To: rsgb_lf_group@blacksheep.org
References: <562685198.17267493.1540633557178.ref@mail.yahoo.com>
 <562685198.17267493.1540633557178@mail.yahoo.com>
From: N1BUG <paul@n1bug.com>
Openpgp: preference=signencrypt
Autocrypt: addr=paul@n1bug.com; prefer-encrypt=mutual; keydata=
 xsFNBFqj1+0BEACggWlaH8oG/AiXSUG3CeQwZ1NrVEP4U7YsA9N9XEffjCDEsnTjHF2BJSgS
 2AicyomkmTGvghEHxrNFfFw07jwgJl97ae/VtNxpERPSE98mb4sPOMpJbwddioMazMDXwhKA
 wpg5fse+Ru8OrIT04KK919xL/pZuAP6pY6d2kVoizjJOfS71pHpiU6N6q3d9cl+w7d2LKhAE
 a3A1ZgDquPvn0WQlrN8K5D66xVrwTRhf1b5H4Ozl8/mMJzCeLG1ZIsDB3Pu2flwE81P8dCJA
 y1azwgY8pTEshVk4em/se9uRiZaDJr/qUSCf6hrV7AGa8g1jpAQDmdGpDNYMqyDqXen4jNi1
 8kNFVu1BMl2vjaI8skw/YPxIxlk/0ROHYhN6SuoDq1mt4AW4FryNa7k3A8dM8Bt7udBoTv0i
 uw4j9R/bmh2vl/QaHRUhDco0xn2z6geWvXkKqha++vzXDrEKUuqgB85SDZPs5W/phs9p0pz1
 xA61d1gn8FQJtpou5dQuAucqMo8eKQY5LUcbC+MH5pebH+M2wIuDCBmFPJHQDSPNepeaxJ4o
 G/HU1hrpzlgLiTTSKR8DcwtMQwYywnCTlm8MgL4jXuPzoGyKDMYyKIjC51G+3AAOJ6oXJAGR
 g0ehhCPtmnCGBaRlUIoUSpbgc4B+onqFKZmDiVm9CRNJhKIWrQARAQABzRZOMUJVRyA8cGF1
 bEBuMWJ1Zy5jb20+wsF9BBMBCAAnBQJao9ftAhsjBQkJZgGABQsJCAcCBhUICQoLAgQWAgMB
 Ah4BAheAAAoJECRS/J8srRGjPBsQAIh+Haz9gqrQJ0OlMI5xmQ0A5nsVWcatWF/Ea4mucNjL
 4n4jmW+Z4Ukn3OVss55chWwrOVMRNWU2d2zRc92ZF7yJhLCoJFV870bZfxNYwdJ3GEBLIu6/
 anmQYX0oXFx8UBsx5K6egNqbeflPA7zrLiQkWrz6JApECdiA1rHDjyJdS7PDxBCG9cKgr/5b
 r4Rn/JlUl9pRPnxlSwHXsV+J6JtFYtWI69MWIVD7Y7OY1wO9+684uOnzeDANzeIwpBDcSm6p
 0D5u0b1hfPl2TD0ozVs6P0NvxkMbimXUhRR1QD0FvydyxmZTLAo+XZDGR8GqWYrYrauoRZ1h
 3m23+bNT2T4AuoFnWekpsZu+sxIf0LKPtEZCa51O65jZ810ROpXg9Lx71gEoQD+kbjO69+kq
 9r7wjytDq/jyhpOGrGYV6kgcQrISY86t9YvkA9Of2HDzZLih3GwecW6fkeV1AO5w4RteE9nL
 zIs2siGw2YqavF6LpTH71Db7cUYyZWn5hkKpwfpLNnPEuqgZACovpH1WUHx+KMqqIL4rMVCH
 GcSLqnH2KF4cEDb6OeTbwuLfpGlN+I3j24eQnB2uz5rDa7/IBjsClLl8S/wdDTP8IikBGixX
 06v3k06tk/OF4UsfJ0cY/ASGP5+kjT4ASMZAIikwVMpKi5A5be77vecKNYlJQ2a6zsFNBFqj
 1+0BEACaujZXo3F17v7QTnub4DjjYvm+nr8J0uU5pPc1UMEz9eWjmtmITm15fx1hPKNtVW+I
 VlT+DG+ShNnYmO2M4CFBoc7PwkAOc70aDxfHz20kotvj1HhXG7oBiqPkN3TK4C7qWV1HUEPA
 V960qPdhsoCqmtkvNwj39w1T0ZR5qwwaqDogs9UwBib7zseQ3OXHG32xYYCMcxM35hgXGkkz
 R7wFL4ZnAPOeFb8LnWtZcrGpwXdsYkXuCxm+A+u9KlFY+w3ZCzZt1F9Ie+/PSZnFIUtbXt2i
 mfc+VkRwOLz5BDAeWuDL09TN81+gbrR3kXlymDcCbuduO/yHOQK085qzE3LuImdy+JNb7oDf
 1C/hvpRvtB02vVy33rzIXT8644SJzFY/mw/W39/BgHKCoL1FrBbfgf0UoIFw5M752i7jQwmv
 j5yFfnVAXIPpCuusMwWMGVpZcGV7QxJxh0HBEhYgOo9v3zKwzNIPm9V/LA67u/rj4a/MlCE0
 mpd6IHaePE1vXDaboPZHZdhAziru5/Jd7KQI0k+HmM/HRANPRNDZ4UeBpgj9PzS6hDN5GHlZ
 fRUbI8JAg9wSaQtEn0bjyaR7lw0yngZTvvjT1Qqt5zGwm1IAall2STes5xK0aS7p+UJJMVbf
 ydZ5VOnocvUkwYxbiqoyuVtGxi4tpWW9CRstYXMkAwARAQABwsFlBBgBCAAPBQJao9ftAhsM
 BQkJZgGAAAoJECRS/J8srRGjTDMP/18q7uhac/naxoFsOqhgXIlvaPgu6GX7s/QOh+bcSV1F
 y50lxo51P/C95H2TVME/CtCjk2xWQcNjWtXloMEsZpl7T3qWgJHvyZYkDtgh3M6UNY+zb08U
 K9E2+rR0AZ6zdMKio7Z1xA9BtbUpSZpvy2NgjoYVqo35NllUWMZJq0u+88PvE5WeCIqLipNI
 EZmUcG9UwolQbPkrRc42ReL+bFbuXGXDA5GbQ0RudXbugI8iUwaw3ftaKElIZtuHW0hw1VrU
 9tVHsxKyEoKgNNT1hr+dgRmvCHmA87Pi4R5cMV0ZkLVOYfPX1motedag7HmSNPi2PkYLts4z
 kyvPEJe2IvaPvjvK1ShRWWgje3uytrhfwyjUZcIuA76RWEfBbwT2Mbrn9O7LvrYtbTiTlsLo
 Zdk2uocuefBvPd2oI7mTn5eLy/VDy2JVnlb9vpZZhriXI4KtCcP6mYyuPxlxqj/30Kn1fU5b
 C4EpnKy6hW1CHM42DbwzT+ChjBpFbX9bfwT4qn6d42+T4mN5wkmfnBRHfcn8Wf1ezRSK3Ome
 Esa3ZDssj23CZHe11uec6Ln14qoB7JyRT9qM3Q99tzvAlmWFM3GrSsG94g4JponQjQWHmr8B
 eMYezwJHzSI7zWElJpzs/OuohstTYfYTy16FygUOEinc1K4ywjEklgRpXRtjKvqc
Message-ID: <938e5339-670c-f8d1-de7e-f60b2b10f6fb@n1bug.com>
Date: Sat, 27 Oct 2018 06:34:57 -0400
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.2.1
MIME-Version: 1.0
In-Reply-To: <562685198.17267493.1540633557178@mail.yahoo.com>
Content-Language: en-US
Subject: Antenna resistance (Re: LF: EbNaut Autodecoder 137490 Hz: EA5DOM
 received)
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8bit
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org

