RadioBanter - View Single Post

Michael Black[_2_] · June 19th 15, 06:38 AM posted to rec.radio.amateur.homebrew

On Thu, 18 Jun 2015, wrote:

hello seen this post , i know its old but do you still have the cleivite
info that someone sent you about these ceramic filters . 73s keith

You really might get a more useful reply if you actually started a thread
asking for information, instead of talking to people who haven't been here
for a long time. Even when Len did post, most of the time it wasn't here,
and he disappeared sometime after the rules changed so he could get a
license without a code test, and then apparently the fun was gone, and he
vanished.

Even if someone else has information, you haven't asked anything. You
sound like a vacuum, hoping to scoop up stuff that was passed around years
back. You haven't specified a problem, or a need, you haven't asked about
some specific Clevite filter, you've just barged in here and rudely
replied to a six year old post. Trying the old way, starting a new
thread, won't work, becuse you've already blown any chance that someone
will feel like helping you, since you replied to a six year old post.

Clevite was a big name in the early days of ceramic filters, maybe the
first source. I remember articles about their filters when they were new,
big and not really great spec'd, but better than a bunch of IF
transformers. But that was the late fifties or early sixties. Since the
early stuff wsan't great, chances are opening any AM radio of not too
recent vintage would turn up some ceramic filters that were better. Find a
scrap shortwave receiver, and that will have a narrower ceramic filter.
CB sets are also a source, though when I finally found an SSB CB set a few
years ago, it turned out to have a crystal filter in the HF range, and it
wasn't particularly narrow, and that was used for both AM and SSB. Wider
filters can be found in FM radios, TV sets (well analog sets), cordless
telephones and scanners, to give some examples. Better filters would be
found in better equipment, early cellphones were a great source of narrow
deviation FM bandwidth filters, for instance.

And while I've never heard anything, I can't help but wonder if those
early Clevite filters suffered over the long term, they being an early
iteration of ceramic filters.

Now if you're hoping to get your grubby hands on the reference someone
else wrote about back in 2009, where ceramic filters were used to make
ladder filters, others have talked about that and even referenced some
articles. I know I have. One trick in the early days of ceramic filters
were when they were two terminal, in effect ceramic versions of crystals,
so if you replaced the bypass capacitors in the cathode of emitter of the
IF stages with those two terminal ceramic resonators, they would act as
crystals, giving selectivity with no real effort. Cascading those should
be like cascading filters, there may be variation needed, but that's
something you could experiment with. Note that later, better ceramic
filters came along, I gather they in effect cascaded stages in a ladder
type filter (again a reason to buy or scrounge a newer filter rather than
hoping to use some fifty year old Clevite filter, or its information.

And then you're still stuck with a 455KHz or other low IF strip. Not good
image wise, you either live with the images, or go to double conversion.
Might as well start with a filter in the HF range, those can be found
surplus nowadays, but also making ladder filters with a bunch of crystals
on the very same frequency has become common, a step away from those
simple receivers of the old days with a 455KHz IF and just IF transformers
for selectivity.

But since you didn't really ask a question, just wanted to mooch
old data sheets, I haven't a clue what you are really asking, so I've had
to guess about what it might be.

Michael

On Tuesday, October 6, 2009 at 1:43:41 PM UTC-4, AF6AY wrote:

In a box of traded parts I found a cylindrical object labeled
"Clevite Ceramic Filter TL10D16A" that may be some sort
of IF filter according to very dusty old memory files. I would
appreciate it if anyone knows of this brand and can give me
an approximate center frequency and, perhaps, impedance
loading of terminations.

Hermetically sealed about 1 1/2" long by 1/4" diameter, leads
coming out ends of metal case. Unused by appearance of
end wires. Perhaps 30 to 40 years old? Trader had no idea
where he got it (probably in a trade of his).

Clevite is an old company and was purchased by Gould
Electronics some time in the late 1960s. Can't find anything
on this part in web search now.

My thanks for reading. If anyone has any info, feel free to
post it privately or publicly.

73, Len AF6AY