substituting old IF cans

I have no idea what's available today, but if you look at my recently posted parts bin list, there were 455kHz ceramic interstage filters and emitter bypasses (from BJT days ;-)

I would imagine the interstages could be used with modern chips... maybe even OpAmps ?:-)

For 10.7MHz, maybe there's a SAW filter?? ...Jim Thompson

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SAW filter? I always thought they were SAWER filters, at least that is what they told me I was working on when I worked at Raytheon in the

Get'em while you still can. Ok, this one is for TV sets but you can still find 455kHz and 10.7MHz:

Look for Toko filters. Maybe on Ebay as well.

That's probably southern speak for SAW :-)

SAW = Surface Acoustic Wave ...Jim Thompson

Ceramic filters. Of course, if you want to learn more about the old-school methods (which are so often fruitful sources of ideas), you could get a copy of the Dover book "Handbook of Inductance Calculations" and one of Terman's "Radio Engineer's Handbook" and/or "Radio Engineering", or even an older (pre-1990) ARRL Handbook.

They'll tell you how to design and align IF transformers, which are actually really pretty.

Cheers

Phil Hobbs

There's ceramic resonators available for both 455kHz and 10.7MHz, in broadcast-band widths. There's also 10.7MHz crystal filters available in commercial narrowband FM widths.

If you're doing it for _fun_, then you have to decide what fun is. Ceramic filters work. Crystal filters are probably too narrow band for AM at 455kHz, but if you set your IF at 9MHz you could probably find some

I have a bunch of old TOKO cans with wind-your-own bobbins. Are those still available?

However, today, aren't we supposed to do everything in software ?:-) ...Jim Thompson

Their website won't give me a URL for a direct link to the page, but you can get the 455 kHz IF transfomers for transistor radios at

Me too. (I have piles of stuff from around 1990.)

You could probably do a pretty good AM radio with something like an ARM and an op amp. FM would be harder.

Cheers

Phil Hobbs

ADC's are power hungry and expensive (as was pointed out to me in another group). There's still a filtering/ADC-ing tradeoff to be made, and I think clock radios will be all-analog for years to come. unless the market goes to spread-spectrum techniques that admit the use of 1-bit ADCs.

I still have a few IF cans left from the 90s and could indeed use them but my goal would be making an old style radio without them. I'll probably do some tests with non tuned bjt/fet stages coupled through ceramic filters. Seems doable. Opamps should also be fine, there are some sold as video amplifiers that go up to several hundred MHz and more (the LMH6550 looks interesting) but that would defeat the "old style" requirement:).

Ceramic filters aren't "old style" either. They were not available back then resp. prohibitively expensive.

I guess that leaves you with winding your own filters. Read up about how they are tapped, and why. How to get the Q high enough and so on. You might want to also learn about Q-multipliers which are a nice way to run a filter at a Q that it doesn't really have. Depends on how fancy your radio should be.

Now if you ever want to build a "new style" radio make sure it has a difficult to read LCD, consumes oodles of watts, needs a fan, the IM performance is the pits, AM reception is next to useless, and the firmware crashes at least once a month requiring a power-cycle :-)

In fact, ceramic filters *are* quite old hat. Clevite Corp were making

Of course, the japs took over the market, just like they did in a lot of other areas...

Regards,

Chris

Does anybody remember "mechanical filters?" I remember seeing them in the mid-1960s or so, while they were designing SSB transmitters in "The Radio Amateurs' Handbook" and various hobbyist magazines. I'm almost sure I've seen them in the Allied catalog. The ones I remember were centered about the 455KHz band, which was pretty much standard IF for AM broadcast.

Speaking of old farts, does anybody remember that plug-in audio phase-shift network that gave two outputs 90 degrees apart from 300 Hz to 3 KHz?

Cheers! Rich

Yes, I remember that and I am not yet classified old, as you! :)

Jamie

Does anybody remember "mechanical filters?" I remember seeing them in the mid-1960s or so, while they were designing SSB transmitters in "The Radio Amateurs' Handbook" and various hobbyist magazines. I'm almost sure I've seen them in the Allied catalog. The ones I remember were centered about the 455KHz band, which was pretty much standard IF for AM broadcast.

Speaking of old farts, does anybody remember that plug-in audio phase-shift network that gave two outputs 90 degrees apart from 300 Hz to 3 KHz?

Cheers!

As I vaguely recall, Collins used a mechanical filter down at 50 kHz. in their 51J and S-line equipment.

Mouser has had both 455 and 10.7 transformers in their catalog for the last 40 years at least. Page 1062 of the current catalog. Or online put in p/n 42IF201 and then parlay that into the whole series. About a buck apiece.

Murata used to have the ceramic filters. Dunno if they still do.

Jim

They were made by Collins and they had the patents on them. Gave the equivalent of > 6 pole cystal bp filter iirc, in a very small package. Only 455 Khz or thereabouts, but they were the best filters around at the time and were being used right up to the 80's or even later. Google Collins Mechanical Filter, for data sheets. Rolloff like the side of a house.

SSB phasing method component, perhaps ?...

Regards,

Chris

Yup. Conceived by Sid Darlington at Bell Labs. (Yes, the same one.)

Anyone have his paper? I seem to have lost/misplaced my copy :-( ...Jim Thompson