Did you check the filament fuse?
73
Mike W5RKL
On 5/26/25 4:33 PM, Mark N2DMI via
groups.io wrote:
toggle quoted message
Show quoted text
I was trying to re-seat the LSB bulb to the chassis because
the bulb was intermittent. In doing so I think the positive side
of the bulb housing touched ground some how because when I
turned the TR-4CW back on and the amp meter light, frequency
light, LSB, and USB lights were not lit. Then the filament fuse
blew! I replaced the wire with #26 AWG and pulled both LSB and
USB out and re-seated them and made sure nothing was shorting to
ground. I quickly turned on the rig but still those lights would
not light. The only light that I get is the round red light on
the right side of the frequency read out. I connected my power
supply to my other TR-4CW and that rig works OK so the power
supply is still good. Not sure what is going on?
?
Mark
|
I was trying to re-seat the LSB bulb to the chassis because the bulb was intermittent. In doing so I think the positive side of the bulb housing touched ground some how because when I turned the TR-4CW back on and the amp meter light, frequency light, LSB, and USB lights were not lit. Then the filament fuse blew! I replaced the wire with #26 AWG and pulled both LSB and USB out and re-seated them and made sure nothing was shorting to ground. I quickly turned on the rig but still those lights would not light. The only light that I get is the round red light on the right side of the frequency read out. I connected my power supply to my other TR-4CW and that rig works OK so the power supply is still good. Not sure what is going on?
?
Mark
|
I should have clarified my statement by saying:
" The transmit speech amplifier's audio "alone" does not
flow
through the IF filters."
73
Mike W5RKL
On 5/26/25 4:19 PM, Mike W5RKL via
groups.io wrote:
toggle quoted message
Show quoted text
The transmit speech amplifier's audio does not flow through the IF
filters.
The "IF" filters are for "RF" not "AF".
The DSSC (Double Sideband Suppressed Carrier) signal from
the BM (Balance Modulator) flows through the LSB IF Filter (side
band switch must be set to "X" which selects the LSB filter).
To operate AM with a TR4 or any of the TR and T4/T4X<any>
transceivers or transmitter, the Side Band switch must be in
the "X" position which selects the "LSB" filter;
Any plug inserted into the "KEY" socket must be removed or
the plug shorted to ground in order to receive and transmit AM.
The same applies when operating SSB, the KEY socket must be
shorted to ground.
PTT and VOX work the same in AM mode as they do in SSB mode.
AM in the Drake TR series radios operates CCSM (Controlled
Carrier Screen Modulation). The Modulator stage controls the
level of the final amp's RF output. With no audio from the speech
amplifier applied to the Modulator stage, the Modulator stage
keeps the final
amplifier's RF output at a low level, 8 to 10 watts. As the
operator speaks
into the microphone, the speech amplifier audio applied to the AM
modulator,
varies the final tubes screen voltage at the same rate as the
speech amp
audio, hence CCSM AM is produced.
73
Mike W5RKL
On 5/26/25 12:43 PM, Gary WB6OGD via
groups.io wrote:
In thinking about this, I think I see what is going on.
?
Audio goes the the screen modulator which modulates the
gain of the final..?? I think this is that same as the old
novice rigs like
the T-60 or DX-40.?? The carrier does go up and down with
the modulation.? But you can hear it with a normal AM (diode)
detector.
Drake marketing made it seem like something new and
special, but it's really just old fashioned screen modulation.
?
I think the audio does not go through the crystal filter,
only the carrier and it is not modulated.? It is fully DSB and
full fidelity should result.
?
Right?
73,
Gary
WB6OGD
|
The transmit speech amplifier's audio does not flow through the IF
filters.
The "IF" filters are for "RF" not "AF".
The DSSC (Double Sideband Suppressed Carrier) signal from
the BM (Balance Modulator) flows through the LSB IF Filter (side
band switch must be set to "X" which selects the LSB filter).
