I've mentioned in previous e-mails that I plan to build (post-retirement) an S-38 from scratch as a tube tutorial for myself.
I'd like to listen to commercial broadcasts, especially from low-powered stations in eastern Europe. (Do many even remain, or have these moved to satellite ?)

I'll have a ~35 ft dipole antenna that won't quite be resonant at 9.5 MHz.
I might set aside the space for an RF stage up front, before the converter stage. Would the RF stage boost the receiver's noise performance such that low-powered stations might be more listenable ? At ~9.5 MHz, does atmospheric noise dominate a conventional S-38's electrical noise anyway? Would an RF stage be a waste ?

Dp any of the later S-38s have RF stages ? Can someone point me to a non-commuications shortwave receiver that does have an RF stage ? Do such receivers have an RF stage, an oscillator stage, and a mixer stage ?
Is such an arrangement useful only for copying amateur stations at powers much, much lower than 20 kW ?

Thanks,
Steve Sherman

:I've mentioned in previous e-mails that I plan to build (post-retirement) an S-38 from scratch as a tube tutorial for myself.
:I'd like to listen to commercial broadcasts, especially from low-powered stations in eastern Europe. (Do many even remain, or have these moved to satellite ?)
:
:I'll have a ~35 ft dipole antenna that won't quite be resonant at 9.5 MHz.
:I might set aside the space for an RF stage up front, before the converter stage. Would the RF stage boost the receiver's noise performance such that low-powered stations might be more listenable ? At ~9.5 MHz, does atmospheric noise dominate a conventional S-38's electrical noise anyway? Would an RF stage be a waste ?
:
:Dp any of the later S-38s have RF stages ? Can someone point me to a non-commuications shortwave receiver that does have an RF stage ? Do such receivers have an RF stage, an oscillator stage, and a mixer stage ?
:Is such an arrangement useful only for copying amateur stations at powers much, much lower than 20 kW ?
:
: Thanks,
: Steve Sherman
:
= = = = = = =

Many "living room" style allwave radios of the 1930's had tracking RF amps ahead of the mixer stage. RCA 810K, Philco 39-116X, Motorola 9Y, and Grunow Chassis 12-B are a few examples that I am aware of; but there was a time when this was a standard feature for mid-range to high-end sets.

The RCA 810K has a separate tube for each of the RF amp, mixer, and oscillator functions. The S-38 used a single tube to accomplish mixing and local oscillator frequency generation.

The S-38 was intended to be an entry-level set for beginning hams and/or shortwave listeners. As such, it had some features absolutely needed for this purpose (bandspread, BFO) but was pretty spartan otherwise to keep its selling cost down- no transformer-based power supply, no S-meter, no tracking RF stage, no DC regulation, only one IF stage, and so on.

Tom,
Thanks.
As you point out, the "pre-1938" RCA 810k has dedicated RF, OSC, and Mixer stages. And there's two shortwave bands, one of them being 6.8 to 22 MHz.
What's not clear to me is whether the RF stage actually improves the overall noise performance of the receiver.
There's a noise versus freq curve in "Reference Data for Radio Engineers", ~1962, page 763 that implies that man-made noise in suburbia at 10 MHz is far greater than atmospheric noise. And, I'm discovering that computers, cables and cable boxes create audible howl on a transistor radio. I did some experiments and, at least for household noise, 300 Ohm twin lead is the way to go from a half-wave dipole into the antenna coupling coil at the receiver front end. (A 1:4 transformer is necessary to go from the dipole to the twin lead.)
Do you have a preferred antenna and lead-in arrangement for listening around 10 MHz ?

Thanks Again,
Steve

::I've mentioned in previous e-mails that I plan to build (post-retirement) an S-38 from scratch as a tube tutorial for myself.
::I'd like to listen to commercial broadcasts, especially from low-powered stations in eastern Europe. (Do many even remain, or have these moved to satellite ?)
::
::I'll have a ~35 ft dipole antenna that won't quite be resonant at 9.5 MHz.
::I might set aside the space for an RF stage up front, before the converter stage. Would the RF stage boost the receiver's noise performance such that low-powered stations might be more listenable ? At ~9.5 MHz, does atmospheric noise dominate a conventional S-38's electrical noise anyway? Would an RF stage be a waste ?
::
::Dp any of the later S-38s have RF stages ? Can someone point me to a non-commuications shortwave receiver that does have an RF stage ? Do such receivers have an RF stage, an oscillator stage, and a mixer stage ?
::Is such an arrangement useful only for copying amateur stations at powers much, much lower than 20 kW ?
::
:: Thanks,
:: Steve Sherman
::
:= = = = = = =
:
:Many "living room" style allwave radios of the 1930's had tracking RF amps ahead of the mixer stage. RCA 810K, Philco 39-116X, Motorola 9Y, and Grunow Chassis 12-B are a few examples that I am aware of; but there was a time when this was a standard feature for mid-range to high-end sets.
:
:The RCA 810K has a separate tube for each of the RF amp, mixer, and oscillator functions. The S-38 used a single tube to accomplish mixing and local oscillator frequency generation.
:
:The S-38 was intended to be an entry-level set for beginning hams and/or shortwave listeners. As such, it had some features absolutely needed for this purpose (bandspread, BFO) but was pretty spartan otherwise to keep its selling cost down- no transformer-based power supply, no S-meter, no tracking RF stage, no DC regulation, only one IF stage, and so on.
:
:
: