@ Zenith
By the time I could have afforded any of those boat anchor radios, I had other priorities, namely the acquisition of a decent HF transceiver, hence the TS140S (the first of Kenwood's modern synthesiser tuned budget HF transceiver models). I bought it at a radio ham rally nearly thirty years ago. It had a 750 quid price tag but I managed to do a part exchange deal which reduced the damage to a mere 500 quid. The strange thing is that I can't recall just what it was I'd offered in part exchange (and I've tried my best to recall just what it had been over the past year or so).
I suspect it may have been a customer return on account half of the commands in the PC control software didn't work. Weird things like the RIT would only tune upwards, the downwards RIT tuning command being ignored amongst similar oddities.
Luckily for me, it used the Z80 cpu in its controller board and I was able to pull the eprom out and copy it to a file which I could run my home brewed Z80 disassembler on to get a full listing from which I was able to track down the command interpreter routine and its look up table. The table search loop counter value had been corrupted to half its intended value, probably by a single bit error in the eprom so was a very easy fix - just a matter of burning another eprom (or two just to make sure of having at least one good spare) and dropping it in as a replacement, after which, the radio worked perfectly with the PC controlling software.
As for the excellent standard of construction in such vintage kit (radio and test gear), it had to be in order to achieve the best possible frequency/timing stability out of the analogue tuning systems employed. Nowadays, it's really only the TCXO or OCXO reference oscillators that need to be protected from mechanical stresses and only when ppb accuracies are demanded. When the requirements demand just a mere 1ppm level of accuracy, the XO module can even be placed directly on the main board, right next to a bunch of analogue voltage regulators if that's a manufacturing convenience where heating it up to 50 deg C isn't deemed any great detriment.
As for the desire to "Tinker", even now, I'm wondering where it'll all end. The GPS module was acquired simply because the R4LW transmitter is at too low a frequency for attempting to trim the TCXO (it's good enough for checking the calibration directly but I'd have to build a 10MHz disciplined reference receiver to turn it into a useful calibration aid) and the 10MHz WWV broadcasts can't be received due to propagation conditions being at an all time low (we're currently in a sunspot minima right now). As things stand, with talk of the R4LW losing its NPL reference status in the next few years, the GPSDO project seemed to be the better option than making a special frequency reference receiver based on the 198KHz broadcast.
Just as it stands, without adding a disciplined 10MHz OCVCXO to it, the 10MHz output on the PPS pin provides a far more stable reference calibration source than the WWV broadcast, free as it is of fading and phase distortion from skywave propagation effects. Indeed, programming it to output 198000Hz to beat against the R4LW transmission as a sanity check that this still justifies its status as an NPL grade reference, revealed no discernible phase shift over the space of 90 minutes. As a sanity check that this zero beat effect was actually real, I'd actually programmed the gps module to output a 1Hz offset each side of the frequency (it can only be programmed in 1Hz steps) to time 60 beats in exactly 1 minute each time (to within 50ms according to my Smiths stopwatch with its 30 seconds per sweep of the dial calibration and high speed escapement).
For the past week or so, I've been monitoring the frequency drift of the signal generator against the third harmonic of the GPS 10MHz output which reveals a small drift with temperature somewhere in the region of plus or minus 5ppb with the odd random shift of one or two ppb every so often (and a spooky reaction to my presence in the morning as I check its overnight drift).
The stability of the TCXO was threatening to become an obsession but I think I've collected enough data to convince myself that it's just about as close to calibrated as a 0.1ppm TCXO can get. The next obvious step is to turn the GPS module into a self contained reference (with or without a 10MHz VCOCXO for it to discipline) with buffered outputs from which I can feed to the generator as a frequency reference locked to the GPS atomic clock standard.
The TCXO module is at least two and half orders of magnitude more accurate and stable than the original XO chip so I'm satisfied that its self contained reference source easily exceeds the accuracy of any other kit I have which might be in need of a calibration check. Any later kit that might boast sub 0.1ppm frequency accuracy will almost certainly be equipped with an external 10MHz reference input socket of its own anyway (as will the FY6600 when I've finished modding it).
