[Lowfer] What kind of antenna ?

Thu Sep 8 15:36:42 EDT 2016

Here are two interesting screenshots I took comparing the difference in VLF
noise between having the DC coupler for my active antenna grounded at the
station end VS leaving it ungrounded. In both screenshots, the active whip
antenna is grounded at the base, which is about 50' from the house. In my
situation, it is far better to leave the coupler "floating".

https://dl.dropboxusercontent.com/u/33457409/z1203grounded.JPG

https://dl.dropboxusercontent.com/u/33457409/z1203%20ungrounded.JPG

D.

On Thu, Sep 8, 2016 at 3:12 PM, Michael Sapp <wa3tts at verizon.net> wrote:

> That would be my HF vertical and the local noise level is 30~40 dB higher
> on it compared to the ground isolated EWEs...
>
> Mike tts
>
> ----- Original Message ----- From: "Douglas Williams" <
> williamsdoug1966 at gmail.com>
> To: "Discussion of the Lowfer (US, European, & UK) and MedFer bands" <
> lowfer at mailman.qth.net>
> Sent: Thursday, September 08, 2016 2:49 PM
> Subject: Re: [Lowfer] What kind of antenna ?
>
>
>
> Have you tried just throwing a wire out the window and using that?
>>
>>
>> JOKE! ;-)  That's an interesting system. I'll have to study it some more
>> and read up on EWEs.
>>
>> On Thu, Sep 8, 2016 at 1:55 PM, Michael Sapp <wa3tts at verizon.net> wrote:
>>
>> Doug: Essentially orthogonal EWEs
>>>
>>> https://www.dropbox.com/s/xw0flkh343xhamg/LFMFEWE.JPG?dl=0
>>>
>>> https://www.dropbox.com/s/5ygrqqv624c73y7/ewegnd.JPG?dl=0
>>>
>>> https://www.dropbox.com/s/x0hu6b30w9gu694/feedsys.jpg?dl=0
>>>
>>> A couple brief notes...
>>>
>>>    The ground return wires between each end of the EWE antenna improves
>>> ground resistance stability and is essential for being able to switch
>>> antenna directions from the shack position by swapping rx input and
>>> termination resistor. For the same reason the 10:1 transformers at the
>>> antenna require a common ground or the receive direction will not switch
>>> by
>>> swapping the rx input and termination resistor.
>>>
>>>    The background noise improved noticeably when I added the mid-point
>>> ground on the feed lines. The two feed lines to the isolation transformer
>>> in the shack have their outer jackets tied together at the isolation
>>> transformer input. That noticeably lowered AM BC surface wave energy as
>>> measured with an O-scope. With those parallel feed lines having the outer
>>> jackets of the coax separate I was able to measure a few hundred
>>> millivolts
>>> of AM BC energy between them at the isolation transformer input.
>>>
>>>    The background noise improved when I added the perimeter ground wire
>>> around the square area defined by the orthogonal EWEs.
>>>
>>>    Cleaning and oiling the ground connections a few times a year seems to
>>> be worthwhile for maintaining antenna performance. I do the sealing
>>> current
>>> treatment once a week or so to keep the loop resistance low for each feed
>>> line run...(the emf blasts away the thin oxide on the F connector and
>>> antenna switch contact surfaces )
>>>
>>>   Sorry if TMI ~:) Mike wa3tts
>>>
>>>
>>>
>>>
>>> ----- Original Message ----- From: "Douglas Williams" <
>>> williamsdoug1966 at gmail.com>
>>> To: "Discussion of the Lowfer (US, European, & UK) and MedFer bands" <
>>> lowfer at mailman.qth.net>
>>> Sent: Thursday, September 08, 2016 12:14 PM
>>> Subject: Re: [Lowfer] MM lowfer beacon update
>>>
>>>
>>> What kind of antenna are you using, Mike?
>>>
>>>>
>>>> On Thu, Sep 8, 2016 at 10:10 AM, Michael Sapp <wa3tts at verizon.net>
>>>> wrote:
>>>>
>>>> Garry: I heard CFH on 76.2 last night but nothing from XND.  Noise level
>>>>
