Hi Mike
The power supply I am using came with the amp. It is enclosed in a
rectangular case which is a sort of lattice material. It sits on the floor
as it is quiet heavy. I am not sure if it is the stock one or not. The amp
as I received it had many mods done to it including one so it will work on
all bands.
It is my first amp and I am not really sure how to evaluate it fully yet
although I am attempting to absorb the manual.
As a example I cannot find anywhere in the manual as to what type of meter
is the power meter (watts) not sure if it is rms or peak reading. Also not
sure if it is reading output to the antenna or input to the circuit.
Bob AD5VJ
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com]
> On Behalf Of Michael Tope
> Sent: Tuesday, April 06, 2010 9:00 AM
> To: amps@contesting.com
> Subject: Re: [Amps] DRAKE L-7
>
> Bob,
>
> Are you using a stock L-7PS or L-4PS power supply with your L-7? The
> numbers you are getting don't seem to make sense. The L-7 runs the
> 3-500Zs in zero-bias mode similar to the SB-220. The resting plate
> voltage in the SSB position is something along the lines of 2500 to
> 2700
> Vdc. Using your numbers, 3200 volts x 640mA = 2050 Watts DC input x 65%
> efficiency = 1330 Watts.. If the 1800 watt number were real, your
> efficiency would have to be on the order of 90%. Also, at 1800 watts
> output with only 100 watts drive, the L-7 would need close to 13dB
> gain.
> That isn't a realistic number unless the anode voltage really is up
> around 3600 Vdc in which case I think you do get a little more gain,
> but
> regardless of gain, efficiency is never going to be any greater than
> 70%. The gain of the L-7 is not much more than 10dB at stock plate
> voltage. Using a realistic numbers for anode voltage, I get 2300 Vdc x
> 640mA = 1472 Watts DC input x 0.65 = 957 Watts @ 9.8 dB gain.
>
> Using my L-7 just now on 160 meters with 90 watts CW drive (Diawa reads
> 90W, FT1K meter reads 100W), I got 2100 Vdc x 700mA x 0.65 = 950 Watts
> =
> 10.3dB gain. The actual reading on my Diawa CN-720B was 900 watts which
> would correspond to 10.1dB gain. The L-7 power meter read 1000 watts. I
> am not claiming that any of my numbers are super accurate, but they are
> consistent with what I would expect from a pair of zero-biased 3-500Zs.
>
> FWIW, the anode voltage reading on my other L-7 reads higher even when
> I
> use the same power supply. I think this is from drift in the carbon
> composition resistors used in the voltage divider in the anode voltage
> metering circuit. Sounds like your watt meter calibration may have
> drifted as well.
>
> 73, Mike W4EF..........
>
>
> On 4/5/2010 7:38 PM, Bob AD5VJ wrote:
> > I would however like to run this by you guys:
> >
> > I am looking at the meter right now in ssb mode and it shows at idle
> 3600
> > Plate Volts and zero plate amps.
> >
> > I know to get to power out to the antenna I multiply the ep by ip and
> take
> > away about 40 percent since ep and ip is input power not the output
> power to
> > the antenna.
> >
> > Leaving the amp in ssb mode and then placing my TS-850SAT in tune
> mode
> > (50watts output) at key down the plate voltage shows 3350 plate
> volts, the
> > Drake Plate current shows 580ma when the plate is dipped to minimum
> and the
> > load is increased to full output until no further change can be
> detected and
> > output is maximum and voltage and current are stabilized.
> >
> > Then I transmit in rtty (pulsing using the mark - no data) at a drive
> level
> > of 100w (alc at midpoint - processor off) - leaving the Drake in ssb
> mode on
> > transmit, I retune the amp using the mark pulse and the plate voltage
> drops
> > to 3200 volts and the plate current shows 640ma of current with a
> power
> > indication of almost 1800 watts output on the drake power meter.
> >
> > I think the power meter is supposed to be reading power out to the
> antenna
> > but not sure it could be power input to the plate. Doesn't the output
> power
> > in this case seem a little high on the drake avg power meter?
> >
> > Since this is an avg power meter, it would be 1.3 or so times this on
> voice
> > transmissions for PEP seems awfully high.
> >
> > Bob AD5VJ
> >
> >
> > _____________________________________________
> > From: Bob AD5VJ [mailto:ad5vj@ad5vj.com]
> > Sent: Saturday, February 06, 2010 4:47 PM
> > To: Amps@contesting.com
> > Subject: DRAKE L-7
> >
> >
> > Can someone pls tell me why when I am loading up my antenna
> > with my Drake L-7, the Keyer on my IC-761 gets stuck. I have to
> depress the
> > VOX then turn the rig on and off to get it to unstuck.
> >
> > Any ideas?
> >
> > 73,
> > Bob AD5VJ
> >
> >
> > _______________________________________________
> > Amps mailing list
> > Amps@contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
> >
> >
> >
>
>
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