Loop
antennas is one compact type of antennas
that offers a high selectivity on a determined band .Practically – by design a loop antenna for this purpose (medium waves )
is a wire wounded in several turns then connected with a variable capacitor .
I already have
designed several years ago antenna of
this type called Australian loop
(two different links the first with videos ) that is a 1 x 1 m
antenna square with 8 turns of wire spaced ca 1 cm and connected to a 1000
pF variable capacitor to form a tuned circuit . This is made in a
wooden base as it is shown in my above photo . The loop is coupled
with another turn of wire diagonally over the loop with wire extension to connect to the radio receiver .
Let just do a little more insight , two important factors concerning the loop antenna philosophy.
1.By design they offer very sharp nulls in one direction , having a directivity shape of 8 with two nulls parallel to the axis of the diameter , That means you can null out a radio station or even the local noise by just turning them by 90 degrees ie laterally to the unwanted signal with the antennas diameter being in parallel to the unwanted signal.
2.
Together with a capacitor the loop has a very narrow range of tuned
frequencies. This can help the radio from overloading while this can
strongly boost the selected tuned frequency range
It is one of my best antennas though quite seldom used due to its low portability . Consider this : every time i have to do some remote radio listening have to carry this big antenna, its wooden base that weighs ca 10 kg, and the radio(s).
Another problem incured with the variable capacitors:the solders many times were broken or capacitors themselves could be described as 'defunct'
Prior to this antenna i have made on late 80s another very similar but cross shaped (diagonal instead of square ) with all wires being wound together over nails (ie not spaced) with nearly similar results to this antenna . But due to it design the wooden rods were easily broken quite shortly.
And
finally two years ago I have received a nice advert booklet from a
German seller VTH de with several radio models and accessories from
mainly Tecsun /Degen .
My
idea for the start was to add the active Degen DE31LM antenna for MW
and LW but i was not sure if my radios are compatible with it since
all these radios use their internal ferrite for tuning . I am unsure
if the antenna connection could disable the built in ferrite rod .
On
the leaflet I found another antenna model though passive Kaito AN
200 with the price of Eu45 together with a frequency book. as for
2009 This antenna has normally been designed to work with the Tecsun
S2000 world band radio (Grundig 750 in USA) also included in the
leaflet Very recently I did a survey for the availability of this
antenna as well as several other products from this company as for
personal interest
And
finally this antenna has been bought but not from VTH but from a
local seller in Athens Greece with a price of 39 same with VTH . I
found him by googling the antenna name . Although I insisted him to
send by standard mail (or even registered ) he sent to me by speed
post that raised the cost by 8 Euros. This was not notified in the
shipment bill and costed me some delay n the post office . I was very
fortunate that the postal officials are 'close friends' (i visit them
nearly every day) and helped me to take the pack immediately.
Fortunately I was not further notified for any additional costs
Here is a picture of the loop after it has been opened from its box:
The
antenna is very simple enough: The loop is a plastic cylinder about 20
cm wide wounded with very thin wire in a also plastic base of
reverse cylinder that has a tuning knob in its one side
On the other side there is a mini jack socket, Walkman's , and a separate wire is provided to connect with open wires to a receiver (Tecsun S2000 is the main suggestion)
And here is a close up photo of the 'ribbon' antenna
While
testing for first time in house and having already some experience with
the Australian loop , i put my De1102 under the radio . Listen to the
video below on how the antenna tunes.
Also look to this video
With some more experiment , i found that once the radio's LCD display is directly under the loop it causes some noise
(update )The antenna has been tested with the HF150 LOWE receiver and has been found to work in between 511 and 1870 kHz
Testing
with other radios, best reception point depends with the radio design
and whee the ferrite loop is placed . As for example the best
reception with Degen 1102 comes with the radio located inside the
loop. Same is for the Chibo K300 . In contrast , the Bolong radio
requires to be under the loop abt 1-2 cm out. And my Walkman Aiwa
required to be in parallel to the antenna's diameter Here are
several photos :
with Kchibo K 330 :
and with Tecsun PL200 (found to be th most in-tolerated radio from all !! ) For this radio i found two quite mystrious things: 1 ) the raso needs to be close to the antenna rather than be inside the loop to have the stronger signal . 2) inside the room with nearly some internal noise , the radio (which has been modifeed ny the company afetr a claim of poor operation) and due to itrs very strong AGC on the higher MW band the loop ofered very little enhancement over the noise heard on the freq .
