Re: ARLA/CLUSTER: Antenas de Emergência

[Fernando Dinis Silva]

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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