined with a FT37-43 toroid having 7 turns  on the coax side. A FT37-61( 4c65) with 3 turns can also be used. The loop is made of 3mm brass wire 1m long. Use only plastic enclosures.  Tuning range is 6.8 - 31 MHz with oustanding performance. This is also a verry good direction finding antenna. A RG-213 loop gives a higher Q with much stronger signals.

The coupling by a FT37-43 with 7 turns

The small loop in action on 80m. by switching a 1500pF capacitor over the tuning capacitor

Disclaimer:I'm not responsable for any damage due to improper reproduction of my projects.