Fw: Fw: Re: [Antennas] 450 Ohm Ladder Line

2002年12月13日 12:46:29 -0800

Jerry,
The equation for dB (power) is
dB = 10*log [Pwr1 / Pwr 2] = 10 * log (600/100) = 10 * log (6) = 7.7 dB
A long time ago, it was said an "S" unit was 6 dB. Also, "S9" represented 50
microvolts at the receiver. However, none of the receivers that I am aware of
(then or now) had their S meters calibrated. I don't know why, but I can
imagine variable gain of many stages of mixing and gain, and the change of
those components over time made it difficult to provide and maintain accuracy.
For a price, it can be done.
Many call the S meter a 'guess' meter. I happen to agree. Especially with many
modern receiver having switchable or variable gain rf stages that effect the
'S' meter.
Rolly W7DGX
> E. Jerold Forwood wrote:
>> >Excuse me! I forgot! How many db's does it take to equal one S unit?
> >In the far field?
> >How much less is the guy on the other end apt to hear me when I am
> >running my linear at 600 Watts v/s barefoot at 100 Watts?
> >73's de Jerry, K�EJF
> >
> >On 2002年12月12日 13:25:37 -0500 "Joe Giacobello, K2XX" <[email protected]>
> >writes:
> >
> >
> >>I happened to save a copy of some test measurements that Tom, W8JI,
> >>made
> >>with 450 ohm ladder line back a few years ago. The experimental
> >>data
> >>show that there is substantial loss when burying the line in PVC
> >>pipe.
> >> His report is pasted below.
> >>
> >>73, Joe
> >>
> >>You will be amazed at the attenuation caused by the soil,
> >>especially if you allow the ladderline to get near the wall of the
> >>buried pipe.
> >>
> >>Balanced lines have a strong field extending at least a few
> >>conductor spacings outside the line in a plane in-line with the flat
> >>
> >>part of the line, and to a lesser extent broadside to that plane
> >>REGARDLESS of the fact they might have little far-field radiation.
> >>
> >>My original post was:
> >>
> >>Since no one knows what happens when open wire line is buried, I
> >>measured some today. The line was heavy duty one inch spaced
> >>twinline, with 14 gauge stranded conductors. The measured dry
> >>impedance of a 50 foot dry sample was 328 ohms, although the
> >>line is advertised as 450 ohm line.
> >>
> >>Digital photographs are available if anyone wants to put this on a
> >>Web Site.
> >>
> >>50 foot 15 MHz loss measured with Wiltron Network Analyzer
> >>(matched line conditions in every case):
> >>
> >>Dry line suspended in air= .12 dB
> >>
> >>Dry line laid on 3 inch tall dry grass, held up off the dirt unknown
> >>
> >>amount by the fairly thick grass= .83 dB
> >>
> >>Dry line pulled in 2" PVC white plumbing pipe laying on grass =
> >>1.55 dB
> >>
> >>Dry line buried 3-6 inches deep in PVC pipe in fairly dry dirt =
> >>4.12
> >>dB
> >>
> >>Same dry line in same pipe with dirt soaked with hose = 6.81 dB
> >>
> >>Same dry line back in air = .15 dB
> >>
> >>Line being wet down with heavy mist = .63 dB
> >>
> >>Line slightly wet but not being misted for several minutes = .28 dB
> >>
> >>Line was rematched to eliminate mismatch loss as impedance
> >>changed, and matching network loss zeroed-out with analyzer.
> >>
> >>
> >>73, Tom W8JI
> >>[email protected]
> >>
> >>
> >>
> >>Dan Richardson wrote:
> >>
> >>
> >>
> >>>At 12:35 PM 12/11/2002 -0600, you wrote:
> >>>
> >>>
> >>>
> >>>>On the other hand...........
> >>>>
> >>>>* Ladder line tests were performed at 50MHz to 150Mhz
> >>>>
> >>>>
> >>(instrumentation
> >>
> >>
> >>>> limitation) where losses are greater .....not at HF, 160m -
> >>>>
> >>>>
> >>10m
> >>
> >>
> >>>Knowing those values it is easy to calculate the losses at lower
> >>>frequencies. The formula is given in the article.
> >>>
> >>>
> >>>
> >>>>* Many of the tests were performed with Wireman Type 554
> >>>>
> >>>>
> >>....should
> >>
> >>
> >>>> also use the larger AWG.
> >>>>
> >>>>
> >>>Not so. He measured Wireman's numbers 551, 552, 553 & 554 the
> >>>
> >>>
> >>results
> >>
> >>
> >>>are shown in Table 1.
> >>>
> >>>
> >>>
> >>>>* The premise is that you are trying to load random length
> >>>>
> >>>>
> >>dipoles
> >>
> >>
> >>>>due to
> >>>> space limitations .....the antennas I feed are "tuned
> >>>>
> >>>>
> >>dipoles".
> >>
> >>
> >>>I believe he was cautioning that substantial losses can and will
> >>>
> >>>
> >>take
> >>
> >>
> >>>place feeding short (less 3/8-wavelength) dipoles with window
> >>>
> >>>
> >>line.
