Ham-related stuff. Billingual when I have the mood. Otherwise it will be single-language only.

Papo de radioamador. Vai ser bilíngue quando estiver a fim. Senão, vai numa língua só.


Back in Blog

Well, here I am, back in São Paulo...

It´s 10 days now, but just today I remembered to post something...

As I foresaw, I was not able to get on air during the past 4 months, nor is the hex-beam ready...

The situation will be pretty much the same over the next 6 months....

Unfortunately, I´ll be away from the aether until march, 2004...<grin>


Everything is still

I'm going to move to another city. Yes, I have a new job.

As I'll probably be living in a hotel for the next 10 months, I'm afraid I won't be able to test my equipment in both TX and RX... luckily I've finished the power source...

That's all. I'm not in the mood to write longer. :-Z


Power Supply Ready / Fonte Pronta

Well, I just finished modifying the AT power supply. I'm only waiting for the paint to dry, but that may take a little while, as the day is pretty rainy.

I've done a _very_ simple mod, as described here (portuguese only, sorry). The mod consists in adding a zener diode and a rectifier diode plus a capacitor in paralell with them. I think this is very similar to the mod described in the final part of this article.

Of course, I've added a personal touch, fitting the back of the modified power supply with PowerPoles, which was chosen as the default power connector at my shack.

BTW, I'm impressed with the engineering embedded in this fantastic product. After buying a couple of contacts, I was able to conectorize all the cables, plus a battery cable in just a few minutes. It is a piece of cake! Although I don't have the proper tooling to crimp the powerpole contacts, it just took me to (wasted) contacts to learn the proper way to crimp them using only a regular nose pliers (with crimping dents). Part number for the pliers is STANLEY 84-053.

Fonte Pronta

Acabei de modificar a fonte de um computador AT para usar na minha estação. A modificação é bem simples, e pode ser encontrada aqui.

Numa próxima etapa, farei a modificação mais complexa descrita neste artigo (em inglês)

Adicionei um toque pessoal na minha fonte, usando os conectores powerpole para conectar ao rádio. Maiores informações sobre estes conectores no site da Metaltex.
Agora, só falta fazer o exame de promoção e conseguir um novo indicativo!


Scrouging DOES reward

Today I FOUND a CHEAP source of Anderson PowerPoles.

I found only the black housings, but for only ridiculous US$ 0.15!

I'll have to buy the contacts in a local reseller for US$0.62 each.

The complete assembly (2 housings+2 contacts) will cost me a total US$1.54, less than half the price if I bought from the local reseller.

To keep to the standards (there is no such thing in PY-land, unfortunately :-( ), I'll paint half the housings red. I bought just 60 of them, but they have a box full of 'em (10 thousand!).

If I realize a way to sell them all, I'll buy the box. I'll try a bargain price (yes, less than US$0.15/ea), but that won't be cheap.


Power Supplies Tested and Working

Having some free time this morning, I decided to test the 3 power supplies are working FB.

The ATX is a 300W ps, that I'll keep if ever need another computer or need to change the power supply from my computer.

One of the AT is a 220W and the other is a 300W one. I'll first do the mods in the 220W, and if it works, I'll mod the 300W. Or maybe I'll just mod the 300W and use right away if it works at all.

More fun to come...I begin felling a HAM!...


Power supply on the way!

Today I was given 2 AT power supplies and one ATX. All of them are presumably not working.

I was to start hacking the AT PS next weekend, but it has to be postponed due to a family lunch and a test in the sunday.


CHEAP source of Amphenol connectors

I found a source of amphenol 97 series connector in Brazil,
they sell for USD 1.16 each

  • 97-3106A-20-7S (8 contacts), without cable clamps, with
    plastic cap
  • 97-3102A-20-7P, with plastic cap

Almost all in original packaging, mint or near-mint
condition, seems never used.

I've seen some cable clamps, but I was not able to determine
their part numbers.

I bought myself a dozen, since this is a very hard-to-find
item here.


Updating the update/Atualizando a atualização

I took a look in some AT power supplies just to realise that many of the things I want in my homebrew PS is are almost done.

The internal connections are ready, since in the PCs, the AC mains is connected to the power switch through the power supply. That means: the four conductor (blue, brown, black, white) cable that comes out from the power supply has both an AC IN (black, white) and an AC OUT (blue, brown).

