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August 1987

Beechlog
 
The on-line magazine of the Burnham Beeches Radio Club.
INDEX AND ACKNOWLEDGEMENTS


ISSUE No.22 AUGUST 1987



Page 1................Index
Page 2................From the Chair
Page 3................Hold the Front Page!
Page 4................Bits 'N' PC's
Page 5................
Page 6................Foxhunt Results /Events
Page 7................Radiotroops '87
Page 8................S.S.B. Part 1
Page 9................
Page 10...............E.G.M.


Final date for articles etc for October.September 19th.



Editor................Dave Chislett G4XDU
Technical Editor......Dave Lomas G4XOW
Printer...............Dave Ayres G6GBC
Computer Editor.......Mike Brown G4RAA

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B.B.R.C. COMMITTEE

Chair.................Dave Chislett G4XDU
Secretary.............John Pumfrey G8SNH
Treasurer.............David Ayres G6GBC
Member................Dave Lomas G4XOW
Member................Paul Shayler G6TSF

Publicity.............Eileen Chislett G6EIL
Library...............Richard G6RTM
Club Equipment........John Sanders G6LYN

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Club Rooms...........Haymill Community Centre
112 Burnham Lane
Slough. SL1 6LZ

Meetings: 1st and 3rd Mondays each month
at 8.00pm Room 48

The Chair's Bit......

The McMichael '87 rally is now past for another year. Once again
the BBRC turned up in force to help organise and man the rally.
This year we suffered the worst weather in the five years of the
event. However, over 700 people turned up, only 150 down on last
year. Most seemed to stay only long enough to look and buy and then
left unlike last year, when with better weather they stayed and
had picnics or drank at the Real ale bar. If we can expect this
number on a bad year then we don't have much to worry about. To
those of you who helped and gave up so much time to make the event
a success, I thank you all very much on behalf of the BBRC. May I
say a special thankyou to Paul (G6TSF) for organising the Talk-in,
Dave (G4XOW) Assistant Secretary and Dave (G6GBC) for making and
putting up the signs.

Recently, I visited the Reading & District Radio Club, who had
arranged a meeting with the RSGB, in particular the President, Joan
Heathershaw, David Evans, Chief Executive and the Zonal Member,
Julian Gannaway. Neill, the Region 6 rep was also present.

Joan outlined her main objectives for this her second year in
office. Her main concern is the rising age of the radio amateurs in
this country, by one year every year. This you may say is normal,
but think about it for a moment; amateurs don't live for ever. Gone
are the days when young people joined our ranks because of the
exciting new technology of radio. If we fail to attract the young
our numbers will decline and it will be more difficult to justify
the large number of frequency bands we enjoy today. We all need to
spread the word, and this means YOU, you have as much to lose as I
do.

Although I was not surprised at the people who were present at the
meeting it does show the apathy of the average amateur. Apart from
the Reading club members and a few committee members from other
clubs, not many ordinary amateurs turned up; a sad reflection
considering the importance of the meeting. Many other things were
discussed including the new proposals the RSGB has on a licence to
take us into the 21st Century. The Reading club made us very
welcome and those of us who attended enjoyed it very much.

RAYNET has formed a new group known as the Maidenhead and East
Berkshire group. I recently went to one of their meetings in the
Emergency Operations Centre, Maidenhead Town Hall. Although they
are a small group and looking for new committed members, and run by
the group controller for West Berkshire, they are already planning
exercises and helping out on a major area exercise. The radio room
at the town hall is well equipped, and the impression I got from
the Emergency Planning Officer was that the contribution of the
RAYNET members to the smooth running of exercises and real
emergencies was very much appreciated.

Well, that's all from me this BEECHLOG except to say that the visit
to the Great British Beer Festival was a great success and many
brews were tested, hic!!! Next issue of Beechlog will be edited by
Jim once again, so please pass all copy once again to him.

73 Dave G4XDU. Area Representative RSGB
Chair BBRC



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HOLD THE FRONT PAGE..?

Read on and find out how all your friends on the air waves can find
out about our activities, if you can't persuade them to come along
and see for themselves.

I "struggle" valiantly with GB2RS and just about manage to get the
BBRC a relevant mention. There have been problems, possibly the
most confusing of which was getting us listed under East Anglia and
missing the Basingstoke news. Presumably the compiler decided that
Burnham Beeches lay close to Burnham on Sea or Crouch.

We are also regularly noted in Radcom and Ham Radio Today (the
other mags aren't so club event oriented). And I do try to get us
mentioned in the What's On spot in the Slough Observer. Local
libraries have all been asked to display posters, so if there isn't
one at your library, please let me know.

