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 Post subject: What was the first year that AC superhets included SW?
PostPosted: Jun Thu 04, 2009 8:04 pm 
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Id be interested in that answer as well as which ones were considered among the best for that year. Plug in coils or bandswitched.

Carl


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 Post subject:
PostPosted: Jun Thu 04, 2009 8:13 pm 
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I'm at work so can't check the dates at the moment, but the Tyrman Imperial "80" covered quite a lot of the (then) SW bands in late 1928, or maybe 29.

Band change was by changing two coils - - - RF & Oscillator, if I remember correctly (it's been a while since I've looked at mine).

.


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 Post subject:
PostPosted: Jun Thu 04, 2009 10:33 pm 
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The question entails interpretation in a grey area. Specifically what constitutes an AC superhet receiver? Does a battery type broadcast receiver with an eliminator and short wave converter with plug-in coils count? If so, both the Leutz Universal Transoceanic 9 and the Scott World's Record Shield Grid 9 (WRSG9) are candidates. In the form received by customers, the WRSG9 was introduced in August 1928. Optional accessories included an AC supply / power amplifier and plug-in short wave coils. Later, a short wave converter using plug in coils was available for the WRSG9. I believe the Leutz was introduced earlier and was also offered with a battery eliminator and short wave converter (making the otherwise TRF receiver into a superhetrodyne model).

If a battery set with accessories does not constitute an AC superhet receiver, what does?

Norman


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 Post subject:
PostPosted: Jun Fri 05, 2009 12:12 am 
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Braithwaite wrote:
If a battery set with accessories does not constitute an AC superhet receiver, what does?


No it does not.
An "AC superhet" is one that was originally
intended to operate from AC mains.
And not a hold over using a battery set
chassis and a AC supply, like a Radiola 30.

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 Post subject:
PostPosted: Jun Fri 05, 2009 12:23 am 
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I can only offer a WAG and that would have to be 1930 or 1931. Prior to that time shortwave was pretty much a ham only thing. And with people having a lot more time on their hands, due to the depression and the advent of foreign propaganda stations starting up in Europe, I think it all fell together at about that time. However, I don't have any clue as to what sets were available at first.
Curt

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 Post subject:
PostPosted: Jun Fri 05, 2009 12:38 am 
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Sheeeh - - - Wow - - - Cover your cornflakes folks.

I did check and the Tyrman Imperial 80 was available at least as early as September or October of 1928.

It was only available as a AC receiver. It used two coil sets, a four prong antenna coil and a five prong oscillator coil.

Little recognized for the accomplishment, the Tyrman was also notable for being one of the first Superhets to use a 475 KC IF frequency - - - pretty much the neighborhood where most IF frequencies would eventually land.

The photos of my Imperial 80 are stuck in one of my dead computers. Here are a couple of advertising/revue article shots:

Image


This rear chassis view shows the interchangeable coils in the left and right front corners of the chassis - - with the coil cover-boxes removed for the photo:

Image
.


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 Post subject:
PostPosted: Jun Fri 05, 2009 1:07 am 
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[quote="Ron in Radio Heaven] An "AC superhet" is one that was originally intended to operate from AC mains.
And not a hold over using a battery set
chassis and a AC supply, like a Radiola 30.[/quote]

By this definition, the Tyrman preceeds the Scott AC-10 introduced in July 1929 with an accessory short wave converter and the Lincoln Deluxe SW-31 (not Deluxe 31) introduced in March 1931 with plug in coils.

Norman


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 Post subject:
PostPosted: Jun Fri 05, 2009 2:28 am 
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Location: Southern NH, 03076
When I specified AC in the title it meant as designed/sold and self contained without an external converter.

I wouldnt think battery tubes to be good for much of anything above the BC band.

My oldest superhet is a Scott AW-12 main chassis only purchased from a forum member which appears to be 1931 and a credible performer. I then jump to a 1933 National AGS-X and a 1934 FB-7X, both using plug in coils.

That Tyrman is neat and will have to go on my want list. What frequencies did it it cover Dale?

Carl


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 Post subject:
PostPosted: Jun Fri 05, 2009 6:16 am 
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Dale Davenport wrote:
I did check and the Tyrman Imperial 80 was available at least as early as September or October of 1928.