To be fair, we've only suffered one 4 hour prolonged outage of supply in the thirty odd years we've lived at our current address and that was just about thirty years ago. I did happen to have my first Emerson30 UPS back then (I still have it but it's currently without a battery pack - two 7AH SLAs).
The power went out in the early evening just as I was about to head off to the radio club so, after shutting down my PC, I moved it onto the first half landing to power a floor standing lamp with a Philips SL13 to keep the hallway and stairs illuminated as a safety measure. I had to leave it running since it couldn't be "Black Started". I don't think we had a downstairs toilet back then, just the one toilet on that half landing. It kept that lamp burning right through the outage, during which the children had used it to do their homework by. The power was back on by the time I returned and we've never suffered any further outages since (just one or two briefly lived brown out events and the odd brief dropout over the years).
On the face of it, there seems very little justification to even keep a UPS up and running but I prefer to have such protection in place even against all perceived need. I know that Murphy will do his best to make my investment in UPS battery packs seem like a complete waste of money but the cost of a set of four 7AH SLAs, especially when the float charging voltage is turned down to the life prolonging 13.5v per 12v SLA from the life sacrifing for maximum autonomy of a brand new battery pack 13.8 volts that not just APC inflict as a default float charging voltage level is a small price to pay.
Looking at how tight the reserve margin has become for winter demand on our national grid due to wilful neglect by recent governments since before the millennium, I'm thinking about the very real possibility of load shedding during our next severe winter. Whilst the SmartUPS2000 can handle extended battery run times given a larger battery (unlike the tiny 500VA rated units which rely on the small battery capacity to save them from burning out), the investment required in a battery capable of providing autonomy for 5 or 6 hours is way too high for my liking when taking into consideration their status as a "Consumable", even when the float charging voltage is chosen to extend the battery life.
A 17AH battery pack as specified by APC for this UPS, would cost 150 quid or more so at just under a hundred quid, that inverter genset was an absolute bargain since it can run for over 5 hours on just a gallon of fuel. TBH though, I'd bought it to prove a point, the point being that it would be free of the overvolting effect on the AVR of a standard 2.8KVA unit by the pair of 4.7μF capacitors effectively in parallel across the mains input of the UPS which gets switched out when running on battery power.
On the face of it, the 2.8KVA genset should have been the solution to providing longer term backup power via the UPS instead of being the problem it turned out to be. All this nonsense about "Poor Quality Power" from a small petrol powered generator was just total and utter bullshit. The real problem was this gross overvolting effect (north of the 275v mark) when presented with any loads possessed of the slightest hint of leading current (a single 4.7μF fluorescent lamp PFC capacitor was all it needed to induce overvolting). The excuse of off frequency and distorted waveforms was total bollix. I discovered just how tolerant of "Poor Quality" these UPSes can be. When you think about the horribly distorted mains waveform, this should really come as no surprise - the sine inverter output of a UPS or an inverter genset is purity personified compared to the mains supply.
Having eventually proved my point (that only the inverter type of emergency genset can be trusted to be free of this overvolting issue), I realised that my underpowered generator may not be all that underpowered after all since virtually all of the lighting load had been upgraded to LED to such an extent that not only could I keep my IT kit running, along with the main TV set, I could light up every light in the house with power to spare for the central heating circulation pump.
The only fly in the ointment was that the fridge would probably trip the generator, leaving the UPS to handle the surge and then start draining the below spec battery pack, necessitating a quick dash to the genset to trick it out of reset by killing the engine until it was almost stopped before unkilling it in the hope the inverter module had reset itself before the engine had actually come to a standstill.
The trick works but it's a close run thing and hard to get right. If it does actually stop, it just means another go on the recoil rope starter. I've considered making up a current sensing relay that sheds any overload that risks an inverter shut down for the 20 seconds or so for the UPS to deal with the fridge compressor startup surge before restoring the power. Assuming such trickery will work, that just leaves the chest freezer to be managed if we have to ride out any prolonged outages lasting more than a day.
