Feedline suggestions?
 

I am using a whip antenna mounted on a metal patio cover. Results are good
on 10 and 12 meters, and contacts have been made down to 40 meters.
(Matches were not obtained on 15 or 30 meters) The whip is 8.5 ft long (a
longer whip is under consideration). It is fed through an antenna tuner and
about 25 feet of RG-58. I'm about to replace that with RG-8.

Any comments on how to hold down feedline losses. One suggestion is to use
two parallel lengths of RG-8 so that half the current runs through each.
Also, site geometry would allow open wire feed.

Possibilities?

Feedline suggestions?
 

On Mon, 5 Dec 2011 09:01:15 -0800, "Wayne"
wrote:

I am using a whip antenna mounted on a metal patio cover. Results are good
on 10 and 12 meters, and contacts have been made down to 40 meters.
(Matches were not obtained on 15 or 30 meters) The whip is 8.5 ft long (a
longer whip is under consideration). It is fed through an antenna tuner and
about 25 feet of RG-58. I'm about to replace that with RG-8.

Any comments on how to hold down feedline losses. One suggestion is to use
two parallel lengths of RG-8 so that half the current runs through each.
Also, site geometry would allow open wire feed.

Possibilities?

Sorry, Parallel cables would give you twice the losses. Also, what it
would do for matching will vary by frequency but not likely anything
you want. Lower loss coax is always a good idea but with only 25 feet
total your losses may not be enough to notice. Vertical antennas are
usually at their best at 1/4 wave length long for the purpose of
radiation. In practice, if you get it tuned up well enough to take
power, it will work!

I have a 28 foot vertical antenna that sometimes outperfoms my 3
element beam. It is tuned with an SGC autotuner.

There is a lot of information on the internet for free, Google a bit
and keep at it. I seem to enjoy working on antennas more than using
them.

BTW, Check out the ARRL.NET site. There is a 10 meter contest in a
week or so that your antenna will around the world...
John Ferrell W8CCW

Feedline suggestions?
 

"Wayne" wrote in message
...
I am using a whip antenna mounted on a metal patio cover. Results are good
on 10 and 12 meters, and contacts have been made down to 40 meters.
(Matches were not obtained on 15 or 30 meters) The whip is 8.5 ft long (a
longer whip is under consideration). It is fed through an antenna tuner
and about 25 feet of RG-58. I'm about to replace that with RG-8.

Any comments on how to hold down feedline losses. One suggestion is to
use two parallel lengths of RG-8 so that half the current runs through
each. Also, site geometry would allow open wire feed.

Possibilities?

As John mentioned, 25 feet of coax is too low of a loss to worry about
especially below 30 Mhz. The other best bet is to use a remote antenna
tuner at the antenna. A longer antenna should work much beter on 80 and 40
meters.

Feedline suggestions?
 

Dear Wayne (no call sign given): The use of "it" causes an ambiguity. If
the antenna tuner is "at" the antenna feed point, then 25 feet of RG-58
running to the shack will contribute very little to the overall loss of the
system.

A colleague has had success with an insulated wire on his roof fed in the
middle with an auto-tuner. The coax from the tuner has several type 31
chokes to kill common mode and the coax itself contributes very little to
the performance of the system.

On the other hand, such a short antenna as you are using (on the lower
bands) fed with RG-58 from a tuner in the shack is expected to have
significant losses. If this is the case, moving the tuner outside should be
tried.

73, Mac N8TT

"Wayne" wrote in message ...

I am using a whip antenna mounted on a metal patio cover. Results are good
on 10 and 12 meters, and contacts have been made down to 40 meters.
(Matches were not obtained on 15 or 30 meters) The whip is 8.5 ft long (a
longer whip is under consideration). It is fed through an antenna tuner and
about 25 feet of RG-58. I'm about to replace that with RG-8.

Any comments on how to hold down feedline losses. One suggestion is to use
two parallel lengths of RG-8 so that half the current runs through each.
Also, site geometry would allow open wire feed.

Possibilities?


