On 26 jun, 02:29, "Justtis" wrote:
Anyone know of a good site offering build plans. *Prefer plans from someone
who has built and used same.
I need a quiet antenna like this and Wellbrook is just too expensive!http://www.wellbrook.uk.com/index.html
Hello Justtis,
When you want to make a tunable loop (so tuning at the loop, or very
close to it), you don't need an amplifier in most cases.
Tuning (with reasonable match) has the advantage of large signal
output for relative small loops and rejection of strong out of band
signals. Also it is easier to get a good balance to avoid conducted
interference traveling via the coaxial feeder to the loop antenna.
Disadvantage is that you have to tune when changing band or frequency
and the tuning unit is outdoors.
Active loops save you from tuning, but may result in inter-modulation
products due to strong signals. Also your receiver may suffer from
this (in that case you need some form of preselection).
From my own experience, loops do best up to the low HF. Above about 5
MHz, the performance difference between a loop and a vertical
capacitive antenna (stick) is minimal. Of course when mounted at a
rotor, the loop has the advantage of directivity for low elevation
signals.
Before buying any loop (or spending a lot of money on parts), first
try one to make sure it solves your problem. When you are interested
in one band only, you can make a provisional tuned loop yourself to
see the improvement over your existing antenna.
Try to get in contact with a radio amateur (HAM) group. Almost sure
people over there will share their knowledge. You may also post in
rec.radio.amateur.antenna
Another less known method is to make a thick single-turn un-tuned loop
with natural balun function in it (that are loops where the tubing is
cut at the top of the loop). An example of a small strip-ype loop is
given he
http://www.tetech.nl/divers/small_H_FieldLoop2.jpg . Go
the shack with low loss cable and do the tuning (and matching) in the
shack. For transmitting this is no good option, but for reception
only, this gives good results and you have the tuning/matching unit
indoors adjacent to your receiver.
Best regards,
Wim
PA3DJS
www.tetech.nl
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