[HCRA] February Zero Beat and more!

[Rick Lindquist]

Thanks, Jim. 

I'm having major surgery next week, so I'll miss the Feb 1 meeting, but it
was good to meet Donna Halpern, after having exchanged some correspondence
with her several years back (and having squandered the early years of my
professional career in radio and TV broadcasting). 

Please note that the CQ WW 160-Meter Contest is this weekend: 

CQ WW 160-Meter Contest -- CW, sponsored by CQ Magazine from 0000Z Jan
26-2359Z Jan 27 (Phone is Feb 23-24). Exchange: RST and S/P/C. Categories:
SO-QRP (<5 W) -LP (<150 W) -HP, MO categories. Enter as MO if packet or
spotting nets are used. QSO points: own entity -- 2 pts, same continent -- 5
pts, diff cont -- 10 pts, /MM stations count 5 points, but no multiplier.
Score: QSO points × states + VE call areas + DXCC entities (KH6 and KL7
count as DXCC only). For more information: www.cq-amateur-radio.com. Logs
due by Feb 28 to 160cw at kkn.net (Cabrillo format only) or CQ 160 Contest, 25
Newbridge Rd, Hicksville, NY 11801. 

Hope to hear some of you on for this. Not sure if I'm going QRP <gasp> or
LP.

I'm happy to see some discussion of antennas in this issue in addition to my
own article. A few comments re the $5 antenna article by the writer who
doesn't wish to identify him or herself:

The author writes: 

"Most importantly, a quarter wave counterpoise is required for each band.
This counterpoise should be a few inches above the ground, insulated, and as
straight as possible. This critical counterpoise is the second half of the
antenna, and provides the RF ground for the tuner/radio. Using a long (or
random) wire here didn’t work for me."

Largely right on target! I alluded to some of these issues in my own
article, "HF Antennas for Morons — Part 2" in this Zero Beat issue (as well
as in Part 1 a few months ago). Folks, ALL antennas have to "work against"
some kind of RF ground. You can't stick a quarter-wave wire up in the air,
horizontally or vertically, without its having a mirror image. "Mystery
Writer" obviously has discovered this — as I did — through trial and error.

In the case of the plain-vanilla center-fed half-wave dipole, the antenna's
two halves complement each other, so you don't need an artificial ground,
counterpoise or radials to make it work well. That's the beauty of the
center-fed half-wave dipole fed with coax (and, presumably, cut to length).
Your short mobile antenna is typically an electrical quarter wave and works
against the body of the car, which isn't cut to any particular "length."

Anytime "RF is present at the rear of the radio, and very close to the
operating position," you've got "RF in the shack." This means your RF ground
at the operating frequency is poor, plain and simple, and your antenna is
essentially showing up on your key, mic or front panel because it has no
place to go. 

The author correctly suggests the use of a quarter-wave "counterpoise,"
which should be connected to the radio's ground lug, to mitigate stray RF
and give the radiating element of the antenna (the 56-foot or 100-foot wire
in this case) something to work against. 

I disagree, however, that a counterpoise must be elevated above ground
and/or laid out in a straight line. Nice but not necessary. It just needs to
look like an electrical quarter-wavelength, so some adjustment in its length
may be necessary (it's not good enough to just cut it to the formula). I've
used quarter-wave counterpoises with the wire draped around the room, across
the floor, thrown out the window or stretched (more or less) across the
lawn. You could also use one of those MFJ "artificial ground" tuners (or
build your own) and a random piece of wire to accomplish the same thing.

When I was in El Salvador, I used an end-fed wire maybe 50 or 60 feet long
for a radiating element and somewhere in the vicinity of a quarter-wave
piece of wire just lying on the floor of the hotel room. I worked into
Europe and the US on both CW and SSB with this setup while running less than
3 W, so the antenna obviously got out.

You can avoid the RF exposure problem by simply placing the antenna far
enough away and running a little bit of feed line to the tuner or radio.
Five watts on 40 or 20 meters won't fry your brain, however.

If you're planning to try an antenna such as the mystery author suggests,
I'd also recommend staying away from a half-wave. What's best, and easier to
match, is a quarterwave or any ODD multiple of a quarter wave. This is why a
99-foot end-fed piece of wire will work on 40 meters (or 48 feet or so on
20), although you'll need to either have a good RF ground or, if fed with
coax, a means of decoupling. This is because a quarter wave presents a low
impedance — typically in the vicinity of 50 ohms — when worked against a
good RF ground, while a halfwave will present a much higher impedance
because it's voltage fed rather than current fed, making it more difficult,
but not impossible, to match without a tuner.

At first I didn't quite "get" the allusion to the original Windom antenna,
which was fed off center with a single wire. By nature (or physics, if you
will), the Windom  — the only design that can call itself that — has to have
a good RF ground to work, whether it's radials, a counterpoise or just a
bunch of really deep ground rods.

Yes, the rubber duckie antenna on the typical VHF-UHF hand-held transceiver
works more or less in this fashion, with your body capacitively coupled to
the radio body, acting as the RF ground. As most know, the rubber duckie is
not a terribly efficient antenna system.

I hope this helps. I encourage comments on this or my article. There's a ton
of experience and knowledge out there. Don't make the newcomers have to
learn the hard way!

73, Rick, N1RL 


-----Original Message-----
From: hcra-bounces at mailman.qth.net [mailto:hcra-bounces at mailman.qth.net] On
Behalf Of Jim Mullen
Sent: Friday, January 25, 2008 10:47 AM
To: HCRA at mailman.qth.net
Subject: [HCRA] February Zero Beat and more!

______________________________________________
-------Hampden County Radio Association-------
-----------e-mail list (reflector)-------------
______________________________________________
Hey gang!

The February edition of Zero Beat is on the web. Point your browser to:
http://www.hcra.org and click the link at the top of the page to see an
issue chock full of good stuff. 

While you are on the website why not check out a few other things. Changes
on the page include the latest info for the 2008 Titanic special event
station and February's upcoming meeting.

It is also time to start thinking about March's 'Show & Tell' competition.
How is your project coming along? The winner in each class (beginner or
expert) will go home with a $50 gift certificate to HRO for their efforts.
You're not going to let a foam paddle take home the big prize this year, are
you?

The bands have been open at times, the new sunspot cycle has officially
started and there is DX out there. Go for it!

'73...

Jim, KK1W

------Hampden County Radio Association-------
An ARRL Special Services Club celebrating 60 years
------------http://www.hcra.org------------
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