My center of a 3.8 Mhz doublet is at about 35 feet and am going to drop
the ends from 30 feet to about 10 to 15 feet. Just wondering if it will
make all that much difference if any?

NOPE!

At those heights it will be an excellent antenna for close-in work.
Close in means ~100 miles daytime and up to ~600 miles nights and evenings.

Big Endian wrote:


My center of a 3.8 Mhz doublet is at about 35 feet and am going to drop
the ends from 30 feet to about 10 to 15 feet. Just wondering if it will
make all that much difference if any?

It will slightly decrease the performance. I'd keep the ends
as high as possible if you want the max performance.
MK

In article . com,
wrote:

It will slightly decrease the performance. I'd keep the ends
as high as possible if you want the max performance.
MK

I'd like to but I'm a little concerned about next door, if you know what
I mean. The poles are on the lot line and in the front yard, but in the
summer they are pretty well shielded by trees, in winter they stand out
their naked in the wind.

Where I live what I do on my property is my business as long as I comply
with the local zoning requirements.

My neighbors don't get a vote on how I install and operate my station.
The town assessor will NOT grant an abatement because my neighbors live
next to a ham station [property value argument].

I run 1 KW when required. My phones are 100% clean. My TV's are 100%
clean. My computer is 100% clean. My computer sound system is 100%
clean. My stereo system is 100% clean.

Don't be concerned about next door. Just make sure your station and
house electronics are clean.

DD, W1MCE

Big Endian wrote:

SNIPPED


I'd like to but I'm a little concerned about next door, if you know what
I mean. The poles are on the lot line and in the front yard, but in the
summer they are pretty well shielded by trees, in winter they stand out
their naked in the wind.

Big Endian wrote in
:


My center of a 3.8 Mhz doublet is at about 35 feet and am going to
drop the ends from 30 feet to about 10 to 15 feet. Just wondering if
it will make all that much difference if any?

There will be a marked improvement in the low angle performance in the
direction off the ends of the antenna (the flattop is very poor at this).
This will come at the expense of a sight loss (about .8db) off the
pattern's top (where you can most afford it). You will also experience a
slight deterioration in the SWR (based on 50 ohm coax) from about 1.34 to
2.05, easily managed by any tuner, including those built into many radios.
You will also find that you need to shorten the antenna very slightly to
maintain the same resonant frequency.

This won't make it into a superior DX antenna but it may allow you to hear
things you missed before. Basically, Bob Heinlein was right. There ain't
any such thing as a free lunch.

--
Dave Oldridge+
ICQ 1800667

Dave Oldridge wrote:

This won't make it into a superior DX antenna but it may allow you to hear
things you missed before. Basically, Bob Heinlein was right. There ain't
any such thing as a free lunch.


TANJ!

Tom
K0TAR

rocky wrote in
:

In article ,
Dave Oldridge wrote:

Big Endian wrote in
:


My center of a 3.8 Mhz doublet is at about 35 feet and am going to
drop the ends from 30 feet to about 10 to 15 feet. Just wondering
if it will make all that much difference if any?

There will be a marked improvement in the low angle performance in
the direction off the ends of the antenna (the flattop is very poor
at this). This will come at the expense of a sight loss (about .8db)
off the pattern's top (where you can most afford it). You will also
experience a slight deterioration in the SWR (based on 50 ohm coax)
from about 1.34 to 2.05, easily managed by any tuner, including those
built into many radios. You will also find that you need to shorten
the antenna very slightly to maintain the same resonant frequency.

This won't make it into a superior DX antenna but it may allow you to
hear things you missed before. Basically, Bob Heinlein was right.
There ain't any such thing as a free lunch.

What I've read is that when the ends are dropped to an inverted Vee
configuration the feedpoint impedance drops closer to 50 ohms, but the
Vee bandwidth is more restricted. Hard to believe that lowering the
ends by 15 feet from 30 would make all that much difference on 75
meters.

It's only really noticeable on low-angle (about 30 degrees or so) signals
from the direction off the ends.


--
Dave Oldridge+
ICQ 1800667

The BeNevolent dbu wrote in
:

In article ,
Dave Oldridge wrote:

rocky wrote in
:

In article ,
Dave Oldridge wrote:

Big Endian wrote in
:


My center of a 3.8 Mhz doublet is at about 35 feet and am going
to drop the ends from 30 feet to about 10 to 15 feet. Just
wondering if it will make all that much difference if any?

There will be a marked improvement in the low angle performance in
the direction off the ends of the antenna (the flattop is very
poor at this). This will come at the expense of a sight loss
(about .8db) off the pattern's top (where you can most afford it).
You will also experience a slight deterioration in the SWR (based
on 50 ohm coax) from about 1.34 to 2.05, easily managed by any
tuner, including those built into many radios. You will also find
that you need to shorten the antenna very slightly to maintain the
same resonant frequency.

This won't make it into a superior DX antenna but it may allow you
to hear things you missed before. Basically, Bob Heinlein was
right. There ain't any such thing as a free lunch.

What I've read is that when the ends are dropped to an inverted Vee
configuration the feedpoint impedance drops closer to 50 ohms, but
the Vee bandwidth is more restricted. Hard to believe that
lowering the ends by 15 feet from 30 would make all that much
difference on 75 meters.

It's only really noticeable on low-angle (about 30 degrees or so)
signals from the direction off the ends.

I am going to have both antennas up at the same time. I'll switch
between the two and see if there is any difference on close in
(100-300 miles) stations hearing me. The antennas will only be a few
feet apart, one will be a dipole cut for around 3.8 and fed with 52
ohm coax, the other is a 130 ft. center fed doublet using 450 ladder
line. This may take a while because we're still in winter.

Assuming the mean RF CURRENT heights are the same and the two antennas
are not violently interacting, you shouldn't see much difference. There
will, of course always be some phasing differences between two different
antennas, even if they are otherwise equal. This cannot be avoided where
signals are being reflected off the ionosphere and the ground.

--
Dave Oldridge+
ICQ 1800667