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G0FTD > ANTENA 26.12.04 02:13l 106 Lines 3975 Bytes #999 (0) @ WW
BID : 7D9098G0FTD
Read: DK6SV DG8DG OE5AKM GUEST
Subj: 80m - 6m DX from shack ant
Path: DB0FHN<DB0RGB<OK0PPL<DB0RES<ON0AR<7M3TJZ<SP7MGD<IZ0AWG<VK6ISP<VK4TTT<
GB7CIP<GB7SXE
Sent: 041225/2312Z @:GB7SXE.#38.GBR.EU #:17281 [Hastings] FBB7.00i $:7D9098G0FT
From: G0FTD@GB7SXE.#38.GBR.EU
To : ANTENA@WW
A Simple 80m to 6m loop antenna that works DX.
Here is a brief description of my simple antenna which is in my bedroom
shack !
A 2.4m square wire quad loop is literally "drawing board pinned" to the
brick wall. The ATU is a T-Match that I've had for nearly 25 years and
there is nothing special about it at all except that it does use a roller
coaster inductance which can help minimise losses.
The 1:1 balun was made from some scrap enamelled copper wire (18SWG) and a
3 inch piece of ferrite rod stolen from a dead broadcast receiver. The
balun is shown as B1 in the diagram. It is fitted into my ATU so that
there is NO coaxial feeds.
This is important.Under NO circumstances should the interconnections be
made by lengths of coax.
The 100æH air wound inductance is used on 24.9Mhz and 28MHz to swing the
radiation pattern around by 90ø however the polarisation will change from
horizontal to vertical. It's best to have this inductance switched in
case you want to electronically "rotate" the antenna.
The antenna can be run without a balun but I have found that on certain
frequencies the transmitter sees conductors within the shack wiring and
surrounding cabling and induces imbalance which can effect performance.
It's easy to check for this problem,just try tuning the antenna whilst
touching the radio casing or atu casing and see if the SWR changes. If it
does you've got an imbalance problem. The balun will sort that out.
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³ 100 æH ³
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³ 2.4m square loop ³
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50ê COAX
Using totally indoor antennas has been a bit of a hobby horse of mine and
I've played with loops for some years now. This is just another variation
of a few I have been trying.
Losses through brick walls don't appear to be very great. In fact hardly
worth mentioning on HF. I tend to use QRP these days, it helps keep TVI
away as well as providing a challenge.
On 80m my best DX has been UZ7HO (I used 25 watts), inter europe on 40m
(10 watts), numerous european and Russian QSO's on 30m CW with 3 watts
plus South Africa,USA,VE and Brasil on the HF DX band using around 15
watts
SSB.
On 6m during the sporadic E season I can easily work around Europe with
3 watts CW and SSB.
Although I have experimented with the antenna on 1650m I have yet to be
satisfied with the performance although it can make a few QSO's on
groundwave for about 30 miles.
If anyone has a way of improving 160m performance I'd be grateful ;-)
For me the advantage of this simple loop system means that it's CHEAP !
No expensive vacuum variable capacitors or heavy duty construction with
copper pipes.
I can work the DX without even having an outside antenna, with low power
and enjoy my hobby everyday.
There is NO excuse for complaining that you don't have space for an
antenna, even a bedroom shack like mine will do - so get cracking.
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ 73 - Andy ³
³ G0FTD ³
³ Whitstable, Kent ³
³ Winpack-AGW ³
³ ÚÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ³
³ ³ Û ³ ³
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