To operate AM with a TR4 or any of the TR and T4/T4X<any>
transceivers or transmitter, the Side Band switch must be in
the "X" position which selects the "LSB" filter;
Any plug inserted into the "KEY" socket must be removed or
the plug shorted to ground in order to receive and transmit AM.
The same applies when operating SSB, the KEY socket must be
shorted to ground.
PTT and VOX work the same in AM mode as they do in SSB mode.
AM in the Drake TR series radios operates CCSM (Controlled
Carrier Screen Modulation). The Modulator stage controls the
level of the final amp's RF output. With no audio from the speech
amplifier applied to the Modulator stage, the Modulator stage keeps
the final
amplifier's RF output at a low level, 8 to 10 watts. As the operator
speaks
into the microphone, the speech amplifier audio applied to the AM
modulator,
varies the final tubes screen voltage at the same rate as the speech
amp
audio, hence CCSM AM is produced.
73
Mike W5RKL
On 5/26/25 12:43 PM, Gary WB6OGD via
groups.io wrote:
toggle quoted message
Show quoted text
In thinking about this, I think I see what is going on.
?
Audio goes the the screen modulator which modulates the gain
of the final..?? I think this is that same as the old novice
rigs like
the T-60 or DX-40.?? The carrier does go up and down with the
modulation.? But you can hear it with a normal AM (diode)
detector.
Drake marketing made it seem like something new and special,
but it's really just old fashioned screen modulation.
?
I think the audio does not go through the crystal filter,
only the carrier and it is not modulated.? It is fully DSB and
full fidelity should result.
?
Right?
73,
Gary
WB6OGD
|
Re: Drake C Line For Sale
Hello Burt, still have this for sale?
joe
WA2L
Acworth, GA
|
From my experience, stick to GE or Sylvania.? Do not mix brands unless you can spot the differences in the internal frame.? There are two or three different frame types.
Steve Wedge, W1ES
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
On Monday, May 26th, 2025 at 1:26 PM, David via groups.io <david.w5xu@...> wrote:
I would stay with one brand. Do not mix. RcA also sells a longer version of the tube that will not fit so make sure you are getting the shorter version.
David Assaf III
W5XU VP8RXU
Gentleman:
For a TR-4C, is there any difference between 6JB6A brands? I'm
buying 3 of them and there's some well known brands available such
as Sylvania, GE and RCA. RCA a bit cheaper. All NIB/NOS.
Any recommendations?
73
Marcus PY2PLL + PY3CRX
GG66rf
|
In thinking about this, I think I see what is going on.
?
Audio goes the the screen modulator which modulates the gain of the final..?? I think this is that same as the old novice rigs like
the T-60 or DX-40.?? The carrier does go up and down with the modulation.? But you can hear it with a normal AM (diode) detector.
Drake marketing made it seem like something new and special, but it's really just old fashioned screen modulation.
?
I think the audio does not go through the crystal filter, only the carrier and it is not modulated.? It is fully DSB and full fidelity should result.
?
Right?
73,
Gary
WB6OGD
|
I would stay with one brand. Do not mix.? RcA also sells a longer version of the tube that will not fit so make sure you are getting the shorter version.
David Assaf III
W5XU??? VP8RXU
Gentleman:
For a TR-4C, is there any difference between 6JB6A brands? I'm
buying 3 of them and there's some well known brands available such
as Sylvania, GE and RCA. RCA a bit cheaper. All NIB/NOS.
Any recommendations?
73
Marcus PY2PLL + PY3CRX
GG66rf
|
Gentleman:
For a TR-4C, is there any difference between 6JB6A brands? I'm
buying 3 of them and there's some well known brands available such
as Sylvania, GE and RCA. RCA a bit cheaper. All NIB/NOS.
Any recommendations?
