I'm mounting an Outbacker Perth just above a long gutter and downspout.
The gutter/downspout is the ground side of this antenna. This
combination will be fed with 300 ohm twinlead.

The ground side of this has me confused. My question is this. Does the
ground jack on the Outbacker need to be connected for it to work properly?

Why does the Outbacker even have a ground jack? A hamstick antenna
doesn't have a ground jack.

If I was using a hamstick then one side of the 300 ohm twinlead would go
to the antenna, the other side to the gutter/downspout. Simple.

If the Oubacker ground jack needs to be connected then should it go in
series or parallel to the gutter/downspout? Or does it even matter?

In other words, should the feedline first go to the Outbacker ground
jack, then on to the gutter? Or could I split the ground at some point
near the antenna, run one wire to the Outbacker and the other to the
gutter/downspout?

Thanks for your help.

Bruce AF8F

In article LjBEc.37229$cj3.17320@lakeread01,
Bruce W.1 wrote:

The ground side of this has me confused. My question is this. Does the
ground jack on the Outbacker need to be connected for it to work properly?

Yes.

Why does the Outbacker even have a ground jack?

As I understand it, the Outbacker has a built-in matching network
which allows the (antenna radiation resistance + antenna loss
resistance + ground loss resistance) to be matched to a 50-ohm
feedline. As this total resistance often sums up to less than 50
ohms, an antenna of this sort is usually matched to the feedline using
an "L" network, which requires a connection to ground.

In the case of the Outbacker, I believe that the "L" consists of some
internal shunt inductance connected between the feedpoint and ground
(via the ground jack), and some series capacitive reactance created by
shortening the whip a bit.

If you leave the ground connection unattached, you're likely to find
that the antenna's feedpoint impedance is quite low when the whip is
adjusted for resonance.

A hamstick antenna
doesn't have a ground jack.

.... and they are not always well-matched to a 50-ohm feedline.

A local Ham had trouble getting a low SWR with his Hamsticks,
especially after he improved the grounding between his feedline and
his vehicle chassis. I measured it out with an MFJ meter, and at
resonance the hamstick's feedpoint impedance was somewhere down in the
15-to-20-ohm range.

He purchased a set of air-wound coils, which connect to the antenna's
3-24 bolt and which have an alligator-clip-equipped lead which goes to
ground. With the correct clip positioning, and a slight readjustment
of the whip length, he now has a 1:1 match.

The Outbacker antennas do the same basic thing, but using an internal
(non-adjustable) matching component.

If I was using a hamstick then one side of the 300 ohm twinlead would go
to the antenna, the other side to the gutter/downspout. Simple.

You may or may not get an acceptable impedance match that way. No
guarantee.

If the Oubacker ground jack needs to be connected then should it go in
series or parallel to the gutter/downspout? Or does it even matter?

In other words, should the feedline first go to the Outbacker ground
jack, then on to the gutter? Or could I split the ground at some point
near the antenna, run one wire to the Outbacker and the other to the
gutter/downspout?

What I'd do would be to minimize the length of the ground lead between
the Outbacker and the feedline, and run as heavy as convenient a
grounding wire or strap to the gutter. This would mimic a proper
automobile installation.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

In article LjBEc.37229$cj3.17320@lakeread01,
Bruce W.1 wrote:

The ground side of this has me confused. My question is this. Does the
ground jack on the Outbacker need to be connected for it to work properly?

Yes.

Why does the Outbacker even have a ground jack?

As I understand it, the Outbacker has a built-in matching network
which allows the (antenna radiation resistance + antenna loss
resistance + ground loss resistance) to be matched to a 50-ohm
feedline. As this total resistance often sums up to less than 50
ohms, an antenna of this sort is usually matched to the feedline using
an "L" network, which requires a connection to ground.

In the case of the Outbacker, I believe that the "L" consists of some
internal shunt inductance connected between the feedpoint and ground
(via the ground jack), and some series capacitive reactance created by
shortening the whip a bit.

If you leave the ground connection unattached, you're likely to find
that the antenna's feedpoint impedance is quite low when the whip is
adjusted for resonance.

A hamstick antenna
doesn't have a ground jack.

.... and they are not always well-matched to a 50-ohm feedline.

A local Ham had trouble getting a low SWR with his Hamsticks,
especially after he improved the grounding between his feedline and
his vehicle chassis. I measured it out with an MFJ meter, and at
resonance the hamstick's feedpoint impedance was somewhere down in the
15-to-20-ohm range.

He purchased a set of air-wound coils, which connect to the antenna's
3-24 bolt and which have an alligator-clip-equipped lead which goes to
ground. With the correct clip positioning, and a slight readjustment
of the whip length, he now has a 1:1 match.

The Outbacker antennas do the same basic thing, but using an internal
(non-adjustable) matching component.

If I was using a hamstick then one side of the 300 ohm twinlead would go
to the antenna, the other side to the gutter/downspout. Simple.