A neat way to solve the fridge compressor startup surge issue is to upgrade to one using a VFD compressor but I haven't seen such technology used in anything but high end overpriced fridge/freezers. Since I'm not ever going to give house room to any such atrocity as a Fridge/Freezer of any sort, it looks like I won't be solving this little problem quite so neatly as the VFD compressored fridge solution.
Those 2KW rated Workzone inverter gensets that Aldi started selling last year for nearly 300 quid looked like a more suitable alternative despite them costing some 50% more per watt of output. However, they turned out to be utter shite as I was finally forced to conclude after returning the third unit as "Not Fit For Purpose". Aside from the very serious issue of almost stalling when the 50% loading is increased to 95%, the other failing is that the fuel shut off is linked to the ignition kill switch so short of modifying the ignition kill switch wiring, you have no means of running the float bowl dry prior to putting it back into storage.
The Parkside units very sensibly kept the ignition kill switch separate from the fuel shut off valve which endowed it with two features absent in the Workzone units. The first being the obvious benefit of running the float bowl dry with the less obvious one being that you could crank the engine on the pull cord with the engine kill switch turned off without fear of snatch back as you primed the float bowl using the vacuum operated fuel lift pump driven from the engine. Mind you, a fuel priming bulb to activate the fuel lift pump pneumatically independently of engine vacuum impulses would have been a nicer touch but at least you had a snatch back free option to do this on the pull cord.
Mention of the fuel going stale and the need to dose it with a product like "Stabil" to extend its life, reminds me that it's been several months now since I last fired the Parkside up. Presently, it's sat in the unused front room with an almost full tank of fuel. There isn't anywhere else where I'd care to store it right now. Luckily, there's very little venting of petrol vapour so there's just the smallest hint of the smell of petroleum spirit to suggest the presence of some 4 litres of petrol in its tank. If the deterioration is due to the loss of the more volatile fractions, that bodes well for its long term fuel storage.
Normally, I'd prefer to run it up for half an hour per month to run fresh fuel through the carb as well as make sure that it's ready to go and not developing any hidden problems through lack of use. I've been a little pre-occupied of late but I'll take the next opportunity to fire it up when the missus can't complain that I'm disturbing our neighbours' peace and quiet on a Saturday or Sunday afternoon. A weekday afternoon seems the least likely time to offend any of our immediate neighbours who may be cursed with overly sensitive hearing. That won't stop 'Her Indoors' from protesting, unasked, on their behalf, it just means I can better demolish her objections just as I have on previous occasions.
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[EDIT 2020-04-15]
I've been browsing these ancient posts trying to track down the point in time when I first mentioned the 85 ohm attenuator issue. Just like "Cat" in "Red Dwarf", I find myself distracted by these old posts of mine in much the same way that Cat gets distracted by every mirror reflection of himself, hence this edit for the benefit of others who may have recently discovered this topic thread and only now, some 14 months late, are acquainting themselves with the gory details of this "Fix-It-Yourself" function generator project so kindly provided by Feeltech.
Today has been a rather pleasant sunny spring Wednesday (the third week , iirc - I've lost track- of the imposition of the Covid19 lockdown/social distancing measures here in the UK). This seemed an ideal opportunity to exercise both myself and that aforementioned Parkside emergency inverter generator (the very same unit - Lidl still haven't gotten round to offering these again as has been their normal annual practice).
It must have been over six months since it was last given an outing and with a refuelling some 6 to 9 months earlier. Mindful of its nasty "Kickback" habit, as all such recoil started gensets are prone to, I turned the fuel on, set the 'eco' switch to 'non-eco', left the kill switch in the off position (no such luxury with that Workzone bag o' shite I'd sampled three of from Aldi before giving up my attempt at a cheap upgrade to an 1800W / 2000W peak output inverter genset) before turning it over a few times on the pull cord, ready for
an actual starting attempt with the
kill switch in the run position.