73
Marcus PY2PLL + PY3CRX
GG66rf
|
This is the way most modern rigs create AM. It is SSB with carrier and has an emission designation. The audio response is limited by the bandwidth of the IF filter and the opposite sideband is attenuated by the filter. It's kind of like vestigial sideband, which TV guys will understand, but the opposite sideband would be VERY vestigial. If this is the actual method used in the TRx rigs than the screen modulation would be a long time constant gain control signal and not an audio modulation. OTOH if the screen is actually the AM modulation then audio into the balanced modulator should be removed in AM mode. Or maybe it is a mix of both. I don't know. Maybe I'll RTFM later.... On Mon, 26 May 2025 08:56:04 -0700 "Gary WB6OGD via groups.io" <winbladgary@...> wrote: SO, if the carrier is shifted but the signal still goes through the filter..
It would be mostly DSB but with (greatly?) reduced fidelity, wouldn't it?? Or does one sideband have the bass and the other sideband
have the treble? -- 73 -Jim NU0C
|
The following items have been added to the Files area of the [email protected] group.
By: Jim Shorney <jimNU0C@...>
Description:
RCA CA3053 differential amp IC data sheet
|
Re: Drake SPR-4 50 Khz IF and 50 Khz Filter alignment
It has been mentioned that T15 and T16 tune broadly. It may be that you will see little or no change with the adjustments. Are you sure your alignment tool isn't just spinning in a cracked slug? Those two adjustments are in the last stage of the IF so they will be dealing with relatively strong signal levels. It may be that you need a very weak signal to see any change. Perhaps a SINAD meter and a signal down into the noise would be a better method. Your voltages on Q25 looked about right. I don't think there is a problem there. IC1 is a differential amplifier for IF circuits, sort of like an op amp. Drawing attached. I found two different pinouts, but this one from an old RCA data book I believe to be correct. I will upload the full data sheet to the group Files section. It might be interesting to just skip for now T15 and T16 and try the adjustments for L11, L12, L13, and L14 so see if you have any change. You should be able to follow the DC voltage from the collector of Q25 to the AVC line and through Q14 and IC1 to see AVC action as you change the signal level. Disconnecting the gate of Q14 from the AVC line should eliminate possible leakage in Q14 as a problem. The AVC line should work but the S meter will not of course. Disclaimer: I have no SPR4 experience. Just throwing things up against the wall to see if anything sticks. Hopefully this will spur some comments from ops who have actual experience. On Mon, 26 May 2025 04:00:23 -0700 "enriqueeeeee2001 via groups.io" <enriqueeeeee2001@...> wrote: I am trying to make a full alignment to a Drake SPR-4 but I have come across with an issue in the first step that the procedure manual indicates, any guidance would be greatly appreciated.
According to the point 5.3.1. I have connected a VTVM and the signal generato where indicated, I can adjust T17 for zero beat? but when adjusting T15 and T16 for maximum deflection there is no a slight movement neither in the voltmeter nor in the S-meter.
Due to the high impedance of the circuit , could be causing this the FET and IC located in the S-meter PCB?? I have seen modifications that recommend to replace them:
Anyone has had this problem before? Or could be caused by other elements. -- 73 -Jim NU0C
|
Thinning the shack Drake TR2770 transceiver for sale
The other night I was in the shack, and looked around at all the stuff I've gathered together over the years. It's time to let some of this stuff go. So, I've decided to sell my Drake TR2770. This is a rather rare two meter rig with a UHF receiver. Yeah, marketing really missed the mark with this product. It's been so long since I used it, but I'm thinking it does multimode, too. I set it up to talk on the local repeater.
?
Anyway... comes with the manual, power cord but no microphone. I rarely call something mint, but damn, this is about a close as mint as you can get.
?
I'm asking $375 plus shipping
?
?
I'm Mike, WB8VGE
|
Mike,
Thank you for that.? I definitely missed that last sentence in the "KEY jack" paragraph.? I guess I wasn't expecting to see something regarding AM mode there.
Barry - N4BUQ
Barry,
Yes, you have to remove the 1/4" plug from the KEY socket or short
the 1/4" plug
when operating AM. This is clearly stated on page 16 paragraph "6"
titled "KEY"
in the TR4 manual (see "KEY" socket discussed in the TR4C manual
below). The
same KEY plug is the same in the TR4C and TR4CW as it is in the TR4.
