The DX code of conduct.

DX CODE OF CONDUCT 1. I WILL LISTEN, AND LISTEN, AND THEN LISTEN SOME MORE 2. I WILL ONLY CALL IF I CAN COPY THE DX STATION PROPERLY 3. I WILL NOT TRUST THE CLUSTER AND WILL BE SURE OF THE DX STATION’S CALL SIGN BEFORE CALLING 4. I WILL NOT INTERFERE WITH THE DX STATION NOR ANYONE CALLING HIM AND WILL NEVER TUNE UP ON THE DX FREQUENCY OR IN THE QSX SLOT 5. I WILL WAIT FOR THE DX STATION TO END A CONTACT BEFORE CALLING HIM 6. I WILL ALWAYS SEND MY FULL CALL SIGN 7. I WILL CALL AND THEN LISTEN FOR A REASONABLE INTERVAL. I WILL NOT CALL CONTINUOUSLY. 8. I WILL NOT TRANSMIT WHEN THE DX OPERATOR CALLS ANOTHER CALL SIGN, NOT MINE 9. I WILL NOT TRANSMIT WHEN THE DX OPERATOR QUERIES A CALL SIGN NOT LIKE MINE 10.  I WILL NOT TRANSMIT  WHEN THE DX STATION CALLS OTHER GEOGRAPHIC AREAS THAN MINE 11. WHEN THE DX OPERATOR CALLS ME, I WILL NOT REPEAT MY CALL SIGN UNLESS I THINK HE HAS COPIED IT INCORRECTLY 12. I WILL BE THANKFUL IF AND WHEN I DO MAKE A CONTACT 13. I WILL RESPECT MY FELLOW HAMS AND CONDUCT MYSELF SO AS TO EARN THEIR RESPECT.

High Voltage Capacitors for Hybrid radios, and a salutory warning.

Hi,

Alter repairing the FT102, I’d like to pass on some info about a good UK supplier of parts.

This is Audiocap, a company who supply capacitors for high Quality amplifiers of the Audio sort.

The specific capacitors I chose were 150uF / 500V DC rated types of 32mm diameter, which nicely fit the capacitor clips in Yaesu radios. I believe Trio/Kenwood use the same size caps but if you are buying for a Trio/Kenwood please double check the diameter before ordering.

The photo above is of the capacitor type I used.  They actually cost less than the Canadian imported ones I’d used and which failed, and which appear to be Chinese.

http://www.audiocap.co.uk/ft-150uf–500v-high-voltage-can-electrolytic-302-p.asp

The German capacitors are about three times the height of the ‘Canadian’ ones and slightly taller than the Yaesu originals.  I should also say that Yaesu and Kenwood radios employ 470K bleed resistors across the smoothing capacitors.  Those bleed resistors are *essential* safety-critical items and if you replace the capacitors, you should likewise replace the bleed resistors with new ones rated at 470Kilohms and a MINIMUM power rating of 2 Watts.  5W is preferable.

The resistors each have around 450V across them, so miniature types are NOT suitable.  If you can find decent 470K / 5W resistors, even better.  Just remember that your life could depend on these resistors working as they should, if you ever have to work on your radio.

I speak from bitter past experience here. Unknown to me, the original carbon bleed resistors in my radio had failed open-circuit and one day when I worked on the radio, I forgot to discharge the capacitors with my chicken-stick.  While turning the radio over (it’s a heavy beast!) I accidentally contacted the  900V DC supply with my right thumb. The current flowed into my thumb and out my right hand to chassis and blew a hole in my thumb at the top-most joint. I didn’t drop the radio!  I put it down on the bench and looked at my thumb where black smoke was still issuing from a puncture wound. I got VERY lucky that day, because the current flow was *only* through my hand.  The injury took many weeks to heal and I couldn’t bend my thumb at all for about a fortnight.  Thats the sort of thing that happens, if you are really lucky…. when you mess with 900 Volts. After I got zapped, I measured the voltage across the filter capacitors and was astounded to find it was sitting at 850V DC!  had the current path been from hand to hand, I probably wouldn’t be around now to warn you of the dangers.

I did take a photo of the damage to my thumb at the time, but I don’t seem to be able to find it. If I do, I’ll post it here.

