[TowerTalk] Dipoles

John E.Cleeve g3jvc at jcleeve.idps.co.uk
Thu Jun 1 11:19:29 EDT 2006

Sorry for this posting, but the reply to Lee <K0wa at swbell.net> is 

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 at 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 
> 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 

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