It was only available as a AC receiver. It used two coil sets, a four prong antenna coil and a five prong oscillator coil.
Image


WOW, that's a great find Dale, good job!
We learn something new every day.

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 Post subject:
PostPosted: Jun Fri 05, 2009 6:19 am 
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Burnt Fingers wrote:
Quote:
That Tyrman is neat and will have to go on my want list. What frequencies did it it cover Dale?


I truly do not know Carl.

I purchased my copy of the set from a Forum member two or three years ago and to date have not finished restoration. My set was/is complete save for the on-board power supply. I was fortunate I think to obtain a complete set of coils, still in their shipping box, with the set .

I initially powered the set for testing with bench supplies - - played with it for a bit on the Broadcast Band, then boxed and stored it while I replicate the missing power supply. I don't remember that I experimented all that much with the other coil sets though, and the coverage isn't listed in either the advertising I have seen or in the construction article I have.

Finding a suitable power transformer proved a lengthy process but now with one in hand recently (courtesy of another Forum member) I'm working toward finishing up this one missing bit.

Eventually will come the somewhat knotty problem of a cabinet to house the beastie, but that is for another day, still a ways in the future.

Here is a full page advertisement from the November 1928 issue of "Callbook:"

Image

With a $199.50 admission price for a kit radio, I imagine not a lot of these were sold.

Extracted and enlarged for ease of reading, the advertisement's explanation of the "Imperial 80's" AC operation seems to meet the criteria for a genuine AC powered set (with SW):

Image

For those interested in the set, here is the schematic:

Image

More or less concurrently, Tyrman offered three other models with lesser tube counts and capabilities. To the best of my knowledge, the "80" was their first effort toward a set including the short wave bands.

The Tyrman sets I am aware of include:

Tyrman "60" using battery or AC eliminator)
Tyrman "70" Amplimax in early 1928 (battrery or AC versions)
Tyrman "72" Amplimax in mid 1928 (battery only)
Tyrman "Imperial 80" mid-late 1928 (A.C. operation)

I know of a couple of other Tyrman sets in collector's hands - - LDHare has or had a Tyrman, though I forget which model - - it might also be an "80."


vitanola
has (or had) a Tyrman "70"

http://www.antiqueradios.com/forums/vie ... ght=tyrman

These sets abound with neat features such as a front panel consisting of a steel plate with a thin wood veneer bonded to it. The dial scale too is not only back lit but also the light is diffused through the translucent dial housing- - - something a bit ahead of its time apparently.

Add:

As far as battery tubes being good for Short Wave operation, some such as the Western Electric 215 "Peanut" tubes and the UX-99's (and permutations such as the W.E. 839) operate quite happily at what then would have been the short wave bands due primarily I suspect, to their small construction and lower inter-electrode capacitance.
.


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 Post subject:
PostPosted: Jun Fri 05, 2009 5:04 pm 
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Thanks Dale, interesting circuit that will be rather marginal on SW since a triode mixer by itself isnt very effective. The pre iron core IF transformers are used so 3 stages were required for acceptable AM selectivity. That 210 or 250 AF output must be plenty loud.....and expensive to buy them these days.

My AW-12 isnt much different circuitwise except for a RF stage which is a big help. Im considering some changes so I can add a hidden AGC circuit, it sure needs it.

If anyone runs across a Tyrman, even non working, let me know please.

Carl


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 Post subject:
PostPosted: Jun Fri 05, 2009 9:44 pm 
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Neat. That's the sort of thing I like.

Did anyone notice that Dale's second photo has a different tube layout than the first? The first photo has a 27 at both ends, the second has a 24 at one end. Either someone retouched the photo, or they were still moving things around at the time the photo was taken.

The four single-tuned IF transformers would give about the same selectivity as an AA5's two double-tuned ones.

I didn't expect the 50 audio; until the schematic I figured two 71's and an 80.

Dave


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 Post subject:
PostPosted: Jun Fri 05, 2009 10:41 pm 
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Changes to circuits during production of a particular model were common in the late 1920s. Scott did exactly the same thing with their AC-10. Ultimately, there were three distinct versions of the AC-10 definable by changes in the tube lineup. The IF transformers in the Tyrman are not single tuned, they are factory fixed tuned. The schematic shows fixed capacitors across the secondaries of the IF transformers, not trimmers. It would be interesting to know if these capacitors are inside the IF transformer housing or outside where they can be easily replaced with trimmers. Dale?

