"RadioGuy" wrote in message
...
The thought came to me the other day whle thinking about the cost of
6JB6's
nearly $100 for a set; I paid $18.00 for a matched set of three at AES
back
in the 1970's and I got plenty of spares. Why did Drake use those cheap
ass
sweep tubes in their final instead of the old standard 6146 to begin with?

Sure, back then it seemed in vogue to use sweep tubes in amateur gear
(yea,
sure, Swan gear...) but as I recall, we thought that Drake was kinda
cheesy
to use those tubes anyway. I gonna stick my neck out and say Drake
engineering wasn't the end all that the youngsters think nowadays.

(Yes... I have a complete Drake station (including amplifier)---the whole
line-up in pristine, vitrually unused condition in crisp factory cartons
including accessories, catalogs and a handful of the right-angle
Switchcraft
microphone (black cap) and key (red cap) plugs that Drake originally
supplied not that PL-whatever. Original owner---me---so it's not sour
grapes.)

RG


When the Drake vacuum tubes rigs were designed, the sweep tubes were being
mass produced for the TV market and WERE very cheap.

However, there may have been another reason.
If I remember correctly, the advertised power output of the TR3/TR4 and the
T4X, etc was higher than the 180 watts input/100 watts output that was
typical from a pair of 6146's. A pair or trio of sweep tubes is capable of
a much high PEP rating than is a pair of 6146's - albeit maybe not for
long....


Thus there was a marketing race at the time.
Each manufacturer was claiming higher and higher power levels for their
"bareful" rigs.
Swan was surely the champ with that - claiming up to 700 watts input and
about 500 watts output for some of their rigs.
Drake didn't go so far but probably still wanted to claim more power than
the 180 watts input/100 watts output of Collins and Heathkit.

National also used sweep tubes in their transceivers. For example, they used
the 6GJ5 in their NCX-3 and the NCX-5 and at first were conservative with
their rating, also claiming just 180 watts in/about 100 watts out. Later
they joined the PEP race with their NCX-500, etc.

Thus part of the answer may simply be marketing.

73,

Doug/WA1TUT

DOUGLAS wrote in message
k.net...

"RadioGuy" wrote in message
...
The thought came to me the other day whle thinking about the cost of
6JB6's
nearly $100 for a set; I paid $18.00 for a matched set of three at AES
back
in the 1970's and I got plenty of spares. Why did Drake use those cheap
ass
sweep tubes in their final instead of the old standard 6146 to begin
with?

Sure, back then it seemed in vogue to use sweep tubes in amateur gear
(yea,
sure, Swan gear...) but as I recall, we thought that Drake was kinda
cheesy
to use those tubes anyway. I gonna stick my neck out and say Drake
engineering wasn't the end all that the youngsters think nowadays.

(Yes... I have a complete Drake station (including amplifier)---the
whole
line-up in pristine, vitrually unused condition in crisp factory cartons
including accessories, catalogs and a handful of the right-angle
Switchcraft
microphone (black cap) and key (red cap) plugs that Drake originally
supplied not that PL-whatever. Original owner---me---so it's not sour
grapes.)

RG


When the Drake vacuum tubes rigs were designed, the sweep tubes were being
mass produced for the TV market and WERE very cheap.

However, there may have been another reason.
If I remember correctly, the advertised power output of the TR3/TR4 and
the
T4X, etc was higher than the 180 watts input/100 watts output that was
typical from a pair of 6146's. A pair or trio of sweep tubes is capable
of
a much high PEP rating than is a pair of 6146's - albeit maybe not for
long....


Thus there was a marketing race at the time.
Each manufacturer was claiming higher and higher power levels for their
"bareful" rigs.
Swan was surely the champ with that - claiming up to 700 watts input and
about 500 watts output for some of their rigs.
Drake didn't go so far but probably still wanted to claim more power than
the 180 watts input/100 watts output of Collins and Heathkit.

National also used sweep tubes in their transceivers. For example, they
used
the 6GJ5 in their NCX-3 and the NCX-5 and at first were conservative with
their rating, also claiming just 180 watts in/about 100 watts out. Later
they joined the PEP race with their NCX-500, etc.

Thus part of the answer may simply be marketing.

73,

Doug/WA1TUT

Well said Doug... I forgot about that---there was a power race back in the
70's. Some of us did get 'big eyes' when Swan came out with the 500. And
now that you mentioned it, I remember some of us looking at the Drake's 300
watt (input) tranceiver as a selling point ( I think the power race ended
somewhat with the advent of solidstate and the fairly uniform 100 watt
specification).

Drake had a problem meeting their power claim later for the TR-4C/CW/CW+RIT
(I don't know about the older models), resulting from the changes to FCC
regs regarding spectral purity (97.73). Drake had a notice that the final
could not be loaded to more that 350 ma. so as to remain within the new
spec. The older tune-up procedure reached maximum output with a plate
current of 380 to 500 ma. I am not going to venture to say if the 6JB6's
had anything to do with having to go to a reduced output as opposed to using
the 6146's in their place regarding spectral purity but I sure would like to
hear comments on this point.

I like the note in the operators manual regarding tune-up:

3-7. TUNE UP. Do not allow plate current to exceed 0.1 Amperes for more
that 6 seconds with the PLATE control not tuned for minimum plate current or
maximum output.

CAUTION Failure to observe the warning above will result in rapid final
amplifier tube deterioration due to excessive plate dissipation.

RG