I'm trying to understand the operation of the B600 Transoceanic's converter stage, specifically the oscillator.
It does not appear to be of the S-38 variety, a Hartley with the 1L6 acting as a cathode follower and a tapped inductor providing voltage gain back to the first grid.

Apparently, the Transoceanic's 1L6 is not operated as a cathode follower. Instead, the voltage (or maybe the current) from the second grid is applied to the primary of a transformer. And the secondary of the transformer is fedback to the first grid.
So, the first and second grids, along with the cathode, seem to form a triode.
Is that right? If not, please explain.
Also, can someone point out another shortwave radio of that era (1957) that uses a 1L6 converter?

Thanks,
Steve

Your 1L6 explanation is good.
---------------
:Is that right? If not, please explain.
:Also, can someone point out another shortwave radio of that era (1957) that uses a 1L6 converter?
:
: Thanks,
: Steve
:

rghines1,
Thanks.
Cab you think of a similar shortwave radio, circa 1957, that uses the 1L6
and an RF stage?

Thanks again,
Steve
? :Your 1L6 explanation is good.
:---------------
::Is that right? If not, please explain.
::Also, can someone point out another shortwave radio of that era (1957) that uses a 1L6 converter?
::
:: Thanks,
:: Steve
::
:
:

Hallicrafters' TW-1000 series used a 1L6 tube. It was a general clone of the Zenith T-O, but had an additional longwave band. I don't know if it had an RF stage in front of the converter tube.

RCA also made a T-O ripoff set which used the 1L6. There were possibly others but the tube went out of production in the 1960's, presumably because the few sets that ever used it didn't create sufficient demand to justify its continued manufacture.

CV,
Where can I find the TW-1000 schematic?
And, do you remember the model name of the RCA version?

Thanks,
Steve

:Hallicrafters' TW-1000 series used a 1L6 tube. It was a general clone of the Zenith T-O, but had an additional longwave band. I don't know if it had an RF stage in front of the converter tube.
:
:RCA also made a T-O ripoff set which used the 1L6. There were possibly others but the tube went out of production in the 1960's, presumably because the few sets that ever used it didn't create sufficient demand to justify its continued manufacture.
:

(1) http://bama.edebris.com/manuals/hallicra/tw1000-2/
(2) No, I don't.

By chance, I today happened upon an RCA Strato-World Model 7-BX-10 on eBay. It appears to use a 1L6 mixer tube. I know nothing about it beyond that.

CV,
I checked out bama, but I think a software download is necessqary to view the TW-1000 schematic.
I did find the schematic at jptronics.
The converter stage is a close cousin of the Transoceanic's.
The TW-1000 schematic is much easier to understand, and more voltages are labeled.
I'm trying to understand how the 1L6 converter stage actually works - is a voltage developed on grid #2, is a current actually sourced, how does the signal grid actually mix with the current that passes through grid #2, etc., etc..
Tubes seem to be way more complicated than transistors. Maybe I'll try to figure this stuff out when I retire in 6 months.(And if I don't die first.)
I'll check out the RCA radio.

Thanks Once More,
Steve
:By chance, I today happened upon an RCA Strato-World Model 7-BX-10 on eBay. It appears to use a 1L6 mixer tube. I know nothing about it beyond that.
:

Steve,

You might consider this link to get a better insight into what is going on in a radio receiver:

http://www.radioremembered.org/

Click on the restoration/troubleshooting tips button and then on troubleshooting the stages of a superhetrodyne receiver.