J. C. Mc Laughlin
Michigan U.S.A.
Home:

Feedline suggestions?
 

"Wayne" wrote in
:

I am using a whip antenna mounted on a metal patio cover. Results are
good on 10 and 12 meters, and contacts have been made down to 40
meters. (Matches were not obtained on 15 or 30 meters) The whip is 8.5
ft long (a longer whip is under consideration). It is fed through an
antenna tuner and about 25 feet of RG-58. I'm about to replace that
with RG-8.

Taking this to mean that the ATU is at the tx end of the 25' of RG58...

It is challenging with that topology get get good antenna system
efficiency when the monopole is less than about 17% of a wavelength.
Working that backwards, your 2.6m whip is 17% of a wavelenght on 15m
wavelength or 20MHz.

The contributions to poor efficiency are feed line loss under standing
waves, ATU loss, and if the whip is magnetic stainless, conductor losses
in the whip.

RG8 will have lower losses, but the result will be a more challenging
load for the ATU and its losses will increase, consuming some of the
benefit.

You really need to take a system perspective because there is a complex
interaction of the system components.


Any comments on how to hold down feedline losses. One suggestion is
to use two parallel lengths of RG-8 so that half the current runs
through each. Also, site geometry would allow open wire feed.

Paralelling two cables reduces Zo to one half, but the matched loss per
metre is the same. The loss under standing waves depends on the actual
load impedance which you probably don't know.


Possibilities?


A remote ATU, a longer monopole.

Owen

Feedline suggestions?
 

"J. C. Mc Laughlin" wrote in message
...

Dear Wayne (no call sign given): The use of "it" causes an ambiguity. If
the antenna tuner is "at" the antenna feed point, then 25 feet of RG-58
running to the shack will contribute very little to the overall loss of the
system.

A colleague has had success with an insulated wire on his roof fed in the
middle with an auto-tuner. The coax from the tuner has several type 31
chokes to kill common mode and the coax itself contributes very little to
the performance of the system.

On the other hand, such a short antenna as you are using (on the lower
bands) fed with RG-58 from a tuner in the shack is expected to have
significant losses. If this is the case, moving the tuner outside should
be tried.
73, Mac N8TT

-
Yes, the wording is confusing. The antenna is fed with about 25 feet of
RG-58 with the tuner next to the rig in the shack. The cable will be
changed to RG-8 tomorrow assuming that the winds finally die down here in So
Cal.

On 10 and 12 meters the performance is quite acceptable. I'm not the big
signal on the band, but it works well.

I'm hoping to slightly lengthen the antenna and get performance from 17 to
10 meters. Since the tuner to antenna VSWR will be very high, I'm pondering
ways of lowering the loss.

A separate loaded whip is used on 20 and 40 meters.

So far, the experiment has been good, and it is one of the few antenna
configurations that meet the established requirements. (established by the
xyl) :)

Thanks
Wayne
W5GIE /6








"Wayne" wrote in message ...

I am using a whip antenna mounted on a metal patio cover. Results are
good
on 10 and 12 meters, and contacts have been made down to 40 meters.
(Matches were not obtained on 15 or 30 meters) The whip is 8.5 ft long (a
longer whip is under consideration). It is fed through an antenna tuner
and
about 25 feet of RG-58. I'm about to replace that with RG-8.

Any comments on how to hold down feedline losses. One suggestion is to
use
two parallel lengths of RG-8 so that half the current runs through each.
Also, site geometry would allow open wire feed.

Possibilities?

Feedline suggestions?
 

In message , John Ferrell
writes










Vertical antennas are
usually at their best at 1/4 wave length long for the purpose of
radiation. In practice, if you get it tuned up well enough to take
power, it will work!

Actually a 5/8 wavelength is what gives the most poke in the horizontal
direction.




--
Ian

Feedline suggestions?
 