"Key
being close" means to short the KEY socket or pull the CW key/keyer
1/4" plug
from the KEY socket. If you do not remove or short the 1/4" plug at
the KEY socket
then the transmitter is disabled in ALL mode and AM receiver will
not work.
If you use a J38 straight key that has the slide switch, simply move
the slide switch
so it shorts the J38 key terminals.
Yes, PTT and VOX work the same in AM mode as they do in SSB mode.
73
Mike W5RKL
On 5/26/25 8:39 AM, n4buq via groups.io
wrote:
Just to help me understand this:
To enable receive mode, it is necessary to close the key
circuit but one is still not transmitting.
To transmit, either PTT needs to be closed or VOX enabled.
Looking at the schematic, I think that's correct but would
like to confirm.
Thanks,
Barry - N4BUQ
The
TR3, TR4, TR4C, and TR4CW transceivers operate "CCSM"
(Controlled
Carrier Screen Modulation) AM in one side band only. The
side band switch
must be kept in "X" which limits the AM transmit in one side
band.
In AM transmit without speaking into the microphone, the AM
Modulator reduces the
final tube Screen voltage, allowing an initial low level RF
output of approximately
8 to 10 watts. As you speak into the microphone, the speech
amplifier audio is
applied to the AM Modulator causing the AM Modulator's
output to vary the
final tube screen voltage at the same rate as the speech
amplifier's audio, hence
CCSM AM transmit.
Operating AM, the XMTR GAIN control should be adjusted to
limit the peak plate current
indication of 200 to 250ma (0.2 to 0.25 amps) since transmit
AGC is not used in AM.
73
Mike W5RKL
On 5/25/25 9:43 PM, n4buq via
groups.io wrote:
I was about half-way through writing a reply to you
when I decided to, yet again, read the section on AM
operation.? That's when I realized that I had
mistakenly been trying to receive in X-AM with the key
inserted and open.? I was thinking that closing the
key (or removing the key plug from the jack) would
cause rig to start transmitting a carrier, similarly
to how a fully plate-modulated transmitter would but
that's not the case.? Since it uses CSSM, it only
transmits when audio is supplied from the mic (at
least that's the way I understand it); otherwise, it's
effectively in receive mode.? I tried this and,
somewhat to my surprise, AM receive is working.? I
feel like such a klutz.
Thanks for all the replies to this.? It finally set
in.? I now want to recheck those tube voltages with
the rig set up this way.? I suspect the cathode and
grid voltages will be much closer to what's in the
chart.
Barry - N4BUQ
The TR-3 uses the a product detector for AM
reception, and needs to be switched to SSB for
receive, but on the? various TR-4, TR-4C, and
TR-4Cw's I have used on AM for both transmit and
receive, the key must be unplugged, or the key
closed when using AM and the mode switch remains
in AM for both transmit and receive.? The same
rule applies for SSB transmit.? Since I operate
also operate CW, I usually rubber band one of my
bugs to one side when operating phone on either
mode. You'll hear the T/R relay click when you
first close the circuit, but it releases just as
fast.
|
Richard,
Interesting..
?
I've never even thought of using a Drake on AM.? When I got my General in 1965, AM is all I had.? I couldn't wait to join the modern
sidebanders!
?
SO, if the carrier is shifted but the signal still goes through the filter..
?
It would be mostly DSB but with (greatly?) reduced fidelity, wouldn't it?? Or does one sideband have the bass and the other sideband
have the treble?
?
73,
Gary
WB6OGD
?
?
?
|
Barry,
Yes, you have to remove the 1/4" plug from the KEY socket or short
the 1/4" plug
when operating AM. This is clearly stated on page 16 paragraph "6"
titled "KEY"
in the TR4 manual (see "KEY" socket discussed in the TR4C manual
below). The
same KEY plug is the same in the TR4C and TR4CW as it is in the TR4.
