'I.F Alignment Aid'

[David G4EBT]

I mentioned in another post that I spotted a neat little circuit on internet for an I.F Alignment Aid'.

I don't need one, and it has its limitations, but as it uses only two ICs and two transistors, it may have some appeal to anyone who is sans signal generator. Because it's an American design, it's for 455 kHz - not 465 kHz. What determines the frequency is a ceramic resonator and a ceramic filter. There is a trimmer which can pull the frequency about 5 kHz max, so for 465 kHz, it would need the resonator and filter to be for 465kHz.

Cricklewood stock the resonator, (only £1.30) but not the ceramic filter.

https://www.cricklewoodelectronics.com/D465.html

I've scoured internet and all I can find is 455 kHz filters, which abound, such as this one:

https://www.aliexpress.com/item/Cera...053_10052_1033

Hence, unless I can find a source of 465 kHz filters this little project is destined to only be a paper exercise. (In any event, it was designed in 2004 and specified a Toko filter and they're no longer available even for 455 kHz). I've amended the original circuit by adding a 6V regulator and provision for an LED and have designed a PCB for it, albeit I've not yet checked it for errors.

If anyone knows of a source of three terminal ceramic filters, I'd appreciate a link.
(I saw one from Italy with a 30 Euro min order plus VAT, plus post, so discounted that).

The original design is here:

http://electronbunker.ca/eb/SignalGen455.html

First pic below is the amended circuit after I tweaked it.
Second pic is the component overlay of the PCB I've designed.
Third pic is the track side of the PCB.

It's kept me occupied on a rainy day - it's nice and toasty, sat here flying a desk!

Memo to self: Stop poking around on internet - it's the thief of time.

"Use what talents you possess; the woods would be very silent if no birds sang there except those that sang best".
Henry Van Dyke. (He was clever).

[camallison]

http://www.ebay.ie/itm/10-stuck-465k...kAAOSwo4pYTUYy

Possible source for 465kHz filter.

Colin

[paulsherwin]

It seems a bit of a palaver when sig gens can be bought for almost no money. Alternatively you could build a single transistor oscillator using a scrap IFT and align to that - there's no need to align to precisely 465kHz so long as all stages are aligned to a common frequency. You don't even need to modulate the signal if you measure the DC voltage at the detector.

[Bazz4CQJ]

With 2 IC's and 2 transistors, that's surely close to creating a wobbulator.
I forget what mines got in it; can't be much more, ... or less

B

[David G4EBT]

Originally Posted by camallison

http://www.ebay.ie/itm/10-stuck-465k...kAAOSwo4pYTUYy

Possible source for 465kHz filter.

Colin

Thanks for reading Colin, and for spotting that link. Very helpful.

[Argus25]

Silicon Chip in Australia recently came up with a project to aligns radios, it is here:

http://www.siliconchip.com.au/Issue/...S?res=nonflash

Obviously to get the the whole article you would have to be a subscriber. No doubt they will be kits. A lot of Silicon Chips stuff gets reproduced in the UK, in other magazines, might be EPE, they do a lot of world beating kit projects.

[David G4EBT]

Thanks for that info – it looks very sophisticated and possibly quite expensive, but often stuff sourced from the orient is at bargain basement prices. The project that is the subject of this thread dates from 2004, so is really quite old now and time moves on, but I rather like simple if dated projects, which is why I’m always delving into old magazines.

Yes, Silicon Chip do some marvellous projects which often appear in EPE magazine - in fact EPE is almost a clone of Silicon Chip as there are few other projects in it. S.C projects tend to be quite complex, using difficult to find parts, custom PICs and double-sided PTH PCBs. I did make a precision 10V Voltage reference for which I was able to make my own PCB for the reference and for the power supply from parts sourced in the UK.

Sometimes Jaycar do kits for S.C. projects or can supply certain items, but with postage and possible import duties if above a certain price, it starts to become expensive here in the UK. At one time Jaycar was to set up in the UK or appoint an agent but nothing came of it. We don’t have any firms the equivalent of Jaycar – the nearest is Maplin, which - though it has some 200 stores (similar to Jaycar) - is just a gadgets, gizmos and toys outfit which doesn’t come close to Jaycar. (It's probably Maplin's presence that inhibited Jaycar). There are a few smaller firms around that do kits – Quasar Electronics for example, but that’s all. It’s really amazing that while the UK has three times the population of Oz, and is only 100th of the area so is much simpler for distribution, we have nothing that comes close to Silicon Chip or Jaycar.

There aren’t any electronics magazines left any more in the UK apart from EPE – a Silicon Chip clone. Practical Wireless isn't very 'practical' and is not about 'wireless' – it’s just a ham radio magazine, nicely produced, but thin on technical and practical content, and then only ham radio stuff. Conversely, in EPE, there’s recently been a high power valve amplifier project running for some months – a Silicon Chip design of course. Quite incredible that there are still people around in Oz who can do the R&D and bring such projects to fruition on a commercial basis for an amateur electronics market. (I do wonder if any EPE projects actually get built in the UK. There was so little activity on the EPE forum ('Chat-Zone') where projects are (were) discussed that EPE has just pulled the plug on it).

It’s also remarkable that Jaycar appears to be going from strength to strength. Latest Catalogue is 548 pages, with over 6,950 products including 400+ new products. Despite the logistics of servicing it stores due to the huge size of Oz (It’s as far from Perth to Sidney as it is from here in Hull to Damascus in Syria), Jaycar have got 200 stores spread right across Oz.

I’ll look forward to seeing the Silicon Chip IF Alignment project in EPE.

Apologies for taking my own thread so far off topic.

