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December 1984

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


ISSUE No.12 DECEMBER 1984

MERRY CHRISTMAS AND A HAPPY NEW YEAR.

Page 1................Index
Page 2................From the Chair
Page 3................News & Views
Page 5................Homebrew
Page 7................BackTrack
................For Sale
Page 8................Tech-ed Notes
Page 9................Noise Bridge
Page 10...............Questionnaire No.1
Page 11...............Questionnaire No.2
Page 12...............Membership List
Page 13...............Membership Form
(Use this please when paying in January)


Editor................Dave Chislett G4XDW
Technical Editor......Gerry Thorn G8VNA
Printer...............Dave Ayres G6GBC

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B.B.R.C. COMMITTEE

Chairman..............Dave Bentley G6LKZ
Secretary.............Paul Robinson G6DVC
Treasurer.............Lynas Newton G6LYN
Member................Mike Brown G4RAA
Member................Martin Heaver G4WSW

Library...............Dave Bentley G6LKZ
Club Equipment........Dave Bentley G6LKZ

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FROM THE CHAIR

As I write this edition of " from the chair", the club is facing a
time of decision and, most probably when you read this copy of
Beechlog, the choice will have been made as to whether we move to
Haymill School Community Centre or not. I would like to take this
opportunity to thank Martin G4WSW for the assistance he gave me at
the various meetings we attended at the centre, and also to the
rest of the committee for attending a meeting at short notice.

Another event that should be taking place at the time of reading
this is the Christmas dinner, and I would like to wish you all a
very pleasant meal. Greetings also to our friends of the Home
Counties T.V. Group who will be joining us for the third time.


As Chairman of this club, it is my responsibility to make sure any
club events that are organised for the benifit of the members are
properly coordinated. It is therefore very disheartening to see
three events this year being cancelled through lack of support. I
refer to the treasure hunt, club contest and the last foxhunt on
which only the Fox G6DRP and myself turned up. Some members say to
me that their non-attendance was due to the fact they didn't know
about the event. These people are obviously licenced under false
pretences as it is a prerequisite of the RAE to be able to read and
reading Beechlog is a good way of finding out about club events.
(Not so in this edition as no details of next years events have
been received. Ed.)


Anyway, enough of this divisive talk and on to more cheerful
things. The DX picnic was a great success with more people than
last year and a good time was had by all, not least Paul G6DVC who
thought he had a 70MHz contact in Scotland which turned out to be
Mike G4KFK in another tent. I think the resulting laughter could be
heard in Slough. I must end by saying that this particular year in
the club's history has been very enjoyable for me in spite of some
particular low points and I look forward to next year with the
expectation of still better things to come. It only remains for
Janet and me to wish you all a very Merry Christmas and a Happy New
Year.

Dave G6LKZ
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Just recently I found out why John G4HMG and Diana G4MVV have
resigned from their activities in amateur radio locally. They are
about to move out west to Zummerzet. Amateur radio in Slough will
be the loser, both John and Diana have made a considerable
contribution to both the BBRC and the ATV group. I do hope that
GB3SN will still be in reach so that the early morning net will
survive, I think they may have 145.2 to themselves down there. I
think you will all join me when I wish them the very best in the
new QTH. I do hope, John and Diana, that you will visit the club
should you visit this area in future. ED.


NEWS & VIEWS

If you are having trouble with the Slough Planning Office in
respect of putting up aerials, a snippet of information in the
local rag may be of interest. Concerning the proposed Cellular
Radio mast in Britwell a planning officer was quoted as saying that
if the mast caused interference to radio and T.V. it was the fault
of the radio or T.V. set! This of course is what we have been
telling them for years. It's funny when big business steps in
everyone gets the message?
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As I said last issue your scribe is now up on Prestel. For anyone
who is interested my mailbox number is 075321896. B.T took their
time in getting me onto the Mailbox service. After repeated
requests via Prestel itself (it should have been automatic anyway)
to get onto the main computer so that I could deposit and receive
mail, I decided to use voice and contacted them direct. Their reply
was ' It all happens Nationally from Monday Sir!' Pity, I
thought, that it could not have been explained on the normal
computer I use, which would have saved me lots of phone calls. Or
is this how they make that big profit each year! Well it has
happened, and the other day I received my first piece of electronic
mail.
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On the subject of mailboxes. Have any of you listened in to the
RTTY mailbox on 145.200 run by G4VRK near Guildford. While tuning
around the band I came upon it by accident. I listened for a while
and then decided to have a word with G4VRK as to the legality of
the system. He assured me all was in order. However, I still felt
the leaving of mail for others was against the licencing reg's. A
phone call to the RSGB cleared the problem up-- it was illegal.
Since that time I've been unable to raise the station by phone. I
do hope he has got the message by now. On the same subject, while
trying to contact G4VRK another RTTY station came up on top of me
repeating 'The quick brown fox....' neither was there a callsign by
RTTY or by phone. I think he was complaining about the use of the
station but he/she was as illegal as the mailbox: I doubt if he/she
thought about that!
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FOXHUNTS 1984. The foxhunt season for the club is now over and this
year the winning teams were as follows:
G6EIL assisted by G8XCK..........April
G4WVX............................June
G6LKZ............................August
G6DRP............................September
The DF mug will be engraved with this year's winners and will be on
show at the AGM.
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NEWS & VIEWS

At long last the Haymill school will be opening its doors to local
clubs in this area. It may be of interest to note that the first
meeting of the users group was attended by Eileen when she was
Chairman. By the time this issue comes out you should have had an
EGM to decide whether to move the club to the Haymill Centre. I
think the local council deserves a cheer for moving the project
along so quickly!
-------------------------------------------------------------------
A recent article in the "Leader" free newspaper about the club's
Open Day, gave quite the best write-up on Amateur Radio I've seen
for a long time. The chairman was seen beside the sign on the front
door of the club HQ with handie-talkie, the text bore non of the
usual embellishment put in by other editors. In a recent article in
the "Slough Observer", your scribe was called a CB fanatic, and the
club had CB added to its name. All of this was, I expect, added by
the editor who, I might add, did not have the courtesy to reply to
a letter sent in to complain about the additions. I must say that
if the "Slough Observer" is worried about losing readers and
advertisements to the free papers then it only has itself to blame.
Well done the Leader!
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I have received a letter from the owner of Brimmer's Farm, thanking
the club for the monies sent. I asked if it would be possible to
hold an event in the springtime as well as in the late summer as
usual. Although he could not give us the same field because of
being laid down to grass he offered no objection. If sufficient
people come forward and say that they wish to take part in a
springtime event we will arrange a suitable date. Please let me
know if YOU wish such an event and don't leave it to others.
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In this issue of "BEECHLOG" we have printed two questionnaires.
Number one is concerned about this very magazine. We get very
little feedback from YOU and although it usually follows that if
nothing is said then we must be giving you what you want, it would
be good to know your opinions. Although we have asked for material
to go into the pages very little ever comes from those not on the
committee or involved with the magazine, I sometimes think it's
just a mouthpiece for yours truly! (This is true!SPELCHEK)
The second questionnaire is about computers. All information will
be handled in strict confidence for obvious reasons and there is no
need to give a callsign if you don't wish to. Please fill in these
and return to Mike and myself and we will try to ensure that the
magazine and activities of the club reflect YOUR views.
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HOMEBREW - IS IT WORTH IT?......

It was just over a year ago that a project to build a VHF/UHF
mobile transceiver came to mind. I had built several transceivers
before, both for 2mtrs and 70cms and was currently running a well
modified Wood&Douglas 70cms rig in the car.

The car was becoming a mess inside with rigs and power amplifiers
all over the place, it was also becoming unreliable with constantly
being removed at night and installed in the mornings. The final
straw came with the converted CB rig for 10mtrs. Something had to
be done!

A 2mtr Wood & Douglas rig was purchased off Ted. It was of a very
early vintage as I was later to find out. The 70cms rig was removed
from the car for the last time. The time had come to put them
together.

If you were at the Open Day this year you would have seen the
results of a year's hard work. The rig is now in daily use on both
bands and although, as with all good projects they are never really
finished, I am pleased with the performance. Only a small
intermittent fault and not quite the Japanese audio modulation
still remain to be sorted out.

