Carter,
That was an excellent question and Carl gave a great answer, but it is also
a little more complex than that.
My questions to Bob would be:
1. What kind of balun (if any) are you using on the coax fed dipole?
2. How is its coax running back to the house? In the air or along the
ground?
3. Do you have an RF choke in the coax line just where it reaches the house?
4. How is the openwire feedline running back to the house? Similar to the
dipole?
5. Have you twisted the openwire on its route to the house?
6. What kind of balun are you using on the openwire fed folded dipole?
7. What kind of noise are you talking about? General band noise or noise in
storms?
8. Is this 1 to 2 S-Units the same in all directions (probably hard to
tell)?
All of these can have an impact on the signal to noise ratio at the radio.
The main factor in most points is common mode current.
I've never used a rotatable beam on 80m but I have on 40m and I can say that
the direction the beam is pointing sometimes makes a HUGE difference in the
noise level. Of course that was here is Europe. It may be different in the
states.
There is an age old debate going on about whether or not a quad is quieter
than a beam.
>From 1980 to 1983 I was lucky enough to have a quad and a beam, both at 33
ft.
Also, that was the days before switcher power supplies and all the other
modern consumer products that cause so much hash in our houses.
My experience was, the quad was definitely quieter than the beam when they
were pointed in the same direction.
It seems to me comparing a folded dipole to a dipole is a lot like the quad
to beam scenario.
Let's remember why the quad was invented in the first place.
It was to reduce the damage to the antenna caused by corona discharges from
the tips of elements of the beam.
In storms, I would expect the folded dipole to definitely be quieter.
That's why I listed "type of noise" above.
ALL of this of course is only secondary.
The added bandwidth of the folded dipole on 80m is its main benefit.
73 - Rick, DJ0IP
(Nr. Frankfurt am Main)
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Carter
Sent: Tuesday, September 09, 2014 10:51 PM
To: tentec@contesting.com
Subject: Re: [TenTec] Eagle Tuner
On 9/9/2014 10:47 AM, Bob McGraw - K4TAX wrote:
> One thing I've clearly noticed about folded dipoles, the one I have > on
the tower is noticeable quieter, 1 to 2 S units, than the 75M > dipole fed
with coax on the same tower at approximately the same > height. Now there
may be some lobes that favor noise source, > typically NW as that's where
the storms originate, or slightly null > to the noise source as the antenna
are about 60 degrees apart, > broadside.
Sorry Bob, but in all sincerity, I gotta ask...
If the *noise* is "noticeable[y] quieter, 1 to 2 S units", wouldn't the
wanted *signal* also be down 1 to 2 S units? Your theory about lobes and
noise has merit, but presumably the signal and noise would be affected
equally. (or could it be that the wanted signal is horizontally polarized
and noise is supposedly mostly vertically polarized?)
Inquiring minds want to know.
73,
Carter K8VT
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|