It failed to fire up. Only then did I think to check if the choke lever had been moved back to the cold start position. Naturally enough (this is The Lord Murphy's playground, after all!) it hadn't. I moved the choke lever and turned the switch to "kill" before giving the starting cord another two yanks for good measure before setting the
kill switch back to the run position for a second attempt. This time (and rather gratifyingly) it fired up on that
"very first pull". It had proved no harder to startup than when I'd last run it up from a dry carburettor bowl state, indicating that the fuel hadn't suffered much (if any) deterioration whilst stored in the genset's tank (possibly a testament to how well sealed against loss by evaporation the filler cap provides)
After a couple or three seconds, I took the choke off and left it to warm up for another half minute or so before setting it into 'eco' mode to enjoy a quieter no-load "idle" (a comparative term - full bore or non-eco mode is a matter of 4,600rpm versus the eco idle speed of 3,100 or so rpm) before carrying it to its allocated spot between the rear of the garage and the back wall.
Surprisingly, as is typical of mid-week in normal times (these aren't normal times), none of our neighbours happened to be out and about in the surrounding back gardens to be slightly disturbed by what little noise could hop over the brick boundary wall from my strategically located 'generator slab'. Despite this, and as I've already mentioned, "Her indoors" played "Devil's Advocate" on behalf of those absent neighbours, suggesting that I relocate it to our front garden which, in order to avoid a pointless argument (men
rarely never win such arguments), I did.
To be honest, this was as much to satisfy my curiosity as it was to satisfy "'Er Indoors"'s demands since this was the one location I hadn't already tested out. This proved convenient for passing an extension lead through the basement window to reach my earth and neutral bonding point (an ex-mains filter plug fitted with a C14 socket repurposed to accept a C13 ended feed cable and pass the generator live and the local supply's ground and neutral connections cross bonded to those of the genset to the 13A "Filtered output" socket.
This 'generator access point' is kept plugged into a handy unswitched twin outlet socket with the mains plug of the SmartUPS2000 plugged into the remaining socket to allow a swift manual transfer from mains supply to emergency generator supply. Having got everything set, I took a deep breath and transferred the UPS plug across to the genset access point socket and then strolled upstairs to check that this procedure hadn't crashed my desktop PC in my first floor office/workshop. The transfer from mains power to genset power had gone as smoothly as I'd expected with the UPS in this mix specifically to make such transitions seamless (the protection against supply outages is a given).
APC specify a 17 or 18 AH 48v SLA battery for their SmartUPS2000 and I had recommissioned it back into 'Protected Supply' service almost two years ago with a set of 7AH SLAs simply as the cheapest possible way to run my inverter genset test to prove the absence of overvolting effect from capacitive (leading current) loadings that afflicts conventional gensets which boast the advantage of AVR.
Despite my taking the precaution of reducing the life shortening float charging voltage setting of 13.8v per 12v SLA to a life prolonging 13.5 volt setting, I wasn't sure how well this 7AH battery pack had held up in its past two years of service. After strolling across the road to experience just how quietly the genset was running whilst supplying a 200W load, followed by a stroll up and down the road to look for any possible 'hot spots' noisewise, I had the pleasure of hearing a distant petrol chainsaw (maybe 100 or more yards distant) drowning out the genset noise at a distance of just 30 to 40 yards.
When I got back to my office/workshop, I decided to try plugging in a 3x150W tungsten filament lamp load whilst listening to its effect on the generator through an opened window. Initially, I added each lamp load one at a time and heard the generator getting a little louder each time. This test confirmed that the mains extension feed to my 'workbench' was powered off of the 'protected supply' after all (I hadn't been sure since the tangle of cables had made it difficult to identify what was plugged into what by visual examination alone).
A while later, I repeated this test with all three lamps plugged into their sockets which caused the UPS to sense the drop in supply voltage from the genset and switch to battery power, shedding its loading on the supply before the genset could react and sabotage the whole enterprise. The UPS would then restore the emergency genset connection after a few seconds delay to verify a restored supply and sync itself to the incoming supply frequency to effect a glitchless change-over.