Installing two separate rigs into a box small enough to install in
the average motor proved quite difficult. The decision was taken
early to also include the power amps and also pre-amps to boost the
overall performance. The control panel was also to control both
bands with just a simple switch to change from one to the other.
Although cross band working was thought about it was decided that
talking on one band when driving was difficult enough without that
added distraction.

Consulting the circuit diagrams showed that it would be possible to
control the two synthesisers simultaneously, and that a single
microphone amp and modulator could be used. When the time came to
wire up the 2mtr synthesiser it was discovered that the boards
bore no resemblance to the circuits I had. A phone call to Wood&D
brought the circuits free and by return of post. At this time
depression set in as it seemed that extensive circuitry would be
required now to control both synthesisers. A look through some of
the data books brought the answer with some analogue CMOS switches.
Converting the transmitters was not needed only DC switching i.e.
Supplies. The receiver side had been tried before and although the
RF sides were separate they combine before the discriminator and so
use the same squelch and volume and audio output. DC switching of
supplies changed the band.

Wiring the whole rig up proved to be quite easy as I had spent some
time putting the various boards in the right places. All that is
left now is to make up some new small PCB's to tidy up some of the
mods that had to take place. Also to tidy up the other small points
mentioned earlier.

Well, after reading all this, you will possibly be asking, was it
worth it? As this is being written there is only one other mobile
rig on the market that offers both bands in one box and that costs
over #400. The cost to me probably has been around #250; a
reasonable saving but most of all the fun of getting it on the air,
and using a unique rig that is tailored to my needs has made it
very worth while.

Dave G4XDW

BACKTRACK FINAL

As 1973/4 progressed, club membership declined sharply, and several
meetings discussed the possibility of winding up the club.
Typically, no decision was made! Happily things improved and during
1974/5 the average attendance was noted at 9.76. However, by
January 1977, fears were expressed about the size of the club
getting out of hand, but "Natural growth and wastage would control
numbers" so said the committee. a cull perhaps being the
alternative.....
In any event the club was threatened by huge rifts in the
membership, and a letter of censure was sent to various members.
The final paragraph reads "BBRC exists to foster interest in
amateur radio, the primary purpose of which is to promote goodwill
by communication. Our club belongs to us all; there is no room for
splinter groups, cliques or divided loyalties. We have had a
moderately successful year. Only by our unselfish devotion to a
common objective can we maintain this progress."
After this serious situation, the club seemed to return to normal
rapidly and in April the committee decided to "...purchase a 7lb
box of broken biscuits from Bracknell Market." I am assured they
have now been consumed, if indeed they were ever bought, but they
may of course be hidden in your Christmas Pudding.

Merry Christmas, readers Eileen G6EIL
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FOR SALE

TR2300 2Mtr Tranceiver complete with case/nicads, battery charger
and power supply. 10watt PA and Mobile Mount.
#80 Contact Dave G4XDW Sl.21896

SME Pickup arm Series 11 Detachable headshell+ extra headshells
#20 Contact Dave G4XDW Sl.21896

DATA Cassettes C15 Brand new 38p each
BASF CR02 C94! " " #1.15 each
Contact Mike Brown G4RAA
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TECH-ED'S NOTES

Not much to say this issue as I have been very inactive radio wise.
One thing I have been trying is an ASCII transmit-receive
programme for the BBC micro which enables all the normal numbers
and letters to be sent from the cassette port at 300 baud (using
the standard CUTS tones of 1200 and 2400Hz). At first I thought
that there would be little activity but that proved not to be the
case, most evenings there are several stations transmitting ASCII
or even Packet Radio in the all mode section around 144.625 MHz.
If anyone has ASCII transceive programmes for their micros let me
know and perhaps we can arrange a contact, who knows we may even be
able to hold the club net on ASCII.


Also in this issue is a questionnaire from which we hope to get
some feedback from members on the contents of "BEECHLOG", so please
let us know if you feel there should be more technical articles or
perhaps they should be of a more general nature on say local events
or problems that members have encountered on planning permission or
tvi etc. Please let us have your ideas or articles so that we have
something to put between the front and back covers!