"Key
being close" means to short the KEY socket or pull the CW key/keyer
1/4" plug
from the KEY socket. If you do not remove or short the 1/4" plug at
the KEY socket
then the transmitter is disabled in ALL mode and AM receiver will
not work.
If you use a J38 straight key that has the slide switch, simply move
the slide switch
so it shorts the J38 key terminals.
Yes, PTT and VOX work the same in AM mode as they do in SSB mode.
73
Mike W5RKL
On 5/26/25 8:39 AM, n4buq via groups.io
wrote:
toggle quoted message
Show quoted text
Just to help me understand this:
To enable receive mode, it is necessary to close the key
circuit but one is still not transmitting.
To transmit, either PTT needs to be closed or VOX enabled.
Looking at the schematic, I think that's correct but would
like to confirm.
Thanks,
Barry - N4BUQ
The
TR3, TR4, TR4C, and TR4CW transceivers operate "CCSM"
(Controlled
Carrier Screen Modulation) AM in one side band only. The
side band switch
must be kept in "X" which limits the AM transmit in one side
band.
In AM transmit without speaking into the microphone, the AM
Modulator reduces the
final tube Screen voltage, allowing an initial low level RF
output of approximately
8 to 10 watts. As you speak into the microphone, the speech
amplifier audio is
applied to the AM Modulator causing the AM Modulator's
output to vary the
final tube screen voltage at the same rate as the speech
amplifier's audio, hence
CCSM AM transmit.
Operating AM, the XMTR GAIN control should be adjusted to
limit the peak plate current
indication of 200 to 250ma (0.2 to 0.25 amps) since transmit
AGC is not used in AM.
73
Mike W5RKL
On 5/25/25 9:43 PM, n4buq via
groups.io wrote:
I was about half-way through writing a reply to you
when I decided to, yet again, read the section on AM
operation.? That's when I realized that I had
mistakenly been trying to receive in X-AM with the key
inserted and open.? I was thinking that closing the
key (or removing the key plug from the jack) would
cause rig to start transmitting a carrier, similarly
to how a fully plate-modulated transmitter would but
that's not the case.? Since it uses CSSM, it only
transmits when audio is supplied from the mic (at
least that's the way I understand it); otherwise, it's
effectively in receive mode.? I tried this and,
somewhat to my surprise, AM receive is working.? I
feel like such a klutz.
Thanks for all the replies to this.? It finally set
in.? I now want to recheck those tube voltages with
the rig set up this way.? I suspect the cathode and
grid voltages will be much closer to what's in the
chart.
Barry - N4BUQ
The TR-3 uses the a product detector for AM
reception, and needs to be switched to SSB for
receive, but on the? various TR-4, TR-4C, and
TR-4Cw's I have used on AM for both transmit and
receive, the key must be unplugged, or the key
closed when using AM and the mode switch remains
in AM for both transmit and receive.? The same
rule applies for SSB transmit.? Since I operate
also operate CW, I usually rubber band one of my
bugs to one side when operating phone on either
mode. You'll hear the T/R relay click when you
first close the circuit, but it releases just as
fast.
|
Just to help me understand this:
To enable receive mode, it is necessary to close the key circuit but one is still not transmitting.
To transmit, either PTT needs to be closed or VOX enabled.
Looking at the schematic, I think that's correct but would like to confirm.
Thanks, Barry - N4BUQ
From: "Mike W5RKL via groups.io" <mikew5rkl@...>
To: "DRAKE-RADIO" <[email protected]>
Sent: Monday, May 26, 2025 1:00:35 AM
Subject: Re: [DRAKE-RADIO] TR-4 AM Mode
The TR3, TR4, TR4C, and TR4CW transceivers operate "CCSM"
(Controlled
Carrier Screen Modulation) AM in one side band only. The side band
switch
must be kept in "X" which limits the AM transmit in one side band.
In AM transmit without speaking into the microphone, the AM
Modulator reduces the
final tube Screen voltage, allowing an initial low level RF output
of approximately
8 to 10 watts. As you speak into the microphone, the speech
amplifier audio is
applied to the AM Modulator causing the AM Modulator's output to
vary the
final tube screen voltage at the same rate as the speech amplifier's
audio, hence
CCSM AM transmit.
