multiband vertical
 

Thanks for the explanation. What you have described would be more convenient
from an operating standpoint since I would have one less thing to tune
during a QSY.

"Cecil Moore" wrote in message
t...
John, N9JG wrote:
What do you mean by optimum length since open-wire feedline has minimal
loss?

By "optimum length", I mean the length where you can
switch your antenna tuner into bypass mode and obtain
a 50 ohm SWR of less than ~1.6:1. For any dipole that
is 1/2WL on the lowest frequency of operation, that
will be at an SWR current maximum point making the
antenna plus tuned feeder system resonant without a tuner.

On 20m, for example, if one can vary the ladder-line
length by plus or minus 15 feet, one can always locate
the SWR current maximum point and usually bypass the
antenna tuner. I have a 20m 1/2WL dipole that I use
on 20m, 17m, 15m, 12m, 10m, and 6m without a conventional
antenna tuner by simply varying the length of the
300 ohm ladder-line.
--
73, Cecil http://www.w5dxp.com

multiband vertical
 

In article ,
"Andre & Sharon Walker" wrote:

now I just
happen to have a house with a nice tin roof. Can I make use of the whole
roof as a ground plain or do I need radials cut to resonance for each band?

Andre,

Several years ago I had a tin roof and tried to use it as a ground
plain. It did NOT work. I gave up and cut some radials

multiband vertical
 

aRKay wrote:
Several years ago I had a tin roof and tried to use it as a ground
plain. It did NOT work. I gave up and cut some radials

Did you lay the radials on the tin roof?
--
73, Cecil http://www.w5dxp.com

multiband vertical
 

Cecil Moore wrote in
:

Andre & Sharon Walker wrote:
I was hoping to get away from traps, but i dont think its possible
:-(. I only have a smallish yard, with just 30m from the chimmny
(brick ) to the back of the yard, so i think a decent wire antenna is
out...but i am open to suggestions. I guess the other considerstion
is to keep "she inside" happy .

A 1/2WL dipole is 20m on 40m and can be made to work on
all HF bands 40m-10m. That's probably what I would do
and then do something romantic to keep the XYL happy.

Cecil, Andre will not have access to most HF bands, just 80, 40, 15, and
10m.

It takes about 6 hours to train and assess a Foundation Licencee, so your
tunerless concept is perhaps more complex than Andre's current knowledge
base.

For example, I worked a FL chap a couple of days ago on 40m with a 80m
half wave dipole fed with a long run of coax, and he was confident that
his antenna worked real well, despite my expectation that it was likely
that well less than 10% of his permitted 10W PEP was radiated. It was
impossible to tell this chap that if he cut the dipole to half the length
it would work better on 40m.

It is no good telling people that an antenna isn't likely to work real
good, they will cite all the contacts that they have had with it, and as
we know, anything "works", doesn't it. However, most people listen to the
positive suggestion that with change, and antenna will work better (and
in the above case, more than 10 times the EIRP).

Andre, keep it simple. A coax fed half wave dipole is easy to get going
will limited knowledge and experience, and you should have a high
confidence that you will be able to deliver a suitable load to your
transmitter (ie it will deliver its rated power), and the antenna will be
quite efficient (ie that most of your 10W PEP transmitter power is
radiated). It will also work well on receive.

If you hear strong FL signals around, they have good antennas, and / or
are flaunting the power limit. It is easy to do the latter, but if you
get the antenna right, you still have the room for improvement when you
upgrade to the higher power limit.

Owen

multiband vertical
 

"Andre & Sharon Walker" wrote in
:

I was hoping to get away from traps, but i dont think its possible
:-(. I only have a smallish yard, with just 30m from the chimmny
(brick ) to the back of the yard, so i think a decent wire antenna is
out...but i am open to suggestions. I guess the other considerstion is
to keep "she inside" happy .

Andre,

There are other options than traps, including other multiband designs that
depend on other devices to deliver a nominal 50 ohm feedpoint.

An unloaded vertical with a tuner at the base is an option.

See my earlier comment about noise in urban areas.

Your yard is obviously bigger than many suburban yards. A 40m inverted V
needs about 8m horizontally each side of the support mast.

Owen

multiband vertical
 

Wow..looks like I opened a can of worms here!
Thanks to all for the many links and advice..much food for thought. I think
ill have to re assess I was considering end fed longwire also, but an
inverted V might be a better option. Anyway, should be on the air within 4
weeks...the licence is the easy bit, diverting funds for the radio from the
XYL is the tricky part!!! But ive been offered a FT101z , inc Yaseu Desk mix
+ spare set of finals ( is too early to rember the number of the tubes off
hand...just finished night shift), so ill have wind the wick WAY back to
start with. I don't care what they say at the club...I like boat anchors!!
( I'd love to replace the Murphy B40 I sold 10 years ago :-( )

Cheers

Andre
"Owen Duffy" wrote in message
...
Cecil Moore wrote in
:

Andre & Sharon Walker wrote:
I was hoping to get away from traps, but i dont think its possible
:-(. I only have a smallish yard, with just 30m from the chimmny
(brick ) to the back of the yard, so i think a decent wire antenna is
out...but i am open to suggestions. I guess the other considerstion
is to keep "she inside" happy .