This sort of thing should adequately demonstrate the importance of having good working bleed resistors. Old carbon composition resistors tend to drift high in value with age, and if your bleed resistors are of this type, treat them with extreme suspicion, or better still, replace them with adequately rated metal film types.

Until next time, 73.

AL GM1SXX

FT102 quits!

Hi,

I’ve been rather busy at work of late and unfortunately for me, my much loved FT102 went U/S.  I didn’t really have the time to fix it until recently, so instead I’ve been using my backup radio, the TS820 described earlier.

FT102 Transceiver

The FT102 had developed a serious fault in the plate power supply and was blowing fuses. This of course is a nightmare for any FT102 owner.On a 240V AC supply, the FT102 needs a 3Amp QUICK-BLOW fuse.

The FT102′s Anode (Plate) supply is a simple voltage doubler circuit using 4 diodes, 4 small 470K resistors, two smoothing capacitors and a pair of 470K bleed resistors across the smoothing capacitors.  How difficult could it be?

The answer it seems is *very* difficult!  Two of the 4 diodes on the RECTB board had failed short-circuit, so I replaced them with modern replacements. I got a pack of new 3A Q/B fuses and tried again.

Loud transformer hum and the fuse blew again!  I checked everything I could and all the resistances checked out fine. I was running out of ideas now!

I disconnected the 320V AC connection at the mains transformer and tried again… fuse didn’t blow, so the fault WAS in the plate supply. I reconnected the 320V AC line.

It didn’t make sense.  All that was left was a few resistors and the two smoothing caps and all of them seemed OK.  Having run out of ideas, I ordered a new pair of smoothing capacitors and fitted them.  This time, success.  The capacitors I’d bought to replace the originals several years previously seemed to be faulty.  They measured OK on a simple resistance check but failed when high voltage was applied.

I’ve never seen a problem like this before, but I’ll sure remember it in future!  Here’s a photo of the dodgy capacitor and it’s bleed resistor.

Very strange!  A capacitor that works OK at low voltages yet fails when it’s rated voltage is applied.

I’m just happy to have the FT102 back in action again.

73 Al.

GM1SXX

Cheap ways into Amateur Radio

Hi All,

Nicolas M1HOG has pointed out that I missed some obvious ways to get on the air cheaply, and I agree with him.  Among his suggestions are –

—————————————————————————–

Loan  equipment from your local radio club / members!   Secondhand  equipment from other club members – Well ones you trust  anyway!   Certainly  Wouxun, which you have already mentioned.   Kits – Walford, SDR and  kanga   Modifiy PMR – Some still very cheap/free and worthwhile.   Sprat – £6  per year!

—————————————————————————–

I agree Nick, and as for myself, I do have some kit equipment including Walford Electronics Midney and Kingsdon (RX and TX), plus several… OK, well a pile really of Ex PMR radios, so I can monitor miltiple bands.   PMR radios are built to high standards and can often be ‘tweaked’ to work on amateur frequencies.  It’s also possible to buy ready converted ones at attractive prices.  Common radios include the Philips/Simoco FM1000 ‘family’ of FM radios and the Storno range.    At home I have a pile of FM1000 and FM1200′s plus a Storno 6000 series radio.  All are good performers.   The Ascom SE550 is another PMR possibility.  My own thoughts are that the STORNO 6000 range of radios is in a class of their own.

Tetra are a well-known UK purveyor of ex-PMR radios.  http://tetra.co/  There are many others too.  Converted radios also appear from time to time on EBay. Sometimes a look under the covers reveals the original owner.  One of my radios originally belonged to the Dutch Fire Service while another was more local, having been fitted in a council van!   For those with the ability to reprogram EPROMs and do general radio work, there are bargains to be had with unconverted FM PMR radios while for the ‘appliance operator’ these radios can be bought for a fraction of their original cost.   Denis PA4DEN seems to have been responsible for a lot of the work needed in converting the Philips/Simoco FM1200 radios to the amateur bands.

http://www.pa4den.nl/fm1200.html  Some of my own radios have PA4DEN control EPROMS fitted.

Club Loans   Some amateur radio clubs have loan equipment avalable to members. This may be a route to take initially until you find your feet.

