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FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator

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Zenith:
@Johnny B Good

The link was garbled but I found the thread with a search. Thanks for trying.

Boat anchor receivers are sought after and some people like to restore them to as issued in WWII condition. Boat anchor test equipment has much less of a following and people don't seem sentimental about old sig gens. If they work, fine, but the size and weight is a pain. It they break and can be fixed easily, fine. If they are too much of a PITA, they go. It's a shame, because the standard of construction can be very impressive.

My valve scopes are from the 60s mainly. They are not quite boat anchors, they are usable as scopes and occasionally I fire them up and use them. I've really enjoyed sorting out their problems and getting them working properly. I think the interest there is that I wanted one as a kid in the 60s, but they were completely unaffordable.

Feeltech may have put in a slightly better crystal lately, or maybe I got a good one. The accuracy is fine for what I bought the FY6800 for, sweeping IF stages for visual alignment, and for that purpose the drift is essentially non-existent. I'm still tempted to tinker 'though.

I've always found the Racal frequency counters very useful and very reliable, and they're quite small. Looking on ebay, I saw a couple for about £30.

From what you say, you have a perfectly good reason for buying the Parkside generator. I'm sure a lot of people buy the Lidl/Aldi specials because they can't resist a bargain and wonder whether they need it afterwards. I've fallen into that trap once or twice. You're probably aware of this, but petrol can go stale and it's hard to start an engine with stale petrol. I think what happens is that volatile fractions, which allow  a spark to ignite the fuel, oxidise. This can be a real problem with engines which aren't used for months, but you expect to start with little trouble when they are needed. However, you can buy fuel stabilisers which stop the fuel going stale. I believe a lot of two strokes oils contain some stabiliser.

It's just possible that your boat anchors have some very desirable parts, such as the rectifier and possibly a KT66 used in a stabilised power supply.



Johnny B Good:
@ 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.

==========================================================================================

[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

Zenith:
@ Johnny B Good,

The boat anchor thing started over 20 years ago when a work colleague had to have his mother move in with him and had to get rid of much of his junk. He knew I had an oscilloscope and liked to mess about, so I ended up buying an AR88, spare valves and manuals for £50. After that the temptation was too much and came all the British WWII stuff, Eddystone, Hammarlund, Racal. It was mostly about £50 a pop and then came the test equipment and chasing down spare valves at radio rallies.

The test equipment followed and was fun to fix and use - for the most part. I have a Schlumberger sweeper which I've had a long rest from, but it will not defeat me.

There's a vintage domestic radio scene which seems healthy and organised, but I find the radios boring. It and the amateur radio scene fit into a boat anchor radio scene. There's a vintage telly scene, which I can see the point of, but don't want to be involved in. There's a vintage radar scene, which apparently involves big bucks. There's a juke box scene, I can see the point of, but it's big bucks and you need a lot of room. Test equipment is generally regarded as functional and complicated, so it's easily junked when something better comes along, which it does. Look at these DSOs and the FY6800. So it goes quite cheap, which suits me.

Then of course, there's the vintage audio scene, which rapidly merges into audiophoolery and nonsense on stilts. I despise it.

I have a couple of Z80 boards and they remind me of a kinder, gentler time, although it didn't seem like that then. A nice one fixing that 'though.

Yes, the old high performance stuff had to use expensive precision construction. A good engineer can do for a shilling what any damned fool can do for ten quid, but these people were good engineers. Times have moved on and we've found better ways of doing things, but what they did is still magnificent. HP and Tek in particular, seemed to go a bit overboard when it came to doing things right, but their gear usually seems to stand the test of time best.

As for the desire to tinker and time standards. Some amateurs have spent a lot of time and money on this. I'd like an off-air standard good for 0.1ppm at least. Don't R4LW receivers need a 198KHz crystal, which can probably be custom made for surprisingly little (£40???) and then you may as well use a published design and buy the circuit boards. A ton at least? I think I'll look into the GPSDO option.

As for where it will all end, I can't see it matters as long as you enjoy it and it doesn't impact others in your life; kids going barefoot to school because daddy has blown the loot on a caesium beam standard.