There are lots of places that we can be heard of and it does work.
But I'll tell you what works better. You. The club members. So
please give us a plug over the airwaves whenever you can. That's
how we ended up in the club; we being your most illustrious bossman
and his XYL. And if you have any other ideas for spreading the
word, do let me know.

G6EIL Publicity Secretary

BITS 'N' PC'S


The hottest news at the time of writing is the launch of Acorn's
latest range of computers. Using an Acorn designed 32 bit Reduced
Instruction Set Computer (RISC) processor the new models are
claimed to be several times faster than even the fastest IBM type
PC.

Unfortunately even the cheapest model, called the Archimedes, seems
to be outside the price range for home computers at #799 + VAT,
even though it does include a 1Mb floppy and 512Kb of RAM in the
price. For an extra #76 Acorn are offering a full 1Mb of memory on
the basic machine (Model 305 with 512K, 310 with 1Mb).

Top of the range is the model 440 which, with 4MB of memory, a 1Mb
floppy, a 20Mb Winchester and a colour monitor, costs #2499 + VAT.
Somehow I don't think I'll be buying one!

Graphics and sound are well catered for. The top graphics
resolution is 640 X 256 pixels with 256 colours selectable from a
palette of 4096. The sound synthesizer has eight stereo channels,
each channel adjustable to one of seven preset stereo positions.

Speed is the main selling point of the new range though and they
certainly don't disappoint. The Archimedes is reckoned to run Basic
programmes four times faster than the Compaq 386, which is the
fastest IBM PC clone available. In fact the computer is so fast
that Acorn have been able to write 6502 and MSDOS emulation
programmes so the new machine will be able to run lots of current
BBC and IBM software. There will be a hardware IBM processor board
for applications that need complete compatibility.

The theory behind a RISC processor is that if you reduce the
complexity of the design the chip can be made to run faster.
Personally I have a RISC processor at the heart of my computer,
it's a 6502, which when used properly (a la BBC) is a very fast
chip.

Several other computer manufacturers are working on RISC designs,
not using the Acorn chip set of course. If the speed of the
Archimedes is typical then there should be quite a revolution in PC
hardware and applications.


********

Most of the latest computers have memories which are measured in
Megabytes, not Kilobytes. Memory technology has leapt onwards at a
staggering pace but what about long term storage?

The 100K floppies that came with the earlier micros such as the
Apples and BBCs were quite impressive when compared to the 8-bit
processor memory limit of 64K. You can cram about 90 mode 7
(teletext style) screen dumps from a BBC or about 10 Basic programs
onto a 100K disk.

Using double density, 80 tracks and double sided drives has pushed
the memory of a single drive up to a maximum of around 1.2Mbytes.
That is quite an improvement, but it looks a bit sick on a micro
with 4Mbytes of memory!

Winchester hard disks aren't exactly the answer either because not
only can't you cart them around but also there is no sensible way
of backing them up. The only way to back up a Winchester (apart
from another Winchester) is a special high speed tape drive - at
the same price as the Winchester!

I just hope that either optical technology or non-volatile memory
come to the rescue, because things are going to look even more
silly in another 5 years. As a start several companies are now
offering battery backed RAM at cheap (ish) prices.

I've been using a Morley 1Mbyte RAM disc on a BBC at work and
whilst it isn't perfect (you have to remember to keep the Break key
pressed when you turn the computer off) it is very fast and ultra
quiet! Unfortunately it doesn't contain non-volatile memory so it
runs off a mains PSU but it does have NiCads which will retain the
information for up to 15 min if the power goes away. It does seem
pretty reliable - it's been plugged in for over a month now and the
information is still intact.



73 for now

Mike G4RAA

FOXHUNT Results.

The foxhunt held on the 3rd August was won by John G1LMI assisted
by Ian G8NMQ. Dave G4XDU with Eileen G6EIL were the fox & vixen, as
John G8SNH who won last time was on holiday. The location of the
fox was at the 'Horns' Public House (Brakspears) Crazies Hill, just
north of Knowl Hill on the A4. Four teams took part and it was
noted that two teams in particular had not done maintainence on
their DF aerials, complaining that they fell to pieces at the
start. However, this didn't stop them and all but one team found
the fox without opening up the envelope.

Final results were as follows:
1st...John G1LMI 44 mins
2nd...Dave G4XOW 65 mins
3rd...Paul G6TSF 71 mins
Dave G6LKZ opened envelope.