This came to greatly simplify my ideas. I just have to run a separate power cord (to have wires in the proper gauge) and connect the black and white leads from the PS to a bus wire inside the case.

The bus wire connects to the power cord through the Power switch. MUCH EASIER than I had thought.

Atualizando a atualização

Aguarde !

Power Supply Project Update: Specification/

Atualização do Projeto da Fonte: Especificações

I've been thinking about this power supply thing and came to the following:

  • The PS must have only ONE power cord (AC mains) and one "power on" switch;
  • The connections MUST all be internal to the case, which may be a computer case;
  • If there is suitable space inside the case (I believe it is) I would like to include some gel-cell batteries;

    • Then, I'll need a good battery charges to be built inside the case, one with good trickle charging or the ability to turn itself off when the batteries are full charged.
    • A system to switch from the PS to the batteries in the event of AC mains failure.
    • An external DC in jack, to add more capacity if needed.

The switching between PS and batteries I plan to accomplish using a DC relay connected to the PS DC out.

I don't have a suitable circuit to do the trickle charging. I would like one tried and working, without exotic components which may be hard to find below the equator...
I don't have either a protection scheme to prevent energy flowing in the wrong direction, simple as it seems I may just put some diodes preventing output to the external batteries and input from the DC output jack and input to the PC power supplies.
The trickle charger may be turned on or off via the same switch that powers the PC PSs, provided that I change it to a 3 position switch (i, 0, ii), being (ii) the trickle charger.

Atualização do Projeto da Fonte: Especificações

Eu escrevi isso tudo antes de ter uma vaga idéia de como funcionava uma fonte de PC. Dê uma olhada nos artigos ao lado.


Another Project/Outro Projeto

As I don't have a power supply, it is quite obvious that I am angry to get one.

25-30 Amps PS are about R$230-250, more than I can afford. Some one posted a question about power supplies on rec.radio.amateur.homebrew, the answer sent me to antenneX. A similar PS like this one will cost me about R$60, less is a friend hands me his unused surplus of PC power sources. Good savings.

Outro Projeto

Como eu já disse antes, eu ainda não tenho uma fonte. Obviamente eu estou ávido para por minhas mãos em uma :)

Uma fonte de 25-30 ampères custa algo em torno de R$ 230-250, o que é mais do que eu posso pagar.

Outro dia, alguém mandou uma pergunta sobre fontes para o rec.radio.amateur.homebrew e resposta acabou me mandando para antenneX. Um projeto similar a este deve custar em torno de R$60, ou menos se um amigo doar algumas fontes de PC que ele tem :)


Prices Research 1/Pesquisa de Preços 1

Today I had the first results from fishing rod blanks.
The chinese ones (fiberglass, I suppose), 4.5m long are less than R$ 20/ea. The final section of this fishing rods is way too thin to make believe they may support the largest wire, this is the main reason I preferred the long rods.
As for my previous calculations, the spreader length would be less than 3m. At this lenght, the fishing rods are still thick enough. Their walls are pretty thin anyway. Maybe some doweling inside them to make the joints tougher.

Pesquisa de Preços 1

Hoje obtive os primeiros resultados sobre as varas de pesca. Aquelas varas chinesas (fibra de vidro, suponho) com 4,5m custam menos de R$20 cada. O último trecho das varas é muuito fino para suportar o maior elemento, e por esta razão é que eu preferi as varas mais longas. Pelos meus cálculos anteriores o comprimento dos espaçadores será pouco menor que 3m. Neste comprimento, as varas tem um diâetro grande o bastante.

As paredes do tubo são bem finas. Talvez alguns tocos de madeira podem reforças essas junções.


Good News/Notícia Boa

Found a better better product than regular (black) VEDAPREN, it's White VEDAPREN, does not have to be covered from sunlight.

Notícia Boa

Achei uma solução melhor que VEDAPREN.

VEDAPREN Branco. Não precisa ser protegido do sol.


Solved Mistery/Mistério Resolvido

I found a suitable sealant in the DIY shop near home.
It has two small disadvantages compared to what Yuri told us... I is NOT UV resistant and comes in a too big flask. In fact it is a (as I recall) 2 1 gallon can.

Mistério Resolvido

Achei o tal impermeabilizante. VEDAPREN. Acho que todo mundo conhece, vem num valde amarelo.

