Topband: Elementary Inverted L questions

[Wes]

Pete,

I was going to suggest possible interference to your measurement by a local BC 
station.  I have a couple of very strong stations near me, one on 1550 kHz 
running 50KW. They are about -3 dBm on my 160 inverted-L.  But I just finished 
looking at my antenna with my AA-55 Zoom and I saw no issues.  In the AZ sun I 
saw no display either and had to save traces and come inside :-)  One of the 
reasons I don't like this box.  The FA-VA5 is the only VIA, out of 5, that I 
have that I can read in sunlight.

Wes  N7WS


On 3/25/2021 11:39 AM, N4ZR wrote:
> Thanks to everyone who has replied so far, and apologies - I did a lousy job 
> of describing the antenna.  First off - I set out to make it 1/4 wave 
> (approximately 128 feet) long, and the starting length of wire (what I 
> actually put up) was 140 feet.   Vertical portion is about 55 feet, and the 
> horizontal part is more or less level. The feedpoint choke is wound on a #43 
> core (I think), which may make it a bit more credible.  The measured minimum 
> SWR is 2.2 at 1925 KHz, and resonance (X crossing zero) is at 1983 KHz.  All 
> measurements made at the base of the antenna
>
> Now here's the part I *really* don't understand - at X=0, the R measures 119 
> ohms. Working from memory, I think the old L was resonant about 1875 KHz, and 
> the R was on the order of 35 ohms, which I was told made sense for a 
> quarter-wave with a lossy ground plane.  The new numbers make no sense at all 
> to me.
>
> 73, Pete N4ZR
> Check out the new Reverse Beacon Network
> web server at <http://beta.reversebeacon.net>.
> For spots, please use your favorite
> "retail" DX cluster.
>
> On 3/25/2021 12:26 PM, Artek Manuals wrote:
>> Technically the insulation should electrically lengthen the antenna about 
>> 1.5-2 % (lower the frequency)
>>
>> As Wes said the dimensions would be helpful. is the flat op horizontal or 
>> does it slope down if it slopes how low is the far end?
>>
>> I dont think 17 turns of RG400 is doing much for you on 160M but with a 
>> ground mounted radials (IMO) not likely needed...what is the "R" at X=0.
>>
>> �Are you measuring R+jX at the antenna or at the shack end of the coax? How 
>> long is the coax
>>
>> Dave
>> NR1DX
>>
>>
>>
>> On 3/25/2021 11:54 AM, Wes wrote:
>>> How long is the vertical section?� The insulation should have minimal effect.
>>>
>>> Wes� N7WS
>>>
>>>
>>> On 3/25/2021 8:07 AM, N4ZR wrote:
>>>> I have been trying to replace my inverted L, which broke a few weeks ago, 
>>>> and am having all sorts of puzzlements. Please be kind - I was a history 
>>>> major.
>>>>
>>>> 1.� The inverted L broke at the turn, so I went looking for sturdier wire.� 
>>>> I wound up with some #14 insulated recommended by our local RF maven, and 
>>>> put up 140 feet initially, figuring I would prune it *up* into the CW part 
>>>> of the band.� Imagine my surprise when it showed up resonating at 1977 KHz 
>>>> (on an AA-55 Zoom).� Does insulation have such a profound effect on 
>>>> velocity factor?
>>>>
>>>> 2.� My feedpoint arrangement has 17 turns of RG-400 as a common mode choke, 
>>>> with the radial field connected to the RG-400 shield at the antenna end.� 
>>>> Initially I tried measuring the resonance without the radial connection.� 
>>>> No resonance and infinite SWR. I connected the radial field (8 X 70-foot 
>>>> radials on the ground) and that's when I saw the 1977 KHz resonance (X 
>>>> crossing zero). SWR at minimum was above 2:1.� Does this make sense?� I 
>>>> know the radial field is inadequate for good performance, but...
>>>>
>>>
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