The kit approach.   For those competent at soldering and kit construction, there’s the excellent MKARS80 which is an 80Metre SSB transceiver kit while other radio kits are available from overseas.   The MKARS80 is a fine little single conversion transceiver with a huff-puff stabilised VFO and PIC based frequency readout.  For the keen constructor, it’s a real bargain.  Mine is built into a plastic electrical equipment box fitted with a clear lid and internal Lithium rechargeable batteries. It only needs a headset and aerial and earth added to get on the air.  Very portable and lightweight.

At home I also have a part finished BITx20 transceiver.    http://www.radio-kits.co.uk/   http://www.qrpkits.com/bitx20a.html

For those who favour QRP operation, and that includes me, there’s the excellent G-QRP group with their magazine Sprat.  I recommend joining the G-QRP group if you have *any* interest in low power operation.

http://www.gqrp.com/

More recently I bought an 80Metre Finningly receiver kit. The Finningley is an SDR (Software Defined Radio) and uses the power of a PC via a soundcard connection to do the signal decoding. This allows a great deal of flexibility, but of course ties up a PC.

Finally, My much loved FT102 threw a hissy fit, made a LOUD buzzing noise, and before I could reach the on/off switch, popped it’s 3 amp fuse!  I’ve traced the problem to the HT section by disconnecting the 320V AC line from the power transformer to the HT voltage rectifier/multiplier.  It’s likely that one of the PSU diodes has failed short-circuit or thePA  anode to Pi-Tank coupling capacitor has gone short-circuit.   I’m sure it can be fixed, but for the moment, it’s PLAN B… using my TS820S instead. The TS820S is a lovely old radio, but is missing the WARC bands, so wish me luck in repairing my FT102.

Until next time…. 73   AL GM1SXX

 

Amateur radio expensive?

Hi,

Today I’d like to talk money.  Not big money, mind you, but the sort of money that many of us could afford, like say £100.  Now, what could you buy for a hundred quid these days?  Well, certainly not a shiny new radio from Kenwood, Icom or Yaesu but of course you could buy a perfectly fine new Wouxun dual band handy for that sort of money, very useful for out and about, and with an external aerial, perhaps some SOTA activity.

But when it comes to HF radio, a hundred quid won’t buy you much… or would it?  I have to admit to having a very well equipped shack here but none of my radios are very modern.  Until I bought an FT817ND a few years ago, my most ‘modern’ radio was an FT290 MK1 bought in 1986!

In the shack, my most used radios are my much loved FT102 and it’s standby radio, a Trio TS820.  Both of these excellent radios were purchased for under 100 Pounds (each).

The FT102 was purchased as ‘known dead on transmit’ from a radio rally.  £5 worth of parts, to repair the driver stage,  had it back up and running again.  It helpsgreatly  if you have the technical knowledge to be able to repair and maintain your own radios, surely a strong incentive to go for a full license and to study as much as you can.  Failing that, it helps to have a friend with the requisite knowledge who can help.  Since repairing the FT102, I have changed out virtually all the relays in it and it performs excellently.   It sees daily use.

The TS-820S was also bought from a rally, for 90 Pounds. It came to me looking rather neglected and grubby but all the screws were in place and none were ‘chewed’. A positive sign.  I gave it the ‘all important’ ‘sniff test’ looking for anything burned or the presence of tobacco smoke (which kills radios!). I checked all the controls for smoothness and it was apparent that the VFO needed some attention.  It smelt ‘neutral’, so I bought it and took it home.

Set up on the bench it was obvious that this was a fully working radio. Apart from being grubby and having a sticky VFO knob, it was in pretty good shape, but transmit power was a bit down on what I’d have expected.  I removed the sheet metal covers and thoroughly cleaned them with AF spray foam cleaner.  They were in near pristine condition under all that ‘grot’.   I removed all the control knobs and used the same cleaner to clean the front panel, spraying cleaner onto a soft cloth and using that plus cotton buds to reach awkward areas. My radio now looked almost brand new.

