40M+80M dual band delta loop?
 

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

Mark,
Yes, to both.
'Doc

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

Actually, that should work pretty well. A loop has a very high
impedance on half its design frequency. Another thing to consider
is breaking the 40m loop opposite the feedpoint for operation on
80m. 1WL on 40m = 1/2WL on 80m.
--
73, Cecil http://www.qsl.net/w5dxp



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

Why not just increase the size of your loop to make it an 80 meter loop?? That
should cover 40m, at least thats what I've read...I'm in the process of
building my 80 meter loop which will hopefully work 10-80...Good luck..

Steve

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

Why not just increase the size of your loop to make it an 80 meter loop??
That
should cover 40m, at least thats what I've read...I'm in the process of
building my 80 meter loop which will hopefully work 10-80...Good luck..

Steve


But remember a loop for 80 fed with coax will make for a high impedeance on
40.

If you feed this 80 meter loop with ladder line, open wire line, etc. You
can use it everywhere via a balanced output tuner of course.

Dan/W4NTI

Dan/W4NTI wrote:
But remember a loop for 80 fed with coax will make for a high impedeance on
40.

Higher, but not too high. A 2 WL loop is resonant in much the same way
that a 1 WL loop is resonant. Perhaps you are thinking about dipoles?
--
73, Cecil http://www.qsl.net/w5dxp



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But remember a loop for 80 fed with coax will make for a high impedeance on
40.

Yeah, you'd probably need to use a tuner but one wavelength on 80 is 2
wavelengths on 40, is 4 wl's on 20, 8 on 10....theoretically an 80 meter loop
should work great on 10-80 and the take off angle supposedly decreases as the
frequency increases...so it should be good at dx too..

Steve
kb8viv

"Cecil Moore" wrote in message
...
Dan/W4NTI wrote:
But remember a loop for 80 fed with coax will make for a high impedeance
on
40.

Higher, but not too high. A 2 WL loop is resonant in much the same way
that a 1 WL loop is resonant. Perhaps you are thinking about dipoles?
--
73, Cecil http://www.qsl.net/w5dxp

Two things to consider he

1. If you cut it for 3850, as an example, it will be way out of band on 40
meters (7700).

2. If you match it with a 1/4 wave section of RG11 on 80 meters, that will
be 1/2 wave on 40, and have no effect.

Having said all that, I find my Ameritron amp with a pi network output will
tune up on 40 meters. My loop is resonant at about 3800. Just in case, I
keep the power down.

Tam/WB2TT

1. If you cut it for 3850, as an example, it will be way out of band on 40
meters (7700).

Will it?? A full wave on 3850 is aprox 261 ft. A full wave on 7700 is aprox
130.52 feet. Looks pretty close to 2 wavelengths on 40..using the 1005/Freq
loop equation..

Again, my loop isnt up yet so I can't comment, I'm just going by equations on
paper...I'd expect a 2:1-3:1 swr on its resonant frq as it should see aprox 100
ohms....easily tuned out with the built in tuner in my rig...I would expect it
to work pretty good on 10-80 but will most certainly need a tuner to keep the
finals happy on freq's above 80....This is what I'm banking on LOL...Mine
should be up saturday..WOOHOO!!

Steve
kb8viv

Will it?? A full wave on 3850 is aprox 261 ft. A full wave on 7700 is aprox
130.52 feet. Looks pretty close to 2 wavelengths on 40..using the 1005/Freq
loop equation..


Woops, this is the eqation for a loop, not sure if it applies to a delta
loop..but it shouldnt be far off...

Steve
kb8viv

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

Lee,

Just curious, what do you feed it with and where (corner or side)? Also,
what are the shapes? I'm amazed at the flat SWR!

73, Al

"DXer" wrote in message
...
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

The apex of the triangle is at 50 ft on a telescoping mast and I feet the
bottom right corner for vertical polarization.

40m is flat across the entire band .. 80m is flat from 3.500 to about 3.700
....

The base is about 5 ft off the ground ...

/lee - k1nt

"Al - VA3KAI" wrote in message
...
Lee,

Just curious, what do you feed it with and where (corner or side)? Also,
what are the shapes? I'm amazed at the flat SWR!

73, Al

"DXer" wrote in message
...
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

What does one use to provide impendence transformation(if needed) at
feedpoint for a dual or multiband loop antenna?
I have two...one cut for 20 meters that I wish to multiband and use
individual loops for each band from 20 thru 10 meters. Could I use a 2 to 1
balun at feedpoint to resolve the impendence match?
The second delta loop is top feed currently with twin lead...and had about
220 feet of wire in the loop. I would like to string in two more additonal
loops...one for 40 and one for 30 meters....
Currently both are fed with 450 ohm twin lead with a pair of old Johnson
Matchboxes.
"DXer" wrote in message
...
The apex of the triangle is at 50 ft on a telescoping mast and I feet the
bottom right corner for vertical polarization.

40m is flat across the entire band .. 80m is flat from 3.500 to about
3.700
...

The base is about 5 ft off the ground ...

/lee - k1nt

"Al - VA3KAI" wrote in message
...
Lee,

Just curious, what do you feed it with and where (corner or side)?
Also,
what are the shapes? I'm amazed at the flat SWR!

73, Al

"DXer" wrote in message
...
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