How big are the ground losses? Are they the difference between an EZNEC
prediction over perfect ground and what it says over average ground assuming
average is what you have? Is it the difference between the model's prediction
of impedance over perfect ground and what you actually measure as Bob Orr said
in his book years ago, for example, the model says the impedance should be 35
+jx over perfect ground and you measure 50 +jx, at the feed point, that's 15
ohms of loss?
Jon
On Aug 3, 2013, at 7:46 AM, Darrell Bellerive wrote:
> The other factor that I don't think has been mentioned is ground loss of the
> transmitted signal. For horizontal antennas, antenna height is the major
> factor, and for vertical antennas, radials.
>
> The impact of ground loss on a low horizontal antenna on the 160 and 80 metre
> bands will be significant compared to feedline losses. A dipole at 25 to 30
> feet above ground for 160 metres is only 0.05 of a wavelength high. As a
> horizontal antenna is lowered below 1/4 wavelength above ground, ground
> losses increase significantly.
>
> Remember though that lots of hams make lots of contacts with low dipoles, and
> any antenna is better than no antenna. So like Bob has stated, striving to
> eliminate that last dB of feedline, tuner, or balun loss may be insignificant
> compared to other factors. We need to be mindful of our complete system of
> transmitter power, losses, propagation, etc. and the impact each has on our
> transmitted signal.
>
> 73, Darrell VA7TO
>
> Darrell Bellerive
>
> On 08/03/2013 06:37 AM, Bob McGraw - K4TAX wrote:
>> Steve et al:
>>
>> I'm not saying that loss does or does not change with the vinyl type
>> window line between wet and dry. I do agree with your results in that
>> loss does increase with a wet line as opposed to a dry line. I also
>> agree that loss is greater per unit at 28 MHz vs. the same length of
>> line at 1.8 MHz or 3.8 MHz regardless if the line is wet or dry.
>>
>> My point, with today's receivers, in most all cases the atmospheric
>> noise and man made noise will mask any receiver internal noise and will
>> easily overtake any loss in the transmission line. However, the loss in
>> the transmission line will affect the NF of the receiver, which on HF is
>> of little significance. In many cases, we worry about 2 or 3 dB loss
>> in the transmission line but run the attenuator of 10 dB to 20 dB at the
>> input of the receiver. Now on transmit, that point makes a different in
>> the power arriving at the antenna. Again, typically less than 1 S unit
>> on the other end. To that point, most of the time I run the Argonaut VI
>> at 10 watts and can work about any station I hear, regardless of line loss.
>>
>> True open wire line, by definition, is two conductors supported only at
>> the source end and the termination end, drawn taught, and without any
>> spacers. This of course is a real challenge to make work reliably in
>> practice unless one uses large conductors and spaced at 6" to 18" and
>> used at lower frequencies and typically with very high power in the near
>> megawatt range. We used this feed line approach in some of the
>> commercial SW stations to which I attended. Some of these feed lines
>> were each several thousand feet in length. All of this is far beyond
>> the scope of most ham installations.
>>
>> I would like to see more data on dry line vs. wet line from natural
>> cause as opposed to "wetted" line. I use the vinyl covered line with
>> 66% of the web spacers removed. {Remove 2, leave 1, remove 2, leave
>> 1.} I see little change from wet to dry on HF.
>>
>>
>> 73
>> Bob, K4TAX
>>
>>
>> ----- Original Message ----- From: "Steve Hunt" <steve@karinya.net>
>> To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
>> Cc: "Phil Sussman" <psussman@pactor.com>; "Bob McGraw - K4TAX"
>> <RMcGraw@Blomand.net>
>> Sent: Saturday, August 03, 2013 8:01 AM
>> Subject: Re: [TenTec] OT: Openwire/Window Line and Bad Wx
>>
>>
>>> We're talking here about reported changes in loss that - if true -
>>> would be equivalent to a 5dB change between dry and wet on a 100ft of
>>> ladderline feeding a doublet on 10m.
>>>
>>> Are you folks trying to tell me that 5dB makes "little to no difference"?
>>>
>>> Steve G3TXQ
>>>
>>>
>>>
>>>
>>> On 03/08/2013 13:27, Phil Sussman wrote:
>>>> Bob is right! In the end, propagation will dictate. External
>>>> conditions have more of an effect than the subtle differences
>>>> over which we have control.
>>>>
>>>> Sure we can increase efficiency, yet the results are subtle.
>>>> It all depends upon whether the band is open, eh?
>>>>
>>>> Well said, Bob!
>>>>
>>>> 73 de Phil - N8PS
>>>>
>>>> ------
>>>>
>>>> Quoting Bob McGraw - K4TAX <RMcGraw@Blomand.net>:
>>>>
>>>>> As I said in my closing remark in an earlier post:
>>>>>
>>>>> "I realize that we'd like to eak out every dB we can, but in the
>>>>> end, it
>>>>> makes little to no difference on HF."
>>>>>
>>>>> If one can match the load, using what ever means and equipment, then
>>>>> energy will be transferred. On receiving, atomospheric and man made
>>>>> noise will overtake any losses in the antenna system and will over
>>>>> ride most all receiver noise.
>>>>>
>>>>> 73
>>>>> Bob, K4TAX
>>>>>
>>>>
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>>>>
>>>>
>>>
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>>
>>
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