> >>
> >>
> >>>>* Wet measurements are made by wetting the line, including an
> >>>>
> >>>>
> >>open wire
> >>
> >>
> >>>> "reference line" which had NO change (indicates that a high
> >>>>
> >>>>
> >>moisture
> >>
> >>
> >>>> "mist" dielectric was not considered) .....this also implies
> >>>>
> >>>>
> >>that the
> >>
> >>
> >>>>change
> >>>> in impedance and attenuation shown is due to a wet ladder web
> >>>>
> >>>>
> >>only.
> >>
> >>
> >>>> Making the web smaller should help this.
> >>>>
> >>>>
> >>>Mist? Really? And how are you going to qualify that one and make
> >>>
> >>>
> >>it
> >>
> >>
> >>>repeatable?
> >>>
> >>>Both wet and dry measurement are shown. (Again Table 1)
> >>>
> >>>
> >>>
> >>>
> >>>>I'd also like to know, for a HF antenna system, do you get more
> >>>>
> >>>>
> >>power
> >>
> >>
> >>>>radiated by the resonant antenna if 1) you have an impedance
> >>>>
> >>>>
> >>mismatch
> >>
> >>
> >>>>of 9:1 (with it's resultant SWR) between 200ft of 450ohm
> >>>>
> >>>>
> >>transmission
> >>
> >>
> >>>>line and the 50ohm antenna .....or 2) if you use a toroidial 9:1
> >>>>transformer
> >>>>(with it's loss) between the balanced transmission line and the
> >>>>
> >>>>
> >>balanced
> >>
> >>
> >>>>antenna ?
> >>>>
> >>>>
> >>>>
> >>>The article addresses the window line losses only. For comparisons
> >>>
> >>>
> >>>with other systems you're going to have to dig deeper elsewhere.
> >>>
> >>>Danny
> >>>
> >>>
> >>>
> >>>
> >>>>Fun stuff.
> >>>>
> >>>>73 Kees K5BCQ
> >>>>
> >>>>--------- Forwarded message ----------
> >>>>From: Sandy and Kees Talen <[email protected]>
> >>>>To: [email protected]
> >>>>Date: 2002年12月11日 11:06:33 -0600
> >>>>Subject: Fw: Re: [Antennas] 450 Ohm Ladder Line
> >>>>
> >>>>Great article, thanks Dan. It's always good to see real data,
> >>>>
> >>>>
> >>determined
> >>
> >>
> >>>>using a controlled experiment, and excellent test equipment.
> >>>>
> >>>>73 Kees K5BCQ
> >>>>
> >>>>
> >>>>------- Forwarded message ----------
> >>>>From: Dan Richardson <[email protected]>
> >>>>To: [email protected]
> >>>>Date: 2002年12月11日 08:24:01 -0800
> >>>>Subject: Re: [Antennas] 450 Ohm Ladder Line
> >>>>Message-ID:
> >>>>
> >>>>
> >><[email protected]>
> >>
> >>
> >>>>For those interested here is URL which provides a very through
> >>>>
> >>>>
> >>analysis
> >>
> >>
> >>>>on
> >>>>this subject.
> >>>>
> >>>>http://users.triconet.org/wesandlinda/ladder_line.pdf
> >>>>
> >>>>Danny, K6MHE
> >>>>
> >>>>
> >>>>No trees were destroyed in the sending of this message.
> >>>>However, a large number of electrons were terribly
> >>>>
> >>>>
> >>inconvenienced.
> >>
> >>
> >>>>- - -
> >>>>
> >>>>Your moderator for this list is:
> >>>>Larry Wilson KE1HZ [email protected]
> >>>>_______________________________________________
> >>>>Antennas mailing list
> >>>>[email protected]
> >>>>http://mailman.qth.net/mailman/listinfo/antennas
> >>>>- - -
> >>>>
> >>>>Your moderator for this list is:
> >>>>Larry Wilson KE1HZ [email protected]
> >>>>_______________________________________________
> >>>>Antennas mailing list
> >>>>[email protected]
> >>>>http://mailman.qth.net/mailman/listinfo/antennas
> >>>>
> >>>>
> >>>Danny
> >>>K6MHE
> >>>
> >>>No trees were destroyed in the sending of this message.
> >>>However, a large number of electrons were terribly
> >>>
> >>>
> >>inconvenienced.
> >>
> >>
> >>>- - -
> >>>Your moderator for this list is:
> >>>Larry Wilson KE1HZ [email protected]
> >>>_______________________________________________
> >>>Antennas mailing list
> >>>[email protected]
> >>>http://mailman.qth.net/mailman/listinfo/antennas
> >>>
> >>>
> >>>
> >>>
> >>- - -
> >>
> >>Your moderator for this list is:
> >>Larry Wilson KE1HZ [email protected]
> >>_______________________________________________
> >>Antennas mailing list
> >>[email protected]
> >>http://mailman.qth.net/mailman/listinfo/antennas
> >>
> >>
> >>
> >>
> >
> >
> >E. Jerold (Jerry) Forwood
> >
> >
> >
> >
>> - - -
>> Your moderator for this list is:
> Larry Wilson KE1HZ [email protected]
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