That was the whole point. 7700 is out of band.

Tam/WB2TT

That was the whole point. 7700 is out of band.

Tam/WB2TT


Yeah, but its two wavelengths, it should probably perform at least as good or
better on 40 than it does on 80?? It would most certainly have a lower angle of
radiation. Again, I'm no electrical engineer, but I've always been led to
believe that the bigger the antenna the better...it should certainly resonate
efficiently on 10-80, in theory anyway..in the same way that a full wave is
better than a half wave or a quarter wave.

See: http://www.ku4ay.net/loop.html and
http://www.cebik.com/atl1.html which are just a few of the sites discussing
these fine antennas..

Steve
kb8viv

Steve,

You are right about the gain. I ran EZNEC on the 75 meter loop, and the gain
at 40 m is about 3db more than on 75. However, it is not resonant in band. I
got an impedance at 3850 of 40 + j5. Impedance at 7700 of 69 +j1, and
impedance at 7300 of 18 + j87 (That is an SWR of 10). Gets worse below
7300.

There is enough feedline and wire loss in the real world antenna that the
SWR measured from the shack is about 5:1 on 40 m.

Tam/WB2TT
"Desmoface" wrote in message
...
That was the whole point. 7700 is out of band.

Tam/WB2TT


Yeah, but its two wavelengths, it should probably perform at least as good
or
better on 40 than it does on 80?? It would most certainly have a lower
angle of
radiation. Again, I'm no electrical engineer, but I've always been led to
believe that the bigger the antenna the better...it should certainly
resonate
efficiently on 10-80, in theory anyway..in the same way that a full wave
is
better than a half wave or a quarter wave.

See: http://www.ku4ay.net/loop.html and
http://www.cebik.com/atl1.html which are just a few of the sites
discussing
these fine antennas..

Steve
kb8viv

You are right about the gain. I ran EZNEC on the 75 meter loop, and the gain
at 40 m is about 3db more than on 75. However, it is not resonant in band. I
got an impedance at 3850 of 40 + j5. Impedance at 7700 of 69 +j1, and
impedance at 7300 of 18 + j87 (That is an SWR of 10). Gets worse below
7300.

There is enough feedline and wire loss in the real world antenna that the
SWR measured from the shack is about 5:1 on 40 m.


Yeah, the rig's not gonna see a 50 ohm impedence, no question about that...It's
a compromise I guess...I'll let you know how it does though, I'll be hanging
wire this weekend for my 80 meter full wave horizontal loop...but if L. B.
Cebik, W4RNL
endorses em - thats good enuf for me hehe...he's sort of an antenna guru...

Steve
kb8viv

Tarmo Tammaru wrote:
You are right about the gain. I ran EZNEC on the 75 meter loop, and the gain
at 40 m is about 3db more than on 75. However, it is not resonant in band. I
got an impedance at 3850 of 40 + j5. Impedance at 7700 of 69 +j1, and
impedance at 7300 of 18 + j87 (That is an SWR of 10). Gets worse below
7300.

But notice the subject line compares 40m and 80m, not 75m.
--
73, Cecil http://www.qsl.net/w5dxp



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On Fri, 31 Oct 2003 19:30:49 -0500, wrote:

Hi group,
just wondering.... can I take a 40M delta loop and add an 80M dipole to it?
Will there be interaction?
SWR problems?

Mark W4UDX


Hi Mark and All,

your Idea of adding a dipole to you 40 meter loop is not a great way
to go.. there will be interaction between the dipole and the loop.
that will cause you problems on both bands.. The better approach would
be to feed the loop with open wire through a good balanced tuner and
feed it on both bands.. on 80m for a 40 m loop you may have to open
the loop opposet from the feed point . If you have room however to
put up a 80 Meter horizontal loop and feed it with Open wire ( Ladder
Line) it will play very well on all bands 80-10m.

Remember a Horizontal loop will get better take off angel as you move
up in frequency. a vertical loop gets worse as you move up in
frequency. (that is higher take off angles) I used a 160M horizontal
loop here for many years .. until a storm took down too of the trees
used for support. But it was a good all round antenna.

73 Dave kc1di

P.S. you may want to read up on loops here's a good place to start.
http://www.cebik.com/vdelt.html

http://www.cebik.com/atl1.html

http://www.cebik.com/fdim/fdim5.html

Mark,
On 40meters, adding an 80 meter dipole to the 40 meter
loop won't 'mess' things up much. It'll change the radiation
pattern, make it sort of directional, kinda. No big deal.
But, on 80 meters, the 40 meter loop acts like a 1/2 wave
'short' between the two halves of the dipole. SWR goes up
close to around 500:1, the transmitter is looking at something
on the order of '300R - 2500J'. Not too good, and as for the
lower radiation angle, it really doesn't make a lot of
difference
at that point.
'Doc

PS - The 'numbers' are approximate, "close enough for 'gum-ment'
work"...

'Doc wrote:
Mark,
On 40meters, adding an 80 meter dipole to the 40 meter
loop won't 'mess' things up much. It'll change the radiation
pattern, make it sort of directional, kinda. No big deal.
But, on 80 meters, the 40 meter loop acts like a 1/2 wave
'short' between the two halves of the dipole. SWR goes up
close to around 500:1, the transmitter is looking at something
on the order of '300R - 2500J'. Not too good, and as for the
lower radiation angle, it really doesn't make a lot of
difference at that point.

Doc, ask yourself - why would the 80m signal rather flow into an
impedance of 300-j2500 than into an impedance of 70+j0? Answer:
it wouldn't. An 80m 1/2wl dipole in parallel with a 40m 1wl loop
is a perfectly acceptable configuration as far as feedpoint
impedances go.
--
73, Cecil http://www.qsl.net/w5dxp



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Cecil,
"Horse hockey"! Try it and see what happens.
Didn't say model it...try it.
'Doc

I have a 40 meter loop inside my 80 meter loop and have been running it for
3 years without any problems.

Both antennas are flat (no SWR) and there appears to be little to no
interaction between the antennas.

73,

Lee - K1NT

wrote in message
...
Hi group,
just wondering.... can I take a 40M delta loop and add an 80M dipole to
it?
Will there be interaction?
SWR problems?

Mark W4UDX