Norman


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 Post subject:
PostPosted: Jun Sat 06, 2009 12:42 am 
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Thanks you for posting the photos and adertisement.

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 Post subject:
PostPosted: Jun Sat 06, 2009 1:19 am 
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Since I enjoy actually using many of my vintage sets Id be more inclined to replace the innards of the first IF with a 8-10 kc wide ceramic filter and associated parts and then retune the other IF's to 455 kc. There is probably a good chance that the IF's are open which would then require compact 455 kc replacements.

Something else to consider would be a broadband 10-12dB gain SS RF amp tucked out of sight. It wouldnt help image rejection but the very low noise gain would still be beneficial.

A 24 mixer would be a nice improvement if it was offered, no socket change required.

Carl


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 Post subject:
PostPosted: Jun Sat 06, 2009 2:33 am 
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Burnt Fingers wrote:
Since I enjoy actually using many of my vintage sets Id be more inclined to replace the innards of the first IF with a 8-10 kc wide ceramic filter and associated parts and then retune the other IF's to 455 kc. There is probably a good chance that the IF's are open which would then require compact 455 kc replacements.

Something else to consider would be a broadband 10-12dB gain SS RF amp tucked out of sight. It wouldnt help image rejection but the very low noise gain would still be beneficial.

A 24 mixer would be a nice improvement if it was offered, no socket change required.

Carl


Good one, Carl.


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 Post subject:
PostPosted: Jun Sat 06, 2009 2:38 am 
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Burnt Fingers wrote:
Since I enjoy actually using many of my vintage sets Id be more inclined to replace the innards of the first IF with a 8-10 kc wide ceramic filter and associated parts and then retune the other IF's to 455 kc.


At what point in all of this does it stop being
an OLD RADIO????

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 Post subject:
PostPosted: Jun Sat 06, 2009 2:48 am 
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Burnt Fingers wrote:
Since I enjoy actually using many of my vintage sets Id be more inclined to replace the innards of the first IF with a 8-10 kc wide ceramic filter and associated parts and then retune the other IF's to 455 kc. There is probably a good chance that the IF's are open which would then require compact 455 kc replacements.

Something else to consider would be a broadband 10-12dB gain SS RF amp tucked out of sight. It wouldnt help image rejection but the very low noise gain would still be beneficial.

A 24 mixer would be a nice improvement if it was offered, no socket change required.


Why not just trash the entire chassis, and install a 2009 solid state replacement? Improved sensitivity, selectivity, and stability.

Duane


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 Post subject:
PostPosted: Jun Sat 06, 2009 2:56 am 
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Ron in Radio Heaven wrote:
Burnt Fingers wrote:
Since I enjoy actually using many of my vintage sets Id be more inclined to replace the innards of the first IF with a 8-10 kc wide ceramic filter and associated parts and then retune the other IF's to 455 kc.


At what point in all of this does it stop being
an OLD RADIO????



When the OWNER says it is.

Some prefer shelf queens. Ive no problem with minor, well thought out changes that are easily reversible without a trace.

If the IF's were open most on here wouldnt know what to do except go on a long, long search for replacements.



Quote:
Why not just trash the entire chassis, and install a 2009 solid state replacement? Improved sensitivity, selectivity, and stability.

Duane


I havent heard that dumb a statement in a long time.

Carl


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 Post subject:
PostPosted: Jun Sat 06, 2009 3:52 am 
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Location: Hinsdale, IL, USA
Personally I am fascinated by the ingenuity of the early radio designs as-is. The radio engineers of the teens and 20's would blow away the so-called RF engineers today. The modern day engineers rely so much on computer simulation they forget or never learned first principals.

Studying the design and performance of the radios prior to 1930 is one of the most interesting facets of this hobby for me. The tricks they used to get around patent infringements, making crude triodes work at RF, getting the most performance out of what was available at the time. This kind of stuff is amazing to me.

Having never seen one of these sets, some of the questions I would have are:
1. What's the bandwidth of one IF transformer? How is it constructed?
2. Is the fundamental of the oscillator used to mix with the RF or does it use a harmonic of the oscillator?
3. What is the function of the cap from the plate of the 1st det to the RF tank? Is this a balance adjustment for the grid circuit bridge?

Thanks for posting the info for this set, it's very interesting.

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