Hi Luis, Markus, LF

This is a very interesting topic for me too.

My antenna resistance is very high, usually more than 100 ohms. I
think there may be a few reasons. There are trees near the antenna
which I presume to be lossy. My antenna ground system is not tied
into the house ground, in order to minimize 120 Hz sidebands on my
transmitted signal. When I tie the grounds together the level of
these sidebands increases almost 20 dB. Also my RX antenna is more
noisy when the TX antenna ground and house ground are tied together.
I suppose this is because more noise is radiated from the TX
antenna, then picked up by the RX antenna which has its own small,
isolated ground.

Rain has no effect on the antenna resistance, but temperature does.
During summer there is little change, just minor variations. But as
the temperature drops and begins to approach freezing, resistance
begins to get lower. There is a big drop right around freezing or
few degrees below, but resistance continues to drop with even lower
temperatures, reaching minimum on the coldest winter nights. Last
winter I saw it reach 40 ohms a few times. :)

I am no expert but I guess the trees are partly responsible for the
high resistance and the drop with freezing temperature?

Anyway I can run enough power to reach calculated 1W EIRP and it's
enough to be heard across that little pond. :)

But here is a related question: I have calculated my EIRP to be one
watt using the measured resistance, antenna parameters and current.
But does this calculation include all the losses in trees? If I had
the proper equipment to make field strength measurements at a
distance, would I find that my EIRP is less than one watt due to the
tree losses?

73,
Paul N1BUG


On 10/27/18 5:45 AM, Markus Vester wrote:
> Hi Luis,
> 
>> Impedance drops a lot after rain
> 
> This seems unusual. I have exactly the opposite effect here:
> Series resistance at 137 kHz is normally around 20 ohms
> (including 5 ohms for the coil). When it rains it get worse up to
> about 40 ohms, whereas best times are cold and dry winter days
> with ~15 ohms when the trees are solidly frozen. So I presume
> that the major contribution to my resistance are
> capacitively-coupled losses in vegetation and other nearfield
> environment. The ground connection itself (the "house earth"
> which is connected to electric grid PE, and also pipe systems for
> water supply and distict heating) seems to have a low resistance.
> 
> 
> My only explanation for lower wet resistance would be if one were
> using a separate radial system in the garden, whose connection to
> ground might be better when the lawn is soaked. But I don't think
> this applies to your setup at all.
> 
> Best 73, Markus
> 
> Von: VIGILANT Luis Fernández
> 
> I'm struggling
> here with the antenna. Most of the time impedance rises and I
> hardly run 1A RF current
>
> Rainy weekend here.
> Impedance drops a lot after rain. Let's see how much current can
> drainLast time I could see almost 4A RF.