In message , Owen Duffy
writes
"Wayne" wrote in
:

I am using a whip antenna mounted on a metal patio cover. Results are
good on 10 and 12 meters, and contacts have been made down to 40
meters. (Matches were not obtained on 15 or 30 meters) The whip is 8.5
ft long (a longer whip is under consideration). It is fed through an
antenna tuner and about 25 feet of RG-58. I'm about to replace that
with RG-8.

Taking this to mean that the ATU is at the tx end of the 25' of RG58...

It is challenging with that topology get get good antenna system
efficiency when the monopole is less than about 17% of a wavelength.
Working that backwards, your 2.6m whip is 17% of a wavelenght on 15m
wavelength or 20MHz.

The contributions to poor efficiency are feed line loss under standing
waves, ATU loss, and if the whip is magnetic stainless, conductor losses
in the whip.

RG8 will have lower losses, but the result will be a more challenging
load for the ATU and its losses will increase, consuming some of the
benefit.

You really need to take a system perspective because there is a complex
interaction of the system components.


Any comments on how to hold down feedline losses. One suggestion is
to use two parallel lengths of RG-8 so that half the current runs
through each. Also, site geometry would allow open wire feed.

Paralelling two cables reduces Zo to one half, but the matched loss per
metre is the same. The loss under standing waves depends on the actual
load impedance which you probably don't know.


Possibilities?


A remote ATU, a longer monopole.

The OP seems to be doing what I did for many years, ie feed an endfed
monopole antenna (of undefined length) with coax, and force match it, as
required, at the shack end. [I believe it was you, Owen, who pointed out
my error in trying to use the graphs showing loss vs SWR when the coax
is electrically short (less than a wavelength.]

Although I now have a remote tuner at the antenna feedpoint, I can't say
I've noticed an outstanding improvement in performance (although, to be
honest, I really haven't really done a lot of operating since I
installed the tuner).

If you don't want use a remote tuner at the antenna feedpoint, the
impedance at the shack end of the coax will be the antenna feed
impedance, transformed by the length of the coax, and also altered by
the loss in the coax. Provided the shack-end tuner can be persuaded to
match the impedance seen looking into the coax, the system will work
tolerably well with low-loss coax.

It is obviously advantageous to use the lowest loss coax you can lay
your hands on. As, in cable TV systems, long coaxial trunk lines have
now been superseded by optical fibers, I would suggest that a cable TV
operator might be persuaded to donate some nice chunky coax (preferably
"as thick as a horse's prick", as one of my bosses once described it).
Failing that, just go for the best you can get.
--
Ian

Feedline suggestions?
 

On Mon, 05 Dec 2011 18:50:53 -0800, Wayne wrote:

"J. C. Mc Laughlin" wrote in message
...

Dear Wayne (no call sign given): The use of "it" causes an ambiguity.
If the antenna tuner is "at" the antenna feed point, then 25 feet of
RG-58 running to the shack will contribute very little to the overall
loss of the system.

A colleague has had success with an insulated wire on his roof fed in
the middle with an auto-tuner. The coax from the tuner has several type
31 chokes to kill common mode and the coax itself contributes very
little to the performance of the system.

On the other hand, such a short antenna as you are using (on the lower
bands) fed with RG-58 from a tuner in the shack is expected to have
significant losses. If this is the case, moving the tuner outside
should be tried.
73, Mac N8TT

-
Yes, the wording is confusing. The antenna is fed with about 25 feet of
RG-58 with the tuner next to the rig in the shack. The cable will be
changed to RG-8 tomorrow assuming that the winds finally die down here
in So Cal.

On 10 and 12 meters the performance is quite acceptable. I'm not the
big signal on the band, but it works well.

I'm hoping to slightly lengthen the antenna and get performance from 17
to 10 meters. Since the tuner to antenna VSWR will be very high, I'm
pondering ways of lowering the loss.

A separate loaded whip is used on 20 and 40 meters.

So far, the experiment has been good, and it is one of the few antenna
configurations that meet the established requirements. (established by
the xyl) :)

Thanks
Wayne
W5GIE /6








"Wayne" wrote in message ...

