[Boatanchors] RE: Classic Tube Rcvrs. (LAST CALL)

[Jack Taylor]

Meir,

Indeed, your description I found to be fascinating!  The R-250 series is
definitely a well designed boatanchor.  This is the first I'd heard of an
emission meter, sounds like an incredibly ingenious idea so's to cut
down on eventually wearing out tube sockets whilst performing routine
maintenance!  (I usta hate pulling tubes to test out of the R-390*s)

I can't help but wonder if these beauties are available and at what
average cost?

73 de Jack

----- Original Message ----- 
From: "WF2U" <wf2u at starband.net>
To: <Boatanchors at mailman.qth.net>
Sent: Wednesday, May 26, 2004 1:43 PM
Subject: RE: [Boatanchors] RE: Classic Tube Rcvrs. (LAST CALL)


The Russians produced an indeed outstanding receiver, the R-250 series. The
first of the series was manufactured in 1948 and was called AS-1,  the next
update was AS-2, then was named according to the (then) new Russian military
nomenclature system R-250 "Kit" ("Whale" in Russian), later was updated to
R-250M  and ended with the R-250M2 version in 1981. The Navy version of the
receiver was the R-670 and R-670M "Rusalka" ("Mermaid" in Russian).

The receiver series is based on a design similar to the Collins type of
conversion scheme: first variable IF, second fixed IF and the bands are
converted by a crystal-controlled mixer stage. As opposed to the Collins 1
MHz bands, the R-250 *** has 2 MHz bands. The variable IF is 1.5 to 3.5 MHz,
the fixed IF is 215 KHz, with infinitely variable bandwidth of  1 KHz to 14
KHz, (similar in principle to the Hammarlund SP-200) and an audio filter
selectable for  8, 5, 2.5 KHz and 300 Hz bandwidth. The BFO knob has a
reduction drive and a calibrated frequency dial displaying in 100 Hz
divisions up to +/- 5 KHz from the carrier frequency. The receiver has IF
outputs for outboard ancillary equipment such an RTTY converter, AGC output
for using two receivers in a dual-diversity system.
There is a built-in tube emission meter, which can test the condition of all
(19 ) tubes while in operation.
Up to the R-250M the frequency coverage is 1.5 to 25.5 MHz, and the R-250M2
extends the coverage to 33.5 MHz.
The CW sensitivity is specified as 0.6 uV for all models. The 115/230 VAC
power supply is external,  the tubes are fed with  only 160 V  plate
voltage. This should keep things cool, and long-lived, as well as low noise.

I own an R-250M, which still uses the standard metal-octal military type
tubes, all equivalents of our metal octal tubes such as the 6SK7, 6V6, 6H6,
etc.
The receiver performs extremely well, considering the old octal tube
complement (although the tubes in my receiver have 1962 manufacturing dates,
and all the NOS spare tubes as well). In fact it is up in performance with
almost any good professional/military  tube receiver.
The later R-250M2 model is basically similar in features and specifications,
except for the extended frequency coverage and the miniature series tubes
(equivalent to the 6BA6, 6BE6 etc. family) and some other circuit upgrades.
It also has a built-in noise generator for more internal testing capability
while in operation.

The R-250M is a real heavyweight, at 175 lbs. plus the power supply...

You can see some photos of the various models at
http://armradio.multishop.ru/review/r/r_250.html  .

Sorry for the long description but I thought there may be some interest by
others as well regarding these receivers.

73, Meir WF2U
Gowensville, SC