Good evening friends,
after the 4-square mini-array (phased verticals), built in 1994, several
Pennants and a rotable Flag, now I am going to try also the K9AY loop.
I have four RG213 feedlines for RX antennas entering in the shack ( three
are completely buried) and I built a switching box which let me switch them
between the Orion Main and Sub receiver (for the dual receiving capability
of this rig) and eventually phase them by switching in, and swapping the
inputs of the MFJ 1025. (No more need to disconnect and connnect
cables on the back side!).
Recently I modified the Pennants buried central hub by switching also the
coax shields and I changed all the transformers on the pole boxes from
FT140-43 (a single one per box with switching on the antenna high
impedance side) into the binocular 73 stuff (one for each loop by switching
on the 50 ohm side); they are matching perfectly and it seems I get stronger
signals and less noise.
But my big problem is the power line (actually a utility line made of three
insulated and twisted wires) and in fact most of the Pennants are performing
very well, but one of them, facing the power line is very noisy.
Since a couple of years also the 4-square phased array (vertical dipoles
10 meters high) became quite noisy.
I just built also a full-size rotable Flag and put it on an old little tower
(used in the past for a 10 meters yagi); it is very close to the power line
but, beeing "completely "above" it, I hoped to overcome its noise: no way!!
As this feedline is not buried but comes down through the roof, I inserted
two common mode chokes (10 turns of RG58 through two FT140A-J)
with the ground tap in the center (4 x 5000 mu, high permeability toroids).
The output level is very high but it's most noise! the S/N ratio on the Flag
is horrible.
Typical S-meter readings of the daily band noise on the Orion with KD9SV
preamplifier are as follows:
- Most Pennants : from S2 to S3
- Worst Pennant: S6
- 4 square mini-phased array: from S6 to S7
- Rotable Flag : from S9 to S9+20 dB
- TX vertical (no preamplifier): S6
BTW: on the Pennants line I usally insert a buried PRE-1 preamplifier by
K9AY which is doing very well (and it is followed by the KD9SV preamp.
in the shack).
I will let the Flag on for the winter season, hoping in any kind of miracle
on the power line but I am afraid that this antenna is useless in this
environment!
Recently I got a further lot available where I can put a K9AY loop; it's
over 100 meters from the Tx antenna and I can reach it with a buried
feedline and a 5 pole control cable. I have an ICE preamplifier left and
I am intended to put it down there.
Now this is my question:
- in the original '97 QST article K9AY uses a trifilar transformer, but
later
it was suggested by many to go to separated windings and to not ground the
coax cable at the antenna (well detailed in the last ON4UN book)
- but if I use a preamplifier in the switching box I must ground it, and
also the feedline and than connect on the same ground the low impedance
side of the transformer, is it right?
I saw the pictures of the new commercial version of the K9AY loop (AYL-4)
on http://www.aytechnologies.com/Products/products.htm through the WX0B site
http://www.arraysolutions.com where the SO239 connector looks grounded,
so I guess that the low impedance side of the transformer is still connected
to ground; but I wonder if the original old trifilar style or a separate
winding type is used.
I have both the FT140-43 and FT114-77 cores: which do you suggest ?
Of course some long staggered Beverages should be better, but that's another
story !
Thanks for reading and best 73
Luis IV3PRK
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