An energy policy constructed without a power generation engineer in sight is worrying. Also, energy policy is long term and so can't very well accommodate the fads of the hour. Most shops these days couldn't open without electricity. Your comments on this have made me reconsider things. In January, with a blocking high for a couple of weeks, things could get miserable. I suppose the least I'd need is 240V AC to produce  a maximum 50W to keep the central heating system going for a few hours. It could come from an inverter and the car battery. The Lidl generator is well worth a thought.

The stale fuel and generator idea came from a friend whose daughter ran a chicken farm. It had an emergency generator which was petrol fired, but when the power went off, always in the winter, daddy was called out to fix it, and the problem was stale fuel.

As for the house moving business, I've gone through the same process and have decided to go home, where property is cheaper, I can be with the folks I dig and can catch up on some fishing and shooting. It's a lot of work and a big decision, but the older you get the harder it gets.

It's been a pleasure to correspond with such a thoughtful person.

For anyone else following this long and possibly completely irrelevant post I'll bring it back to the FY6800.

IMHO it's a remarkable product for the money. It's a shame Feeltech haven't chased up some of the observations and improvements made and maybe incorporated them in a deluxe version or options at extra cost, then they could have had a killer product.

I'd recommend it without hesitation for anyone wanting a function generator and judging it by the standards of function generators. Features such as the burst function and arbitrary functions I can see being useful in sorting out knotty problems. It wouldn't cut the mustard compared to a halfway reasonable RF or decent low distortion AF sig gen. If you are interested in low level signals it's questionable.

Generally well worth the money.


 

Johnny B Good:

--- Quote from: Zenith on February 20, 2019, 10:35:05 pm ---@ Johnny B Good,

The boat anchor thing started over 20 years ago when a work colleague had to have his mother move in with him and had to get rid of much of his junk. He knew I had an oscilloscope and liked to mess about, so I ended up buying an AR88, spare valves and manuals for £50. After that the temptation was too much and came all the British WWII stuff, Eddystone, Hammarlund, Racal. It was mostly about £50 a pop and then came the test equipment and chasing down spare valves at radio rallies.

The test equipment followed and was fun to fix and use - for the most part. I have a Schlumberger sweeper which I've had a long rest from, but it will not defeat me.

There's a vintage domestic radio scene which seems healthy and organised, but I find the radios boring. It and the amateur radio scene fit into a boat anchor radio scene. There's a vintage telly scene, which I can see the point of, but don't want to be involved in. There's a vintage radar scene, which apparently involves big bucks. There's a juke box scene, I can see the point of, but it's big bucks and you need a lot of room. Test equipment is generally regarded as functional and complicated, so it's easily junked when something better comes along, which it does. Look at these DSOs and the FY6800. So it goes quite cheap, which suits me.

Then of course, there's the vintage audio scene, which rapidly merges into audiophoolery and nonsense on stilts. I despise it.

I have a couple of Z80 boards and they remind me of a kinder, gentler time, although it didn't seem like that then. A nice one fixing that 'though.

Yes, the old high performance stuff had to use expensive precision construction. A good engineer can do for a shilling what any damned fool can do for ten quid, but these people were good engineers. Times have moved on and we've found better ways of doing things, but what they did is still magnificent. HP and Tek in particular, seemed to go a bit overboard when it came to doing things right, but their gear usually seems to stand the test of time best.

As for the desire to tinker and time standards. Some amateurs have spent a lot of time and money on this. I'd like an off-air standard good for 0.1ppm at least. Don't R4LW receivers need a 198KHz crystal, which can probably be custom made for surprisingly little (£40???) and then you may as well use a published design and buy the circuit boards. A ton at least? I think I'll look into the GPSDO option.

As for where it will all end, I can't see it matters as long as you enjoy it and it doesn't impact others in your life; kids going barefoot to school because daddy has blown the loot on a caesium beam standard.

An energy policy constructed without a power generation engineer in sight is worrying. Also, energy policy is long term and so can't very well accommodate the fads of the hour. Most shops these days couldn't open without electricity. Your comments on this have made me reconsider things. In January, with a blocking high for a couple of weeks, things could get miserable. I suppose the least I'd need is 240V AC to produce  a maximum 50W to keep the central heating system going for a few hours. It could come from an inverter and the car battery. The Lidl generator is well worth a thought.

The stale fuel and generator idea came from a friend whose daughter ran a chicken farm. It had an emergency generator which was petrol fired, but when the power went off, always in the winter, daddy was called out to fix it, and the problem was stale fuel.

