[Boatanchors] RF Comm SB-6F

[Skip Frolik]

Ah yes .... the SB-6F.
If I remember correctly the Mobile Alabama COE used them
for some function on the river. Not a bad unit except for
the final. It used an RCA "Wonder" type 7270 that would
go soft if you just gave it a dirty look. They changed those
things out on a regular basis. Tube was developed back in
1959 and apparently was so troublesome that RCA dumped it.
Only variant back then was the 7271 with a 13.5 volt heater.
Fact there was a jumper block in the radio to select either
the 7270 (6.3V) or the 7271 (13.5V) tube. I never actually
saw a 7271 and eventually the source of the 7270 dried up
so the Corp took them out of service and replaced them with
the RF Comm Compact. Compact was the only name I ever saw
them referenced against and was a similar unit only 4 channel
and used a pair of 6146's in the finals. There was also a
companion matching Linear Amp that was installed with the
SB-6F at base locations. All in all they were impressive
looking when installed in a comm center for the time.
Also I never worked on those units. Only on the freestanding
units. Maybe they cranked back the power and got better
service out of the finals when paired with the linear amp.
Anyway all I can say is be careful with the final if yours
is still good cause many a radio got scraped because of that
tube. I kept a pristine example with desktop case that I
rescued from the dumpster because of a bad final with the
thought of someday redesigning it for use of other tubes.
But with all the other toys to play with these days why
bother. Especially for a limited use channelized radio.
If any other vendor used the 7270/7271 I never came across it.
Maybe RCA made it special for RF Comm ????
Also before closing .... another example of an RF product that
had a troublesome final is the VHF FM Model RF-400 series.
While being clever for the time the 400 series used an 8509
quick heat 2V filament version of the 5894 fed off a winding
of the DC/AC inverter module. Whether it was an RF Comm design
issue or what if you got a radio on the bench with no output
better reach on the shelf for a new 8509 cause there was a
pretty good bet that final had cracked. GE and Motorola had
failures of their 5894/8643 finals but not on the RF Comm
scale of the 8509. Or at least that was my experience.
It was so bad someone (can't remember the vendor now) made
a drop in solid state final to replace the 8509. After that
they were pretty decent radios. I always thought they had
good receivers and when they scrapped the fleet I kept back
a few to use as monitors. But as Bob said, that was then and
now days all this stuff is considered useless. What all these
units really offer these days are parts for those that still
like to build. There are some sweet parts in these models
but again how many "TONS" of parts do we need to keep for
that last project since most of us (Thankfully) are getting
up there in age. That is the hard question to answer and is
one that so far I'm doing poorly at determining as can be
noted from the swelling of the door on the storage shed.
But as the dumpster diver motto goes .... Better to have and
not need then to need and not have so that's why it's so hard
not to check the trash bins on a regular basis .... Hehehe.

Skip WB4GMQ

-----Original Message-----
From: Boatanchors [mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of Bob
Groh
Sent: Wednesday, December 07, 2016 11:13 AM
To: Jack Antonio; BoatAnchors QTH
Subject: Re: [Boatanchors] RF Comm SB-6F

That is a bit of a step back in time!  I worked at RF Communications
(Rochester, NY) back in the day (i.e. from 1967 to 1977 when I went to
Heathkit) as a design engineer.  The SB-6F was even before my time - must
have been one of the first products to have come out (at the time I started
there, they had only been in business for a few years - RF Comm was started
by 4 engineers from General Dynamics - also in Rochester). It probably uses
same basic circuitry as the later 12 channel unit so, if you can find a
manual for it, that might be a starting point.  I used to have a few pieces
of RF Comm gear and manuals but all long gone. I would suspect your radio
is, regretfully, just a possible source of used parts.  Tubes, power
transformer, etc. As I get older (luckily getting older is still
happening), I increasingly have to admit that some old gear just has zip
value and that, because I really need to get stuff out of the house, the
only way out is to tear it down, sell what I can, scrap what I can and
throw away the rest.  Ugly but reality.  Best of luck with your new radio.

73
Bob Groh, WA2CKY

On Wed, Dec 7, 2016 at 10:15 AM, Jack Antonio <scr287 at att.net> wrote:

> One of these found its way to me. It is a
> 6 channel crystal controlled rack mount
> sideband transceiver. I literally saved
> ir from the scrap pile.
>
> And I'm on the fence about it.
>
> Half of me looks forward to the challenge of
> waking it up and making it play, but,
> the other half says I don't really need another
> project, and what am I going to do with it once
> its done? It doesn't really fit into my collection.
>
> So either.....
>
> One. Does anyone have the manual, or at least a schematic
> to get started on doping it out? It looks like it has a
> gazillion remote control terminals on the back. On line
> searches turned up nothing but an ad for what looks
> like the 12 channel maritime version.
>
> OR....
>
> Two.  Would anyone like to have it? Cost would be only
> for shipping. It is heavy, so shipping would not be
> cheap from central Georgia.
>
> Thanks
>
> Jack Antonio
> WA7DIA/4
> ______________________________________________________________