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Big old-fashioned IF transformers for tube-type homebrewing?



 
 
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  #1  
Old September 14th 05, 01:08 AM
Tim Shoppa
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Default Big old-fashioned IF transformers for tube-type homebrewing?

Are the big old-fashioned IF transformers-in-a-can available
anywhere anymore? I want to make a receiver, probably double
conversion,
which would mean that I'd want several each of the 50kHz and some
higher frequency (455kHz likely).

Are these things that can be made from scratch without a lot of
difficutly? I can wind coils etc. but don't
have any transformer slug-tuned cores.

Tim KA0BTD

  #2  
Old September 14th 05, 01:49 AM
gb
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Posts: n/a
Default

"Tim Shoppa" wrote in message
ups.com...
Are the big old-fashioned IF transformers-in-a-can available
anywhere anymore? I want to make a receiver, probably double
conversion,
which would mean that I'd want several each of the 50kHz and some
higher frequency (455kHz likely).

Are these things that can be made from scratch without a lot of
difficutly? I can wind coils etc. but don't
have any transformer slug-tuned cores.

Tim KA0BTD


YES. Almost every hamfest that I attend in the Chicago area has a gentleman
with 455 kHz IF transformers like we are use to seeing in older tube
designs. I also had replacement 10.7 MHz units for the older FM tuners.
Check with the surplus houses for units.

gb


  #3  
Old September 14th 05, 01:50 AM
Gregg
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Posts: n/a
Default

Behold, Tim Shoppa scribed on tube chassis:

Are the big old-fashioned IF transformers-in-a-can available anywhere
anymore? I want to make a receiver, probably double conversion, which
would mean that I'd want several each of the 50kHz and some higher
frequency (455kHz likely).

Are these things that can be made from scratch without a lot of
difficutly? I can wind coils etc. but don't have any transformer
slug-tuned cores.

Tim KA0BTD


Hi Tim,

Check out my article he
http://geek.scorpiorising.ca/455KHz.html

Cheers!

--
Gregg "t3h g33k"
http://geek.scorpiorising.ca
*Ratings are for transistors, tubes have guidelines*
  #4  
Old September 14th 05, 02:34 AM
[email protected]
Guest
 
Posts: n/a
Default

On 13 Sep 2005 17:08:48 -0700, "Tim Shoppa"
wrote:

Are the big old-fashioned IF transformers-in-a-can available
anywhere anymore? I want to make a receiver, probably double
conversion,
which would mean that I'd want several each of the 50kHz and some
higher frequency (455kHz likely).

Are these things that can be made from scratch without a lot of
difficutly? I can wind coils etc. but don't
have any transformer slug-tuned cores.

Tim KA0BTD


Hi Tim,

They are homebrewable. I needed a few 455khz for a tube RX I was
building and basically resused some old "IF like" cans by replacing
the guts with handwound coils and caps. The forms for the coils were
Horz width coils from a few dead monitors, used the slugs too. Used
one of the basic programs for solonoid coils to get a rough number of
turns and then then wound 30% less in scramble form. That gave a
basic coil and then resonated it with a cap to 500khz. Once the slug
was added it easily tuned down to 400 so I cut the slug shorter (1/2)
and it was fine for 455. The distance between the two coils (for
double tuned IFs) determines the coupling factor, or more directly
the selectivity and losses. Once you have the recipie for one winding
you can easily reproduce it.

Theres nothing special about IF cans save for they have to tune the
desired range, have a decent Q and are shielded. The outer can
however is important or that IF amp will become an IF osc. But even
the can can be liberated from salvage or made from copper, tin or
aluminum stock. I made some really nice looking cans using 1"
Copper pipe and pipe caps, heavy but well shielded. Soda straw
was the coil form and holes in the ends supported it and allowed
access to tuning slugs. Leads came out using insulated Teflon
feedthroughs. Looked very industrial.

Allison
KB1GMX

  #5  
Old September 14th 05, 05:23 PM
Henry Kolesnik
Guest
 
Posts: n/a
Default

Buy a couple of beatup Command sets or other mil surplus and salvage. You
can always get 455Kc IF xfmrs from old tube radios. Making your own is too
much work, so salvage and spend that extra time on making a better radio.
hi hi

--

73
Hank WD5JFR
"Tim Shoppa" wrote in message
ups.com...
Are the big old-fashioned IF transformers-in-a-can available
anywhere anymore? I want to make a receiver, probably double
conversion,
which would mean that I'd want several each of the 50kHz and some
higher frequency (455kHz likely).

Are these things that can be made from scratch without a lot of
difficutly? I can wind coils etc. but don't
have any transformer slug-tuned cores.

Tim KA0BTD



  #6  
Old September 15th 05, 04:39 PM
Mike@Lincoln
Guest
 
Posts: n/a
Default


"Tim Shoppa" wrote in message
ups.com...
Are the big old-fashioned IF transformers-in-a-can available
anywhere anymore? I want to make a receiver, probably double
conversion,
which would mean that I'd want several each of the 50kHz and some
higher frequency (455kHz likely).

Are these things that can be made from scratch without a lot of
difficutly? I can wind coils etc. but don't
have any transformer slug-tuned cores.

Tim KA0BTD

J.Birkett,
25, The Strait,
LINCOLN.
LN2 1JF. (Tel: 01522-520767 )
He had a few in the shop some months ago, failing that he often has old
portable radios of 1960s vintage and he does not ask a great deal for them.
Great little surplus shop of the old fashioned type....full of all kinds of
junk .
( Closed Sun/Mon/Wed. )
Mike.


  #7  
Old September 27th 05, 02:43 AM
Ken Scharf
Guest
 
Posts: n/a
Default

Tim Shoppa wrote:
Are the big old-fashioned IF transformers-in-a-can available
anywhere anymore? I want to make a receiver, probably double
conversion,
which would mean that I'd want several each of the 50kHz and some
higher frequency (455kHz likely).

Are these things that can be made from scratch without a lot of
difficutly? I can wind coils etc. but don't
have any transformer slug-tuned cores.

Tim KA0BTD

You can still find junk AA5 radios in the trash from time to time and
rip out their 455khz if cans. 85khz transformers from arc-5 radios are
STILL out there at hamfests, and the bc453 radios they came from show up
often on ebay. I think I have a few of these cans in my junk box. You
can pad them down to 50khz if you want, but there is nothing wrong with
the 85khz if frequency. The arc5 cans have a feature where the spacing
between the primary and seconday windings is variable. Remove the top
cap and pull up on the fiber rod to increase the spacing, push down on
it to move the windings together. With the windings spaced out you get
a nice sharp peaked bandwidth, with the windings together they are over-
coupled and you get a bandwidth well suited for ssb phone,
A Q multiplier and/or t-notch filter both work well at this frequency.

Some of the ARC-5 85khz cans had tapped windings to get better Q by
connecting the grid and plate of the tubes 'below' the high impedance
end of the coils by a few percent. If you exchange the hot and cold
ends of the coils, the taps might work out well for bipolar transistor
impedance matching connections!
 




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