As for the house moving business, I've gone through the same process and have decided to go home, where property is cheaper, I can be with the folks I dig and can catch up on some fishing and shooting. It's a lot of work and a big decision, but the older you get the harder it gets.

It's been a pleasure to correspond with such a thoughtful person.

For anyone else following this long and possibly completely irrelevant post I'll bring it back to the FY6800.

IMHO it's a remarkable product for the money. It's a shame Feeltech haven't chased up some of the observations and improvements made and maybe incorporated them in a deluxe version or options at extra cost, then they could have had a killer product.

I'd recommend it without hesitation for anyone wanting a function generator and judging it by the standards of function generators. Features such as the burst function and arbitrary functions I can see being useful in sorting out knotty problems. It wouldn't cut the mustard compared to a halfway reasonable RF or decent low distortion AF sig gen. If you are interested in low level signals it's questionable.

Generally well worth the money.

--- End quote ---


@ zenith

 Apologies for the tardy response but I've had several distractions consuming my 'spare time' of late.

 I never became a 'collector' since I didn't have the space for more than the most basic of signal generator and 'scope kit, hence my only owning just two boat anchors. Of course, now that modern T&M kit is not only so relatively cheap but compact and lightweight, there is now a real danger of expanding my T&M gear into a collection that goes beyond my cheap (but excellent value) Siglent DSO and the even cheaper (and supremely excellent value) FY6600.

 Perhaps I will eventually land up investing in an SA and perhaps even a LA, keeping the existing T&M kit as backup to yet more highly specified versions that I might feel justified in splashing out on in the event that the needs of future projects will justify such extra expenditure. It's never a good idea to invest in T&M upgrades whilst the existing T&M kit can still serve its purpose even if not so conveniently as an overdue upgrade would do. Like desktop PCs, it's always best to wait until you can feel a tangible benefit from the upgrade rather than doing such purely for the 'bragging rights'. The longer you can put off an upgrade, the more value you'll get from the investment.

 As for vintage audio gear, whilst I respect it for the qualities that old fashioned valves (tubes) could offer (600v/microsecond slew rates versus the 2 to 10 volts per microsecond slew rates of 2N3055 power transistors) which belatedly revealed itself as SID in the first of the "modern solid state" power amps (the electronic equivalent of tracking distortion with pick up cartridges that were either set up with too little down force or else simply had too large an effective tip mass for even down force settings at the highest allowable limit could fix), the time has long since passed by where this is true. I don't see too much virtue in using such ancient valved gear other than as expensive (to both own and run) space heaters.

 I must admit to hankering after the simpler times of coding in Z80 assembler but I'm faced with a broken Transam Tuscan S100 bus home built from a kit desktop computer that had fallen victim to the damp basement environment I'd kept it in for two decades. I've got a spare main board which had been stored in a dryer and warmer part of the same basement which I'm planning on using, assuming I ever get round to testing it before applying all the necessary hardware mods required to undo the many "Skoolboy Howler" design errors that had been inflicted upon it (address decoding faults and tuning the modem chip used for the original tape interface to the 300 baud rate rather than the 1070/1270 Hz carrier frequencies used in the echo mode it was set up for (echo mode being required for tape storage use) being just two examples that come to mind right now - I'm sure there were other similar design errors).

 I don't think there are any cost effective Z80 versions of the cheap as chips Arduino Nano board I shelled a whole 3 quid out on just on the off chance that I might actually get to use it with my u-blox GPS module. If there were, I'd be into it in a shot since I'm so familiar with Z80 assembly, it's like an old friend. I guess I'll just have to resume my studies into C (actually open and read the "Beginning C" book I bought nearly three decades ago). They say, "You're never too old to learn.". Perhaps the Arduino Nano might give me enough motivation to demonstrate whether that saying has any validity or not (the three quid investment should, in my case, provide ample motivation!).  :)

 You don't need a 198KHz crystal to make up a 198KHz R4LW locked reference. You can use an old transistor radio with LW and a bunch of cmos ttl logic (divider chips) to generate a 2KHz tone locked to the 198KHz to mix with the 198KHz signal to generate a 200KHz reference from which to phase lock your 10MHz OCVCXO module at a 50:1 ratio as per the original 200KHz frequency standard that was used prior to the 9KHz channelising of the long wave broadcast band in (iirc, the late 60s) which so inconveniently resulted in the 2KHz drop in frequency that applies to this day.