[David G4EBT]

Originally Posted by paulsherwin

It seems a bit of a palaver when sig gens can be bought for almost no money. Alternatively you could build a single transistor oscillator using a scrap IFT and align to that - there's no need to align to precisely 465kHz so long as all stages are aligned to a common frequency. You don't even need to modulate the signal if you measure the DC voltage at the detector.

Yes, it's true Paul - signal generators can often be had for little money.

There's recently been a working Advance E1 in reasonable cosmetic condition listed twice with a starting price of £10.00 but no bids. Heavy, large, old, but internally it will be pristine. (Collection only due to size and weight). Trouble is, that many who want/need a signal generator tend to be novices at the early stages of setting up a workshop, so probably won't have other equipment to check the generator for accuracy or waveform etc, such as a frequency counter or 'scope. One thing tends to lead to another, and instead of the generator being an aid to aligning a receiver undergoing restoration, it becomes a project in its own right.

The circuit that is the subject of this thread can be simplified by omitting the output stage and that option was in the original design though I omitted to show that earlier, so I've attached it below. Just two ICs, two controls, the crystal resonator and filter. But you're right of course - it's possible to peak up the IFs without a signal generator, and I rarely find that IFTs have been tampered with on valve radios, though the same can't always be said for transistor sets. I think mixer/oscillator stages tend to pose more of a problem.

[FIXITNOW]

seems you can down load it for free here

https://psv4.userapi.com/c816228/u44...4VE-HPeZZs07ZO

[Argus25]

Originally Posted by David G4EBT

It’s really amazing that while the UK has three times the population of Oz, and is only 100th of the area so is much simpler for distribution, we have nothing that comes close to Silicon Chip or Jaycar.

Not only that, we do world leading and ground breaking medical research here too.

Everybody wonders how we do it. Its all "Aussie know how" and we keep it simple by loving beer, meat pies, kangaroos and Holden cars.

We also have no pretentious social class structures to tie us up in knots and prevent collaboration between theorists and engineers, which is a disease that severely affected the UK in the development of computers in the 1950s and allowed IBM and the collaborative structures in Silicon Valley to get the jump on them.

Around here, engineers, scientists and everyone at the coal face have barbecues with the professors at the weekends. So we cut through a lot of the barriers and get the jobs done. Its great to be an Aussie.

[paulsherwin]

The 1950s were 60 years ago. Australian culture was rather different back then too.

Back on topic please.

[Argus25]

Back on the topic of IF alignment.

I have found over the years that, in the case of AM radios , its seldom necessary to do a sweep of the IF. The reason being that in many cases (for transistor sets) the IF's are single tuned and for double tuned ones they are intended to be set (peaked) to the same frequency. The band pass characteristics are set by the design of the IF transformers by the manufacturer. So they are simply peaked. Its not necessary to see the shape of the response.

It is totally different for TV IF's where they cannot be set up very well without a sweep. Many manufacturer instructions for peaking at specific frequencies turn out to be pretty hopeless when you check with a sweep after you have done it.

The one exception though, is the FM detector in a radio, be it a discriminator or ratio detector. To get its symmetry correct and center frequency right, a sweep is really needed.

But for any standard AM radio, an IF sweep in my view has very limited utility (unless you are making home made IF transformers)... just to throw a cat into the pigeons here.

[ms660]

It depends on what you mean by sweep, a manual sweep with a signal generator can be a very handy feature indeed...To bring back lost resonances...

Lawrence.

[Argus25]

I mean a sweep where you visualize the band pass response on a scope in X-Y mode using a sweep generator. Sure, you can laboriously copy the detector voltage output and hand graph it on specific frequencies, but that's not nearly as good as seeing the band pass response in real time and how its affected by adjustments.

[ms660]

You might have missed my point.

Lawrence.

[Argus25]

I must have, but I was suggesting the same thing, a signal generator set on the IF frequency is all that is required to align AM radio IF's to peak them, it doesn't even need to be modulated if you look at the DC out of the detector. I was not suggesting not using a signal generator, just that most of the time a sweep of the frequencies around the center IF frequency was not needed for radios (unless you have an FM detector), so maybe you missed my point?

[David G4EBT]

Originally Posted by FIXITNOW

seems you can down load it for free here

https://psv4.userapi.com/c816228/u44...4VE-HPeZZs07ZO

I couldn't - 'Page not Found'

[David G4EBT]

I've got the Silicon Chip article now - basically, it looks to me as though there are only two ready built modules plus a few resistors, caps, connectors and an enclosure, so not much in the way of assembly - no SMDs peppered all over a PCB to solder in place!. Just curious to know what the cost might be - as I said earlier, electronic modules sourced from the orient (DDSs etc), are ludicrously cheap.

Excellent magazine - something of interest on every page. Even the many pages of ads are quite enthralling.

Long may it continue - as I said earlier, all the UK electronic mags have long since gone down the gurgler.

[Philips210]

Hi.

I seem to recall some sets have two slugs in their IF transformers and are stagger tuned to give a broader response so tuning is not as sharp. The primary is tuned to about 2kHz below the nominal IF frequency and the secondary 2kHz above the nominal IF frequency. So peaking the transformer won't give the best performance.

David's circuit does look very useful though and is worth building. It's another good project to build but I must complete the loop aerial project first, I wish I had more time, it's been a busy year! It's small size and simplicity makes it handy to have around the workshop. Maybe a small modification so that a 470kHz IF as in many Philips sets can also be achieved.

Regards
Symon

[Ian - G4JQT]

The BVWS Bulletin volume 29, number 3 (Autumn 2004) published a design I tweaked slightly from an old RSGB circuit and had published (with RSGB agreement) in the Bulletin. It's a solid-state wobbulator suitable for valve or transistor sets with an IF of anything between about 500 and 600 kHz.

It's got a pip-maker input for centring the curve, along with variable amplitude.

Ian