Next to attack the sticky VFO.  I got the service manual from the WWW and proceeded to strip out the VFO unit. It was a bit fiddly but it was obvious that the lubricant used on the bearings and spindles had dried out, hardly surprising in view of it’s age.  The original lubricant had turned into a sticky goo. All the VFO mechanical parts were carefully cleaned and re-lubricated sparingly with lithium grease and the VFO was returned to the radio. It now was silky smooth in operation.  I finished reassembling the cabinet and control knobs, and the radio looked very good indeed.

Here are a few photos of it after it’s service.

The radio actually looks better in real life than it does in the photos, for which I used flash. In reality, it’s a very clean and well cared-for radio.

Although these radios were built in the 1970′s, when I still had long hair, they still perform very well and should not be overlooked if your need is for a solid dependable HF transceiver.  They are capable of excellent performance and are fairly easy to work on and maintain.  Being ‘Hybrid’ radios… transistors and valves, high voltages are used in the driver and PA stages and you do have to be aware of that when servicing them or working on them.

Here is the basic spec of the TS820S

Type:Amateur HF transceiver
Frequency range:10-160 m + WWV
Mode:SSB/CW/FSK
RF Power output:Max 100 W
Receiver system:Single conversion superheterodyne IF: 8.83 KHz
Sensitivity:0.25 uV (10 dB S+N/N)
Selectivity:SSB: 2.4 KHz (-6 dB), 4.4 KHz (-60 dB) CW: 500 Hz (-6 dB), 1.8 KHz (-60 dB) Image rejection:N/A
Voltage:Mains (or 13.8 VDC with DC-DC option DS-1)
Current drain:RX: 0.6 A (5 A heaters on) TX: Max 15 A @ 13.8 VDC
Impedance:50-75 ohms, SO-239
Dimensions (W*H*D):335*155*340 mm

Wouldn’t look out of place today really!

Don’t let the use of valves in these radios put you off.  The 12BY7A driver valve is long obsolete, but being a TV valve can still be found second hand and generally tested, on that great E**y emporium!  The 6146B PA valves are still in production, so pose no problems at all to find. Taken proper case of, the PA valves can last the life of the radio, but the 12BY7A drivers do have a finite life in amateur radio duty where they are being deliberately over-driven to do a job they were not really designed for.  I therefore keep a small stock of 12BY7A valves to keep my old radios working.   Expect 5 years hard use from a good 12BY7A.  My TS-820S still has the original 80′s vintage S2001A PA valves (a Japanese ‘clone’ of the 6146B), and they will if asked still deliver full output. If you take care of PA valves and don’t over-drive them, they can, and will’ last a LONG time. I replaced the 12BY7A which was a bit weak, with one from my personal stash.

Bear in mind that some of these hybrid radios were made before the WARC bands (30,17 & 12M) came into being and may therefore not have these bands present.  Whether or not that matters is for you to decide. I’m a big fan of 17M so I can operate on 17M on the FT102, but not on the TS820S which doesn’t have that band.

In the case of hybrid radios, if you find the transmit power is low (and you should expect it to vary across the bands, with less power as you go UP in frequency), before you even think of replacing the PA valves, substitute a different 12BY7A driver valve, to see if that helps. In my experience, it almost always does.  As for finding operating and service manuals for old radios, there’s an absolute wealth of information on the WWW.  I get all my manuals there… for free.

If you are looking for an HF transceiver and don’t want to spend a fortune, these hybrids can fill the need. I’d also like to mention that some people I know have sold their shiny new ‘Rice Boxes’ and purchased hybrids instead.  None of them would ever be willing to return to using modern radios.  Something worth considering IMHO.  Ease of use and the lack of bells & whistles can be a big advantage for the serious operator. All the controls on the front panel and easy to use. It’s quite persuasive.

Until next time.

73 AL

GM1SXX

 

‘OUR’ Amateur Radio Frequencies

HI,

I hope you all had a good holiday and a Good New Year.

This time I’d  like to mention a bit about the amateur radio allocations.  I often hear complaints from radio amateurs about others who use ‘our’ radio frequencies, and no more so than from those who use amateur radio satellites.  It has to be understood that the radio spectrum is a busy place and no one group ‘owns’ frequencies within the spectrum.  Instead, The ITU (International Telecommunications Union) divides up the available spectrum space with a view to making the most of whats available.

http://life.itu.int/radioclub/rr/rindex.htm

As radio amateurs, if you look at the current bandplans for whichever IARU / ITU region YOU live in, you will see that some bands have Primary and some have Secondary status.

Having Primary status infers that WE are the primary user of that band, but one should be aware that other users may also use that band by permission of the relevant authorities, but have to accept that  they may suffer interference from Primary users… i.e. US!

Secondary status means exactly that. We are secondary users of that or those bands, and MUST accept interference from the PRIMARY users.  We also have a duty NOT to CAUSE interference to the PRIMARY users.  A case in point is the 70Cms band, where in Region 1 we are Secondary users, and so must accept interference from RADAR, Military systems and other PRIMARY users, and must not cause interference to those users.  Many amateur satellite users don’t seem to understand this. some spot frequencies on 70Cms are also used for car-locking systems and Short-range-devices.  These users also have secondary status and for example cannot reasonably make a complaint against being locked out or in their cars by RADAR and other Primary user activity, and yes, it does happen.

For 70CMs in Region 1, the following conditions apply…

Amateur Service: Secondary User.    Amateur Satellite Service: 435-438MHz: Secondary User

Exclusion: 431-432MHz not available within 100km radius of Charing Cross, London.

So, no matter what some people think, in Region 1, we get to use 70Cms as SECONDARY Users.

More recently there have been web postings about the 23CMs band and the possibility of radio amateurs causing interference to the Galileo GPS satellites, which among other things, operate on the 23CMs band.    http://www.southgatearc.org/articles/galileo.htm

We are also SECONDARY users on 23Cms, so in addition to accepting interference from the Primary users, we must not cause interference to them.

You’ll remember the bit when you were studying to become a radio amateur which generally goes… ‘Use only as much power as is required to maintain the contact.’

Why then do I hear so many stations giving out 599 reports?  Surely a 599 report should be considered a lousy one?

Until next time.

73

AL GM1SXX

The RACAL RA1772 PSU (Observations from Scotland)

I’ve owned an example of the superb RACAL RA 1772 HF receiver for a number of years, having purchased it as a refurbished radio from Telford Electronics in Shropshire. This radio receiver has given me excellent service and I consider it to be the best HF radio receiver I’ve owned or used.  It’s sensitive, selective, ergonomically superb, and is a joy to use. It is however  ‘getting on’ a bit in years, like myself, and of course with age, comes aches and pains! 

The first problem I had was a faulty 723 regulator in the -7 volt line. This was a few years ago, and because of the scarcity and cost of obtaining a replacement round canned Ua723, I chose to build an off-board regulator using a modern negative voltage adjustable regulator IC. This proved to be very easy to do and restored the radio to a working condition.  

I’ve had other problems too. The PSU is a linear type and supplies
+20, +12, +5, -1V and -7V and is fitted on a single PCB with pass transistors mounted on the rear apron of the set. If the RA1772 has any real design issues,  it’s in that PSU. It’s very cramped and being a linear type with multiple voltage regulators, runs hot, so has a tendency to ‘bake’ the wiring, leading to brittle insulation that can crack and fall off, which of course can lead to short circuits:-)

This ‘Observation’ has some large images that may take time to load.  Just be patient.

My most recent receiver fault also turned out to be PSU related.  The bridge rectifier listed as D2 on the schematic disintegrated… at least the positive output tag somehow separated from the rectifier leading to a total failure of the receiver.  D2 generates most of the heat that emanates from the PSU.  My first thought was to replace it with a potted bridge rectifier purchased from Maplin, so I proceeded to go about replacing the faulty bridge rectifier with a new one.

In the photo above, you can see the rear panel of the receiver folded down and the PSU board is just visible in the jumble of wires on the left of the photo.

Here you can see the offending rectifier as removed from the radio. The positive connection tag just lifted free  as I was about to unsolder the leads from it!

This photo shows the PSU board with the new metal cased rectifier bolted into place and ready to connect up.  The PCB pads marked ML1 are the site of the original Ua723 that was used in the -7V supply, and which I removed years ago.

In the event, I deceided to take the recfifier off-board completely, a simple matter of arranging a few flying leads from the PCB to the rectifier, in it’s new position, so the photo above is NOT how my PSU looks now!  That new metal canned rectifier has been moved!