 You can search for the original construction articles which will provide the necessary BoM by which to construct such a frequency reference but if your time is precious, you might do better to go the GPSDO route and create a more futureproof solution. The 10MHz OCVCXO will still be in the BoM list if you want to create a nice clean and steady jitter free 10MHz reference. Otoh, it is possible to use the 10MHz output from the u-Blox NEO M8N module directly as a frequency calibration source if you don't mind the low level of noise modulation (weird beeps) and the periodic 'ticking' at just under 1Hz which can be heard alongside of the 10MHz or its third harmonic when zero beating an HF rig to precisely the required frequency. Despite all these "Noises Off", it still makes a much better alternative to the 10MHz WWV broadcasts you just might be able to receive in around five years time.

 For the very first time today (yesterday in fact), I finally set my 'scope up on that pesky desk that sits in the window bay, close enough to let me connect to the GPS module's PPS output pin so as to actually get a picture of the waveform. It's a surprisingly accurate square wave shape at 10MHz allowing for the inevitable jitter you get from dividing the module's own internal 48MHz TCVCXO down to a non integer 10MHz output and the ringing created by using the longish "Ground Wire" connection to the probe tip circuit.

 I can eliminate the jitter by choosing frequencies of 12, 8, 6, 3 or 2 MHz so an obvious way to obtain a jitter free 10MHz reference would be to set it to output 2MHz and multiply back up to 10MHz with an ultra low jitter PLL chip programmed to give a 5 times multiplication. Indeed, there's little to stop me using the same jitter free PLL chip to multiply up from even lower frequency options which may well completely sanitise my 10MHz of all of the modulation noises including that weird not quite synchronised to once a second 'ticks' that appear in the modulation noise pollution. Using a PLL is a good way of filtering out such noise leaking onto the PPS output pin from the rest of the GPS module's digital processing activity.

 I managed to short out the gnd and 5v Vcc line with my 'scope probe which corrupted the antenna power settings, dropping the sat signals by some 30dB. The antenna settings, as usual, failed to be accepted until, as before, I programmed the module back to defaults, requiring me to reprogram its PPS line to 10MHz output and to reprogram the antenna power settings to get back to the 30 to 55 dB C/N levels I'd been getting prior to this little 'accident'. Just out of curiosity, I pulled the external antenna to see whether I could get usable signals from the module's built in patch antenna with microscopic LNA chip and found it was receiving almost as many satellites though barely strong enough to decode usable fix and time data. It seemed to be stable so I left it alone for a half hour or so only to find it had stopped receiving any satellites strongly enough get a lock on so had to reconnect the external antenna again.

 This issue with the built in patch antenna is a rather strange one which looks like it may just be a cock up in the reference circuit used with the microscopic LNA chip. I'm beginning to wonder whether a strategically placed resistor might restore a missing bias current/voltage to the LNA. This delayed failure has all the signs of a charge on a coupling capacitor biassing an ultra high impedance pin slowly decaying away, resulting in the LNA becoming disabled. You've read the other thread so you'll be aware that this is a problem that has been seen with at least one other similar M7N based u-blox module.

 Luckily, this isn't a "Show Stopper", just an irritating feature of a non functioning built in patch antenna that, by all accounts, could prove a serviceable alternative, given suitable reception conditions, to the use of an outside antenna. It would have been far better if the manufacturer had decided to forego the built in patch antenna option altogether and reduce their BoM costs (and, hopefully its final selling price).

 I've mentioned this before but I'd thought I'd raise the subject again. I've noticed (but only after doing the TCXO upgrade) that my FY6600 is sensitive to any HF transients causing it to effectively disable its outputs. Initially, almost every time I connected a grounded DUT to the BNC ground shields as it shorted out the voltage from the Y cap. Fitting the C6 mains connector and wiring the ground rail to the mains earthing pin via an 11K resistor cured this particular issue but I've recently discovered that it's still possible to recreate this effect by switching a lamp plugged into the same mains extension lead 4 way socket that serves the FY6600 with mains power on and off several times until the signal generator finally succumbs, disabling both channel outputs.