This was an unexpected bonus arising out of the use of a 2KVA 1.5KW UPS between the genset and its load. Not only did it afford protection against the genset giving up and falling over from a modest overload that exceeded its 1200W for 30 seconds rating overload trip out point, it also prevented the genset reacting immediately to greater transient overloads that would otherwise have immediately shut the inverter down, leaving the prime mover idling with no load.
Unfortunately, this doesn't protect against modest sustained overloads in the 980 to 1180 watt range which would cause the genset to disable its inverter after 30 seconds, allowing the prime mover to keep running indefinitely and the UPS to exhaust its battery pack if the situation isn't remedied within a matter of minutes.
That behaviour might well overcome the fridge's and the freezer's transient compressor starting overloads inducing a genset shutdown. The normal power demand of the fridge (and also very likely that of the chest freezer) is only some 70W or so at a 50% duty cycle (2 hours run time with 2 hours idle time having been noted for the fridge).
The freezer can be manually managed by scheduling when it's allowed to run so we can shut everything off in the daytime for the brief period required to allow the freezer to successfully start up and then run it for the few hours required to bring the temperature down to -28 deg C so we can leave it disconnected for the rest of a 24 or possibly 48 hour period between scheduled restarts. The fridge is a little trickier to manage since it has less temperature margin to play with (1 to 8 deg C range at most if we want to avoid freezing stuff that should not be allowed to freeze - normally a 5 to 8 deg range).
I have the impression that our fridge is near to the end of its life. I might replace it with a modern design that uses a VFD compressor that completely lacks this compressor startup surge current demand. Unfortunately, when I last looked at VFD based fridges just over a year ago, there were none. You had to resort to overly priced fridge/freezer models to take advantage of this technology (you pay one hell of a premium over and above the additional manufacturing costs + rational profit margin for this privilege).
The main point of this edit is that provided you shut off the fuel feed and let the generator run the carburettor float bowl dry before storing it away for another 6 to 12 months, you're less likely to be faced with a 'gummed up' carburettor next time you come to use it. Also, the issue of fuel left in the tank going stale appears to be non-existent over periods of 12 months or so (at least in this case).
As for the 20 litre jerrycan of unleaded, I'm hoping that'll remain viable for several more years yet. The seal on the filler seems to be gastight - there's not the slightest hint of petroleum vapour fumes to be had which bodes well for a long shelf life.
As for our hoped for house move, we're still looking to relocate to a nicer locale and property. However, this Covid19 business has rather put a stop to casual house hunting excursions - we could well land up leaving our current property in a box or two for all we know.
[END_EDIT 2020-04-15] I now return you back to the distant past ======================================
If it comes to the matter of scrapping my boat anchors, I'll certainly be retrieving the valves to add to my existing, though modest, collection (along with anything else that might come in handy). However, that may be some years off. We're currently considering a move from this six bedroom semi-detached Victorian house into a more modestly sized house or bungalow (empty nest syndrome) with a garage/shed suitable for conversion into a workshop.
The problem is that we're in a reasonably good area with good access to local amenities and we're undecided whether it's worth all the hassle and expense of moving to a smaller property in a nicer but less well served area or stick with the Devil we know and replace the garage (which was already a ramshackle affair when we moved in over thirty years ago and now in danger of collapsing in the next big winter gale) with a more substantially constructed garage come workshop that's actually fit for purpose.
It's a rather frustrating position to be in but staying or leaving is a major lifestyle decision worthy of more than just casual thought. We've looked at several properties, mostly from the outside it has to be admitted - but there seems little point in proceeding to the guided tour unless you're happy with the surrounding area and the property's setting. Further developments along the line of fitting out a decent workshop are basically on hold for the time being.
I'm reduced to tinkering about in a spare bedroom I'd commandeered as an office come computer repair workshop just over twenty years ago when going it alone as a sole trader in the business of assembling, selling and repairing desktop computers seemed such a good idea. Since I retired from this business some two years ago to collect my pension, the room has now become my "Man Cave". Hopefully, we'll arrive at a decision on whether to stay put or move onto greener pastures in the next few months to break the impasse we're currently facing.
JBG