, November 24, 2004 8:14 PM
Subject: Re: [AMRadio] AM Usage with Linear AMPS
> QST for February 1956 in the Technical Topics section has a nice three
page
> write up on the use of Linear Amplifiers for AM. It starts on page 39.
>
> " This leads to the rule of thumb that on a.m
QST for February 1956 in the Technical Topics section has a nice three page
write up on the use of Linear Amplifiers for AM. It starts on page 39.
" This leads to the rule of thumb that on a.m. the carrier power output
that can be obtained from a linear amplifier is equal to half the rated
dissip
Donald Chester wrote:
It doesn't get any better either. With modulation the dissipation does
not decrease even though the efficiency increases at the peak power
levels. The carrier power is still there 100% of the time at 30%
efficiency. The audio is in the form of separate side bands that
It doesn't get any better either. With modulation the dissipation does not
decrease even though the efficiency increases at the peak power levels. The
carrier power is still there 100% of the time at 30% efficiency. The audio
is in the form of separate side bands that is additional power that
Geoff/W5OMR wrote:
When you tune up you tune it for max output at the 200 watt level with
full drive. At that tune setting the tube will be around 60% efficient.
Assuming Class C about 60 to 70% yes.
No. Class C is typically 70 to 75%. 60 to 65% is more likely for linear
(AB1/AB2) opera
, November 23, 2004 6:25 AM
To: Discussion of AM Radio
Subject: RE: [AMRadio] AM Usage with Linear AMPS
I thought that the WRL DuaoBander mobile was only SSB.
On 22 Nov 2004 at 22:11, John Coleman, ARS WA5BXO wrote:
> My experience (which is very little when it come to these sweep tube
> rigs) i
- Original Message -
From: "Brian Carling" <[EMAIL PROTECTED]>
To: "Discussion of AM Radio"
Sent: Tuesday, November 23, 2004 6:25 AM
Subject: RE: [AMRadio] AM Usage with Linear AMPS
> I thought that the WRL DuaoBander mobile was only SSB.
it is.
>
- Original Message -
From: "John Coleman, ARS WA5BXO" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>; "'Discussion of AM Radio'"
Sent: Monday, November 22, 2004 10:11 PM
Subject: RE: [AMRadio] AM Usage with Linear AMPS
> My experience (whi
On 22 Nov 2004 at 23:40, [EMAIL PROTECTED] wrote:
> Yaesu's instructions were "don't hold key down for more than 10 sec on
> tune
> up!" Otherwise - POP! Voice is a low duty cycle signal. In SSB
> service
> the average dissipation level can be kept within reasonable limits unless
> heavy
n Carling
> Sent: Monday, November 22, 2004 9:55 PM
> To: Discussion of AM Radio
> Subject: RE: [AMRadio] AM Usage with Linear AMPS
>
> Aren't there a lot of commercially built amateur radio linear
> amplifiers and RF finals that exceeded he manufacturers MAX
> Pdi
strips
> securing the tank coil tend to soften and droop at 50 watts RF output when
> on 160 meters. Maybe I actually am getting closer to 30% PLATE efficiency on
> AM.
>
> Regards,
> Jim Candela
> WD5JKO
>
> -Original Message-
> From: [EMAIL PROTECTED]
>
> > When you tune up you tune it for max output at the 200 watt level with
> > full drive. At that tune setting the tube will be around 60% efficient.
>
> Assuming Class C about 60 to 70% yes.
No. Class C is typically 70 to 75%. 60 to 65% is more likely for linear
(AB1/AB2) operation.
> I
The plate efficiency at full output under practical conditionsis
usually of the order of 50 to 65 per cent. With less than the
full output, the efficiency is proportional to the driving
voltage. When the signal to be amplified is a carrier wave
modulated 100 per cent, the carrier amplitude is h
In a message dated 11/22/04 7:56:07 PM, [EMAIL PROTECTED] writes:
> One thinks of MANY sweep tubes rated for so-called Pdiss of 16
> watts and 20 watts that are regularly run at hundreds of watts of
> RF! The tubes don't seem to melt.
