Re: ARLA/CLUSTER: Antenas de Emergência

Terça-Feira, 23 de Julho de 2013 - 13:49:44 WEST

ok Hugo
vou-te telefonar


2013/7/23 Hugo Barata <ct2hmx  gmail.com>

> 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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>>>>
>>>>
>>>
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