Re: ARLA/CLUSTER: Antenas de Emergência

[Hugo Barata]

Boa tarde Luis.

Tenho uma gama de toroides FT xxx pelo que poderei ter algum que seja o que
possas precisar para os testes.
Alguns FT 140-43, FT 140-44 e semelhantes. T200 não tenho.

73 de Hugo Barata CT2HMX

On Tue, Jul 23, 2013 at 12:22 PM, Fernando Dinis Silva <scacem  gmail.com>wrote:

> Amigo Luis pois eu não o posso ajudar pois não tenho esse material.
> Mas pelo que sei o teu pai CT1EN tinha muito material que poderias
> aproveitar digo eu, as antenas que ele deixou por lá na torre e que tu
> sabes quais são, são umas antenas boas necessitam é de manutenção e
> digo-te que ficavas com uma boa antena melhor do que essas que tu queres
> fazer.
> Um abraço
> CT1DZ
> Fernando Dinis Silva
>
>
> 2013/7/21 Luis Valadas <valadas.luis  gmail.com>
>
>> Boas noite a todos
>> Em primeiro lugar queria explicar o porquê de ter utilizado este email
>> para dirigir-me a todos
>> Bom , eu queria perguntar se alguem tem e que possa dispensar :
>> - toroide 140-43
>> -toroide T200-2
>> - toroide T200-6
>> - alguns metros de fio de 1mm esmaltado
>> Devem estar a pensar que vou fazer um balum pelo menos de 9:1, de facto
>> tem razao, queria fazer umas antemas , e sei que existe a venda baluns ja
>> feitos mas confesso que gostava de eu os fazer, quanto a comprar no ebay ou
>> no estrangeiro tenho alguma dificuldade em faze-lo por isso peço a alguem
>> que tenha e que possa dispensar, claro pagando o justo valor do mesmo
>> material e os devidos portes
>> 73
>> CT1DTE
>> Luis Valadas
>>
>>
>>
>> 2013/7/18 João Costa > CT1FBF <ct1fbf  gmail.com>
>>
>>> More on HF – SSB - Antennas
>>>  Carrying on from my previous blog on engineers antennas HF and SSB<http://www.expeditioncoppelia.com/2010/10/engineers-antennas-hf-ssb.html>,
>>> in this second part I will more fully describe our emergency antenna setup.
>>>
>>> I draw your attention to a very useful set of resources available free
>>> on the internet:
>>> Field Antenna Handbook - US Marine Corps<http://frrl.files.wordpress.com/2009/02/usmc-antenna-hb.pdf>
>>>
>>> Radio Operators Handbook - US Marine Corps<http://hilltoparmyradios.com/usmc-radio-ops-hdbk.pdf>
>>>
>>> In the previous post I worked out the length of antenna for a given
>>> frequency that would provide the best chance of effective communication.
>>> This certainly does not mean for a given frequency if the length is
>>> different you can not communicate, it just means that there is more chance
>>> at the lengths specified.
>>> So how is it all going to work on the boat.
>>> **
>>> *Situation one – the antenna is broken, but the tuner is intact. *
>>> Cut a new antenna from a piece of wire of a length greater than 7m as
>>> specified for our ICOM tuner.
>>>
>>> One end of the antenna would need to be lifted towards the sky, if the
>>> mast or part of it is still standing the wire could be hoisted on it,
>>> otherwise some other pole, like the prod, kite pole or boom could be used.
>>> The resulting antenna would have the characteristics of this sloping wire
>>> antenna show below:
>>>
>>> [image: sloping wire]<http://lh6.ggpht.com/_rK1oaS0yOa8/TNNujQUNbNI/AAAAAAAAFTc/kuMS4ZHLEUg/s1600-h/sloping%20wire%5B2%5D.png>
>>> Sloping Wire – source: US Marine Corps (1991) “*Field Antenna Handbook*”
>>> pg 4-34
>>> *Situation two – the antenna is broken, the tuner is broken*
>>>
>>>
>>>
>>> This is the situation where  having the antenna length appropriate for
>>> the frequency you want to transmit of is important. Normally the tuner,
>>> tunes between length suitable for the frequency and the actual antenna
>>> length using a series of capacitors and inductors. Without a tuner each
>>> time you change frequency, to optimise the chance of being able to
>>> communicate the length of the antenna must be changed.
>>>
>>> The length of antennas required for international emergency frequency
>>> range between 32.6m for 2182 Hz to 11.6m for 6125Hz.
>>>
>>> 32.6m is greater than distance between the back of Coppelia and the mast
>>> head. Therefore the sloping wire arrangement used above can not be used.
>>> Moreover, it is likely that if we have broken the tuner, we might have
>>> suffered damage to the mast, and therefore we would not even be able to
>>> make a 11.6m sloping antenna.
>>>
>>> The answer is a different sort of antenna, a vertical half rhombic
>>> antenna.
>>> [image: Slide2]<http://lh6.ggpht.com/_rK1oaS0yOa8/TNNumH0uAaI/AAAAAAAAFTk/r08mwsGQ8lI/s1600-h/Slide2%5B1%5D.png>
>>> Vertical half rhombic antenna – source: US Marine Corps (1991) “*Field
>>> Antenna Handbook*” pg 4-37
>>>
>>> The plan onboard would be to make some sort of pole in the middle of the
>>> boat. A shielded cable would then be run from the radio to the back of the
>>> boat, and a second wire from the ground plate to the same location. A
>>> piece  of wire equal to the length of antenna required for the frequency to
>>> be used would then be attached to these wires, and hoisted aloft in the
>>> middle, then fastened at the bow. The resulting antenna setup would form a
>>> vertical half rhombic antenna.
>>>
>>>   *Emergency Antennas for VHF and UHF Use*
>>>
>>>     Get a piece of RG-58 coax and using the chart below, strip the outer
>>> jacket of the coax to that appropriate length, depending on the band you
>>> choose to work.  Once the outer covering has been stripped, carefully open
>>> the copper braid near the bottom of where you stripped the outer jacket.
>>> Once the braid is open, carefully bend the center conductor over and pull
>>> it out of the hole you opened in the copper braid.  Once you have the
>>> center conductor pulled free, straighten it and either form a loop at the
>>> top end for hanging, or solder on a terminal lug.  Remember, the antenna
>>> length is measured from the very end of the look or terminal lug, and they
>>> do add length to your antenna.  Trim as necessary.
>>>
>>>
>>>
>>>  *MHz*
>>>  *Length in Inches*
>>>  *Length in Metric*
>>>  52
>>>  54"
>>>  137.2 cm
>>>  146
>>>  19.2
>>>  48.8 cm
>>>  223
>>>  12.5"
>>>  31.8 cm
>>>  445
>>>  6.3"
>>>  16cm
>>>
>>>
>>>
>>> Fontes:  Expedition Coppelia e WCERC *VHF UHF Emergency Antennas*
>>>
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>>> CLUSTER  radio-amador.net
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>>>
>>>
>>
>> _______________________________________________
>>
>
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