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262 or 250KC I.F. transformers and 455KC BFO coils




 
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Author Topic: 262 or 250KC I.F. transformers and 455KC BFO coils  (Read 1506 times)
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Opcom
Patrick J. / KD5OEI
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« on: January 17, 2019, 12:24:08 PM »

How common are 262KC I.F. transformers? I'm told they were used mostly in old vacuum tube car radios.

I want to do an old style 1940s-50s panoramic adapter but am always stopped by the lack of one thing or another. Usually it's the 262KC IF transformers, or some other odd thing. Don't want to start before having what's needed.

There are sometimes 262KC units found on ebay, but no info on what they came from, only the part number, difficult to be sure of or look up. Some designs use 175KC I. F. transformers.

455KC units are also required but can be found in old 'All American Five' and other cheap old AM tube radios, plenty of which are not collectible, therefore no evil is done by stripping for parts.

The called-for "BFO Coil" is also a bit of a mystery. There are many designs using these. Nearly all of the tube type panoramic adapters/band scanners that are simple to build require that "BFO coil".

L1 B.f.o. coil for 455-kc., or 1.1 mH choke or coil tapped at 0.2 mH.
T1,T2 Replacement 455-kc. i.f. transformer.
T3,T4 Replacement 262-kc. i.f.transformer.


* Build_your Own Panoramic sch.png (676.26 KB, 1319x919 - viewed 133 times.)
* Build your own panoramic adapter.pdf (579.85 KB - downloaded 42 times.)
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« Reply #1 on: January 21, 2019, 12:19:03 PM »

An excellent source of 250 kC parts are the BFO and IF modules from the 618S1 XCVR. Fair used to sell these loose. You would actually use the IF module as-is with the fine mechanical filter for the swept portion. And of course the BFO parts might be useful as well.


* 618S1_IF.jpg (81.7 KB, 640x480 - viewed 96 times.)
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« Reply #2 on: January 22, 2019, 10:03:33 AM »

I've restored a few 50's - 60's car radios and they all had 262 kc IF's. You can probably find a few "as-is" on EBAY, otherwise not working and get the cans that way.
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« Reply #3 on: January 22, 2019, 10:15:52 AM »

I've got a bunch of cans from a surplus buy I made of old parts.

I'd be happy to cram them in a box and ship them to someone who could use them for the cost of shipping them.

Most, probably, are NOS still wrapped in waxed paper in their boxes.

I've no idea how many.

I'm not really into receivers, so if someone can use them, I'd love to pay it forward.

--Shane
KD6VXI


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Opcom
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« Reply #4 on: January 22, 2019, 04:35:23 PM »

PM Sent.

Wow I would never cannibalize one of my 618S1s.. the horror! but that's right, Fair may have some modules yet and I have not explored ebay for the old car radios. I have almost no 'cans' and should have a small collection to experiment with.
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« Reply #5 on: January 23, 2019, 07:14:52 PM »

Opcom,

They are yours.  I found I e tray today, I do believe their are more.  I'll keep looking but if I don't find them by the end of the weekend I'll fire these off.

Should fit in a flat rate.

--Shane
KD6VXI


* 20190123_133233.jpg (3147.35 KB, 4160x3120 - viewed 149 times.)
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« Reply #6 on: January 28, 2019, 02:12:00 AM »

Wow thank you! I can see a bunch of excellent candidates there!
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« Reply #7 on: January 28, 2019, 08:21:49 AM »

There are more pat.  I'll be sending out what I can locate after this Saturday.  Have a guy coming and picking a hunch of stuff up so I'll actually have access to my bulins and such!  Had someone drop two truck loads of work a month ago.

Anywho.

--Shane
KD6VXI
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« Reply #8 on: January 30, 2019, 11:21:24 AM »

Hey Pat,
Why not just pick up a real Panoramic panadaptor at the next hamfest ?  That QST article seems to be a slight recast of the Panoramic PCA-2 with a different power supply and the crt boosted from 2" to 3".   The Panoramic SA-1 that you had previously was a far nicer unit.
73,
Chuck K7MCG
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« Reply #9 on: January 31, 2019, 09:04:10 PM »

I could adapt a Panoramic or similar unit (heath, Kenwood.. but prefer to use tubes) There are a few reasons why I think I would prefer to do it myself.