A 1/2WL dipole is 20m on 40m and can be made to work on
all HF bands 40m-10m. That's probably what I would do
and then do something romantic to keep the XYL happy.

Cecil, Andre will not have access to most HF bands, just 80, 40, 15, and
10m.

It takes about 6 hours to train and assess a Foundation Licencee, so your
tunerless concept is perhaps more complex than Andre's current knowledge
base.

For example, I worked a FL chap a couple of days ago on 40m with a 80m
half wave dipole fed with a long run of coax, and he was confident that
his antenna worked real well, despite my expectation that it was likely
that well less than 10% of his permitted 10W PEP was radiated. It was
impossible to tell this chap that if he cut the dipole to half the length
it would work better on 40m.

It is no good telling people that an antenna isn't likely to work real
good, they will cite all the contacts that they have had with it, and as
we know, anything "works", doesn't it. However, most people listen to the
positive suggestion that with change, and antenna will work better (and
in the above case, more than 10 times the EIRP).

Andre, keep it simple. A coax fed half wave dipole is easy to get going
will limited knowledge and experience, and you should have a high
confidence that you will be able to deliver a suitable load to your
transmitter (ie it will deliver its rated power), and the antenna will be
quite efficient (ie that most of your 10W PEP transmitter power is
radiated). It will also work well on receive.

If you hear strong FL signals around, they have good antennas, and / or
are flaunting the power limit. It is easy to do the latter, but if you
get the antenna right, you still have the room for improvement when you
upgrade to the higher power limit.

Owen

multiband vertical
 

"Andre & Sharon Walker" wrote in
:

Wow..looks like I opened a can of worms here!

Not really Andre.

Thanks to all for the many links and advice..much food for thought. I
think ill have to re assess I was considering end fed longwire also,
but an inverted V might be a better option. Anyway, should be on the
air within 4 weeks...the licence is the easy bit, diverting funds for
the radio from the XYL is the tricky part!!! But ive been offered a
FT101z , inc Yaseu Desk mix + spare set of finals ( is too early to
rember the number of the tubes off hand...just finished night shift),
so ill have wind the wick WAY back to start with. I don't care what
they say at the club...I like boat anchors!! ( I'd love to replace the
Murphy B40 I sold 10 years ago :-( )

Ok, now that more detail unfolds, a 7MHz half wave dipole, cut to
formula, with a modest length of coax, even RG58 up to 20m in length,
will deliver most (80%) of the transmitter power to the antenna to be
radiated, and the pi-coupled output in the '101Z will be tolerant of
the load presented to the transmitter. This is a pretty good way to
start, and you should be heard. You are about to be licenced to learn!

Unless you have an inline power meter specifically designed to measure
PEP, and that works properly, you can be assured that your PEP is less
than the maximum that the '101Z runs, which I think is close to 200W. The
tendency for FLs is to "talk it up to 10W" on an inline power meter that
doesn't respond to PEP, I call that 10 "Foundation Watts", they are not
PEP and they are not average watts, something else, but undefined since
most inline power meters don't give valid readings on anything but a
steady carrier.

If you would like to read some high level stuff about the PEP measurement
problem, see http://www.vk1od.net/VSWR/MeasureSSBTxPower.htm .

Catch you on air Andre.

Owen

multiband vertical
 

"John, N9JG" wrote in
et:

Thanks for the explanation. What you have described would be more
convenient from an operating standpoint since I would have one less
thing to tune during a QSY.

You might have misunderstood Cecil. I think he is describing a system where
the "optimal length" may be different on each band, so whilst you don't
tune an ATU, you tune the feeder length.

Cecil will confirm or deny... Owen

multiband vertical
 

Owen Duffy wrote:
"John, N9JG" wrote in
et:

Thanks for the explanation. What you have described would be more
convenient from an operating standpoint since I would have one less
thing to tune during a QSY.

You might have misunderstood Cecil. I think he is describing a system where
the "optimal length" may be different on each band, so whilst you don't
tune an ATU, you tune the feeder length.

Throwing a couple of knife switches is certainly an easier
and faster QSY than rotating a coil switch and twisting
two interacting capacitor knobs.
--
73, Cecil http://www.w5dxp.com

multiband vertical
 

"Cecil Moore" wrote in message
t...
Owen Duffy wrote:
"John, N9JG" wrote in
et:
Thanks for the explanation. What you have described would be more
convenient from an operating standpoint since I would have one less
thing to tune during a QSY.

You might have misunderstood Cecil. I think he is describing a system
where the "optimal length" may be different on each band, so whilst you
don't tune an ATU, you tune the feeder length.

Throwing a couple of knife switches is certainly an easier
and faster QSY than rotating a coil switch and twisting
two interacting capacitor knobs.
--
73, Cecil http://www.w5dxp.com

Cecil, I was thinking of trying your no= tune antenna and the 16 ft piece
may not be doable at my QTH, I have to keep it all hidden behind the bushes.
Could this piece be replaced with a circuit using lumped LC values.

Jimmie