Best choice for what? The best choice to choke or not to choke, or the
best choke?
My thoughts?
I want an antenna with a balanced pattern and with a more or less
conventional feed system whether it requires a choke or not. Reasonable
gain and f/b. to me f/b is important as I have major signals off the
back no matter the direction I use for DX except South America.
I'd probably use a choke (based on K9YC's tutorial, giving on the order
of 4,000 to 5000 ohms isolation) anyway because, even antennas with a
balanced design tend to become unbalanced in the real world for a number
of reasons. A properly designed choke also reduces feedline "pick up"
and reduces noise. Jim's designs have made a great difference here even
with simple antennas. His tutorial also changed what I thought I wanted
and/or needed.
As to performance, on here we all have opinions as do I. But almost any
antenna "works". I've made some impressive mobile contacts. Impressive
at least to me and when we talk mobile we are looking at some real
negative gains in reference to verticals or dipoles.
When some one reports, "man!" you sure have a strong signal! It's
difficult to give credit to anomalous band conditions when your new,
$2000 pile of educated Aluminum was just installed. Yet I had a nearby
ham (now a SK) call on the phone looking for a way to get his new,
large, very heavy, and expensive pile of educated Aluminum to do as
advertized. It just wasn't performing as well as his old inexpensive
antenna. He expected to see/hear some real changes. Real he had, but
not the ones he wanted. Sounds more like "Hope and change<:-))
No study is perfect and even a PHD thesis does not address all the
problems, so under the conditions I think K7LXC's study is quite
thorough even with the short comings that have been pointed out. It is
after all, the most comprehensive comparison available. Anyone who
wants, has the time, and money is welcome to do a new study, or send him
some relative updates that can be replicated.
"I think" I know what I want in and from an antenna. What I know has
changed a number of times to the point where I say "I think I know" what
I want.
In nearly 54 years as a ham, I've seen many antenna and equipment
claims. Enough that I'm usually skeptical of claims even from old and
well established firms.
I'm not talking about just antennas. Look at today's top end rigs (one
of my pet peeves as many already know). I have no reason to doubt those
really impressive numbers for the receiver sections. Even if those
numbers are conservative, do they mean anything useful? Many receiver
dynamic range, selectivity and IM numbers are well past the point of
relevance, or usefulness. They are a valid number but only good for
bragging rights
What good does an HF sensitivity and noise figure do for me when the
noise floor on those bands is 10 to 20 times that figure even when I
ignore local noise? What good do super narrow, steep sided filters do
for me when a station 10 KHz up (or down) is 20 KHz wide or trying to
get the legal limit out of 4 811s? (even get what the amp builder claims
the amp will do) What good do all these outstanding (and useless), but
impressive numbers do when most of the transmitters on the band have an
IM3 of 30 to 35 db?
IF and that's a mighty big if all new transmitters went to an IM3 of -45
to -50 db today, how many years would it take for the bands to show a
noticeable improvement to where some of these fantastic receiver numbers
would become relevant?
Some, like sensitivity and noise figure, never will because of the
slowly, ever increasing noise floor, but selectivity and dynamic range
will. Actually, dynamic range is the one number that can make a
difference under certain conditions, today. I have, on occasion
moved the antenna off the desired heading to null QRM off the back, or
in a side lobe.
One other condition: Today's hams need to learn how to properly set up
their rigs. Then master how to tune and use amplifiers!
73
Roger (K8RI)
On 4/19/2015 8:37 PM, Bry Carling wrote:
So, what IS the best choice?
Best regards - Brian Carling
AF4K Crystals Co.
117 Sterling Pine St.
Sanford, FL 32773
Tel: +USA 321-262-5471
On Apr 19, 2015, at 7:18 PM, Pete Michaelis - N8TR <pete.n8tr@gmail.com> wrote:
I just downloaded a Mosley Pro 67-C Manual from:
http://www.radiomanual.info/schemi/ACC_antenna/Mosley_PRO-67-C-3_user.pdf
Apparently they now do recommend an RF choke. It says "You want to insert
a R. F. Choke into the Coax line to eliminate any RF on the Coax line". They
do go on to suggest a 10 turn choke made from coax which often is not the best
choice.
73 Pete - N8TR _______________________________________________
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73
Roger (K8RI)
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