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Wyrepak Packet Radio Group Newsletter

Third Edition, Winter 2001/2002

CONTENTS:

Happy New Year!
Welcome to this edition of the WyrePak Newsletter, and may I take this opportunity to wish all WyrePak members a very Happy 2002!

AGM Report
The first AGM took place on 20th November at the Sutton Arms and, for those of you who couldn't attend, the key points to note are: no change to the Committee, the Group's finances are sound and membership numbers remain steady. The Chairman's, Secretary's and Treasurer's Reports are reproduced below, and if anyone wishes to see the full minutes of the AGM before they are posted on the website, just drop me a line to G4SPZ @ GB7PZT and I'll send them on to you. The AGM was attended by Jim G0HTF, Richard G0EWH, Brian M0MBG, Derek G3KFD, Eric G8BKL and Paula G8PZT with apologies from Phil G4SPZ, Don G0ESR, Nigel G4YUD, and Wayne M0BRU.

Chairman's Report
I am pleased to be able to address the first Annual General Meeting of the WyrePak group after what has been a year of considerable achievement, thanks to the effort and activity of many individual members.

Many of you will recall the appeal which Paula G8PZT put out to the local amateur Packet Radio community just over a year ago, to the effect that the node and BBS which she had been running single-handedly for over ten years was at risk of closing down. The workload of operating, maintaining and managing the system was becoming too much for one enthusiast, and Paula herself was receiving little feedback from users to indicate that her efforts were appreciated.

Not wishing to lose such a valuable facility, the majority of local Packet users responded willingly in terms of time, money and effort. WyrePak was formed to channel the enthusiasm and to help users get more out of Packet Radio.

So, where are we, a year later? We have shown that Packet is still alive and will hopefully remain so. We have raised a substantial amount of money through voluntary donations. We have acquired, on Paula's behalf, materials and parts to help with the ongoing maintenance of the node and BBS. We have bought a new antenna and, at this point, we have a robust plan for the refurbishment of the antenna systems at GB7PZT. Most of all, we have established a firm link between the Sysop and the users, which is beneficial in helping the exchange of knowledge in both directions, one of the founding principles of the Group.

In summary, I believe that the Group has met many of its initial aims and I feel that the year has been a successful one. I should like to thank the Committee and membership for their contributions, and I look forward to our second year with confidence that Packet Radio in the Wyre Forest has a bright future - Jim, G0HTF, Chairman

Secretary's Report
I hope the meeting will accept my apologies for absence, which is due to work commitments which were "dropped" on me after the revised AGM date was agreed! I must also tender my apologies for the fact that the September AGM date was changed. Again, this was due to my absence, but this time on holiday, which unfortunately clashed dates. Faced with a choice between the AGM and two weeks in Switzerland, I chose the latter!

From my point of view, it has been an enjoyable year and one which has seen some notable achievements, to which Jim has referred in his Chairman's Report. In terms of the aims of the Group, I think we have achieved several of them. The Group has been set up with a proper Constitution, committee structure and meeting schedule, sound financial management, and a robust membership database, and I have enjoyed being involved in this work.

I realise, however, that Packet Radio is simply a hobby and I have no wish to make the administration of the Group too formal. It was agreed at our first meeting that we should meet on a monthly basis, at least while the Group got going. It may now be the case that we should review this - certainly, after an enthusiastic start, we saw attendances at the monthly meetings decline until, at one meeting, only two of us were present! However, it is through the mechanism of regular meetings that a lot of the benefits of our Group can come to the fore, particularly the expertise of Paula and other more experienced Packet users which can be shared with the relative newcomers to the mode, such as myself. Those of you who have attended the meetings will, I hope, agree with me, and I would encourage those members who up to now haven't been at the meetings to come along for what is frequently a lively and informative debate.

I am pleased that we have been able to produce a half-yearly members' Newsletter, and that we have an excellent working website. We have also had a WyrePak committee member present at as many Fourpak meetings as we could. I think that we have been able to demonstrate to Paula that her efforts are appreciated by many of the local users of her system. I wish that we had been able to complete the antenna overhaul by now, but we have made progress and the materials needed are all to hand. There are limits to everyone's spare time, and patience is needed! I am confident that the antenna system overhaul will be completed in time for next Spring.