I am using a whip antenna mounted on a metal patio cover. Results are
good
on 10 and 12 meters, and contacts have been made down to 40 meters.
(Matches were not obtained on 15 or 30 meters) The whip is 8.5 ft long
(a longer whip is under consideration). It is fed through an antenna
tuner and
about 25 feet of RG-58. I'm about to replace that with RG-8.

Any comments on how to hold down feedline losses. One suggestion is to
use
two parallel lengths of RG-8 so that half the current runs through
each. Also, site geometry would allow open wire feed.

Possibilities?

If its an autotuner, best place for it is at the base of the vertical.

Feedline suggestions?
 

"Ian Jackson" wrote in message
...
In message , Owen Duffy
writes
"Wayne" wrote in
:

I am using a whip antenna mounted on a metal patio cover. Results are
good on 10 and 12 meters, and contacts have been made down to 40
meters. (Matches were not obtained on 15 or 30 meters) The whip is 8.5
ft long (a longer whip is under consideration). It is fed through an
antenna tuner and about 25 feet of RG-58. I'm about to replace that
with RG-8.

It is obviously advantageous to use the lowest loss coax you can lay your
hands on. As, in cable TV systems, long coaxial trunk lines have now been
superseded by optical fibers, I would suggest that a cable TV operator
might be persuaded to donate some nice chunky coax (preferably "as thick
as a horse's prick", as one of my bosses once described it). Failing that,
just go for the best you can get.
--
Ian

Way too much time and money is being wasted in the change over from the rg58
coax. Even with a 20 to 1 SWR the rg-58 will loose about 3 db of signal due
to the large mismatch. the rg-8 will still loose atleast 1 db. This 'big'
gain of 2 db is hardly worth it. More time and money should be put into a
beter antenna. Maybe one of the trap type verticals that is 30 or more feet
tall. You gain by a beter radiation efficency and at the same time cut the
loss in the coax due to the beter match. Even the screwdriver type antenna
would probably be much beter. With that you get rid of the losses in the
antenna tuner.

Feedline suggestions?
 

"Ralph Mowery" wrote in
:

....
Way too much time and money is being wasted in the change over from
the rg58 coax. Even with a 20 to 1 SWR the rg-58 will loose about 3
db of signal due to the large mismatch.

The OP mentioned a 2.5m whip down to 40m. VSWR(50) of such a thing is
likely to be around 1000 so your estimates of loss for VSWR(50) are not
applicable to that scenario. (Estimating loss based on VSWR is prone to
error in any event.)

An NEC model suggests that feedpoint Z might be something like 10-j800.
Taking that for example with 25' of RG58, line loss is more like 17dB.

RG213 is better, but it does not solve the fundamental problem that R at
the feedpoint is very low, and a large current is required to deliver
power. Large currents contribute to high loss in feedlines.

Owen

Feedline suggestions?
 

"Wayne" wrote in
:

....
For clarification, there are two antennas. One is a bugcatcher type
whip covering 40, 30, and 20. That part of the "farm" is working
well. and requires no tuner.

Go back and read what you wrote:

===
I am using a whip antenna mounted on a metal patio cover. Results are
good
on 10 and 12 meters, and contacts have been made down to 40 meters.
(Matches were not obtained on 15 or 30 meters) The whip is 8.5 ft long
(a
longer whip is under consideration). It is fed through an antenna tuner
and
about 25 feet of RG-58. I'm about to replace that with RG-8.
===

No mention of loading coils, other antennas and you make specific
mention of using this antenna on 40m (QSOs offered as evidence,
notwithstanding that EIRP is probably very low due to extreme line loss
as calculated in another post).

If you can't express the scenario clearly, the advice you get is even
less reliable!

Owen

Feedline suggestions?
 

"Owen Duffy" wrote in message
...
"Ralph Mowery" wrote in
:

...
Way too much time and money is being wasted in the change over from
the rg58 coax. Even with a 20 to 1 SWR the rg-58 will loose about 3
db of signal due to the large mismatch.