Using
now the loop with its provided wire , I tested it with the R75 and my
wife's hifi system. Both use external loop antenna to tune into the MW
and LW bands . In the R75 the signal was relatively low comparing to
my 2x16 inverted V antenna as will be seen in the photo below The 16 m
antenna raised signals to S9+30 . But the stereo system was somehow
overloaded
while the standards antenna of 16 inv V gives
And
here is another surprise: for any radio tested - except for the HiFi
system :Little radio tuneup requires antenna tuneup even very fine ! Yes , even a 9 kHz
tune up requires a little fine tune in order to achieve the maximum
signal! And this is contrary to what i found with my Australian loop
and the variable capacitors i have ever tested (they have a lower Q).
Using it with the HF150 the lower band part (530+ ) had sharper curves than the upper band part (1700)
Her
is my idea on how to tune the antenna and the radio: I first place the
radio several inches far from the antenna then i tune the antenna for
the maximum signal and then i place the radio as close as possible.
Now some measurements with this antenna in my QTH Thessaloniki on 1600LT before there was any ionospheric propagation . Local noise from lamps , DSL lines and other causes interfere quite much the reception.
864 Horizont (Bu) fair
963 Horizont poor
1296 Christo Botev (Bu)
1350 Era Pyrgos (GR)poor
1458 Albania CRI fair
1512 ERA Chania fair to good
1602 ERA KOzani of 1 form 200
km poor to fair
and since then signals with iono propagation :
873 UKR? 1654 poor
945 Galei Zahal ? poor
963 BU : Zhumen and Horizont
999 (1658)Arab poor (Morocco?) and a russian (Moldova?)
774 1727 Arab good (Egypt? )
855 1729 Romanian good (Romania Actualitati )
531 1735 poor
and here a short report in Litohoron in a clear environment from local noises
684 1550 Beograd poor
963 Bulgaria fair
1404 ERA good
1080 ErA poor
Also heard : 530 540 as marginal
and to add a few more incredible stations heard local late nights in Chalkidiki again from my blog in Multiply on Agugust 2011
540 Nigeria 2000/28.7 once again with news mention B Ajaz 2014 about Indonesia Ramadan and Muslims FAIR
540 R Nigeria Sokoto 2035 /26.7best with //to Athens line with OM taking in Hausa and many laughs . A sudden carrier in 2040
594 RTWKaduna ? 2057 ? /26.7 Nigeria with good signal mixed with a Russian and Arabic station
846 Russian station with rock & roll songs mixed with Athens pirate R cannibal on 2054 /26.7
873 AFN 2100/4.8 "NPR News wire' by YL then with news . Fair
891 NL radio 538 2041/27.7 with talks in NL , Poor on clear freq
1044 R Ethiopia 2045/25.7 with HoA songs with better signal than RIK At 2055 signal dropped to leave MDR from Germany in clear (temps heard on 2058 )
1088 RNA Angola? 2153/25.7 with very poor signal and music . ID 2156 "R N Angola" then fade our
1179 ROM R Rom Actualitati 2118/31.7 Y with talks in Romanianby mrs Stoianescu mixed with nice pop songs 45544
1197 Family Radio Lesotho 2206/31.7 with religious program and talks in English Poor
1215 Absolute radio ??? 2155/28.7 talks in AmEng then a rock song
1251 Radio 5 2150/28.7 poor with talks
1269 SP COPE 2100/31.7 with ID then immediately with news 'Good '
1395 R Rosiie 2120/25.7 with news in Russian
1440 Nigeria Adamawa 2138/28.7 with hilife songs m talks in Hausa , ID (?) mentioning Adamawa 2x422
1567 TWR? 20203 X boy with hi life songs on 2025 OM 26.7 with talks in FR , start of a hilife song with immediate talks by OM in a African language fair signal . I suppose it can be R Benin with prg in Ibo that time
As
a result this little antenna offers a big boost for very poor signals
(quite good during the day) During the night with the overcrowded
bands with the very strong signals it is nearly unnecessary to use it
unless you use it iin dead channels (very few in Europe ) or for
separating 2 stations on the same frequency. This is also very good for zeroing out local noise!
Rating :5/5
Another great review can be found here:
http://www.scanningtasmania.org/tecsun.html
and a photo
http://www.brunero.it/loop/index01.html
and 3 videos
http://www.youtube.com/watch?v=uU42YlOmHN4
http://www.youtube.com/watch?v=AC8Q0...eature=related
http://www.youtube.com/watch?v=CylwtG3rJpM
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