Radio Electronics, February 1986

[Francisco Jos=E]

Hello Everybody.

I'm looking for an article published in Radio Electronics, February

1986, starting on page 16 about a plywood dish (I think this is just a correction of the main article on Radio Electronics, October 1985).

If anyone haves the magazine and can send the pages I want to [e-mail] ( I prefer this email) or to [e-mail] I will be very pleased.

Thank you very much for reading me, and continue keeping the group alive and interesting as it is :)

Regards, Francisco.

[Graham.]

[x-posted to uk.tech.digital-tv where I know it will be of interest]

I wonder what the correction was. Wrong warp factor I guess!

[Francisco Jos=E]

I wonder it too, so hopefully anyone will have it and can scan and send it to me :)

Thank you very much for your reply.

Regards, Francisco.

[www.GymRatZ.co.uk]

I have a copy of "Amateur Radio" September 1987 next to me. Preserved under a pile of papers as it has the complete article and circuit board diagrams for the 20 Amp PSU I built for my practical electronics course.. ....... I thought it was a bit of a long shot.

Wonder why it took 4 months to realise the mistake on the dish. Perhaps the original design wooden' work?

:¬)

[Francisco Jos=E]

I wonder it too, so I hope anyone has it an can send the scan to [e-mail] or [e-mail]

Thank you very much for your reply.

Francisco

[The Natural Philosopher]

Its likely that te sketches on the back of a piece of used bogpaper that the author supplied the artwork department, were so clueless as to lead to the original problem, and the article so unilluminating that it took several months for anyone to spot the mistake, and by then, another couple to work the correction back into the magazine..

[Graham.]

Back in the '80s people would go to all sorts of lengths to construct a dish, as the little that was available to the public was expensive. I knew someone who was a sound engineer for the BBC, he borrowed a microwave radio-link dish to use as a template or former for the one he moulded with fibre-glass.

[The Natural Philosopher]

well that was in essence no different to how they were made 'professionally'

Large plaster moulds from CNC cut formers, lovingly smoothed, and chicken wire and fiberglass applied over..might have had a coat of conducting paint or something or a metal loaded gel coat..

[Graham.]

But a wooden dish? I found this

I am taking it with more than a pinch of salt.

[J G Miller]

On Wed, 24 Sep 2008 19:25:37 +0100, Graham. wrote: > But a wooden dish?

How about using trees as antennas?

From

Abstract : Communications over short ranges through dense wooded or jungle terrains remains a major problem for our armies today. An approach to solving this problem is to use a Hybrid Electromagnetic Antenna Coupler (HEMAC) toroid as a transformer-coupler to excite secondary radiation from the vegetation. The combination of the electric and magnetic fields emitted by the toroid are shown to be as effective as a whip antenna for communicating in the wooded areas adjacent to Fort Monmouth. Initial experiments comparing a HEMAC toroid to a whip antenna are discussed. (Author)

And a Scientific American article at

QUOTE

It is not a joke nor a scientific curiosity, this strange discovery of Gen. George O. Squire, Chief Signal Officer, that trees --- all trees, of all kinds and all heights, growing anywhere --- are nature's own wireless towers and antenna combined. The matter first came to his attention in

1904, through the use of trees as grounds for Army buzzer and telegraph and telephone sets, which, in perfectly dry ground and in a dry season, functioned poorly or not at all with ordinary grounds. Right then he began experiments with a view to seeing what possibilities, if any, the tree had as an aerial. But in 1904 radiotelegraphy was far more undeveloped than at present, and vacuum amplifying tubes were not thought of.

UNQUOTE

[The Natural Philosopher]

Sure. Stick foil on it and its a pretty fair mirror to Ghz frequencies,

[Francisco Jos=E]

Maybe they forgot to add some information (for example on how to find satellites, which was unclear in this dish). However, is interesting that AFAIK, it's a correction and not an added text. Anyways, If I manage to get it, I will publish it here.

Thank you very much for your reply.

Francisco.

[Francisco Jos=E]

Yeah. And I think many of the designs were interesting to try, even today. In fact, some of then were of "high gain", and the LNBs there had a high noise figure and the satellites were not so powerful, so, what will happen if we apply the designs today, but with a low noise figure block (and knowing that satellites are powerful thna in the

80's)? I hope I'll get a good result (or a not bad result).

However, as you may know, in the times of good old analogues signals, If a signal was weak, you can see a image with many sparklies, but still viewable. Instead, today, with digital signals, I can get the whole signals or no signal at all (or an unusable pixelized image), so this can be a big failure.

Regards, Francisco.

[Francisco Jos=E]

But that is a "regular" parabolic prime focus dish. The antena that is explained in the Radio Electronics I have (and in the correction I want is a flat "dish" -in fact, is not a dish itself, but a lens-).

Thank you very much for your reply.

Regards, Francisco

[Francisco Jos=E]

They seem nteresting. I will take a look into them.

Thank you for your reply.

Francisco.

[Colin Stamp]

If a standard dish gives you an acceptable fade margin, then a larger, higher gain one will give you an unnecessarily high fade margin. Go large enough and you'll be able to stand right in front of it and still get a good signal - for all the use that may be.

The down-side is that the satellite will become harder to find. Big dishes can be a real pig to set-up. In fact, above a certain size*, the fact that the satellites aren't properly geo-stationary becomes a problem. Then You'll need a tracking system to follow the satellite's little figure-of-eight movements.

*I've long-since forgotten what the critical size was. 5 metres seems to ring a bell.

Cheers,

Colin.

[John Rumm]

Might also be worth posting your query over in uk.tech.digital-tv

[Francisco Jos=E]

I think John Graham did that in the first reply (second message of this thread). However I'm crossposting this message to: uk.tech.digital-tv

However, If in a week or so I haven't had any answers I will repost the answer there.

Thank you very much for your reply.

Regards, Francisco

[Graham.]

I think John Graham did that in the first reply (second message of this thread). However I'm crossposting this message to: uk.tech.digital-tv

However, If in a week or so I haven't had any answers I will repost the answer there.

Thank you very much for your reply.

Regards, Francisco

I suspect there are some hoarders of old mags in u.t.d-tv. AFAIK there isn't a specific UK electronics group. I wonder why that is?

[Francisco Jos=E]

In fact, Electronics groups on Usenet are almost non-existant or without users. The only group that helped me in the search for similar infos was this (d-i-y).

Thank you very much for your reply.

Regards Francisco.