The OP mentioned a 2.5m whip down to 40m. VSWR(50) of such a thing is
likely to be around 1000 so your estimates of loss for VSWR(50) are not
applicable to that scenario. (Estimating loss based on VSWR is prone to
error in any event.)

An NEC model suggests that feedpoint Z might be something like 10-j800.
Taking that for example with 25' of RG58, line loss is more like 17dB.

RG213 is better, but it does not solve the fundamental problem that R at
the feedpoint is very low, and a large current is required to deliver
power. Large currents contribute to high loss in feedlines.

Owen

The whole point was that going from rg-58 to rg-8 or the rg-213 or lmr-400
would not make hardly any differant. While the loss may be something like
17 db in the rg-58, it would still not be beter than 3 db going to another
type of 50 ohm coax.

Feedline suggestions?
 

"Owen Duffy" wrote in message
...

"Wayne" wrote in
:

....
For clarification, there are two antennas. One is a bugcatcher type
whip covering 40, 30, and 20. That part of the "farm" is working
well. and requires no tuner.

Go back and read what you wrote:

===
I am using a whip antenna mounted on a metal patio cover. Results are
good
on 10 and 12 meters, and contacts have been made down to 40 meters.
(Matches were not obtained on 15 or 30 meters) The whip is 8.5 ft long
(a
longer whip is under consideration). It is fed through an antenna tuner
and
about 25 feet of RG-58. I'm about to replace that with RG-8.
===

No mention of loading coils, other antennas and you make specific
mention of using this antenna on 40m (QSOs offered as evidence,
notwithstanding that EIRP is probably very low due to extreme line loss
as calculated in another post).

If you can't express the scenario clearly, the advice you get is even
less reliable!

Owen
-
You are right. I should have simply asked "how does one lower real world
transmission line loss when the VSWR is high", and skipped the commentary.

Feedline suggestions?
 

On Dec 5, 12:01*pm, "Wayne" wrote:
I am using a whip antenna mounted on a metal patio cover. *Results are good
on 10 and 12 meters, and contacts have been made down to 40 meters.
(Matches were not obtained on 15 or 30 meters) The whip is 8.5 ft long (a
longer whip is under consideration). *It is fed through an antenna tuner and
about 25 feet of RG-58. *I'm about to replace that with RG-8.

Any comments on how to hold down feedline losses. *One suggestion is to use
two parallel lengths of RG-8 so that half the current runs through each.
Also, site geometry would allow open wire feed.

Possibilities?

Years ago I had put up a similar antenna to be able to get onto the
local 10M net. I then as you have tried to tune it up on other bands
after upgrading from Tech+ to General and got similar results to what
you have discribed. Changing the radiator to 5/8 wl on 10M improved
operation of the antenna not so noticably on 10M as it did the other
bands. Good luck, have fun and learn.

Jimmie

Feedline suggestions?
 

"JIMMIE" wrote in message
...

On Dec 5, 12:01 pm, "Wayne" wrote:
I am using a whip antenna mounted on a metal patio cover. Results are
good
on 10 and 12 meters, and contacts have been made down to 40 meters.
(Matches were not obtained on 15 or 30 meters) The whip is 8.5 ft long (a
longer whip is under consideration). It is fed through an antenna tuner
and
about 25 feet of RG-58. I'm about to replace that with RG-8.

Any comments on how to hold down feedline losses. One suggestion is to
use
two parallel lengths of RG-8 so that half the current runs through each.
Also, site geometry would allow open wire feed.

Possibilities?

Years ago I had put up a similar antenna to be able to get onto the
local 10M net. I then as you have tried to tune it up on other bands
after upgrading from Tech+ to General and got similar results to what
you have discribed. Changing the radiator to 5/8 wl on 10M improved
operation of the antenna not so noticably on 10M as it did the other
bands. Good luck, have fun and learn.

Jimmie
-
So far it has been fun. I've been able to check out the antenna on 10 and
12 and it works well. I need to fix a rig problem before 15 testing. 17 is
working, but propagation hasn't been good enough for much testing.

