Re: Tuning a pi-Network Output
Mike,
I've read where there are some circuits that can have individual circuitry for each band that allows for "tweaking" the neutralization on each of the lower bands.? Of course, the Drake circuits don't have that but I presume it is possible.
I'm currently only using the watt meter in my MN-2000 for CW as I don't have a mic wired up for the TR-4 yet.
Thanks, Barry - N4BUQ
Barry and Steve,
?
Neutralizing an RF amplifier is occurs ONLY on the frequency
it is performed on. This typically is done on 10 meters on an amateur
radio transmitter/transceiver final amplifier.
?
Once the neutralizing adjustment is performed on 10 meters, do NOT
make any changes to the neutralizing circuit on any lower band. You
will not see the same maximum RF output at maximum PLATE current
dip on any lower band. This is NORMAL and should NOT mean you have
to make changes to the neutralizing circuit on the lower bands.
?
Follow the manufacturer's transmitter loading/tuning instructions
in the operator's manual.
?
The Drake MN-2000 watt meter is an "average watt meter". Do not
expect to see "SSB PEP" RF levels on the MN-2000 watt meter.
?
73
Mike W5RKL
?
?
?
|
Re: Tuning a pi-Network Output
Barry and Steve,
?
Neutralizing an RF amplifier is occurs ONLY on the frequency
it is performed on. This typically is done on 10 meters on an amateur
radio transmitter/transceiver final amplifier.
?
Once the neutralizing adjustment is performed on 10 meters, do NOT
make any changes to the neutralizing circuit on any lower band. You
will not see the same maximum RF output at maximum PLATE current
dip on any lower band. This is NORMAL and should NOT mean you have
to make changes to the neutralizing circuit on the lower bands.
?
Follow the manufacturer's transmitter loading/tuning instructions
in the operator's manual.
?
The Drake MN-2000 watt meter is an "average watt meter". Do not
expect to see "SSB PEP" RF levels on the MN-2000 watt meter.
?
73
Mike W5RKL
?
?
?
|
Re: Could be the end of my Tr7
Have you tried anything as simple as using an ohmmeter to test continuity between the +10R source and the +10R at the filter board? I mean to the actual +10R point on the board¡
Gary
W0DVN
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On Apr 4, 2025, at 9:28?PM, Jim Shorney via groups.io <jimNU0C@...> wrote:
?
A word on the nomenclature. Sources marked as +10V are +10 always. +10R is receive only, +10T is transmit only. As Stan commented the R and T voltages are switched on the Transmit Exciter board. The text descriptions of every board are very good. It will be to your benefit to study them. The +10T/R switching transistors can be considered to be three-legged fuses. They will pop from even a momentary short to ground while the bus is ON. So be very careful when making live measurements.
Don't bin it. The TR7 is very repairable. And worthy of it.
On Fri, 04 Apr 2025 18:31:26 -0700
"Mike Davidsohn G3ZCC via groups.io" <mike@...> wrote:
Hi everyone,sad news.
I traced the issue,finally, no 10R getting to the filter board, not even on the socket.
Checked the 10R on the psu board, exactly 10.0v
Removed The front panel and the two banks of switches. No 10R but 13.6 v. On A and B
The switching seems,to work though.
At a complete,loss now.
Last gasp the circuit is hard to read where do the switches derive the 10 R from? Just in case I am missing something.
