Dumb question #433,444,007
 

If I prune the driven element on my 6m 3el quad for best
swr, do I have to do anything to the reflector or director?
--
73's de Ken KG0WX - Kadiddlehopper #11808,
Flying Pigs #-1055, Grid EM17io, FT-857D, AL-84,
Elecraft XG2, 4SQRP Tenna Dipper, Heath GD-1B

Dumb question #433,444,007
 

no

"Ken Bessler" wrote in message
news:%Gyig.40099$4H.35436@dukeread03...
If I prune the driven element on my 6m 3el quad for best
swr, do I have to do anything to the reflector or director?
--
73's de Ken KG0WX - Kadiddlehopper #11808,
Flying Pigs #-1055, Grid EM17io, FT-857D, AL-84,
Elecraft XG2, 4SQRP Tenna Dipper, Heath GD-1B

Dumb question #433,444,007
 

Ken Bessler wrote:
If I prune the driven element on my 6m 3el quad for best
swr, do I have to do anything to the reflector or director?

For beams, the desired radiation pattern is usually
more important than minimum SWR. Using EZNEC, I've
seen a 4:1 SWR yield the desired pattern where
at the minimum 1.5:1 SWR point the F:B ratio was
terrible.
--
73, Cecil http://www.qsl.net/w5dxp

Dumb question #433,444,007
 

"Cecil Moore" wrote in message
. com...
Ken Bessler wrote:
If I prune the driven element on my 6m 3el quad for best
swr, do I have to do anything to the reflector or director?

For beams, the desired radiation pattern is usually
more important than minimum SWR. Using EZNEC, I've
seen a 4:1 SWR yield the desired pattern where
at the minimum 1.5:1 SWR point the F:B ratio was
terrible.
--
73, Cecil http://www.qsl.net/w5dxp

I did model this antenna with EZNEC but I forgot to take
into account the fact that the wire used is insulated. I think
that screwed up the resulting antenna. Maybe? Would an
insulating jacket reduce the VF of the wire? I've accounted
for everything else, wire gauge/loss, ant height, type of
ground, etc.

Ken
KG0WX

Dumb question #433,444,007 - Answer from ARRL Ant Book?
 

"Ken Bessler" wrote in message
news:O3Dig.40117$4H.36191@dukeread03...

"Cecil Moore" wrote in message
. com...
Ken Bessler wrote:
If I prune the driven element on my 6m 3el quad for best
swr, do I have to do anything to the reflector or director?

For beams, the desired radiation pattern is usually
more important than minimum SWR. Using EZNEC, I've
seen a 4:1 SWR yield the desired pattern where
at the minimum 1.5:1 SWR point the F:B ratio was
terrible.
--
73, Cecil http://www.qsl.net/w5dxp

I did model this antenna with EZNEC but I forgot to take
into account the fact that the wire used is insulated. I think
that screwed up the resulting antenna. Maybe? Would an
insulating jacket reduce the VF of the wire? I've accounted
for everything else, wire gauge/loss, ant height, type of
ground, etc.

Ken
KG0WX

OK now I'm really starting to think I should prune my reflector
and director - here's a quote from the ARRL Antenna Book
2003, page 12-4:

"In practice, it has been found that the length around the loop
should be approximately 3.5% greater than the self-resonant
length if the element is a reflector, and about 3.0% shorter than
the self-resonant length if the parasitic element is a director."

I built my 6m quad with a 240.64" driven element which I had
to trim 6" to get the SWR where I wanted it (low end of 50mhz).

My reflector is 246.64" and my director is 233.41".

Help? Do I trim or not? I have done some tests with the ant
up and I'm noticing my F/B ratio is not as good as the EZNEC
model predicted (30.62 db predicted, I'm seeing maybe 2-3db)

Ken KG0WX
Always learning......

Dumb question #433,444,007 - Answer from ARRL Ant Book?
 

Ken Bessler wrote:
Help? Do I trim or not? I have done some tests with the ant
up and I'm noticing my F/B ratio is not as good as the EZNEC
model predicted (30.62 db predicted, I'm seeing maybe 2-3db)


The Handbook means the self-resonant frequency with no other elements
around. They do NOT mean compared to the size of the driven element.

A driven element can move higher or lower in frequency as you add other
elements, depending on the tuning of the other elements.

I usually do all my F/B tuning first, and then SWR last. By the way, I
HOPE you have a balun at the feedpoint. Without a balun at the
feedpoint, the F/B can be seriously diminished.

73 Tom

Dumb question #433,444,007 - Answer from ARRL Ant Book?
 

wrote in message
oups.com...

Ken Bessler wrote:
Help? Do I trim or not? I have done some tests with the ant
up and I'm noticing my F/B ratio is not as good as the EZNEC
model predicted (30.62 db predicted, I'm seeing maybe 2-3db)


The Handbook means the self-resonant frequency with no other elements
around. They do NOT mean compared to the size of the driven element.

A driven element can move higher or lower in frequency as you add other
elements, depending on the tuning of the other elements.

I usually do all my F/B tuning first, and then SWR last. By the way, I
HOPE you have a balun at the feedpoint. Without a balun at the
feedpoint, the F/B can be seriously diminished.

73 Tom


I have about 8 turns of coax at the feedpoint. Is that good enough or
do I need a 1:1 balun also?

Thanks for the help!

Ken KG0WX

Dumb question #433,444,007
 

Ken Bessler wrote:
I did model this antenna with EZNEC but I forgot to take
into account the fact that the wire used is insulated. I think
that screwed up the resulting antenna. Maybe? Would an
insulating jacket reduce the VF of the wire?

Yes, most of us have been bitten by that bug in our
thinking. Exactly the same thing happened to me with
"My Favorite Loop Antenna" on my web page. If I remember
correctly, the insulated effect is around 3% on VF.
--
73, Cecil http://www.qsl.net/w5dxp

Dumb question #433,444,007
 

"Cecil Moore" wrote in message
. com...
Ken Bessler wrote:
I did model this antenna with EZNEC but I forgot to take
into account the fact that the wire used is insulated. I think
that screwed up the resulting antenna. Maybe? Would an
insulating jacket reduce the VF of the wire?

Yes, most of us have been bitten by that bug in our
thinking. Exactly the same thing happened to me with
"My Favorite Loop Antenna" on my web page. If I remember
correctly, the insulated effect is around 3% on VF.
--
73, Cecil http://www.qsl.net/w5dxp

Thanks for the info, Cecil - I just got back in the shack from
trimming all 3 elements. The SWR is now pretty close to what
EZNEC predicted. I can't tell if I've got any pattern on SSB
because 6 is wide open and full of contesters. There is a beacon
80 miles away that I'm hearing and I'll try to see what kind of
pattern I have receiving that.

Ken KG0WX