Fw: Fw: Re: [Antennas] 450 Ohm Ladder Line
Joe Giacobello, K2XX
[email protected]
Thu, 12 Dec 2002 13:25:37 -0500
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: Wed, 11 Dec 2002 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: Wed, 11 Dec 2002 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.
>>
>> - - -
>>
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>
>
> 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]
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