 The sensitivity to such mains borne transients is still there, it just needs more effort to recreate an effect I could guarantee almost every time just by simply connecting a grounded DUT to the signal generator. I suspect it's an issue that would go away whenever the generator is plugged directly into a ring main fed wall socket (or at least plugged into a mains extension lead that's not also serving any other potential switching transient  sources). I'm just wondering whether anyone else has witnessed similar sensitivity to such transients or whether either my TCXO mod has introduced such sensitivity or I've been just plain unlucky in landing up with a unit that was cursed with this defect to begin with.

 With regard to the residual distortion of the AWG at audio frequencies, this isn't necessarily a show stopper when it comes to determining distortion levels in audio gear since you can use what was once a common technique of nulling out the signal generator's signal voltage waveform from that of the output from the amplifier under test and look at what's left over (which is essentially the distortion signals introduced by the amplifier itself). Whilst a distortion free test signal is nice to have, it's not an essential requirement for measuring distortion levels in an amplifier.

 AFAICR, the distortion levels at audio frequencies are less than half a percent with these signal/function generators which is better than a lot of the older and venerated HP signal generator kit and more than adequate to get high quality measurements with. I wouldn't be too concerned with the distortion figures for a device intended to serve the needs of the hobbyist rather than that of a busy professional audio testing lab where time is money and speed of measurement is of the essence. The hobbyist user has the luxury of time by which to get results matching those of a professional testing lab which can justify the time saving costs of a 'distortionless' signal generator.

 Incidentally, when I came to run some tests with the Parkside genset a few days ago, involving the refrigerator as the test load, I discovered a fault that stopped it generating output from its inverter module. The symptoms are entirely indicative of a poor contact in the plug/socket connection between the PM generator output and and the inverter input. I've no doubt that this is simply the result of my 'starter motor' testing forcing the plug connectors open when I inserted the solid core wires obtained from a length of 2.5mm flat twin and earth mains cable to connect it up to the BLDC controller module I was using.

 I didn't bother to sort it out since I plan on doing yet more testing once I've determined the pole pair number of the PMG (which is where the 'scope earns its keep) and purchase a pre-programmed Adapter Board with AS5047P rotary encoder chip to provide the "Hall Effect" commutation signals to drive the BLDC motor controller with commutation signals that are hard locked to the rotor position (sensorless mode just doesn't cut the mustard in this application - the mechanical loading is far more difficult than that of a predictable fan or propeller load for a sensorless control algorithm to handle). The refrigerator load test can hang fire for the time being whilst I get things organised to verify the PMG pole pair number and place an order for that adapter board with pre-programmed chip.

 I had, rather optimistically, hoped I could get away with sensorless operation for my add on BLDC controller but tests revealed the stark truth that in this usage case, I have no choice but to use commutation signals that are positively locked to the rotor position after the fashion of a purpose made BLDC motor with Hall Effect sensors built in by design.

 The only consolation with retrofitting the PMG with HE signalling using the programmable AS5047P rotary encoder chip is that I get a superior position sensing system that outperforms that of even the best purpose made BLDC motor with HE sensors built into it by design. It involves a little more modification than that of merely adding extra electronic components, without gross mechanical modifications as I'd originally hoped, in that I now have to attach a magnetic disk to the end of the crankshaft and attach the sensor PCB to the crankcase mountings, positioned so as to detect the magnetic field from the sensor magnet.

 Sensorless operation only worked when the sparkplug was removed by way of testing that it was actually possible to run the PMG as a motor but as soon as I blocked the sparkplug hole with a finger, the extra load was enough to confuse the sensorless algorithm and put the controller into a stalled state. The test confirmed that, given a reliable position only dependant commutation feedback system, there was every chance that I could utilise the PMG as a starter motor - it just wasn't going to be quite so simple a task as merely adding a bunch of electronic components alone in order to achieve this.  :(

JBG

d3m0:
Hi everyone, I found this post looking for a cheap DDS. I read a few pages but my lack of knowledge makes me lost sometimes. My short question is: should I go for 6800 or 6600 model? both are kind same price....

Regarding to improving them What are necessary / recommended mods?

I catch:

  - Linear 317 337 PSU
  - Heatsink every chip gets hot
  - adding / changing opamps  <-- is there a specific post that explains it for a kid?  ;D


anything else? can be upgrade max frequency? I think 60Mhz for me is enough but if it's free.....  ::)


Thank you very much, great effort everybody.
 

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