1.) 2-3" displays are OK for desktop stations. 5" displays are fine, but the units are not always rack-mountable. Most existing units have green short or medium phosphors, non-aluminized CRTs, and use relatively low acceleration voltages so they are not so bright in a well lit room.

2.) There are a lot of schematics to choose from. Beyond the basic unit, I want to add features, like intensification of pips and dimming of the baseline when no/low signal is present. The kind of instrument I'd like to use is basic but with much better display, so a dual phosphor is a good idea for adding lower sweep speeds.
I was accustomed to using a Singer 0.05 to 27MHz spectrum analyzer for 455KC I.F.s. The Singers are so old now they drift all over the place and they are not at all easy to work on.
I don't need anywhere near the function or accuracy of an analyzer, and don't want to turn 10 dials to make it work, but I do want a better experience and versatility than the stock storebought/kit bandscopes offer. I am willing to do mods to those simpler instruments designed to do just the one job. I've worked with scopes and analyzers and CRTs so much that the improvement ideas are not mysterious. intensification or dimming - just an added tube or two.

3.) There are at least two 7" CRTs here and several 10" CRTs with interesting choices of phosphors*.  I'd like something highly visible without squinting from 4-8FT away. I have plenty of rack space, should take only about the same room as a 12" rackmount video monitor. Junk Sony professional and broadcast rack-mount monitors are available to be gutted for re-use of cabinets. The bezel may be a challenge, but 1/2" thick plywood with a Masonite front painted black or grey is a possible material to support the CRT front.

4.) That 5" panoramic I had was a real mouse-urine mess. I have gotten ill from mouse/rat mess so it was not for me. I sold it to someone who wanted to try and restore it. I previously gave up a Collins 3-1000 'autotune' amp for the same reason. Every time I worked on it, I felt ill a couple days. Had a duge dead rat with a hole burned through him in the power supply and he'd made his nasty home in the RF deck. People vary in their sensitivity to rodent mess.

5.) I could pick up a used panadaptor and hack, but don't want to ruin an expensive or classic piece of equipment. I'm also on a budget, so unless there are donations of a basket case, I would rather not buy an entire instrument.

Now, if there were a unit that was free of bio-waste products /corrosion and mostly free of rust, but had other parts issues like the CRT or burnt power transformer so that it was a basket case then it would be perfect. I would also consider repurposing a 'modern' hamscope such as a Heathkit SB620 or others. Those are still pretty simple.
I would prefer a tube unit, that is my goal. To avoid drift, I might have to use a regulated power supply. The issue there is having the VFO its sweep control, whatever method be stable. I built a spectrum monitor in the 1980s covering 50-900MHz with a digitally stepped tuning voltage and option to smooth that into a ramp, and it was great but this is another thing, another purpose.

* phosphors on hand in round 7" &10" tubes:
7" P1 type - green medium persistence non-aluminized
7" P7 type - Blue short + Yellow long persistence aluminized
10SP4 - White short  persistence
10UP14 - Blue medium + Orange long persistence
10VP15 - Blue-Green extremely short persistence 504,391 nm
10VP47 - Blue extremely short persistence 400 nm (may be hard to see)

The 10" tubes on hand have aluminized screens and high acceleration voltages. They are easily visible in room lighting except the P47, which is for flying spot. The 10UP14 may do well at lower sweep rates which is important in some cases. The P4 would be super bright as it's an actual TV set CRT.

For a bandscope purpose with those larger magnetic deflection CRTs, it is pretty simple to make a deflection amp that uses current feedback so the display is not distorted. Bandscopes are pretty low frequency where the display is concerned.
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« Reply #10 on: February 01, 2019, 07:40:31 AM »

Winding your own IF transformers? No way!

Way!
http://www.angelfire.com/electronic/funwithtubes/winding_if_transformers.html
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« Reply #11 on: February 01, 2019, 08:11:37 PM »

Shipped, Pat.

A medium size flat rate was too small.  So, I got a large and put all the xformers and cans I found in it.  Then their was space left.

So I filled all that with oil filled caps.

You have a few now.  Like 30 to 50 maybe?

--Shane
KD6VXI
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« Reply #12 on: February 26, 2019, 12:52:37 AM »

Plenty I think to give it a go. Have to test them out!
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