*********************************
* A very Merry Christmas to all *
*********************************

Gerry G8VNA
===================================================================

NOISE BRIDGE CIRCUIT


NOISE BRIDGE

This name is used to describe an RF bridge which is energised from
a wideband source of noise obtained from a zener diode operating at
a low current level. The frequency range of this white noise
extends up to 200MHz. The noise source which is followed by a three
stage wideband amplifier to raise the noise level to around 100
microvolts enables a receiver to be used as the null indicator. The
noise output is applied to a quadrafilar-wound toroid providing two
arms of a bridge circuit which has a variable resistor in the third
arm to obtain a balance against the aerial in the fourth arm.

When the noise across the resistance arm equals the noise across
the aerial the bridge is balanced. Co-incident adjustment of the
receiver tuning and of the variable resistance is necessary to
discover the point of minimum noise, which occurs at the resonant
frequency of the aerial.

Toroid cores can be obtained in several grades and ferrite suitable
for the frequencies of interest should be chosen. Dust-iron cores
are also suitable and may be more readily available. The winding
may consist of four lengths of 30swg enamelled copper wire twisted
together to form one multistrand length: five or six turns are then
spaced around the circumference. The four wires are are divided
into two pairs and each pair connected in series so that the end of
one wire is connected to the beginning of the other. Check that
the two series pairs are insulated from each other. Lead lengths
from the transformer to the bridge should be kept as short as
possible and the layout symmetrical. The variable resistor should
be a good quality carbon type with low capacitance and linear
track. A scale should be fitted and calibrated by means of an
ohmmeter.

OPERATION

With a receiver connected to the centre point of the secondary
winding and a resistor or 50 across the aerial terminals, a
noise minimum should be obtained when the variable resistor is set
at the value of the test resistor.

With an aerial instead of the resistor connected to the socket a
noise minimum should be found when the receiver is tuned to the
design frequency of the aerial, and should approach a null when the
resistor is set to the characteristic impedance of the line. If
the frequency is not as expected , the length of the aerial needs
adjusting; if the resistor value is not that of the line, the
aerial is not matched to the line. The ratio between the impedance
and measured resistance gives the VSWR.

Gerry G8VNA



QUESTIONNAIRE No.1

CALLSIGN: .................. NAME: ...........................

DO YOU THINK BEECHLOG A GOOD IDEA: ................

Beechlog is published every three months would you like it more
often, or less often.

MORE OFTEN [ ] NO CHANGE [ ] LESS OFTEN [ ]

DO YOU READ THE FOLLOWING ITEMS: YES NO

From the Chair [ ] [ ]
News & Views [ ] [ ]
Technical Ideas [ ] [ ]
Tech-Eds Notes [ ] [ ]

If you answered no to any of the above would you like them replaced
by something else. Please give ideas for topics.

...................................................................
...................................................................

YES NO
Do you think the technical items are useful [ ] [ ]
Would you like to see more [ ] [ ]
Would you like more theory [ ] [ ]
More practical [ ] [ ]
More construction [ ] [ ]

Is the members list useful [ ] [ ]
Is the diary of events useful [ ] [ ]


Have you contributed anything to Beechlog. [ ] [ ]
Have you anything you wish published. [ ] [ ]

If yes to the above please outline it below.

...................................................................
...................................................................

Please hand this back to Dave G4XDW. Thankyou for taking part.

QUESTIONNAIRE No.2

1) Do you own a computer? YES [ ] NO [ ]

2) If yes, what model? .........................................

3) Do you own or want any of these? OWN WANT

Printer [ ] [ ]
Monitor [ ] [ ]
Disc Drive [ ] [ ]
Floppy Tape
(Microdrive) [ ] [ ]
Modem [ ] [ ]
RTTY Terminal [ ] [ ]

4) What programmes do you own or want?

RTTY [ ] [ ]
Packet Radio [ ] [ ]
Morse Tutor [ ] [ ]
Morse TX/RX [ ] [ ]
ASCII TX/RX [ ] [ ]
HF Propagation Predictions [ ] [ ]
HF Aerial Design [ ] [ ]
VHF Aerial Design [ ] [ ]
Transistor Equivalents&Data [ ] [ ]
Basicode [ ] [ ]
Logbook [ ] [ ]
Beacon Data [ ] [ ]
Repeater Data [ ] [ ]

5) Have you used any of these Morse aids?