The wiring connected to the pins at the bottom of this photo suffers badly from being ‘cooked’ over many years of use. The insulation tends to become very brittle, and the wires inside oxidise, none of which is a good thing. In the photo sandwiched between the new rectified and the small IR bridge rectifier to the right of it are some pins that have thin ‘fuse wire’ soldered across them in normal use, to provide on-board fuses for the various supply lines. There are a number of these links used in the PSU board and ALL of them must be present and correct for the radio to function. In this photo, I had removed the links.  I fitted new ones later.

I’m not sure what sort of ‘fuse wire’ RACAL used for these links, but I use a single strand of wire culled from normal stranded hookup wire as replacements.  Works fine for me!  The links protect the transformer secondaries in the event of a fault condition.

This photo shows the eventual setup I used!  Since the bridge rectifier D2 produces most of the heat generated by the PSU, I decided to take it ‘off-board’, so I unbolted it and placed some ‘copper island’ pads where the rectifier had sat, so I had convenient connection points for the new wires I installed to connect to the rectifier. The advantage of this arrangement is that I take the heat generated to another part of the radio chassis where it can’t do so much harm.  The RA1772 is very ‘tight’ for space so I had to do some thinking about where I could place the rectifier to dump the excess heat while being a safe position to avoid short circuits etc.  

Here’s another photo of the PSU area showing the main reservoir capacitors  and the PSU panel folded down.

 

My eventual solution was to bolt the rectifier to the rear of the card-cage that holds all the modular boards.  This has decent ventilation while providing a large surface into which the heat can be dissipated.  The wires from the rectifier are routed back to the PCB where the old one used to live. Unfortunately, I’m a bit like Henry Ford when it comes to wire colour… black, black, or err, umm… red!  Ideally I’d have preserved the RACAL wiring colour-scheme…. but where to buy grey wire with blue stripes evades me!  I used a load of small ty-wraps to tidy up the wiring and although not as nice as the original lacing-cord, it does a job of work.

The bridge was fitted below the level of the edge of the card-cage in order to clear the cage lid when it was re-fitted.

In this photo, you can see the modified PSU board and my earlier repair to the -7V supply, where I used a regulator  fitted in the space vacated by the -7V supply’s pass transistor  I ripped out along with the 723 regulator associated with the -7V line, identified on the PCB as ML1.    I used an LM337T regulator and a pair of fixed resistors and decoupling capacitors for the new -7V supply.  Because this is a non-standard mod- I also labelled it as I have now also done with the D2 rectifier.

You can see the -7V supply more clearly in the photo above. The heavy wire goes to an earth tag on the chassis. I used ‘copper island’ PCB pads cyano-glued to the heatsink to make the various connections. This repair has seen daily use for several years now without any problems.

This photo shows the relocated rectifier D2 and associated wiring. The box to the right is the RF stage, preselector etc.

The old and new rectifiers for comparison. The new one is rated at 10 amps.

Almost back together again!  You can see how little space there is around the PSU board on the left side of the photo and also how much metal is available for the rectifier to dump heat into. The rather ‘chunky’ mains transformer can be seen to the left of the photo in it’s steel box.  RACAL didn’t do things by halves. It’s a very nice varnish impregnated job, and very quiet indeed.  The grey box situated between the transformer and the front panel is the ovened 5MHz frequency reference for the synthesizer. To the left of the loudspeaker (on the rear of the front panel) you can see the 30 position band-switch. I imagine this was a ‘special’ for RACAL and it’s beautifully made. One thing you can’t see is the tuning encoder which is an optical quadrature type constructed as a bespoke item for RACAL.  It’s beautifully made and a complete delight to use. Silky smooth.

Here you can see the receiver with the card-cage screening cover  in place. The edge of the rectifier just clears the lip of the cover… whew!

Copy of the PSU PCB overlay… from the RACAL service manual.  D2 causes most of the heat (and trouble).

Back together and working. 331?  That’s the Glasgow Airport NDB navigation beacon… just for a quick test!

The unit below the 1772 receiver is the RACAL MA1720 transmitter exciter.

73 Al.

GM1SXX