[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [IRCA] Indoor vertical update
Craig - I think that a higher ratio transformer at the feedpoint will
give you more output at MW.
Try a 49:1 (7 to 1 turns ratio) with an FT140A-J (or FT140A-75)
toroidal core having 70 turns occupying about 80% of the core for the
4900 ohm antenna winding and 10 turns placed evenly over it for the 100
ohm winding that goes to the balanced feed. This should improve the
low band performance.
The 2:1 balun on the other end of the feeder stays the same.
I use ordinary parallel 16 or 18 gauge speaker wire or "AC zip cord"
with basically the same results as you'd get with the CAT5.
Two of these antennas placed outdoors about 150 ft. apart would be good
for phasing. Verticals inherently reduce high-angle pick-up so you're
getting an advantage over loops right away.
Two verticals on an east-west axis with a spacing in the 150-200 ft.
range have worked very well for me at the Rowley salt-marsh. You have
to delay the west antenna's pick-up so signals from the west are coming
to the receiving position from it at the same phase (time) as the
westerly signals as picked up on the east vertical. Then you combine
the two sources through a transformer to invert one antenna 180 deg.
relative to the other to get the null west / peak east for TA DX.
Nulls produced are wideband and suitable for SDR spectrum capture.
Mark Connelly, WA1ION - Billerica, MA
-----Original Message-----
From: Craig Healy <bubba@xxxxxxxxxxxxxxxxxxxx>
To: ABDX <abdx@xxxxxxxxxxxxxxx>; Mailing list for the International
Radio Club of America <irca@xxxxxxxxxxxxxxxx>; AM-DX List
<am@xxxxxxxxx>; badx@xxxxxxxxxxxxxx
Sent: Wed, 11 Feb 2009 10:12 pm
Subject: Indoor vertical update
I made a minor change in the indoor balanced vertical this evening and
it
was a good improvement.
Until now it had been a couple of rooms away fed by a 40' length of
RG-58 50
ohm coax. There was a significant noise issue and a number of birdies
that
swamped a number of frequencies. And, some electrical buzz would run
for 30
seconds on and a minute off. Gave me 2/3rds DX time.
I replaced the RG-58 with CAT5 ethernet cable of about the same 40'
length.
At each end is a 110 to 50 ohm balun. The 50 ohm side goes to the
antenna
and the receiver. The CAT5 cable is a nominal 110 ohm impedence.
Additionally I use a 450 to 50 ohm balun on the antenna. I really could
have just used a 450 to 110 ohm transformer if I had such a beast, but
no...
What it did was to pretty near remove all the noise and birdies. I can
listen to weak signals now and the noise is under them. Some problem
noises
simply vanished and none are really a pest right now. 1330 was
unuseable
most of the time but WSPQ-1330 Springville, NY has been fading in and
out.
The noise would have buried it before the cable change. 1140 was
equally
unusable, but now it's clear.
I have to say I am very pleased with using CAT5 ethernet cable instead
of
coax. Noise and signal ingress is much less. It's also cheaper and
much
easier to put connectors on the ends. I have tried it to connect a
ferrite
loop in my truck but it really didn't help reduce the ignition noise. I
think I'm stuck with that until I swap the 350 Chevy V8 for a Cummins
4BT
diesel.
For those who may not have seen the vertical antenna article, it's here:
http://www.am-dx.com/vertical.htm
Craig Healy
Providence, RI
_______________________________________________
IRCA mailing list
IRCA@xxxxxxxxxxxxxxxx
http://montreal.kotalampi.com/mailman/listinfo/irca
Opinions expressed in messages on this mailing list are those of the original contributors and do not necessarily reflect the opinion of the IRCA, its editors, publishing staff, or officers
For more information: http://www.ircaonline.org
To Post a message: irca@xxxxxxxxxxxxxxxx