Clifton

:CV,
:I checked out bama, but I think a software download is necessqary to view the TW-1000 schematic.
:I did find the schematic at jptronics.
:The converter stage is a close cousin of the Transoceanic's.
:The TW-1000 schematic is much easier to understand, and more voltages are labeled.
:I'm trying to understand how the 1L6 converter stage actually works - is a voltage developed on grid #2, is a current actually sourced, how does the signal grid actually mix with the current that passes through grid #2, etc., etc..
:Tubes seem to be way more complicated than transistors. Maybe I'll try to figure this stuff out when I retire in 6 months.(And if I don't die first.)
:I'll check out the RCA radio.
:
: Thanks Once More,
: Steve
::By chance, I today happened upon an RCA Strato-World Model 7-BX-10 on eBay. It appears to use a 1L6 mixer tube. I know nothing about it beyond that.
::
:
:

Clifton,
The 6A8 converter stage in radioremembered is identical in form to the those in the Transoceanic, TW-1000 (jptronics) , and the RCA Statoworld 3BX-671 (oldtech). I guess these radios, based on the 1L6, cannot use the 12SA7 cathode-follower Hartley approach because the 7-pin miniature's cathode must be part of the filament string, and, so, cannot be configured as a follower.
On Mike Yancey's site I found an RCA Institutes publication, Electronic Fundamentals, on converter fundamentals.
It covers the pentagram and says the oscillator section is based on the cathode, grid 1, and grid 2, which all form a triode, with grid 2 serving as the plate. But, most of the cathode current flows though the grid 2. As the electrons pass grid 2, they are attracted back toward grid 3 and most pass through it. Grid 4 (the RF signal input) is biased in such a way that the electrons do not readily pass through it. So, a puddle of charge collects between grids 3 and 4, and forms a "virtual cathode" , against which the RF signal grid works.

A Tung-Sol datasheet for the 1L6 specifies both a conversion transductance (300 uMHOS) and an oscillator transconductance (650 uMHOS) for a given set of bias conditions.
So, I thought that I now knew how much current would flow from grid 2 if a signal is applied to grid 1. This was my original question, i.e., what's the voltage gain around the oscillator loop. However, RCA Institutes goes on to point out the for part of the oscillator cycle voltage at the grid becomes negative-enough to drive the oscillator triode into cut-off.
So, I guess a calculation of the gain around the loop becomes less straightforward.

I do have some practical questions.
I noticed that the tuning capacitor on my S-38A has widely-separated plates, undoubtably to improve oscillator frequency stability.
Can I buy cheap tuning capacitors, with wide plate separation for standing off high voltages in transmitters? Where could I find these?

In the Radiotron Designers Handbook is a section on the design of a 6SA7 converter. I've also seen a data sheet that has the same circuit with the same signal voltage labels. Does such a write-up exist for the 1L6?

For the Transoceanic's oscillator transformer at 16M, what is the likely turns ratio? What's the range of tuning capacitor?

In Radiotron, there's a third converter scheme based on the 1R5. The plate current flows through the primary of the following IF transformer.
The other side of the primary is returned to the primary of the oscillator transformer, and so on back through the secondary to the oscillator grid.
Does this scheme have any advantages?

I also saw somewhere that the 1R5's frequency range is not as high as the 1L6's. Is this true?

All this is a tube tutorial for myself. Any comments or instructions would be appreciated.

Thanks,
Steve Sherman

:Steve,
:
:You might consider this link to get a better insight into what is going on in a radio receiver:
:
:http://www.radioremembered.org/
:
:Click on the restoration/troubleshooting tips button and then on troubleshooting the stages of a superhetrodyne receiver.
:
:Clifton
:
::CV,
::I checked out bama, but I think a software download is necessqary to view the TW-1000 schematic.
::I did find the schematic at jptronics.
::The converter stage is a close cousin of the Transoceanic's.
::The TW-1000 schematic is much easier to understand, and more voltages are labeled.
::I'm trying to understand how the 1L6 converter stage actually works - is a voltage developed on grid #2, is a current actually sourced, how does the signal grid actually mix with the current that passes through grid #2, etc., etc..
::Tubes seem to be way more complicated than transistors. Maybe I'll try to figure this stuff out when I retire in 6 months.(And if I don't die first.)
::I'll check out the RCA radio.
::
:: Thanks Once More,
:: Steve
:::By chance, I today happened upon an RCA Strato-World Model 7-BX-10 on eBay. It appears to use a 1L6 mixer tube. I know nothing about it beyond that.
:::
::
::
:
: