This page chronicles the life-events of GB3KD, and is arranged in reverse time order, i.e. with the newest entries at the top.

(If you're pondering the significance of the picture on the right, it depicts the world's first programmer; a woman of course! She was Ada King, Countess of Lovelace and daughter of Lord Byron, who wrote programs for Charles Babbage's Difference Engine.)

October 2007

The squelch was being intermittently held open, and weak signals degraded, by an intermittent blank carrier just below the input frequency. The source was unknown.

September 2007

The repeater was intermittently going very "deaf", but was OK most of the time. The cause was found to be another faulty cavity in the duplexer, this time on the receive side. The fault was cleared (for the time being) by vigorously adjusting the cavity a few times to clear the oxidation. The problem will keep recurring until the cavities are replaced by silver-plated units.

27th June 2007

Following a request from two members, the restriction on incoming connects from overseas stations between the hours of 19:30 and 22:30 UK local time has been removed. The restriction had been implemented 18 months ago, to enable local amateurs to use their own repeater during the evening (e.g. to travel to and from club meetings) without constant interruption from overseas ragchewers. There are currently no restrictions on incoming connections.

25th June 2007

KD was disconnected from the Internet for up to 18 hours, due to a major equipment failure. The repeater itself remained operational however. At the repeater site, broadband Internet is routed to 8 computers, not by a hardware router, but by an ancient DOS PC running XRouter software. This had been running faultlessly 24/7 since 2002 and was buried and forgotten under half a ton of junk. Over the last year, the hard drive had been getting noisy, and as a precaution, some of the configuration data had been saved to another PC. Unfortunately, the vital bits, such as the Ethernet drivers and the IP routing tables, weren't saved!

Today, the hard drive failed completely, requiring several hours work to move junk and gain access to the machine. Half a dozen "surplus" drives were tried before a workable one was found, and it took a further 6 hours work to reinstate and configure the software, mostly by guesswork! Some work still remains to be done, and this highlights the need for fastidious hardware and software backups. There is currently NO backup equipment for GB3KD. If something fails, the system will go off until the original equipment can be repaired.

June 2007

The repeater is occasionally held open in late evening by intermittent interference. The origin is unknown, but the nature of the interference suggests that it could be a plasma TV within a few hundred yards of the repeater site. It is strong enough to hold the repeater squelch open, even on its tightest setting, with a 10db attenuator in the receiver, and it will obliterate weaker stations. For most stations though, it is merely an annoyance between overs. There is little hope of resolving this problem, and the best we can do is live with it until the offending equipment expires!

5th August 2006

Despite our best efforts to use only our own artwork, and "royalty free" images, a copyright image had inadvertently been used on the GB3KD website, resulting in the author receiving a four-figure invoice for royalties! This site, and all related sites were immediately destroyed pending investigation. It was later partially reinstated, without images. The remainder of the site would be reinstated as time allowed.

One of the regular jammers has been located, reported to the radio authorities, and is being kept under observation. We are gradually closing the net on the others, and they will be severely dealt with. We do not take jamming lightly.

July 2006

The modified computer PSU failed for unknown reasons, and was replaced by a "proper" 13.8v 25A switched-mode PSU.

June 2006

Due to problems with people using the DTMF commands to disrupt QSOs, many commands were withdrawn, and others will now operate only when the repeater is not in use. All the disconnect commands now require users to clearly announce their callsign and the word "Disconnecting" prior to the command.

May 2006

Despite warnings, users persisted in making random connects, then leaving them linked without actually using the connection. As a consequence, the random connect facility was permanently withdrawn.

1st April 2006

The Derby repeater GB3DC became operational on GB3KD's frequency, resulting in occasional QRM on our repeater. Well-sited stations now experienced co-channel interference on the output frequency.

Over the past few days, the extremely windy weather had begun to destroy the repeater's aerial, causing crackling on weak signals when the wind blwe. The problem was getting steadily worse, and it was feared that the transmitted signal might also deteriorate. Unfortunately, to rectify the problem the mast would need to be taken down again, which would be a major undertaking, requiring several strong people.

Users were warned that, if they used DTMF commands, they had a legal obligation under the terms of their licences to identify themselves in voice at the beginning and end of a "period of transmission". This meant that they should identify at least *before* sending the first command, and after sending the *last* command. If a session lasted more than 15 minutes, they must identify themselves after each 15 minute period. This was not only the law, it was courteous to other users. Users were also asked to be aware that their transmissions had unique characteristics enabling the repeater software to identify them. DTMF users who failed to identify themselves in voice would be reported to OFCOM. Ultimately, if the practice of "anonymous" DTMF persisted, all DTMF facilities would be permanently withdrawn, and users would have to ask the repeater keeper to make and break connections on their behalf!

December 2005

Incoming connects from overseas stations were disallowed between the hours of 19:30 and 22:30 UK local time. The purpose of this was to enable those UK amateurs who work all day to use their repeater during the evening without constant interruption from abroad. Overseas stations were allowed for the other 21 hours each day, which was more than enough! Outgoing connections were not prevented during the "curfew" time. Users were advised that local mobiles may wish to use the repeater between 19:30 and 20:00, and were asked to remember that not everyone likes ragchewing, "nets" and foreign stations, especially when they only have a few minutes to use the repeater.

29th October 2005

The "new" repeater tx/rx unit underwent its first on-air test on 27th October. The test lasted 23 hours, and a number of problems were identified for resolution. The sharper receiver filtering revealed that several people were significantly off-frequency, and others were found to be over-deviating. Talkthrough levels were low, and significant quantisation noise and distortion were observed, due to insufficient drive into and out of the radio. All these problems will be resolved in due course.

Summer 2005

In response to requests from users, the talkthrough time was reduced from 5 to 3 minutes, and the maximum number of concurrent Internet connections was raised from 5 to 10.

29th June 2005

The final section of RG213 was replaced with Heliax, so it is now Heliax all the way from the duplexer to the aerial.

26th February 2005

In near-freezing temperatures, with a strong North wind whistling up the escarpment and a hint of sleet in the air, Bill G0WVT and his workmate Colin kindly gave up their Saturday morning to replace the mast which had folded over in January's freak storm (picture). Unfortunately the space was too restricted to contain the full length of the mast plus aerial prior to hinging it up into position, so a shorter top section had to be fitted. Colin had to venture down into the woods and emerged with blood pouring down his face from bramble scratches! The C5 collinear was replaced with a WX4 dual band collinear.

23rd February 2005

There was a complaint that the audio from some Echolink stations sounded "quiet" compared to RF stations, which made them difficult to copy on the move. In fact, the peak level of both Echolink and RF talkthrough was equalised by the vogads. But whilst RF stations tend to have high "talk power" due to the use of filters, compressors and clippers in the TX audio, Echolink stations have no such refinements. Thus they have a high peak level, yet low "talk power". They're designed for armchair copy rather than punchiness! So GB3KD now uses intelligent speech processing on signals received from Echolink stations, to boost the "talk power", making them sound louder.

Since May 2004, GB3KD had been using the radio interface and computer belonging to the G8PZT-L simplex gateway, thus the gateway was QRT. Richard G0EWH has constructed a new interface, which is now in use (pictures). This has higher quality cables and connections, and has removed the slight reverberation effect sometimes experienced. The old interface will now be refurbished allowing the gateway to be put back on air.

8th January 2005

A freak gust of wind bent the aerial mast over to 45 degrees at the 21 foot level, just above the guys. Until this can be replaced, the repeater is operating on a temporary aerial, a lot lower down.

20th November 2004

For several hours per day over the past week, GB3KD had been affected by a "buzzing" signal, which obliterated weaker stations, causing DTMF command errors, and "raspy" squelch tails. It sometimes held the squelch open, although this had been counteracted by de-sensitising the receiver for the time being.

The baffling thing was that there was no trace of the QRM when the repeater TX was off, which suggested some form of non-linear mixing process, the most likely non-linear element being the aerial itself. We had problems with corroded joints and water ingress in the early days of GB3KD, but the aerial seemed to be OK after it was refurbished. On the assumption that the aerial was faulty, what was the signal that was being mixed with the repeater's output signal to create a signal on the input? Over several days, hundreds of possible mixes up to 10th order were calculated and checked, but no signal was found on any of them! There is no signal mixing in the aerial.

Just to be sure, all the repeater components were substituted, with no effect. Eventually it was realised what was going on.... The non-linear element was not the aerial, nor anything close to the aerial such as a rusty joint. In fact, it appeared to be some sort of electronic appliance in a neighbouring house, which generated wideband 50Hz modulated QRM when "illuminated" by any strong VHF source, such as the repeater TX. The QRM extended from roughly 140 to 200 MHz, with another block between 308 and 360 MHz.

The neighbour was contacted, but denied that there was any apparatus switched on at the times when the QRM was logged.

14th October 2004

Please note new node number 78750 (like the frequency 145.78750 - get it?)

8th October 2004

Since the toneburst detector was tightened to meet RMC's specification, some stations have had difficulty opening the repeater. It seems tonebursts, even crystal-controlled ones, aren't always within +/- 25Hz of 1750 Hz, and it's certainly very difficult to whistle that accurately. It was therefore concluded that the RMC specification is unnecessarily tight, and the detector has been loosened accordingly. If anyone is still having difficulties, please let us know.

September 2004

Someone, trying to open an adjacent repeater on the same channel, noticed that 'KD was opening up on CTCSS tones other than 118.8Hz. The detector had deliberately been made very "forgiving", to accommodate the wide range of CTCSS levels encountered in practice (we didn't want to exclude people whose tones were a few percent off frequency, or too loud / quiet / distorted etc.). However, users need to be able to work other repeaters without opening 'KD, so we have tightened up the CTCSS detector. It now responds only to 118.8Hz, at deviations down to 2%, and will not respond to the (unused) CTCSS frequencies 4Hz above and below. So far no-one has complained, and detection seems solid, but we *have* seen an increase in the number of failed access attempts. This may simply be due to people using the wrong tone of course, but if people won't identify themselves when they attempt to open the repeater, we can't help them can we?
We also tightened up the 1750Hz toneburst detector, to meet the RMC specifications.

15th August 2004

Raised aerial by approximately 10 feet, and replaced part of the RG8 feeder with LDF-450 Heliax. The combined effect of the height gain and reduced losses amounted to approximately 6db, and made a worthwhile improvement to the coverage.

July 2004

Reinstated the repaired C5 collinear in its original position. This aerial had slightly higher gain than the dual-band collinear, but the cable losses were higher due to the long run of inferior cable, so there wasn't much noticeable diifference.

29th May 2004

Replaced faulty "white stick" aerial with a new dual band collinear, on short term loan. At the same time, replaced 12 metres of RG58 with approximately 14 metres of Westflex 103. As a result, the desense went away and the repeater now seemed more sensitive.

Audio from GB3KD to the Internet was reported to be a little low, as the radio didn't give enough output to drive the sound card line input. A x5 audio preamp was required - yet another job for a rainy day...

28th May 2004

Receive performance relative to transmitted was still very poor. The RX, being ex- PMR was built for strong signal handling rather than sensitivity, and was about 6db less sensitive than a 20 year old Ham rig! There were also relatively large losses in the circulator, duplexer and notch filters. Fitted a low-gain preamp, which brought the overall sensitivity up a long way, but performance was still poor. As suspected, the temporary aerial, which was known to have had water ingress, was generating white noise on the RX frequency when energised by the TX, and this was now the limiting factor. A replacement aerial had been obtained on loan, but weather was too windy to allow the swap.

24th May 2004

Changed to temporary (lower gain) aerial, fed by a long length of RG58. ERP is now approximately 4 watts, and RX correspondingly deafer. This "white stick" aerial is of unknown origin, and shows evidence of water ingress. But it's the only thing we had available at short notice! Upon disassembly. the original collinear was found to have loose internal joints, some evidence of water ingress, and an element which had suffered a large fatigue crack and was about to fail.

23rd May 2004

Source of the intermittent crackle traced to the collinear. The slightest movement in the wind would start it crackling.

22nd May 2004

The repeater was being heard over a wide area, but the receive performance was disappointing. Shortly after the transmitter was energised, signals were engulfed by a "frying" noise, which would eventually disappear after 15 minutes or so. There were also intermittent "crackling" noises, and sidebands from various broadcast stations. A 15 metre run of extremely poor quality RG58 was replaced by 12 metres of RG213, so the ERP was now up to about 8 watts.

21st May 2004

Faulty joint traced and repaired. Also replaced the commercial patch leads between duplexer and rigs, as these too were faulty. Crimp-type BNC connectors are rubbish, as are the cheap chrome plated and non-captive-pin types. Cheap patch leads use low grade coax with poor braid coverage, and consequently lots of loss and leakage. The new patch leads use good quality coax and genuine Greenpar plugs.

20th May 2004

GB3KD switched on at 13:05 BST. Unfortunately there was a faulty connector in the aerial lead, so it was radiating no more than a few milliwatts.

19th May 2004

Simplex gateway (G8PZT-L 434.500 MHz) switched off for the time being, the computer and interface hardware being redeployed for GB3KD. The intention is to construct a new interface unit and re-instate the simplex gateway as soon as possible. ELINK gateway / repeater controller logic switched into duplex mode, tested and settings tweaked. It was now all ready to go.

17th May 2004

Half the month lost due to other commitments, but construction began in earnest today, with the addition of carrier detect circuitry to the existing simplex gateway's interface unit.

April 2004

Still no movement through the approvals process according to the RMC web site, then without warning, received the Notice Of Variation! Unfortunately this contained several errors, so these had to be corrected. Suddenly there was a need to do lots of work on the hardware...

March 2004

Duplexer tuned, and radios plumbed into their temporary home. Experiments with the extra cavities, with the aim of producing deep notches in the RX path to keep 144.800/850 MHz packet from desensing the RX at 145.1875. This was successful - with the antenna separation and the notches, the packet signals can be taken well below the desense level. Unfortunately the notches are so sharp that it required one on each frequency - a single notch on 144.825 was not broad enough to cover both 144.800 and 144.850.

15th January 2004

At last! GB3KD's application, along with many others, moved one measly step in the approval process. Still a long way to go, so no urgency to get the hardware ready.

December 2003

Radios modified and tuned by G0EWH. Radiocommunications Agency became "Ofcom", and GB3KD became one of the longest-waiting applications. Presumably everyone was too busy settling into their shiny new offices and attending Christmas parties.

16th November 2003

Obtained 6-cavity duplexer, plus a couple of extra cavities to ensure co-existence of the repeater and Packet Radio systems.

Oct 03

Site clearance submitted by RMC to RA.

Summer 2003

Continued developing and testing the Internet linking / repeater logic software.

9th July 2003

Completed the site clearance form and dispatched it to RSGB Repeater Management Committee proposals manager.

June 2003

Obtained ex-pmr transmitter and receiver units. These will require some modification, but they are well designed and robust.

13th May 2003

Phone call from RMC saying there's no way they'd allow a 70cm repeater, even a wide-split one, in a semi-urban area like this, due to potential problems with car keyfobs operating on 433.9 MHz. It was suggested that we try for another band such as 2m, 6m or 23cm.

Bummer! We already had a 6m repeater (GB3BY) in Kidderminster, and 23cms is as much use a a chocolate teapot, which left only 2 metres. With at least two 144MHz Packet Radio transmitters on the site, 2m seemed out of the question unless we used a different site, and that made the Internet connection more difficult, even if we could find a site.

After some initial resistance to the idea, G8PZT realised that a 2m repeater was exactly what Kidderminster had been lacking all these years. It was what we originally wanted back in 1981, but had been prevented from doing so by antiquated planning rules. Instead we'd been forced to put GB3KR on 70cm.

So, no matter what the technical challenge, we would do it this time! The calculations began.

April 2003

Kidderminster radio amateurs deserved a full duplex VOIP repeater, and G8PZT seemed to be the logical person to make it happen, as she had the experience of both repeater engineering and VOIP, plus a site with good visibility of the town, and most importantly a full-time Internet connection.

One of the new 70cm wide-split allocations would be just the job, as it would fit in with the Packet Radio system, it would be easy to implement, and wouldn't affect GB3KR. This was to be a completely separate project, used only by the VOIP community.

The RSGB Repeater Management Committee and Radiocommunications Agency were duly contacted with a view to licensing such a unit.