It's the dustbin if I can't find the problem
Thanks
Mike G3ZCC
--
73
-Jim
NU0C
|
Re: Another TR7 Journey begins
Yay! Progress! What you have found is definitely not normal. Total hack job. If the ALC is indeed disabled that could be a cause of oscillation if the predriver gain has been set too high. Running a TR7 at 200+ Watts output is asking for trouble. Drake over-designed for a conservative 150W PEP output for good reasons. On Fri, 04 Apr 2025 12:07:21 -0700 "Bill NZ0T via groups.io" <nz0tham@...> wrote: I think I found the cause of the watt/SWR meter not working is.? Somebody in the past soldered a white wire from the ground terminal of R2001 directly to ground bypassing C2001 which is supposed to be the path to ground.? Also R2001 does not vary from 32K ohms throughout it's range.? R2002 does vary from 0 to 30K ohms as it should.? R2001 is the forward? wattmeter adjustment and R2002 is the reflected wattmeter adjustment.? I wonder if this wasn't some kind of crude mod to disable the watt/SWR meter which would disable ALC allowing the rig to transmit to it's full capabilty way past the normal 100 to 130 watts?? Also I should mention that the live (opposite from the ground side) wire from R2001 was soldered directly to the terminal instead of to the board.? So somebody did something weird in the past.
I attached a couple of pics of the area.? Looks like I'll need to find a 30K pot to replace the bad one along with C2001.? Has anyone ever seen anything like this?
73, Bill NZ0T
-- 73 -Jim NU0C
|
Re: Could be the end of my Tr7
A word on the nomenclature. Sources marked as +10V are +10 always. +10R is receive only, +10T is transmit only. As Stan commented the R and T voltages are switched on the Transmit Exciter board. The text descriptions of every board are very good. It will be to your benefit to study them. The +10T/R switching transistors can be considered to be three-legged fuses. They will pop from even a momentary short to ground while the bus is ON. So be very careful when making live measurements. Don't bin it. The TR7 is very repairable. And worthy of it. On Fri, 04 Apr 2025 18:31:26 -0700 "Mike Davidsohn G3ZCC via groups.io" <mike@...> wrote: Hi everyone,sad news.
I traced the issue,finally, no 10R getting to the filter board, not even on the socket.
Checked the 10R on the psu board, exactly 10.0v
Removed The front panel and the two banks of switches. No 10R but 13.6 v. On A and B
The switching seems,to work? though.
At a complete,loss now.
Last gasp the circuit is hard to read where do the switches derive the 10 R from? Just in case I am missing something.
It's the dustbin if I can't find the problem
Thanks
Mike G3ZCC -- 73 -Jim NU0C
|
Re: Could be the end of my Tr7
+10R is provided by Q307 on the transmit exciter board.? Sounds like
you probably have a bad transistor or other problems on the transmit
exciter board.
If you want to get rid of it, you can send it to me :)
73
Stan
KM4HQE
On 4/4/25 20:31, Mike Davidsohn G3ZCC
via groups.io wrote:
toggle quoted message
Show quoted text
Hi everyone,sad news.
I traced the issue,finally, no 10R getting to the filter
board, not even on the socket.
Checked the 10R on the psu board, exactly 10.0v
Removed The front panel and the two banks of switches. No 10R
but 13.6 v. On A and B
The switching seems,to work? though.
At a complete,loss now.
Last gasp the circuit is hard to read where do the switches
derive the 10 R from? Just in case I am missing something.
It's the dustbin if I can't find the problem
Thanks?
Mike G3ZCC
?
?
|
Could be the end of my Tr7
Hi everyone,sad news.
I traced the issue,finally, no 10R getting to the filter board, not even on the socket.
Checked the 10R on the psu board, exactly 10.0v
Removed The front panel and the two banks of switches. No 10R but 13.6 v. On A and B
The switching seems,to work? though.
At a complete,loss now.
Last gasp the circuit is hard to read where do the switches derive the 10 R from? Just in case I am missing something.
It's the dustbin if I can't find the problem
Thanks?
Mike G3ZCC
?
?
|
Re: T-4XC "On" Decreases RX Performance?
Thanks Rob and Steve; I'll put this behavior down as "normal"?
--
Craig/W8CS
Greenville, SC
|
I couldn't find the relay in Garey's BOM for the T-4XC.? I have found the listing of the original relay in the TR-4C -- it is a P&B R10-E1-Y4-V2.5K
I can't see why they shouldn't be the same.? The keying circuits in the two sets are identical and switched to the 6FQ7 on both rigs.
Anyone with a T-4XC open could do us a favout by reporting back to the group as to the relay part number is.
73,
Steve Wedge, W1ES
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
|
Re: Tuning a pi-Network Output
I never got that far but I have learned to avoid "off" tuning positions with the RF TUNE control. Some of the rigs are more sensitive than others.
Steve Wedge, W1ES
Time flies like an arrow.? Fruit flies like a banana.
Sent with Proton Mail secure email.
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On Friday, April 4th, 2025 at 2:04 PM, n4buq <n4buq@...> wrote: When there are spurious oscillations in the PA tubes, is there a particular frequency this usually occurs? In other words, does changing bands change the frequency of the oscillation? I'm just wondering what frequency I might try listening to in order to hear them.
Thanks,
Barry - N4BUQ
It is NOT normal. It is a sign that the amplifier needs to be
neutralized. Plate dip and power peak should be simultaneous. The
coincidence of these two is a very sensitive measure of neutralization.
For the T-4 and some other models Drake specifies setting the
neutralization using the coincidence but if the neutralization is not
almost correct this may be a difficult adjustment to make. A better way
to check neutralization is to measure the feed through of drive power to
the plate by disconnecting the screens of tetrodes or the plates of
triodes. Use something sensitive like a receiver or scope to see what is
coming through, then set the neutralization adjustment to null it. Once
that is adjusted you can check the neutralization via the Drake method,
that is see if the plate dip and power peak are simultaneous.
There is a great deal of information on neutralizing on the web.
You should be familiar with the theory of what is being done. The idea
is roughly to eliminate any positive feedback through the tubes by means
of a sort of bridge circuit. It is done to prevent the tubes from
oscillating. If that happens the oscillation will be uncontrolled and
destroy the tubes. In general neutralization is more critical at higher
frequencies. You can get approximate neutralization at, say 20 meters,
and then check it at 10 meters making any small adjustments necessary.
BTW, this is not a matter of the type of circuit used to match the
output to the antenna, neutralization is necessary for any type of
output pi-network or otherwise.
On 4/3/2025 6:53 AM, n4buq wrote:
I don't think I've ever owned a power meter and now I have one in my MN-2000.
Tuning up my TR-4, I notice that maximizing the output power doesn't
necessarily coincide with the "dip" in plate current but, instead, seems to
occur on the "edge" of that dip. Is this normal?
From many, many years ago, with only a plate meter, I always adjusted with the
dip at its minimum value but now I'm wondering if that wasn't yielding maximum
power output. Furthermore, I presume that getting the dip first and then
tweaking for maximum output is the most efficient way to run. Is that correct?
Is what I'm seeing normal? I presume so but after all these years, I'm
beginning to wonder.
If it matters, I'm currently only tuning into a Drake dummy load.
Thanks,
Barry - N4BUQ --
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Re: Another TR7 Journey begins
I think I found the cause of the watt/SWR meter not working is.? Somebody in the past soldered a white wire from the ground terminal of R2001 directly to ground bypassing C2001 which is supposed to be the path to ground.? Also R2001 does not vary from 32K ohms throughout it's range.? R2002 does vary from 0 to 30K ohms as it should.? R2001 is the forward? wattmeter adjustment and R2002 is the reflected wattmeter adjustment.? I wonder if this wasn't some kind of crude mod to disable the watt/SWR meter which would disable ALC allowing the rig to transmit to it's full capabilty way past the normal 100 to 130 watts?? Also I should mention that the live (opposite from the ground side) wire from R2001 was soldered directly to the terminal instead of to the board.? So somebody did something weird in the past.
?
I attached a couple of pics of the area.? Looks like I'll need to find a 30K pot to replace the bad one along with C2001.? Has anyone ever seen anything like this?
?
73, Bill NZ0T  
|
Re: Transceive with DDS VFO
I have been using a DD-103 digital dial on my R4C to operate in transcieve mode with my T4XB for a number of years.? Works great.? I really like the digital frequency readout. Just be sure to set the proper offset for the R4C.? I'm using a "Y" connector on the injection line with no problems.
- Steve? W7SJT
"Always look for a positive solution then Improvise, Adapt, and Overcome" - U.S. Marine Corp
"There are no rules here!...We're trying to accomplish something!!" - Thomas Edison
"Someone may be born with more talent than you, but there is no excuse for them to work harder than you." - Anonymous
You are braver than you believe, stronger than you seem, and smarter than you think!" - Winnie the Pooh
?
On Thursday, April 3, 2025 at 09:54:48 PM MDT, Gary Follett via groups.io <xntrick1948@...> wrote:
In order to do what you suggest, you would need a device to offset the ¡°T¡± VFO signal to the transmitter operating frequency since the 2-C has no local oscillator or mixer to convert the VFO signal from the 5.0 to 5.5 MHz range to the transmitter operating frequency.?
Now one could possibly program a digital VFO such as yours to sense transmit status and automatically perform the offset in transmit. That would be a neat product for someone to produce!
Gary?
W0DVN
On Apr 3, 2025, at 1:49?PM, Gary WB6OGD via groups.io <winbladgary@...> wrote:
? Well, I have..? sort of.? I think you are missing some important steps though.
?
Signals available in an R-4 are the PTO (5-5.5MHz on all bands) or the INJ (11.1MHz above operating frequency).
The 2NT needs an on operating frequency (or sub-harmonic?) signal.
?
And don't forget you need a frequency offset of your desired cw audio tone.
?
I built a "transceive adapter" with an Arduino and Si5351 board.
I measure the PTO frequency, do a calculation, then program the Si5351.
?
I used it to transceive my 75S-3B with my T-4XB.? Worked slick.? I also modified my B-Line with Arduinos and Si5351s in both
R-4B and T-4XB and transceive by one-wire digital bus.
?
Can't just use a "T " connection but it is possible with some hardware and software creativity.
73,
Gary
WB6OGD
?
|
Re: T-4XC "On" Decreases RX Performance?
Hi Craig,
?
What you are observing all has to do with mixer injection levels and the source of 5645 kHz local oscillator (LO).??
?
The 100 Hz shift is occurring on SSB when the T-4XC is turned on. The 5645 kHz LO is now coming from the transmitter not the 5645 kHz LO in the receiver.? Assuming
the carrier oscillator in the transmitter is actually on the proper frequency, then you could adjust the 5645 kHz oscillator in the receiver to be on the same frequency.?
?
The TX carrier oscillator may or may not be properly centered for equal 300 Hz TX audio roll-off on both LSB and USB.? You can easily measure the RX 5645 kHz
LO at the LO jack near the rear S meter pot by using a counter.? Note that that the RX LO tends to drift down in frequency as much as 100 Hz as the receiver warms up.? The TX carrier oscillator may also have a similar warm-up frequency drift. ?
?
The change in S meter between separate operation and transceive on the R-4C or the T-4XC has to do with the pre-mix injection levels not being equal.? None
of the R-4/T-4 mixers are saturated from an LO injection level standpoint.? Thus a change in the LO source affects RX and TX gain.? It doesn¡¯t much affect sensitivity but it does affect the S meter and the AGC threshold.?
?
The basic design of the R-4 / T-4X came to market in 1965 with changes to the R-4A and then the B-Line and finally the C-Line.? Minor imperfections in a design
from 60 years ago now seem archaic, but at the time improvements in the 4-Line were major compared to a TR-4 and its limitations.? 160m didn¡¯t even exist in the TR-3/TR-4. ?Also we are blessed that all the WARC bands are available in any 4-Line with the addition
of a few (scarce) band crystals.
?
In a perfect world the injection levels would all be the same on all bands, but that rarely happens.? Similarly the two 5645 kHz oscillators drift around and
there isn¡¯t anything you can do about that either.
?
Rob, NC0B ??
?
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Show quoted text
From: [email protected] [mailto:[email protected]]
On Behalf Of Craig W8CS via groups.io
Sent: Friday, April 04, 2025 6:07 AM
To: [email protected]
Subject: [DRAKE-RADIO] T-4XC "On" Decreases RX Performance?
?
Not really a big deal but thought I would check in to see if this is common.?
R-4C tied into T-4XC in normal transceive config. I'll listen around on the R-4C for a while, and I'll turn on the T-4 if I think I'll be transmitting in the next few minutes.?
Immediate drop in RX signal by a few S-units. Rx signal also shifts in frequency by maybe 100Hz. I can even duplicate this with the 25KHz calibrator.?
Turning off T-4XC "lights up" the receiver again.?
|
Re: Tuning a pi-Network Output
When there are spurious oscillations in the PA tubes, is there a particular frequency this usually occurs? In other words, does changing bands change the frequency of the oscillation? I'm just wondering what frequency I might try listening to in order to hear them.
Thanks,
Barry - N4BUQ
toggle quoted message
Show quoted text
It is NOT normal. It is a sign that the amplifier needs to be
neutralized. Plate dip and power peak should be simultaneous. The
coincidence of these two is a very sensitive measure of neutralization.
For the T-4 and some other models Drake specifies setting the
neutralization using the coincidence but if the neutralization is not
almost correct this may be a difficult adjustment to make. A better way
to check neutralization is to measure the feed through of drive power to
the plate by disconnecting the screens of tetrodes or the plates of
triodes. Use something sensitive like a receiver or scope to see what is
coming through, then set the neutralization adjustment to null it. Once
that is adjusted you can check the neutralization via the Drake method,
that is see if the plate dip and power peak are simultaneous.
There is a great deal of information on neutralizing on the web.
You should be familiar with the theory of what is being done. The idea
is roughly to eliminate any positive feedback through the tubes by means
of a sort of bridge circuit. It is done to prevent the tubes from
oscillating. If that happens the oscillation will be uncontrolled and
destroy the tubes. In general neutralization is more critical at higher
frequencies. You can get approximate neutralization at, say 20 meters,
and then check it at 10 meters making any small adjustments necessary.
BTW, this is not a matter of the type of circuit used to match the
output to the antenna, neutralization is necessary for any type of
output pi-network or otherwise.
On 4/3/2025 6:53 AM, n4buq wrote:
I don't think I've ever owned a power meter and now I have one in my MN-2000.
Tuning up my TR-4, I notice that maximizing the output power doesn't
necessarily coincide with the "dip" in plate current but, instead, seems to
occur on the "edge" of that dip. Is this normal?
From many, many years ago, with only a plate meter, I always adjusted with the
dip at its minimum value but now I'm wondering if that wasn't yielding maximum
power output. Furthermore, I presume that getting the dip first and then
tweaking for maximum output is the most efficient way to run. Is that correct?
Is what I'm seeing normal? I presume so but after all these years, I'm
beginning to wonder.
If it matters, I'm currently only tuning into a Drake dummy load.
Thanks,
Barry - N4BUQ
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Re: T-4XC "On" Decreases RX Performance?
That's what I meant to say.? Was sitting at the lunch counter with my phone.? That's my obvious first check when something like this happens, because that switch won't affect the receiver unless the TX is on.
If you pull out the INJ cable, does it still change?? How about the PTO OSC cable?
When you turn on the TX, do you hear the relay click?
Steve Wedge, W1ES
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
On Friday, April 4th, 2025 at 12:25 PM, Craig W8CS via groups.io <craig_severson@...> wrote:
The "Transceive" switch on the T-4XC is set to "rcvr"
--
Craig/W8CS
Greenville, SC
|
Re: T-4XC "On" Decreases RX Performance?
The "Transceive" switch on the T-4XC is set to "rcvr"
--
Craig/W8CS
Greenville, SC
|
Re: T-4XC "On" Decreases RX Performance?
Is your receiver function set to RCVR?
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Fri, Apr 4, 2025 at 08:06, Craig W8CS via groups.io < craig_severson@...> wrote:
Not really a big deal but thought I would check in to see if this is common.?
?
R-4C tied into T-4XC in normal transceive config. I'll listen around on the R-4C for a while, and I'll turn on the T-4 if I think I'll be transmitting in the next few minutes.?
?
Immediate drop in RX signal by a few S-units. Rx signal also shifts in frequency by maybe 100Hz. I can even duplicate this with the 25KHz calibrator.?
?
Turning off T-4XC "lights up" the receiver again.?
?
Common??
--
Craig/W8CS
Greenville, SC
|
Re: Tuning a pi-Network Output
The GE tubes are equivalent to the Sylvanias.? No problems.
Steve Wedge, W1ES
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
On Friday, April 4th, 2025 at 8:42 AM, n4buq <n4buq@...> wrote:
This one has GE tubes.? Not sure if those are considered the "good" ones (like the Sylvanias) or if they need more capacitance.? Hopefully I'll get to the neutralization adjustment today or tomorrow.
Thanks, Barry - N4BUQ
From: "Steve Wedge, W1ES/4 via groups.io" <w1es@...>
To: "DRAKE-RADIO" <[email protected]>
Sent: Friday, April 4, 2025 7:17:29 AM
Subject: Re: [DRAKE-RADIO] Tuning a pi-Network Output
IIRC, you need a slightly higher value parallel cap with RCA tubes.
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Thu, Apr 3, 2025 at 9:50 PM, Jim Shorney via groups.io <jimNU0C@...> wrote:
I would say your PA is not neutralized, although IIRC the parallel capacitor needed to be changed for a certain brand of tube. Someone else probably knows.
On Thu, 3 Apr 2025 21:25:37 -0400 (EDT)
"n4buq via groups.io" <n4buq@...> wrote:
> I then noticed the neutralization capacitor is fully open. I don't know if that's necessarily a bad thing but I can't help but think it should have at least a little capacitance.
--
73
-Jim
NU0C
|
Re: PTO makes scraping sound
This weekend I should be able to figure it out because I have off on Saturday and Sunday.
I will try to share with the group of what I find.
Mark
|
Re: Tuning a pi-Network Output
This one has GE tubes.? Not sure if those are considered the "good" ones (like the Sylvanias) or if they need more capacitance.? Hopefully I'll get to the neutralization adjustment today or tomorrow.
Thanks, Barry - N4BUQ
From: "Steve Wedge, W1ES/4 via groups.io" <w1es@...>
To: "DRAKE-RADIO" <[email protected]>
Sent: Friday, April 4, 2025 7:17:29 AM
Subject: Re: [DRAKE-RADIO] Tuning a pi-Network Output
IIRC, you need a slightly higher value parallel cap with RCA tubes.
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Thu, Apr 3, 2025 at 9:50 PM, Jim Shorney via groups.io <jimNU0C@...> wrote:
I would say your PA is not neutralized, although IIRC the parallel capacitor needed to be changed for a certain brand of tube. Someone else probably knows.
On Thu, 3 Apr 2025 21:25:37 -0400 (EDT)
"n4buq via groups.io" <n4buq@...> wrote:
> I then noticed the neutralization capacitor is fully open. I don't know if that's necessarily a bad thing but I can't help but think it should have at least a little capacitance.
--
73
-Jim
NU0C
|
Jim Shorney
Mike Davidsohn G3ZCC
Craig W8CS
Rob Sherwood
Mark N2DMI