Re: {Collins} Drake TR4C With Collins 30L-1 Amp ??



Carl,

I will ignore the obvious temptation to chide you for ever wanting to drive
a nice Collins amp with a piece of Drake gear...  :-)
I wanted to make a couple of comments to add to the good advice you have
been getting.
First, adding the amp (requiring reducing the drive of the Drake) will then
yield you just around a 5 db gain from the Drake/Amp combo as opposed to the
Drake running full up at 200 watts. The Drake will be a lot happier though.
I want to add some info relative to the drive comment that Stan made. 60-70
watts is about the right ballpark.  - - But, after that there are a couple
of details to consider. The Drake is designed with a linear final PA with
the idle current adjusted for producing optimum linearity at about 200 watts
PEP. If you reduce loading on the drake, and load it for about 100 watts (I
would not go all the way down to 70 because you are risking non-linearity
from the driver - Drake - then), you should also reduce the idle current
adjustment on the Drake PA which is also set for optimal performance at 200
watts. The idle current will be too high if you are running the Drake finals
at only eventually 60-70 watts PEP. This will also impact distortion
negatively.
So, bottom line, reduce idle current and load only down to 100 watts to stay
in the linear range. Collins called out reducing the driver plate current
loading to 200 mA from the normal 250 mA and reducing idle current by 10 mA.
Finally, (no pun intended) once you have the Drake loaded for 100 watts
output, back off the carrier control and key the amp, and then bring in the
drive while carefully watching the rate of increase of the Pout vs the rate
at which you increase the carrier control (in tune mode).
You will see and "Feel" a linear rate of increase of the 30L-1 output as you
turn up the carrier control. Watch for the output "Knee" of the 30L-1. The
Pout rate of increase will start to fall off and the output of the amp will
not go up as fast as you are turning up the drive. As Stan said, this will
happen at about 60 watts drive. 
When you see this knee, that is where the 30L-1 starts to go non-linear. You
do not want your peak drive to even nudge into this area. Set your carrier
control just below - but BELOW - this knee so that Pout vs. Pin is linear.
This is where you should operate and then DO NOT change the carrier control
(mic Gain).
The power out when you talk and the Plate Current on the amp you see when
you talk, are impacted by meter ballistics and will not even come close to
the Pout you saw when you adjusted the carrier control, but it is there. You
can come close to seeing actual Pout PEP if you whistle up the amp, but even
then, you will not see it all. If you have a peak reading wattmeter, then
you should see the same result as in tune.
Set in that manner, your Drake Collins combo will produce nice results. You
will have to decide if the 5 db gain over your barefoot Drake is worth it.
Regards, Bill

Bill Carns, N7OTQ
Trustee K0CXX
President, Collins Collectors Association
Editor, Signal Magazine
Wimberley, TX
512 618 2762  (Cell)
512 847 7010  (Home)

 

-----Original Message-----
From: Collins [mailto:collins-bounces+wcarns=austin.rr.com@xxxxxxxxxxxxx] On
Behalf Of carl domanico
Sent: Saturday, June 21, 2014 6:50 PM
To: collins@xxxxxxxxxxxxx
Subject: {Collins} Drake TR4C With Collins 30L-1 Amp ??

Hello to everyone in the group..Recently I picked up a a Drake Station TR4C
, AC-4 , MS-4 all in Excellent Condition.Now I also have a Collins 30 L-1
Amplifier here and I have a couple of questions to pose to the group that
all you pro's out there could help me out with ! First and foremost does it
make sense to use the 30L-1 with the TR4C as an exciter ?? I noticed that in
the Drake Manual they mention the power Rating of the TR4C really does not
warrant the use of an amplifier unless it is at least 1000 Watts and
preferable 2000 Watts..The TR4C has a power rating of 300 Watts PEP
input.When i tuned it up in the X-CW mode on 7.300 MHz..into a Bird Dummy
load Both my Drake W4  and Bird 43 showed 200 Watts.and they say in the
manual that in the X-CW mode the screen Voltage is reduced to prevent those
sweep tubes from getting too hot ! So My question 1 ) Is the gain worth it
exciting the amp with the TR4C ? 2 ) I wonder if anyone can give me a Step
by Step procedure to connect the two units ? Notice the Drake has no Relay
switching plug on the rear which I can plug into the 30L-1 ?? As far as ALC
would I leave that disconnected and just be careful not to over drive the
30L-1.thats if I even know where the ALC is on the Drake !! Last but not
least would you have to build some sort of attenuator pad to go between the
output of the TR4C and Input of the 30L-1..I know that I've never seen this
combination in the 30 or so years I've been useing radios !! So maybe there
is good reason for that.?? Anyway people any and all input shall and will be
greatly appreciated !!

Thanks 
Carl
WB2PVY
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