You may or may not get an acceptable impedance match that way. No
guarantee.

If the Oubacker ground jack needs to be connected then should it go in
series or parallel to the gutter/downspout? Or does it even matter?

In other words, should the feedline first go to the Outbacker ground
jack, then on to the gutter? Or could I split the ground at some point
near the antenna, run one wire to the Outbacker and the other to the
gutter/downspout?

What I'd do would be to minimize the length of the ground lead between
the Outbacker and the feedline, and run as heavy as convenient a
grounding wire or strap to the gutter. This would mimic a proper
automobile installation.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

I'm mounting an Outbacker Perth just above a long gutter and downspout.
The gutter/downspout is the ground side of this antenna. This
combination will be fed with 300 ohm twinlead.

The Outbacker or the Hamstick are not usually fed with 300 ohm line. I have
never used either, but it is my understanding they are both designed for mobile
operation and a 50 ohm feed.
If you are planning to transmit with the Outbacker fed with 300 ohm line you
will need a Balanced Antenna Tuner at the shack. Even with this arrangement, I
would not expect very good results because of ground losses and a low radiation
resistance at the antenna input. You will be feeding a very unbalanced antenna
with a balanced transmission line. My suggestion would be to feed the antenna
with 50 ohm coax, and adjust the antenna for the best match at the transmitter.
And yes, you will still need to connect the antenna ground jack to some sort
of ground.
73 Gary N4AST

I'm mounting an Outbacker Perth just above a long gutter and downspout.
The gutter/downspout is the ground side of this antenna. This
combination will be fed with 300 ohm twinlead.

The Outbacker or the Hamstick are not usually fed with 300 ohm line. I have
never used either, but it is my understanding they are both designed for mobile
operation and a 50 ohm feed.
If you are planning to transmit with the Outbacker fed with 300 ohm line you
will need a Balanced Antenna Tuner at the shack. Even with this arrangement, I
would not expect very good results because of ground losses and a low radiation
resistance at the antenna input. You will be feeding a very unbalanced antenna
with a balanced transmission line. My suggestion would be to feed the antenna
with 50 ohm coax, and adjust the antenna for the best match at the transmitter.
And yes, you will still need to connect the antenna ground jack to some sort
of ground.
73 Gary N4AST

JGBOYLES wrote:


The Outbacker or the Hamstick are not usually fed with 300 ohm line. I have
never used either, but it is my understanding they are both designed for mobile
operation and a 50 ohm feed.
If you are planning to transmit with the Outbacker fed with 300 ohm line you
will need a Balanced Antenna Tuner at the shack. Even with this arrangement, I
would not expect very good results because of ground losses and a low radiation
resistance at the antenna input. You will be feeding a very unbalanced antenna
with a balanced transmission line. My suggestion would be to feed the antenna
with 50 ohm coax, and adjust the antenna for the best match at the transmitter.
And yes, you will still need to connect the antenna ground jack to some sort
of ground.
73 Gary N4AST
=================================================

So the ground jack is needed for matching. I thought that might be the
case.

The 300 ohm feedline was connected to an antenna tuner.

Well I completed installing the antenna and it didn't work for sh*t. So
I tore it down. Chalk one up to experience.

Thanks guys.

JGBOYLES wrote:


The Outbacker or the Hamstick are not usually fed with 300 ohm line. I have
never used either, but it is my understanding they are both designed for mobile
operation and a 50 ohm feed.
If you are planning to transmit with the Outbacker fed with 300 ohm line you
will need a Balanced Antenna Tuner at the shack. Even with this arrangement, I
would not expect very good results because of ground losses and a low radiation
resistance at the antenna input. You will be feeding a very unbalanced antenna
with a balanced transmission line. My suggestion would be to feed the antenna
with 50 ohm coax, and adjust the antenna for the best match at the transmitter.
And yes, you will still need to connect the antenna ground jack to some sort
of ground.
73 Gary N4AST
=================================================

So the ground jack is needed for matching. I thought that might be the
case.

The 300 ohm feedline was connected to an antenna tuner.

Well I completed installing the antenna and it didn't work for sh*t. So
I tore it down. Chalk one up to experience.

Thanks guys.

Well I completed installing the antenna and it didn't work for sh*t. So
I tore it down. Chalk one up to experience.


Hi Bruce, Don't give up just yet. A 25' dipole fed with 300 ohm line and a
tuner will work well on 20m-6m. If you could manage 50', then you have 40m.
An inverted vee configuration requires only one support. A dipole costs very
little and will work great compared to what you were attempting.
73 Gary N4AST

Well I completed installing the antenna and it didn't work for sh*t. So
I tore it down. Chalk one up to experience.


Hi Bruce, Don't give up just yet. A 25' dipole fed with 300 ohm line and a
tuner will work well on 20m-6m. If you could manage 50', then you have 40m.
An inverted vee configuration requires only one support. A dipole costs very
little and will work great compared to what you were attempting.
73 Gary N4AST