[R-390] Russian HF Radios

Bob Camp ham at cq.nu
Sat Aug 7 22:37:46 EDT 2004 

Hi

So how do you get one of these beasts?

Obviously we need more R390 to R250M2 comparisons.

	Take Care!

		Bob Camp
		KB8TQ


On Aug 7, 2004, at 10:01 PM, WF2U wrote:

> The Russians indeed built a receiver in the same class and purpose as 
> the
> R-390 and R-390A. The frequency display was not the Veeder-Root
> mechanical-digital counter as in the R-390* series, but an analog 
> system
> comprised of a coarse dial displaying each 2 MHz band  in 100 KHz 
> increments
> and a "fine" frequency dial which was projected from the rear, 
> displaying
> increments of  1 KHz, above the coarse dial. The receiver has  a dual
> conversion system based on a tunable first IF of  1.5 to 3.5 MHz, 
> mixed down
> to  the 215 KHz fixed IF. The rest of the bands are converted with a 
> crystal
> oscillator/mixer to the variable IF, a la Collins. The difference is 
> that
> the bands are 2 MHz wide instead of the 1 MHz in the Collins system, 
> and the
> tuning is not a permeability tuning arrangement with slugs moving in 
> and out
> of the coils, but a multi-section main tuning capacitor and a drum
> bandswitch system. The selectivity is infinitely adjustable (by 
> variable
> coupling of the 215 KHz IF stages, between 1 KHz and 14 KHz, and an 
> audio
> bandpass filter is provided as well, selectable between 8, 5, 2.5 and 
> 0.3
> KHz.
> The receiver contains a thermostat-controlled ovenized crystal 
> calibrator,
> the BFO is tuned with a reduction drive, with a dial displaying   -5 
> KHz -
> 0 - +5 KHz frequency in  100 Hz increments. AGC time constants 
> available are
> 1, 0.1 and 0.05 seconds or AGC OFF.
> The RF input is selectable with a front panel switch  between a 60 to 
> 400
> ohm (nominal), balanced and unbalanced dipole, whip/long wire or 
> ground,
> antenna  trimmer control on the front panel.
> There are jacks for AGC in/out for diversity, 1st and 2nd IF out, and 
> 600
> ohm audio line out (besides the headphone jacks).
> The construction is modular: the RF/first IF/crystal oscillator/mixer 
> is in
> the bottom drawer in the cabinet, the top drawer contains the second 
> IF,
> BFO, AGC, detector and audio circuits, as well as the metering circuit 
> - the
> receiver has a built-in emission tester and each tube can be selected 
> for
> test while the receiver is in operation, or the meter can be switched 
> by the
> selector to monitor the audio line output or the received signal 
> strength.
> The power supply is external, and interestingly the input is selectable
> between 220 and 120 VAC...
>
> The first version of this receiver was put in service with the (former)
> Soviet Armed Forces in 1948 with the military nomenclature of R-250
> ("Whale"), and the improved version, the R-250M was issued in the early
> 1950's. Both these models used standard metal octal tube types, which 
> are
> equivalent to the US types. In the early 60's the receiver was 
> modernized
> and standard miniature tubes were used together with some circuit
> improvements. The self testing arrangement got an additional feature, a
> built-in noise generator, so besides emission testing of the tubes, a
> sensitivity check could be performed without external test equipment 
> (like:
> "Hey, Sergey, I can't copy headquarters!"  "Check the receiver with the
> noise generator, Ivan!" "click, click, click as the meter switch is 
> turned
> to check each tube, and the input with the noise generator"- "There is
> nothing wrong with the receiver"  "S**t! The ice broke the antenna 
> again!")
> This version was the R-250M2 and was in production until 1981.
>
> Incidentally, in all these receivers the B+ is 160 VDC, giving the 
> tubes a
> real long and cool life, with a total current draw  of 120 mA!  The
> filaments are series-parallel connected (all 6.3 V tubes) for 12.6 V 
> at 6 A.
>
> I own a pristine R-250M model. Its performance is simply incredible,
> considering an early 50's design with all octal tubes (19 of them). It
> outperforms many receivers 10 years more advanced. The spec on the
> sensitivity is 0.6 uV  for S/N ratio of 10 dB at 3 KHz IF and 2.5 KHz 
> AF
> bandwidth, with a 100 ohm antenna. Audio output is 0.5 W into 600 ohms 
> at 4%
> (AF output tube is a Russian 6P6, which is the exact equivalent of the 
> 6V6).
> Frequency stability is specified as maximum 200 Hz drift after a 
> warm-up of
> 2 hours!
> The tube complement in US equivalent designations is  10 x 6SK7, 3 x 
> 6AC7,
> 3 x 6SA7, 2 x 6H6, 1 x 6V6, + a voltage regulator tube (I have to find 
> the
> US equivalent) and the power supply has a 5Z4 rectifier.
> The detector/BFO injection is good enough for good SSB reception, even 
> with
> the AGC on, as well as CW is just great to copy on it with all the
> selectivity options.
> It's no slouch in AM quality, although  .5 W  is really not enough to 
> drive
> a big speaker without an outboard amp.
>
> All this in a real "boatanchor" package of 26" wide, 18" deep and 21" 
> tall
> (with the shock mounts), weighing 209 pounds, without the power supply,
> which weighs about 35 pounds.
> Options available were RTTY demodulator, high precision AFC (Automatic
> Frequency Control) system, which provides tuning with a servo motor 
> and a
> diversity control interface. There was also a vibrator power supply 
> option,
> for 12 VDC input.
>
> Construction is really excellent quality and it looks like good US 
> mil-spec
> work. The wiring and soldering are also first-class, the components 
> look
> high quality. The transformers are potted, cased and painted, just 
> like the
> US mil. stuff. Incidentally, I got a couple of sets of NOS spare 
> tubes, with
> 1972 manufacturing date. Pretty late for still making metal octal 
> military
> tubes!
>
> There are photos of the various versions at a Russian web site
> http://www.cqham.ru/trx/r_250.html .
>
> Well, I hope this wasn't boring, but there is not too much traffic here
> tonight anyway...
>
> 73, Meir WF2U
> Gowensville, SC
>
>
>  -----Original Message-----
> From: 	r-390-bounces at mailman.qth.net 
> [mailto:r-390-bounces at mailman.qth.net]
> On Behalf Of Bob Camp
> Sent:	Saturday, August 07, 2004 5:15 PM
> To:	Cecil Acuff; R-390 HF Receiver List
> Subject:	[R-390] Russian HF Radios
>
> Hi
>
> Well obviously we need to get something going.
>
> How about did the Russians build a better all tube HF receiver than the
> R-390A? From what I hear the answer may be yes ....
>
> That's the way to see if anybody's listening.
>
> 	Enjoy!
>
> 		Bob Camp
> 		KB8TQ
>
>
> On Aug 7, 2004, at 4:57 PM, Cecil Acuff wrote:
>
>> Test...
>>
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