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