Re: [IRCA] Indoor vertical update
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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



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