Problem #1. The swr indicates about a 140Khz plus < 2:1 bandwidth (2 *
1880-1810) which implies a high radial resistance. Are the elevated
radials fully insulated from trees, not contacting foliage, etc? Add
three more.
Problem #2. Your coiled coax choke may be making things worse. Check
out the just released designs from K9YC and build one. 17 turns RG400
on one FT240-31.
Problem #3. The increased gain of the T may be causing BCB desense of
the 7300. You need a BCB filter. Also the poor choke may be letting a
lot of common mode noise into the antenna.
Grant KZ1W
On 12/28/2018 19:39 PM, Todd Goins wrote:
A person emailed me to ask if I could take SWR readings at the rig without
a tuner. Since my antenna analyzer is non-op due to the AM station nearby.
The feedline is about 140' of LMR-240.
Here is the indicated SWR at the 7300:
1.810 1.2:1
1.830 1.3:1
1.850 1.5:1
1.870 1.8:1
1.900 2.3:1
1.940 3.0:1
Todd - NR7RR
On Fri, Dec 28, 2018 at 7:30 PM Todd Goins <tgoins@gmail.com> wrote:
Charlie,
Yeah, I know the 100w is not ideal. This is night #2 with the elevated
radials on the 100' vertical. I spent every day last week trying to use the
100' vertical against my buried radial field. It was horrible on transmit
and mostly deaf (high noise) on receive. The attenuator didn't help, it
just isn't hearing stations. My 43' vertical top loaded with 90' of
horizontal wire is way, way more effective.
I'm using a 230' BOG as my primary receive antenna right now but I can
switch in the transmit antenna to listen just by throwing a switch.
I'll stick with this 100' antenna for a while and try to use it this
weekend on the Stew Perry but I have a feeling I'll be back with the 43'
before it is over.
Thanks,
73
Todd - NR7RR
On Fri, Dec 28, 2018 at 7:19 PM charlie carroll <k1xx@k1xx.com> wrote:
Todd:
So, I might shorten the antenna up a bit to get the lowest SWR point a
bit higher in the band. But, as it sits right now, your SWR is not
indicating a problem. You're talking only a 100 watts which gives you at
least 1 strike. I would play with it as is for a few days and get some
idea as to how well you are hearing and how well you are transmitting.
Without detailing you, 160 is a place where you need patience and/or a
low-noise receiving antenna. Plus, you also need to know whether you are
being affected by local noise sources. Another reason why I encourage you
to spend more time evaluating the antenna.
73 charlie, k1xx
On 12/28/2018 10:07 PM, Todd Goins wrote:
Hi Charlie,
I can measure SWR at the rig. Feedline is about 140' of LMR240 coax.
SWR at:
1.810 1.2:1
1.830 1.3:1
1.850 1.5:1
1.870 1.8:1
1.900 2.3:1
1.940 3.0:1
I wasn't too worried about the choke situation but I connected in-line
what I had on hand, figured it wouldn't hurt. Mike had just asked what I
was using so I let him know. I'm not having any symptoms of RF in the shack
but I'm only running 100 watts.
73,
Todd - NR7RR
On Fri, Dec 28, 2018 at 6:56 PM charlie carroll <k1xx@k1xx.com> wrote:
Todd:
So, what do you expect the air-wound choke to do for you? Many, many,
many antennas operate fine without a choke. Don't get yourself wrapped
around the axle that the antenna won't work without a "correct" choke.
What's SWR are you measuring at the transmitter? How long is the
feedline? Sure, it would be better to know what the Resistance and
reactance are. But, SWR will give you some idea as to where you are at. I
think right now, you don't really know what your ground truth is. Tell me
the SWR at 1.8, 1.85, 1.9, etc.
73 charlie, k1xx
On 12/28/2018 9:30 PM, Todd Goins wrote:
Hi Mike,
Oh, I would totally believe that the air-wound choke is ineffective at
160m. It just happens to be what I had available to use when I rigged up
the elevated radials in the cold rain yesterday. I figured I'd put it in
line just in case.
Thanks for the choke links, I will read the info on those sites.
The air-wound choke is what I'm using when I'm feeding the antenna using
the elevated radials. When I was testing using my buried radial field it is
a different setup. There I have a DX Engineering radial plate that neatly
ties everything (remote tuner, and DX Engineering Maxi-core Feedline
Current Choke) together at the feed point.
Thanks for the comments and info.
73,
Todd - NR7RR
On Fri, Dec 28, 2018 at 5:57 PM Mike Waters <mikewate@gmail.com>
<mikewate@gmail.com> wrote:
Hi Todd,
I'll bet the farm (if I had one) that your air-core choke is ineffective.
Take at look athttp://www.karinya.net/g3txq/chokes to see what I mean.
A very, very good common mode choke is the one I have on mine,
fromhttp://audiosystemsgroup.com/RFI-Ham.pdf. There is no better material
written on this subject, either in print or on the Internet.
73, Mikewww.w0btu.com
On Fri, Dec 28, 2018 at 7:34 PM Todd Goins <tgoins@gmail.com>
<tgoins@gmail.com> wrote:
... I do have a common mode choke at (near) the feed point. It may or may
not
be effective at 160m. It does work on 10-80m. It is about 25' of RG-8 coax
wrapped around a 4" PVC pipe as a form. Perhaps not ideal... No RF noted
in
the shack.
73,
Todd - NR7RR
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