Não tem nada de latex. Apenas latex é como os americanos se referem a emulsões a base de água.

Next Phase/Próxima Fase

Now I think I have enough food for thought...

It's time get out and figure out how much it will cost me.
I'll not convert currencies everywhere, but will post most in Reais (brazilian currency). For those inclined, the exchange rate is about R$ 3.5 to US$ 1.

Próxima Fase

Agora já tenho bastante informação para continuar o projeto.

Agora eu vou dar uma volta por aí e ver quanto eu vou gastar para montar a danada...


First results/Resultados Preliminares

This is just to put some preliminay results. Thanks to the many that sent suggestions.

  • Feb, 27: Boian Petkov had built a hex-beam just like mine using 4m long telescoping fishing poles. Just removed the last, thinnest section and glued the others together
  • March 5:

    • Dave Platt pointed the effects of sunlight over bamboo and fiberglass. In both cases, a good coating with UV resistant varnish or paint will be in good order. Also other construction thoughts (will post in due time)
    • Yuri suggested coating the bamboo spreaders with latex based driveway surface coating. Says it works.

  • March 6: Bill Spurrier told me about a 2 element cubical quad he built for 10m using 1/2" grey PVC tubing
  • March 7: Orlando emailed me about a cubical quad he built using resin reinforced bamboo. This was published in a brazilian electronics magazine in the 70's. He promised to dig the article and send me. More info coming soon.
  • Many others posted several sources of fiberglass spreaders, mainly ham-oriented bussiness. Thanks to them.

Resultados Preliminares

Só para dar alguns resultados...

  • 27/Fev: Boian Petkov construiu uma hex igual a minha, usando varas de pesca telescópicas. Ele apenas removeu a última seção, mais fina e colou as restantes no lugar.
  • 5/Março

    • Dave Platt apontou os efeitos da radiação solar sobre o bambú e a fibra de vidro. Em ambos os casos, uma boa pintura com verniz ou tinta para exteriores deve resolver. Também mandou algumas idéias sobre a construção da antena, que logo mais coloco no ar.
    • Yuri sugeriu aplicar uma cobertura de impermeabilizante para pistas de rodagem a base latex. Ele diz que funciona. No entanto, não sei de que se trata.

  • 6/Março: Bill Spurrier contou sobre uma cúbica de quadro de 2 elementos para 10 que ele construiu usando tubo de PVC de 20mm.
  • 7/Março: Orlando mandou um email sobre uma cúbica de quadro construída segundo um projeto da revista Eletrônica Popular da década de 70. As varetas eram feitas de bambú reforçado com bandagens e resina. Ele disse que ia procurar o artigo
  • Outras pessoas deram indicações de fontes de fibra-de-vidro, a maioria delas é orientada para radioamadores. Obrigado a todos.


First Post / Primeiro

I am Paulo Marcondes. I've been a ham since 1995, but my first rig was bought last december (xmas gift...).
I don't have a PS yet, but it'll come soon.

For now the project is a 5 band hex-beam antenna, expandable to 7 band. I am planning to have 10-12-15-17-20 in the first go, then, as time permits, I will add 30-40m.

Project is just starting. I have wire dimensions, as per EI7BA spreadsheet (
Now I am researching suitable materials for use on the spreaders. It seems that the obvious, ubiquitous fiberglass will be chosen.

I think about using telescoping sections in a way I can add more sections later without disassembling the entire antenna.


Eu sou Paulo Marcondes, radioamador desde 1995. Meu primeiro rádio foi comprado em dezembro último, um ICOM 735 e um acoplador TEB. EU ainda não tenho uma fonte, mas está para vir.

O Projeto do momento é uma hex-beam, uma direcional de 2 elementos, feita de fio. O projeto está apenas começando. Já tenho as dimensões dos elementos, de acordo com a planilha do EI7BA (
). Agorea estou pesquisando materiais para usar nos braços da antena. Parece que a fibra-de-vidro é o melhor caminho a seguir.

Inicialmente devo fazer a antena com cinco bandas 10-12-15-17-20, e depois, com o tempo adicionar 30 e 40 metros. Estou pensando em usar seções tescópicas de tubos redondos, de tal maneira que quando eu for adicionar as outras bandas, não tenha que desmontar a antena inteira.