Records [ ]
Cassettes [ ]
Computer [ ]
Morse Tutor [ ]
Slow Morse Transmissions [ ]

Any difficulties with the above? .................................
..................................................................

Please return to Mike G4RAA all details held in strictest
confidence.


MEMBERSHIP LIST

001 Eileen Chislett G6EIL Sl.21896
002 Dave Chislett (Editor) G4XDW Sl.21896
003 Tony Alderman G4LQD Fc.3286
004 David Ayres (Printer) G6GBC Md.28108
006 Paul Shayler G6TSF Sl.41396
007 Bill Perkins SWL Sl.32171
008 Lynas Newton (Treasurer) G6LYN Bn.66759
009 Mike Brown (Committee) G4RAA Bn.4262
010 John Duel G6CHO GX.84366
011 Dave Lomas G4XOW Lt.Grn.2847
012 Ann Lomas SWL Lt.Grn.2847
015 John Betts G4HMG Iver.651652
016 Diana Betts G4MVV Iver.651652
017 Gerry Thorn (Tech-Ed) G8VNA Wey.52775
018 Caroll Thorn SWL Wey.52775
021 Peter Harman G4XGD Sl.28826
022 David Tanswell G6LAU Iver 652412
024 Brian Page G1BAP Coln.5029
025 Dave Bentley (Chairman) G6LKZ Sl.25101
026 Kevin Hadley G4HDK 0734-731026
027 Graeme Platts G4XOF Sl.78495
028 Ian Rae G8BUE Sl.20757
029 Graham Stewart G6HEJ Fc.5897
030 Richard Ashberry G6RTM Sl.46012
031 Ted Swaby G4XOE Sl.75099
033 Dave Hemmins G6DRP Bn.64436
034 John Williamson G4XJN Sl.24008
035 George Wall G4XPR Fc.5954
037 Dave Clifford G6UFV Bn.64567
038 Paul Robinson (Secretary) G6DVC Rslp.72125
041 Martin Heaver (Committee) G4WSW ********
042 Ron Howlett G1BSQ 0895-445006
043 Bruce Gilson G4WVX Bn.64415
044 Mike Thomson G6WNU Bn.62328
045 Peter Phelps ***** ********
046 Janette Phelps ***** ********
047 Peter Melling SWL** Sl.29025
048 Mike Gathergood G4KFK 0895 834167
049 B. Mockett G1DSI ********

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Please note if your details are not correct please the form on the
back of the magazine and hand to a committee member. This will help
us to keep the records up to date.

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THE BURNHAM BEECHES RADIO CLUB

G3WIR G6WIR

The Burnham Beeches Radio Club, affiliated to the Radio Society of
Great Britain, serves the Slough/Windsor area, although it got its
name from its original meeting place - or that vicinity.

We meet twice a month, and our activities cover a wide range of
topics related to radio communications, such as lectures,
demonstrations, and club operating nights; there is also a keen
interest in home computing among our members.

We welcome members of any age and sex, who have an interest in
Amateur Radio, whether they be licenced amateurs or 'Short Wave
Listeners'.

Meetings: 1st & 3rd Mondays of each Month at 8.00pm
St John Ambulance Brigade HQ
Burlington Road
Slough.
Secretary: Paul Robinson G6DVC. Telephone. Ruslp72125.

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MEMBERSHIP DATA FILE
Membership Renewal 1985.

NAME:.................................... CALLSIGN:................
ADDRESS:................................. DATE:....................
................................. TELEPHONE:...............
................................. POSTCODE:................

BANDS WORKED: HF( ) VHF( ) UHF( )
MODES USED: CW [ ] SSB [ ] FM [ ] RTTY [ ] ATV [ ]

MAIN INTERESTS: (Building, contests, ATV, RTTY etc;)
...................................................................
...................................................................
...................................................................

SUGGESTIONS FOR CLUB ACTIVITIES:
...................................................................
...................................................................
...................................................................

COMPUTER INTEREST:...................... MODEL:...................
[All details held in confidence by the committee]

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