Tests on 20, 30, and 40 yielded qsos, but with low signal reports. Those
bands have been written off for the tuner/coax/whip. However, I'll try 20
again if I get a longer radiator up.

Wayne
W5GIE
exiled to W6 land :)

Feedline suggestions?
 

On Dec 8, 4:01*am, "Wayne" wrote:
However, I'll try 20 again if I get a longer radiator up.

5/8WL on 10m is ~0.3 WL ( 1/4WL) on 20m so it will have an
inductively reactive feedpoint impedance around 78+j200. A series
capacitor of ~56 pf at the feedpoint on 20m should result in an SWR on
the coax of ~1.5:1.
--
73, Cecil, w5dxp.com

Feedline suggestions?
 

On 2011-12-08, Wayne wrote:

On Dec 5, 12:01 pm, "Wayne" wrote:
I am using a whip antenna mounted on a metal patio cover. Results are
good
on 10 and 12 meters, and contacts have been made down to 40 meters.
(Matches were not obtained on 15 or 30 meters) The whip is 8.5 ft long (a
longer whip is under consideration). It is fed through an antenna tuner
Wayne
W5GIE

Something for consideration for lengthing the whip: Buy a 3 or 4 ft 3/8 inch
aluminum rod from local hardware store and thread it on both ends with
3/8x24. Use a coupler nut to fit it to the bottom of the whip. I've used
this technique with mobile antennas and seems to work fine.

Also, you mentioned the ability to use open wire/ladder line. Wonder if you
considered ladder line to a 4:1 balun and then short coax to tuner? I'm not
sure that presently with such a short run of coax to the patio you would
gain much, but for longer runs, it would definitely be a consideration.

73 ...Edwin, KD5ZLB
__________________________________________________ __________
"Once you have flown, you will walk the earth with your eyes
turned skyward, for there you have been, there you long to
return."-da Vinci http://bellsouthpwp2.net/e/d/edwinljohnson

Feedline suggestions?
 

"W5DXP" wrote in message
...

On Dec 8, 4:01 am, "Wayne" wrote:
However, I'll try 20 again if I get a longer radiator up.

5/8WL on 10m is ~0.3 WL ( 1/4WL) on 20m so it will have an
inductively reactive feedpoint impedance around 78+j200. A series
capacitor of ~56 pf at the feedpoint on 20m should result in an SWR on
the coax of ~1.5:1.
--
73, Cecil, w5dxp.com
-
Thanks for the info Cecil. It turns out that a 10m 5/8 would be too long to
meet the wife's "requirements".

I haven't gotten into describing the antenna "problem" in detail, but here
is a synopsis:
Space is available for 2 verticals to be mounted on top of a metal patio
cover, and they should not be prominently visible. That limits the total
length of each to about 11-12 feet. A base mounted remote antenna tuner is
not desired.

Band coverage is desired for 40 through 10 meter cw. One antenna, a 11 foot
bugcatcher, is used on 40/30/20. The other antenna that is being pondered
has a configuration of tuner/ 25 ft of coax/11 ft whip, tunable at least
from 10 through 17 meters....thus the interest in low feedline loss.

With further consideration it appears that the loss in 25 ft of coax is not
a game changer. Experimentation continues, and results are positive so far.

Wayne
W5GIE

Feedline suggestions?
 

On Dec 8, 11:26*am, "Wayne" wrote:
It turns out that a 10m 5/8 would be too long to meet the wife's "requirements".

Humor mode on: I had the same problem so I upgraded to a better
wife. :)
--
73, Cecil, w5dxp.com

Feedline suggestions?
 

"W5DXP" wrote in message
...

On Dec 8, 11:26 am, "Wayne" wrote:
It turns out that a 10m 5/8 would be too long to meet the wife's
"requirements".

Humor mode on: I had the same problem so I upgraded to a better
wife. :)
--
73, Cecil, w5dxp.com
-
LOL......
Well, after 40 years with this one, I might as well stick with it. BUT,
I'll never get married again. I'll just find some woman I hate and buy her
a house.

73
Wayne
W5GIE