>>>>> was about constant S6 from a local source when I checked this AM
>>>>> daylight.
>>>>> Not much chance of hearing XND through that kind of noise wall... now
>>>>> and
>>>>> then the local noise turns off and I have S1 or so noise level when no
>>>>> lightning static is around, but even that lower background noise seems
>>>>> like
>>>>> an order of magnitude higher than what I have on 137 kHz. I did the AC
>>>>> voltage measurement on the speaker output the other day on 75 kHz with
>>>>> a
>>>>> trusted analog meter with the ALC off and pretty much confirmed that 10
>>>>> dB
>>>>> "by ear" perceived noise difference between 75 kHz and 137 kHz.  Seems
>>>>> like
>>>>> I have broadband noise sources 10~15 kHz wide either side of 37 kHz,
>>>>> 60kHz, and 75 kHz....  This noise source or sources is coming in on the
>>>>> antenna as my converter is dead quiet with no antenna signal input.  My
>>>>> common mode coaxial chokes are around 12mH or so, perhaps not enough to
>>>>> suppress much VLF energy. The noise level is much lower on the NW
>>>>> direction
>>>>> versus SW but still too high for weak signal detection.  I added a 2 x
>>>>> 3
>>>>> ft
>>>>> aluminum earth capacitor plate at the feed line midpoint ground but
>>>>> that
>>>>> did not help much. I suppose I should be grateful with being able to
>>>>> hear
>>>>> reasonably well on 137, 185, 485 kHz and most of the LW BC and NDB
>>>>> bands...but it would be nice the solve the VLF noise issue...
>>>>>
>>>>> I did not check for MM or WM overnight, I'll have to give that another
>>>>> shot some evening when the QRN is low...
>>>>>
>>>>> 73 Mike wa3tts
>>>>>
>>>>>
>>>>> ----- Original Message ----- From: "N8OOU" <n8oou at meekfarm.us>
>>>>> To: "Discussion of the Lowfer (US, European, & UK) and MedFer bands" <
>>>>> lowfer at mailman.qth.net>
>>>>> Sent: Thursday, September 08, 2016 9:08 AM
>>>>> Subject: Re: [Lowfer] MM lowfer beacon update
>>>>>
>>>>>
>>>>> Garry, Thanks for the capture and report. I just looked at a weather
>>>>>
>>>>> forecast, and maybe the storms will stay North of here.  It is fairly
>>>>>> dry
>>>>>> here, so some rain would be welcome.
>>>>>>
>>>>>> I have removed the "umbrella" style tophat/guywire that I used last
>>>>>> winter on the vertical, and put back to the Marconi style flattop
>>>>>> which
>>>>>> is
>>>>>> supported by taller trees. I am thinking the top 3rd of the vertical
>>>>>> was
>>>>>> shielded too much with the droopy umbrella wires. I am not sure if my
>>>>>> new
>>>>>> supports will survive the winter winds. Time will tell.
>>>>>>
>>>>>> In the next week or so I will move WM to the vertical, and get it back
>>>>>> to
>>>>>> normal operation.
>>>>>>
>>>>>> 73   de   N8OOU - Mike Meek
>>>>>>
>>>>>> On 09/08/2016 07:13 AM, Garry wrote:
>>>>>>
>>>>>> Mike, noticeable boost in SNR for lowfer MM this morning here so the
>>>>>>
>>>>>>> higher power is showing up at more than just your local receiver. The
>>>>>>> higher power particularly helps since storms are all around. See no
>>>>>>> sign
>>>>>>> of WM so far.
>>>>>>>
>>>>>>> Got a late start looking for WH2XND on 75 kHz WSPR-2 but because of
>>>>>>> storm racket that probably didn't matter much. Had to depend on the
>>>>>>> usual near-sunrise enhancement to get a few, minimal SNR decodes.
>>>>>>> Interestingly, found wideband source CKN on 76.2 kHz from BC active.
>>>>>>> Don't see that one too often. Usually CFH is running on 73.6 kHz from
>>>>>>> NS
>>>>>>> but it's been off the air for quite awhile now. Neither one bothers
>>>>>>> reception of WH2XHR, at least not here.
>>>>>>>
>>>>>>> 73, Garry, K3SIW, EN52ta, Elgin, IL
>>>>>>>
>>>>>>>
>>>>>>>
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