Do I Insulate the yagi boom from the mast
barett
from the metal mast?
Are there any benefits in insulating the boom from the mast or not when
mounting?
Thanks
nm...@wt.net
> When mounting any yagi beam to a metal mast, is it best to insulate the boom
> from the metal mast?
No. At least from a lightning point of view. I never insulate the boom
from the mast.
>
> Are there any benefits in insulating the boom from the mast or not when
> mounting?
Not that I can think of.
Gerard
news:dMNjm.257432$bA.3...@newsfe16.ams2...
> When mounting any yagi beam to a metal mast, is it best to
> insulate the boom from the metal mast?
elements, so there is no need to insulate the boom
from the mast.
> Are there any benefits in insulating the boom from the mast or
> not when mounting?
I can think of no benefits to insulate. NOT insulating has the
benefit that static can run to ground if the mast is grounded.
Log-per antennas should be insulated from their masts as the
booms are part of the feed, and should not contact each other
or ground.
73 - Gerard - PE1OUD
E-mail: pe1oud(NOTTHIS)@amsat.org
barett
from the mast and choked the coax just below the beam it would guarantee to
solve my TVI problem and improve the efficiency of the antenna. What do you
think?
It's a lot of work to drop the beam back down to ground level to do this.
"barett" <bar...@blueyounder.co.uk> wrote in message
news:dMNjm.257432$bA.3...@newsfe16.ams2...
Cecil Moore
> When mounting any yagi beam to a metal mast, is it best to insulate the boom
> from the metal mast?
The voltage at the center of the elements is supposed
to be zero. Therefore, the boom is supposed to have
zero potential and thus can be mounted to a metal mast.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com
Cecil Moore
> I am causing TVI at the moment and I was told that if I insulated the beam
> from the mast and choked the coax just below the beam it would guarantee to
> solve my TVI problem and improve the efficiency of the antenna. What do you
> think?
>
> It's a lot of work to drop the beam back down to ground level to do this.
Get the guy who made the guarantee to do the work.
Don't pay him if it doesn't work.
JB
corrosion anywhere, even at the cost of replacing hardware and any rusty
masts. rust and corrosion can actually cause broadband noise and harmonics
that doesn't come out of the transmitter. Perhaps there is an issue with
your rotor?
Richard Clark
<bar...@blueyounder.co.uk> wrote:
>I am causing TVI at the moment and I was told that if I insulated the beam
>from the mast and choked the coax just below the beam it would guarantee to
>solve my TVI problem and improve the efficiency of the antenna.
Stop listening to those people who "told" you this and "guarantee"
(whatever that means) it as a solution.
TVI is most frequently caused by your feedline's proximity to RF
sensitive devices AND the presence of Common Mode currents on the
feedline. Put a choke on the transmission line at the feed point and
another choke one quarter wavelength away from the feed point towards
the transmitter.
This is a very common topic here and if you were to Google the group's
combined postings about it, you would find a world of education that
goes beyond this simple prescription. (Google the terms TVI and
Common Mode and Choke.)
73's
Richard Clark, KB7QHC
barett
Thanks all for your help. The search I did on Goole has given me loads to
read up on, so I should be fine now.
Thanks again
Bob Bob
In Sydney in I guess the late 70's two broadcast FM stations came online
on 105 and 106MHz (Approx). Their antennas were both mounted on one of
the big TV towers in the northern suburbs.
Individual tests proved positive, good range etc etc. When they were
both turned on however they caused severe interference to the AM BC band
(1MHz or so) and also the CH10 TV (212MHz or so). As I remember hearing
the fault was a rusty rivet holding some tower sections together.
This information is anecdotal. I havent verified it!
Cheers Bob VK2YQA
Sal M. Onella
"Bob Bob" <bob3...@suddenlink.net> wrote in message
news:qjq5m6-...@p400bob.personal.cox.net...
> Kind of off topic but maybe interesting.
>
> In Sydney in I guess the late 70's two broadcast FM stations came online
> on 105 and 106MHz (Approx). Their antennas were both mounted on one of
> the big TV towers in the northern suburbs.
>
> Individual tests proved positive, good range etc etc. When they were
> both turned on however they caused severe interference to the AM BC band
> (1MHz or so) and also the CH10 TV (212MHz or so). As I remember hearing
> the fault was a rusty rivet holding some tower sections together.
>
> This information is anecdotal. I havent verified it!
Oh, yes! The "rusty bolt effect" is well known to those of us who have
worked US Navy EMI problems. I did it off and on for almost thirty years.
A non-linear junction mixes two or more signals and the structure involved
reradiates the sums and differences of the fundamentals and their harmonics.
The structure can be any topside metallic item or collection of items.
The result is a comb of frequencies which can cause widespread interference
literally for miles. In some cases broadband noise is also present. In
really bad cases, HF receive is effectively non-functional.
The solution is to bond or insulate everything topside in areas of high RF
energy -- eliminate as many non-linear junctions as possible.
Cecil Moore
> A non-linear junction mixes two or more signals ...
I once had a cracked/cold solder joint in a 40m downspout
vertical that seemed to partially rectify the source
signal generating undesirable harmonics on 15m detected
by another ham 1/2 mile away. A jumper across the bad
junction cured the problem.
Sal M. Onella
"Cecil Moore" <nos...@w5dxp.com> wrote in message
news:%Y8lm.154347$0e4....@newsfe19.iad...
> Sal M. Onella wrote:
> > A non-linear junction mixes two or more signals ...
>
> I once had a cracked/cold solder joint in a 40m downspout
> vertical that seemed to partially rectify the source
> signal generating undesirable harmonics on 15m detected
> by another ham 1/2 mile away. A jumper across the bad
> junction cured the problem.
Yup. Navy ships have from a few dozen to several hundred such jumpers,
depending on ship type. Many are welded but some are bolted, especially if
the object must be moved for use, etc.
I have heard that hams who use a tin roof as an HF ground plane are apt to
generate harmonics.
Sal
christofire
"Sal M. Onella" <salmo...@food.poisoning.org> wrote in message
news:Grnlm.152588$FP2....@newsfe05.iad...
Some of the towers and masts used for broadcasting in the UK have welded-on
tabs that are welded together after the sections are bolted together. A
particular potential problem has existed since Band II was extended up to
108 MHz: that of generation and radiation of IPs in the band above, used for
VOR and ILS.
Chris
Michael Coslo
> I have heard that hams who use a tin roof as an HF ground plane are apt to
> generate harmonics.
As well as those who spend too much time around the wimmin!
- 73 de Mike N3LI -