Topband: Inverted L improvement question - Part 2

[Grant Saviers]

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 at 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 at 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 at 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 at gmail.com> <mikewate at 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 at gmail.com> <tgoins at 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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>>>>
>>>>
>>>>
>>>>
>>>
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