"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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