The DF Mug will be held by the winning team once it has been
engraved. The DF mug was given to the BBRC by Mark Johnson then
G8ZRT and now G4ZRT. I am pleased to announce that Mark and Sue
Betts G4YKU are to be married on 22nd August, on behalf of the club
may I wish them every success and happiness for the future.

Ed.

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Burnham Beeches Radio Club Events 1987

August
17th...........Design of a Digital Sound Desk. G4XDU

September
7th............Packet Demonstration and natter nite
12/13th........Autumn DX Picnic
21st...........E.G.M.

October
5th............Junk Sale
19th...........Pascal Computer Language. Tony Watson

November
2nd............Natter Nite
16th...........HF Transceiver. From bits to cream box. G4XOW

December
7th............Christmas Dinner
21st...........Natter Nite

Adventures of the Radiotroops '87

Mobile log: Rallydate nearly here

As usual, the Brilliantly Busy Radio Commandoes rise to the
occasion and start plans well ahead. Well, ahead. There are
fleeting glimpses of TSF pressganging people into the guidance
control ship, kindly supplied by the great "antipodean" visionary.
Out in the meteor belt, the beacons are slow to materialise, and
the controlling officer is untraceable. There are problems brewing
in the base station staffing levels and all leave is cancelled. In
Mission Control, the tension is beginning to show in finger trouble
and nervous frequency jumping.

Mobile log: Rallydate tomorrow

Beacons now set in meteor belt. But heavy showers expected. Large
movements of equipment are reported in the area and mission Rally
is now committed. We are past the point of no return.

Mobile log: Rallydate today.

Early movements by the radiotroops are noted, although they may not
be early enough. The stage is set. Base station is set up and
Guidance control is fully operational. Our visitors are homing in
despite appalling meteor showers. BBR Commandoes are heavily
deployed in base station, guidance control and local traffic
control. Base station reports lots of local interest and general
queries. Hot liquid refreshment hard to track down. Base to base
line communications broke down for no BT reason, threatening
disaster of a monetary kind.

Mobile log: Supplementary report.

Triumphant weary troops return to respective home asteroids. All
made supreme efforts in clearing the debris of a busy schedule. Our
Captain will recommend mentions in despatches.


Single Sideband.

Much is talked about SSB, and most of us use this mode but in
general I have found few of us really know the ins and outs of the
mode. My purpose is to try and explain why it goes further than AM
and has been universally adopted as the DX voice mode.

In order to understand SSB it is first necessary to understand AM.
Most of us are aware of what AM is: a carrier is modulated in
amplitude by the audio signal (Fig 1). If we look at the case of a
single-tone 2Khz modulating a carrier of 1000Khz we see (Fig 2)
that the carrier has been joined by 2 sidebands above and below the
carrier at 1002Khz and 998Khz. In the case of normal communication
speech, which ranges from 300Hz - 3000Hz, the sidebands will
stretch from 1003Khz down to 997Khz a channel bandwidth of 6Khz Fig
3. If the modulation is 100% then the power distribution is :

Carrier........100%
USB............ 25%
LSB............ 25%

Total Power 150%














Reception of AM usually but not always requires a receiver
bandwidth of 6Khz and the demodulated audio will contain the wanted
signal plus noise; this we will have to assume to be constant and
its level is usually related to the bandwidth of a receiver.
Various figures are quoted for this noise contribution but the
Radio Communications Handbook quotes relative to 1, 0.1 volts for
6Khz bandwidth and 0.07 volts for 3Khz bandwidth. If the received
audio is 1 volt then the signal to noise ratio will be :
1
20log -------- = 20db
0.1

This may not mean much at the moment but when we consider SSB in
the next part all will become clear.





















To sum up, AM requires a bandwidth of 6Khz. Since all the
intelligence we require is in one sideband, only one sixth of the
power actually transmitted is really required to get the message
across. Transmitted power is wasted and higher noise figures in
receivers lead to a very inefficent mode. However against this is
easier contructed transmitters and receivers. More efficent use of
the available spectrum and power would be had by only transmitting
one sideband, at last you say SSB.... Part 2 next issue!

Dave G4XDU


Burnham Beeches Radio Club.

€CENOTICE OF EXTRAORDINARY GENERAL MEETING


Notice is hereby given that an EGM has been called on Monday
21st September 1987 at 8.00pm in

Room 48 Haymill Youth & Community Centre
112 Burnham Lane
Slough

The following resolution has been agreed by the committee:

That the members of the Burnham Beeches Radio Club accept the draft
constitution as detailed on Pages 11/13 of Issue 21 of Beechlog,
being a replacement for the existing constitution.

Proposed by: Dave Chislett G4XDU Chair.

Seconded by: Eileen Chislett G6EIL.