] wrote:

However, her question has piqued my curiousity, and I'll ask the rrab
readers to answer one of mine: why were the transmitters of "twin"
receiver/transmitter combos, such as the R-4/T-4 pair, designed with
separate supplies?

Look at a T4-X for example and look at the PS. Then try to figure out
how to fit that same PS in with the xmtr.
:-)

-Bill

] wrote:

However, her question has piqued my curiousity, and I'll ask the rrab
readers to answer one of mine: why were the transmitters of "twin"
receiver/transmitter combos, such as the R-4/T-4 pair, designed with
separate supplies?

Look at a T4-X for example and look at the PS. Then try to figure out
how to fit that same PS in with the xmtr.
:-)

-Bill

As one who designs and builds tube audio amps, the hum and noise
performance is greatly improved.

This may seem moot for a xceiver, but even a -60dB hum can unbalance a
7360 rather annoyingly.

--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca

As one who designs and builds tube audio amps, the hum and noise
performance is greatly improved.

This may seem moot for a xceiver, but even a -60dB hum can unbalance a
7360 rather annoyingly.

--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca

On Sun, 12 Oct 3903 00:01:12,
] wrote:

I just bought a TR-4 for my brother's birthday, and his wife asked me
why it needs a separate power supply. I explained that mobile and
fixed stations need different supplies, and so they're sold
separately.

However, her question has piqued my curiousity, and I'll ask the rrab
readers to answer one of mine: why were the transmitters of "twin"
receiver/transmitter combos, such as the R-4/T-4 pair, designed with
separate supplies?

If there are any historians reading this, I'd appreciate your
insights into why the design went in this direction.

TIA.

73, Bill W1AC

(My email address is in the headers)

Some were, some weren't. 32S3, SB-400, HT-44, T-599.

de ah6gi/4



On Sun, 12 Oct 3903 00:01:12,
] wrote:

I just bought a TR-4 for my brother's birthday, and his wife asked me
why it needs a separate power supply. I explained that mobile and
fixed stations need different supplies, and so they're sold
separately.

However, her question has piqued my curiousity, and I'll ask the rrab
readers to answer one of mine: why were the transmitters of "twin"
receiver/transmitter combos, such as the R-4/T-4 pair, designed with
separate supplies?

If there are any historians reading this, I'd appreciate your
insights into why the design went in this direction.

TIA.

73, Bill W1AC

(My email address is in the headers)

Some were, some weren't. 32S3, SB-400, HT-44, T-599.

de ah6gi/4



In article ,
] writes:

why were the transmitters of "twin"
receiver/transmitter combos, such as the R-4/T-4 pair, designed with
separate supplies?

First off, some receiver/transmitter pairs put the power supply in side the
transmitter as well as the receiver. This was more common before about 1960
than after. In fact, before WW2 it was common for receivers to have separate
supplies!

Several reasons:

Size/weight/minaturization: The power supply for a 100-200 watt transmitter
like the T-4 is much larger and heavier than the power supply for the matching
R-4. In order to keep the tx and rx to the same size and about the same weight,
the transmitter power supply was made external. As rigs got smaller, this
became more and more of an issue because most power supply parts could not be
made much smaller.

Heat: The heat produced in tube rigs is always a concern, and transmitters
produce lots from the final tubes to begin with. Making the power supply
external eliminated having to deal with the heat from it.

Magnetic fields: The power transformer and filter choke(s) have magnetic fileds
around them which can induce hum in various components and wiring. The fields
are much stronger in a transmitter like the T-4X because the power level is
much higher than in a receiver.

Cost/manufacturing considerations: IIRC, the same power supply that was used
with the TR-4 was used with the T-4. This saved the Drake folks the cost of
designing a power supply into the T-4. It also reduces the *apparent* cost of
the T-4X. (Same sort of marketing gimmick that has an item priced at $599.99
instead of $600 - they think we're so math-impaired that we'll be more inclined
to buy the "less expensive" item.)

Homebrewing/existing supply/upgrading: Some hams might want to save money by
building their own power supplies (they aren't complicated). Others might have
a TR-4/AC-4 setup, and then decide to get the R-4/T-4 compbo for the shack and
use the TR-4 mobile. Such a move would require buying a DC supply for the car
and just the R-4/T-4X for the shack, since the AC supply was already on hand.
Brand loyalty is/was a big thing with manufacturers, so being able to offer
inducements like that was a selling point. (And the TR-4 could still be used in
the shack).

73 de Jim, N2EY

In article ,
] writes:

why were the transmitters of "twin"
receiver/transmitter combos, such as the R-4/T-4 pair, designed with
separate supplies?

First off, some receiver/transmitter pairs put the power supply in side the
transmitter as well as the receiver. This was more common before about 1960
than after. In fact, before WW2 it was common for receivers to have separate
supplies!

Several reasons:

Size/weight/minaturization: The power supply for a 100-200 watt transmitter
like the T-4 is much larger and heavier than the power supply for the matching
R-4. In order to keep the tx and rx to the same size and about the same weight,
the transmitter power supply was made external. As rigs got smaller, this
became more and more of an issue because most power supply parts could not be
made much smaller.

Heat: The heat produced in tube rigs is always a concern, and transmitters
produce lots from the final tubes to begin with. Making the power supply
external eliminated having to deal with the heat from it.

Magnetic fields: The power transformer and filter choke(s) have magnetic fileds
around them which can induce hum in various components and wiring. The fields
are much stronger in a transmitter like the T-4X because the power level is
much higher than in a receiver.

Cost/manufacturing considerations: IIRC, the same power supply that was used
with the TR-4 was used with the T-4. This saved the Drake folks the cost of
designing a power supply into the T-4. It also reduces the *apparent* cost of
the T-4X. (Same sort of marketing gimmick that has an item priced at $599.99
instead of $600 - they think we're so math-impaired that we'll be more inclined
to buy the "less expensive" item.)

Homebrewing/existing supply/upgrading: Some hams might want to save money by
building their own power supplies (they aren't complicated). Others might have
a TR-4/AC-4 setup, and then decide to get the R-4/T-4 compbo for the shack and
use the TR-4 mobile. Such a move would require buying a DC supply for the car
and just the R-4/T-4X for the shack, since the AC supply was already on hand.
Brand loyalty is/was a big thing with manufacturers, so being able to offer
inducements like that was a selling point. (And the TR-4 could still be used in
the shack).

73 de Jim, N2EY

Heat: The reduced heat of a separate power supply also helped inprove the
frequency stability of the VFO. Until the advent of PLL circuits, frequency
stability was a major design consideration.

Heat: The reduced heat of a separate power supply also helped inprove the
frequency stability of the VFO. Until the advent of PLL circuits, frequency
stability was a major design consideration.