I will conclude by stating my willingness to continue as Secretary for the coming year should that be the wish of the membership. Best wishes to you all - Phil, G4SPZ, Secretary

Treasurer's report
The accounts have been prepared for the financial year in accordance with our Constitution, which is the year to 31 March 2001. These showed a total income of £238.10 and an expenditure of £11.13, leaving a balance of £226.97. However the actual balance as of today's date is £53.78 following the purchase of new antenna equipment for the Kidderminster Node. The accounts were still to be audited as an auditor had not yet been elected.

It is proposed that we amend our Constitution to change our account year to 1 September to 31 August, to fit in with our AGM dates, and I hope that this can be dealt with at the end of the AGM.

There are currently 14 paid up members and all those who joined before 1 January 2001 did have their membership extended to the start of the year to cover the initial setting up period of the group, and will need to renew by 1 January 2002 - Richard, G0EWH, Treasurer and Membership Secretary

(Under 'Any Other Business', the change to the financial year dates were approved, and Roger G4OBA, KDARS Treasurer and Don G0ESR, the Fourpak Auditor, were elected as Auditors for WyrePak - Ed)

Subscriptions For 2002
Sharp-eyed readers will have spotted in the Treasurer's Report that subs are due on 1st January 2002... you'll be pleased to hear that there is no change to last year's basic subscription of £5.00. If you're unlikely to be attending a meeting in the near future to cough up in person, please let Richard G0EWH have a cheque, made payable to 'WyrePak', and posted to him at 74 Walker Avenue, Stourbridge,West Midlands DY9 9EL.

Many thanks to all members for their continuing generosity.

The Committee
Contact details for the Committee members are simple - by Packet to G0HTF, G4SPZ, G0EWH or G8PZT @ GB7PZT!

Technical Topics
A general discussion took place after the AGM on different aspects of Packet, with some demonstrations by Eric using his Laptop PC. Paula reported on work she had been doing with the Node Software regarding APRS, UIPath 32 and UISS.

It is now possible to do APRS messaging via any User port into the Node. At the Node prompt, "AM 13" will take the user to Port 13 which will then link out to the APRS port. Commands are "/H" = help, "/Q" = quit, "/T callsign" = target call sign, all followed by . Contact Paula if you encounter any difficulties.

Packet Clinic - Now You See It, Now You Don't...
One of the most frustrating faults with a Packet system is where you can connect perfectly to some stations, but not to others. This was the subject of the WyrePak technical meeting on October 16th 2001 when Paula G8PZT explained some of the lesser-known features of the AX25 data transmission standard.

Unlike conventional analogue transmissions where intelligibility is gradually lost and distortion increases as the signal strength drops, digital modulation schemes provide perfect reception until the signal drops below a certain threshold, when the transmission fails completely. Put very simply, digital signal decoding depends on the receiver being able to decide simply whether a pulse is present or absent at a particular point in time, and this can be done very effectively in the presence of noise, interference or fading. Anyone who has operated RTTY on the HF bands will know that even the old-fashioned teletype terminal unit can pull perfect copy out of the noise, when the actual signal is virtually inaudible to the human ear. Indeed, some advanced digital systems can decode signals below noise levels.

So it is with Packet, which tends to either work perfectly or not at all. However, as with all electronic systems, there is a range of tolerances over which normal operation will be obtained. This is encompassed within the AX25 standard, and as long as all stations transmit signals that are within these tolerances, all other stations should be able to connect and exchange data without problems. The parameters are numerous, and any one being outside the tolerance band can cause transmission to fail. However, given the usual assumptions about the wide range of TNC's, modems and transceivers in daily use by amateurs for Packet radio, one could probably say that 99% of Packet operators are happy 99% of the time.

WyrePak member Derek, G3KFD was one of the unhappy 1%! Having invested in a new YAM (Yet Another Modem?) modem from Maxpak, Derek found that he could connect to some nodes and BBS's and even to the Packet satellite, but could not connect to GB7PZT and some other local stations. Exhaustive tests showed that this fault was independent of signal strength, as a failure was experienced between two Packet stations operating in the same shack!

Most amateur Packet TNC's or modems are linked to the transceiver via the microphone and speaker sockets, and in most circumstances this arrangement works satisfactorily. However, one of the parameters in the AX25 standard which is crucial to correct operation is the relative levels of the "mark" and "space" tones, which should (in a perfect system) be equal in level, although a differential of 2:1 is permitted. The tones generated by the TNC are 1200Hz and 2400Hz, and when fed to the transmitter via the microphone socket, they pass through the audio pre-emphasis circuit which have a non-linear amplification characteristic, which can result in the 1200Hz and 2400Hz tones being sent to the reactance modulator at different amplitudes. After being transmitted as an FM signal, demodulated and subjected to de-emphasis in the receiver, there can be a considerable imbalance between the amplitude of the two tones when they enter the receiving TNC for decoding, not to mention the phase shift resulting from the whole process.

TNC's and modems vary widely in the degree of distortion they can tolerate in the incoming Packet signal. The best in terms of tolerance to out-of-spec signals is the KPC-3 design, modified versions of which are understood to be used in the latest Packet satellite. The worst, or the least tolerant, are YAM modems, which employ a sampling technique unlike the dedicated modem chips used in most TNCs or BayCom modems. Where many TNCs can successfully decode a signal where the mark/space amplitude differs by up to 4:1, YAM modems struggle at anything over 2:1.

Node and BBS sysops take great care to ensure that the mark and space tones are at equal amplitude when they are transmitted. Using, as many do, ex-PMR equipment seems to help in this respect, whereas amateur radio transceivers can be less consistent where audio pre-emphasis and de-emphasis are concerned. If a particular Packet link contains an unfortunate combination of an out-of-balance signal and an intolerant YAM modem, the link is likely to fail, whereas another link where the audio balance is slightly better would work perfectly. Some of you may have heard of Sod's Law, or more politely the Law of Maximum Cussedness, which states that: "If a thing can happen, it probably will. The higher the inconvenience potential, the greater the probability" which is never more true than in Packet radio!

So, what is G3KFD to do? Maybe adjusting the balance of his received signal would help. Certainly, he could get his money back from Maxpak!

Deviation - again
Richard G0EWH has kindly contributed the following comments...

It has been said that all decent nodes and stations should be able to communicate with all sorts of other station set-ups with their widely variable tone balance.

In the summer issue of 'WyrePak Newsletter' G4SPZ discussed the AFSK level on Packet and problems that had been experienced. While the level of activity on 2 metres is not what it used to be, the band plan now shows the channels as being 12.5kHz for most of the FM section, with one of the exceptions being 144.975KHz which is the 9k6baud packet channel and needs the higher bandwidth and receive filtering of a 25kHz channel.

It was stated that "we should be aiming for a deviation around +/-2.5kHz", however this is not quite correct. The maximum deviation that a transmitter should be set to on 25kHz channels is +/-5kHz and half that figure on 12.5kHz channels (i.e.+/-2.5kHz), but the normal level will be less than these and the recommended setting for 1200baud packet on the 12.5kHz channels is +/-1.5 to 1.75kHz, which again is about half that previously used with 25kHz channels. The nodes in our area all seem to be running with these levels, although there are some groups that still run with higher deviation. For 9k6baud the deviation is much more critical and would be something like +/-2.75kHz, the actual figure being determined by observing the eye diagram on the received end. (More about eye diagrams in a later issue - Ed)

I have recently been doing some testing with the YAM type of modem, which performed well at 9k6baud, but did not respond well at 1200baud. The problem is with the receive, and would work well with some nodes, but the transmissions from other nodes and stations failed to be decoded despite being received. Further tests are planned and any outcome will be reported later.

A few little tips for any Winpack users. The AutoBBS session is used as part of the automatic operation of the program for getting bulletins and mail sent or downloaded. However, there are times when this part of the program will start-up on its own when it is not required, such as the radio being used for another QSO, but still connected to the PC with Winpack running. Although you can disable this option via the "Action Menu", this is a "one time" event and when Winpack is started again, the option is enabled again. The answer is to enter the File - Selection List Editor Menu option and remove all or some of the default "Auto Times" that are listed, no times means no automatic session. You may wish to edit the other default options that you will see if you are not aware of the facility of automating bulletin downloads which match various criteria.

GB7PZT is "Winpack-friendly" and users should be aware of the special instructions document that is available for the exact method of setting up the program with the BBS. One nice feature is that compressed forwarding and downloading is available which does speed up message transfer and gives some coding of the text.

(Late news - at the WyrePak meeting on 18th December 2001, Richard G0EWH demonstrated the add-on Tuning Aid recently released for WinPack. This software provides an on-screen display of the received packet signal quality and includes a waterfall plot and an eye diagram. This can be an extremely useful tool in helping to solve decoding problems. For further detailsa and technical info, please contact Richard direct at GB7PZT - Ed)

Old Computers for Packet
One of the beauties of Packet Radio as a mode is that you can use the oldest and lowest-spec PC that you can find, and in many cases such machines are becoming available at sub-bargain prices. By that, I mean free! Packet will run on computers which are considered worthless by most people.

I have recently been given three working 386/486-vintage PCs, all of which are perfectly capable of running Baycom or similar Packet software. Small hard drive, 100MB or less? No problem! Short of RAM, only 4MB? Plenty! One of the machines in my collection is a very compact Olivetti system unit with a 20MB hard drive and a 3.5" floppy disk drive on which my Packet system now runs 24 hours a day. This has displaced the large tower-cased unit with 5.25" and 3.5" floppy drives which I have used for the last two years. Another is in a small tower case with a 100MB hard disk, and the third is a conventional desktop PC - this is a 486 25MHz computer onto which I intend to load Windows NT4 and give to my son. However the other machines are available - in return for a small donation to WyrePak, of course - to anyone wishing to try Packet without spending a packet or tying up the home PC. Just drop me a line to G4SPZ @ GB7PZT for further information.

Don't forget that just because it doesn't have a Pentium inside doesn't mean that it can't be useful... I am a firm believer in the three R's (Repair, Re-Use, Recycle...) Indeed, this Newsletter is being prepared on a 33MHz 486 laptop running Windows 3.11 and Word 6.0. Cost of computer - nil!

A History Lesson
For those WyrePak members interested in the history of computing, it is generally acknowledged that the birthplace of the digital stored program computer was actually Bletchley Park, near Milton Keynes. Contrary to the popular misconception, the "Colossus" programmable computer was actually designed towards the end of the Second World War to help codebreakers decipher specially encoded RTTY messages, generated by the fiendishly complicated Lorenz encyphering machine which the Germans used for the most secret messages to and from Hitler and his High Command. It had nothing to do with the Enigma codes, of which more later...

Colossus comprised some 1,500 thermionic valves and read data from punched paper tape at the phenominal speed of 5,000 bits per second, an incredible achievement for a 1940's mechanical system. "But what has this got to do with the average WyrePak member?" I hear you ask. Nothing, unless you happen to be interested in such developments! Read on... Returning to the Enigma codes, which were used for the majority of the enciphered German military communications, the success of the codebreakers at Bletchley was in no small part due to the development by the brilliant mathematician Alan Turing of a device known as the Bombe. This was a large electro-mechanical machine which enabled various Enigma settings to be "tried" and dramatically reduced the time taken to break into a particular day's encoding settings.

Following on from the successful project by the Bletchley Park Trust to rebuild "Colossus", a group of enthusiasts including members of the IEE and the British Computer Society are recreating a working Bombe at Bletchley Park. In reality, numerous machines were built and used during the War, but all were destroyed on Churchill's orders when the War ended. The company which built these machines was the British Tabulating Machine Company, a British off-shoot of the American Tabulating Machine Company set up by Herman Hollerith of punched-card fame. BTM grew into ICL, while the American company went on to become IBM. Which brings us neatly back to old IBM-compatible PCs...

Any WyrePak members with an interest in such historical matters are warmly invited to the 8th January 2002 meeting of the Kidderminster and District Amateur Radio Society, where Rosemary Lyman will give a talk on her work as a Y-Service radio intercept officer during the War. Rosemary's intercepts were deciphered at Bletchley Park. Relevent websites are www. bletchleypark.org.uk and www. jharper.demon.co.uk/bombe1. htm

It is perhaps interesting to note that, by the early fifties, computing had developed to the point where on 17th November 1951 LEO (the Lyons Electronic Office) computer ran the first ever business application. The RAM used on the computers of this era was constructed from tiny ferrite rings in a frame, threaded together with four thin wires. These frames were assembled by female operatives in Poland, and other Eastern European countries with a strong lace-making tradition, such was the dexterity required to thread the tiny wires through the beads, and they were truly works of art. Few of these survive, and a 1k (1,000 BITS, not bytes) store was about the same physical size as a typical laptop computer today with 512MB...

(Some details from IEE Review, November 2001)

WyrePak Meetings
Publication of this issue should hopefully be in time for the 22nd January 2002 WyrePak meeting which will be at the Sutton Arms, starting at 8.00pm. This will be a general Open Meeting and all are welcome.

Other meeting dates for your diary (all Tuesdays) are:

19th February
19th March
16th April
21st May
18th June
16th July
20th August
17th September (AGM)
19th November
17th December

Windows Software for Baycom Hardware
Well, not exactly your up-to-date Windows 2000, ME or XP, but I have been trying out WinTNC version 1.01g by G7JJF. This runs under Windows 3.1 or later, and provides much of the functionality normally associated with Winpack, but instead of a TNC you can use a good old Baycom modem. These are available cheaper than a TNC, are compact and reliable, and the WinTNC software is available - free, of course - from our own Treasurer Richard G0EWH. Richard has put together an extensive collection of Packet and radio-related freeware and shareware which is available in exchange for the appropriate number of floppy disks.

WinTNC 1.01g loaded straight away on my elderly '386 shack PC and worked first time, even with the default settings unaltered. I have two Baycom modems and the software drove both without problems.

Although Graphic Packet is actually a DOS program which displays itself as a Windows look-alike screen, it is also available from Richard's collection. Again, this program loaded and ran faultlessly. This does not offer quite the range of functions as WinTNC but being a DOS program it will probably run on 286 computers which won't take kindly to Windows.

I can't really provide a proper review of these programs. Firstly, I haven't had much time to play with them, and secondly they date from the mid-1990's and hence hardly qualify as being news-worthy! Some of these programs are heading towards the category of "abandon-ware"... however, in keeping with my three R's philosophy, I also like to make use of old software if it continues to do the job. In this instance, it offers the opportunity to get going on Packet quickly and very cheaply.

The following Packet software is available from Richard G0EWH:

(If someone would like to submit other software or hardware reviews I would be delighted to publish them - Ed)

Late news... WyrePak has a presence on the Communigate community website within the Kidderminster and District Radio Society's signpost website. Go to www.communigate.co.uk/worcs/kdars and click on the Packet Radio Page. Links from other parts of this site will also take you to our main WyrePak website. At the time of writing, searching the Communigate domain only brings up two amateur related sites, one up north and KDARS, so there is some scope for more. If anyone is interested, contact G4SPZ.

That's all for this edition, folks. Thanks for reading!

WyrePAK Newsletter is compiled and published by Phil Harris MIEE, G4SPZ, 22 Bramley Way, Bewdley DY12 2PU 01299 403025.

Please forward items for inclusion in the Newsletter by e-mail to g4spz@aol.com or by Packet to G4SPZ @ GB7PZT.

©G4SPZ 2001

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