>
> I think of the ubiquitous 6JS6C with a rating of 30 watt
Sweep tubes are a little different animal. They are designed for high
peak power levels in TV sweep circuits. SSB has a pretty high peak to
average power level. The average power is only in the order of 10 to 20%
of pep. Unless you run heavy processing and then the sweep tubes will
take a dive.
.
Regards,
Jim Candela
WD5JKO
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Behalf Of Gary Schafer
Sent: Monday, November 22, 2004 9:23 PM
To: [EMAIL PROTECTED]; Discussion of AM Radio
Subject: Re: [AMRadio] AM Usage with Linear AMPS
Brian,
What he is saying is
Hi Brian:
Consider what the efficiency is with no drive. The tube is drawing
current and has voltage therefore it has input power but no output.
Efficiency is 0%.
As input drive is applied the efficiency increases but so does the plate
current. The trick is to reach the 25% power point (or 50 Vo
Aren't there a lot of commercially built amateur radio linear
amplifiers and RF finals that exceeded he manufacturers MAX
Pdiss rathings over the years, by adding a COOLING FAN to take
away the extra heat?
One thinks of MANY sweep tubes rated for so-called Pdiss of 16
watts and 20 watts that a
On 22 Nov 2004 at 22:23, Gary Schafer wrote:
> Brian,
>
> What he is saying is: you need to have the 811A tuned up at 200 watts
> output on cw or pep for a 50 watt carrier out. (pep is 4 times carrier)
AH ha - I thought we were talking INPUT.
For 50 watts per tube to this Quad 811A amplifier,
I've got to get in on this HIHI.
Some readers may not fully understand what you guys or talking
about.
So I will try to confuse it all some more. HIHI
Plate dissipation is the heat that the plate of a tube is
emitting.
The manufacture of the tube has what is known as max plate dis
I don't know, I never had any linear amps.
I suppose you can run them as high as you like provided:
The plate dissipation is not exceeded (ccs45 watts, icas 65 watts per tube),
The modulation peaks don't get cut off,
The power supply can take the constant current and peaks.
The actual class of
Brian,
What he is saying is: you need to have the 811A tuned up at 200 watts
output on cw or pep for a 50 watt carrier out. (pep is 4 times carrier)
When you tune up you tune it for max output at the 200 watt level with
full drive. At that tune setting the tube will be around 60% efficient.
On 22 Nov 2004 at 20:23, [EMAIL PROTECTED] wrote:
> Going to shorten it's life considerably.
Theoretically maybe. Have you tried it. How can you know
for sure? Theory says a bumble bee can't fly. My 811A tubes
never burned up.
Where did you get your 30% number from? Who transmits
their AM w
On 22 Nov 2004 at 20:23, [EMAIL PROTECTED] wrote:
> Going to shorten it's life considerably.
Theoretically maybe. Have you tried it. How can you know
for sure? Theory says a bumble bee can't fly. My 811A tubes
never burned up.
> To properly adjust a linear amp for AM it is necessary to tune
On 22 Nov 2004 at 8:29, Brett gazdzinski wrote:
> Hu,
> How many 811a's in that amp?
>
> If 4, then I think the 811a has 65 watts of plate dissipation, 4x65=260.
> Cut 260 watts in half for 130 watts of carrier output, but I doubt I
> would
> run them
> that hard. The power supply likely wont
Hu,
How many 811a's in that amp?
If 4, then I think the 811a has 65 watts of plate dissipation, 4x65=260.
Cut 260 watts in half for 130 watts of carrier output, but I doubt I would
run them
that hard. The power supply likely wont take that much abuse, its designed
for
ssb service, very low dut
Ralph Rote:
> ... what are some operationa guidelines as regards i/p and o/p power, duty
cycle, cooling etc.
Ralph, ultimately what you're looking for is to run the amp at 1/4 the
maximum CW output of the amp. In other words, if the amp runs 800 W output
on CW you want to drive it to only 200 W o
Ralph,
A good rule of thumb to follow is simply this: the maximum carrier output
you're going to safely get out of your separate linear amplifier is limited
to HALF of the plate dissipation of your linear's tube(s)...
Example: I sometimes drive my HB 2 x 813 as a linear for AM. Each tube has a
pl
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