Sorry for this posting, but the reply to Lee <K0wa@swbell.net> is
undeliverable.
Hello Lee,
Many years ago, when I was a junior TV engineer, working at a BBC
Engineering research facility, I wandered into the aerial laboratory
one day, and asked similar questions. The response I received was that
I would be well advised to stick to dipoles, and multiples thereof,
and carry out all my measurements by using an electrical half wave, or
multiples thereof, length of co-ax, at the frequency for which the
dipole has been cut, between the measuring device and the dipole
centre point. For the past 50 years or so, I have always followed that
advice. I feed my W3DZZ inverted vee, apex at 40 feet, multiband
dipole with an electrical half wave length of co-ax, cut for 3.525
Mhz, this gives exact multiples of half waves for the harmonically
related bands, I feed my tower mounted tri-band yagi in a similar way,
and the ATU trims the system, when the wanted frequency of operation
is off the "design" frequency. For measurement, I have always used a
noise bridge, using a small 50 ohm, or 75 ohm fixed carbon resistor,
for calibration, and a receiver as the detector, with the AGC turned
off, to avoid chasing ones tail, as the receiver AGC tries to
compensate for the falling signal, as the noise null is reached. Any
slight difference between the null of the calibration resistor, and
the attached feeder/antenna under test, can be attributed to the
distributed inductance and capacity of the feeder cable.......I hope
this information is of some use....sincerely, John. G3JVC
On Thu Jun 1 15:26 , Lee Buller <k0wa@swbell.net> sent:
>Ladies and Gents....
>
> Recently, I had to replace my 40 meter dipole (more of an Inverted-
Vee) antenna because the coax center lead had broken off the. The
dipole worked OK, but I was never really sure that I liked it. What
is there not to like about a dipole antenna? (I sure I get some wise
cracks here). The dipole did not seem to have a resonate point. It
was below 1.8:1 on CW and was about 3:1 on SSB. So, the antenna was
long.
>
> The new antenna, using a Budwig connector this time, shows the same
characteristics. I cut the the antenna at 66 feet and I made sure
that both sides of the antenna were the same length....33 feet. The
antenna is mounted at 45 feet using a bracked that runs through the
tower. The antenna in question is on the east side of the tower while
an 80 meter antenna is on the west sime of the tower mounted on the
same bracket. The feed points are about three feet apart....on
seperate coax feeds.
>
> The end of the Inverted-Vee on 40 comes down to about 20 feet off
the ground...while the 80 meter antenna ends about about 12 feet off
the ground. The 80 meter antenna is in a straight line, while the 40
meter antenna has a slight VEE to to the tie points. So it has VEE to
the the east....and a Vee down. This is hard to explain in words. I
hope you experts get this.
>
> The new antenna was failry good on SSB but not great ... about
1.8. I attached two test leads to each end and the antenna show that
it was at 1.8 on CW...around 7.025. It seems that the test leeds were
too long and now it is resonate below 7.0.
>
> But, there seems to be a crazy problem that I cannot get the
anntenna any lower than 1.8 to one....thinking that there should be a
length in there that should be "perfect." I cannot find the "perfect
point" which I would like to have around 7050.
>
> Reading the Antenna Handbook...this antenna is working as stated
although I did not anticpate the length of an inverted Vee to go
longer. I've read the articles, but it seems there is something wrong
with the antenna.
>
> Is there an interaction between the tower...the 80 meter
antenna...the Vee to the east?
>
> Is the coax bad? IT has been up there for quite some time and it
was used at another location before I put it up here.
>
> Comments, flames, postulations, editorials, and pontifications are
all welcome. They might show on my web pate later on....so...you have
been warned.
>
> Thanks for the discourse on a simple dipole
>
> Lee Buller - K0WA
>
>
>In our day and age it seems that Common Sense is in short supply. If
you don't have any Common Sense - get some and use it. If you can't
find any common sense, ask for help from somebody who has some common
sense.
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