Operating AM, the XMTR GAIN control should be adjusted to limit the
peak plate current
indication of 200 to 250ma (0.2 to 0.25 amps) since transmit AGC is
not used in AM.
73
Mike W5RKL
On 5/25/25 9:43 PM, n4buq via groups.io
wrote:
I was about half-way through writing a reply to you when I
decided to, yet again, read the section on AM operation.?
That's when I realized that I had mistakenly been trying to
receive in X-AM with the key inserted and open.? I was
thinking that closing the key (or removing the key plug from
the jack) would cause rig to start transmitting a carrier,
similarly to how a fully plate-modulated transmitter would but
that's not the case.? Since it uses CSSM, it only transmits
when audio is supplied from the mic (at least that's the way I
understand it); otherwise, it's effectively in receive mode.?
I tried this and, somewhat to my surprise, AM receive is
working.? I feel like such a klutz.
Thanks for all the replies to this.? It finally set in.? I
now want to recheck those tube voltages with the rig set up
this way.? I suspect the cathode and grid voltages will be
much closer to what's in the chart.
Barry - N4BUQ
The TR-3 uses the a product detector for AM reception,
and needs to be switched to SSB for receive, but on the?
various TR-4, TR-4C, and TR-4Cw's I have used on AM for
both transmit and receive, the key must be unplugged, or
the key closed when using AM and the mode switch remains
in AM for both transmit and receive.? The same rule
applies for SSB transmit.? Since I operate also operate
CW, I usually rubber band one of my bugs to one side when
operating phone on either mode. You'll hear the T/R relay
click when you first close the circuit, but it releases
just as fast.
|
Drake SPR-4 50 Khz IF and 50 Khz Filter alignment
I am trying to make a full alignment to a Drake SPR-4 but I have come across with an issue in the first step that the procedure manual indicates, any guidance would be greatly appreciated.
?
According to the point 5.3.1. I have connected a VTVM and the signal generato where indicated, I can adjust T17 for zero beat? but when adjusting T15 and T16 for maximum deflection there is no a slight movement neither in the voltmeter nor in the S-meter.
?
Due to the high impedance of the circuit , could be causing this the FET and IC located in the S-meter PCB?? I have seen modifications that recommend to replace them:
?
?
Anyone has had this problem before? Or could be caused by other elements.
?
?
?
?
?
?
?
?
?
|
This is a little confusing.? The X position allows the carrier to be shifted so it can pass through the sidebar filter.? It is explained in the handbook.? The same system is used in the T4B series.?? ? ?The AM is NOT single sideband,? it is double sideband.? The difference is Thea the carrier is varied in proportion to the modulation so that it is essentially 100% modulated at all levels.? Of course not in the absence of a modulating signal but down to very low levels.? As a result, the average level remains nearly constant and is compatible with a linear amplifier giving similar efficiency to a carrier suppressed SSB signal.? It is interpreted by a conventional AM receiver as AM.? To jeep the AVC from pumping too much? a compromise must be made with the minimum level of carrier transmitted.? This method allows AM with nearly the same PEP as SSB to be transmitted.?? This same system has been adopted for broadcast use to increase the power efficiency of transmitters.? If done carefully it's capable of reasonable fidelity.
toggle quoted message
Show quoted text
-------- Original message -------- From: "Mike W5RKL via groups.io" <mikew5rkl@...> Date: 5/25/25 11:00 PM (GMT-08:00) Subject: Re: [DRAKE-RADIO] TR-4 AM Mode
The TR3, TR4, TR4C, and TR4CW transceivers operate "CCSM"
(Controlled
Carrier Screen Modulation) AM in one side band only. The side band
switch
must be kept in "X" which limits the AM transmit in one side band.
In AM transmit without speaking into the microphone, the AM
Modulator reduces the
final tube Screen voltage, allowing an initial low level RF output
of approximately
8 to 10 watts. As you speak into the microphone, the speech
amplifier audio is
applied to the AM Modulator causing the AM Modulator's output to
vary the
final tube screen voltage at the same rate as the speech amplifier's
audio, hence
CCSM AM transmit.
Operating AM, the XMTR GAIN control should be adjusted to limit the
peak plate current
indication of 200 to 250ma (0.2 to 0.25 amps) since transmit AGC is
not used in AM.
73
Mike W5RKL
On 5/25/25 9:43 PM, n4buq via groups.io
wrote:
I was about half-way through writing a reply to you when I
decided to, yet again, read the section on AM operation.?
That's when I realized that I had mistakenly been trying to
receive in X-AM with the key inserted and open.? I was
thinking that closing the key (or removing the key plug from
the jack) would cause rig to start transmitting a carrier,
similarly to how a fully plate-modulated transmitter would but
that's not the case.? Since it uses CSSM, it only transmits
when audio is supplied from the mic (at least that's the way I
understand it); otherwise, it's effectively in receive mode.?
I tried this and, somewhat to my surprise, AM receive is
working.? I feel like such a klutz.
Thanks for all the replies to this.? It finally set in.? I
now want to recheck those tube voltages with the rig set up
this way.? I suspect the cathode and grid voltages will be
much closer to what's in the chart.
Barry - N4BUQ
The TR-3 uses the a product detector for AM reception,
and needs to be switched to SSB for receive, but on the?
various TR-4, TR-4C, and TR-4Cw's I have used on AM for
both transmit and receive, the key must be unplugged, or
the key closed when using AM and the mode switch remains
in AM for both transmit and receive.? The same rule
applies for SSB transmit.? Since I operate also operate
CW, I usually rubber band one of my bugs to one side when
operating phone on either mode. You'll hear the T/R relay
click when you first close the circuit, but it releases
just as fast.
|
The TR3, TR4, TR4C, and TR4CW transceivers operate "CCSM"
(Controlled
Carrier Screen Modulation) AM in one side band only. The side band
switch
must be kept in "X" which limits the AM transmit in one side band.
In AM transmit without speaking into the microphone, the AM
Modulator reduces the
final tube Screen voltage, allowing an initial low level RF output
of approximately
8 to 10 watts. As you speak into the microphone, the speech
amplifier audio is
applied to the AM Modulator causing the AM Modulator's output to
vary the
final tube screen voltage at the same rate as the speech amplifier's
audio, hence
CCSM AM transmit.
Operating AM, the XMTR GAIN control should be adjusted to limit the
peak plate current
indication of 200 to 250ma (0.2 to 0.25 amps) since transmit AGC is
not used in AM.
73
Mike W5RKL
On 5/25/25 9:43 PM, n4buq via groups.io
wrote:
toggle quoted message
Show quoted text
I was about half-way through writing a reply to you when I
decided to, yet again, read the section on AM operation.?
That's when I realized that I had mistakenly been trying to
receive in X-AM with the key inserted and open.? I was
thinking that closing the key (or removing the key plug from
the jack) would cause rig to start transmitting a carrier,
similarly to how a fully plate-modulated transmitter would but
that's not the case.? Since it uses CSSM, it only transmits
when audio is supplied from the mic (at least that's the way I
understand it); otherwise, it's effectively in receive mode.?
I tried this and, somewhat to my surprise, AM receive is
working.? I feel like such a klutz.
Thanks for all the replies to this.? It finally set in.? I
now want to recheck those tube voltages with the rig set up
this way.? I suspect the cathode and grid voltages will be
much closer to what's in the chart.
Barry - N4BUQ
The TR-3 uses the a product detector for AM reception,
and needs to be switched to SSB for receive, but on the?
various TR-4, TR-4C, and TR-4Cw's I have used on AM for
both transmit and receive, the key must be unplugged, or
the key closed when using AM and the mode switch remains
in AM for both transmit and receive.? The same rule
applies for SSB transmit.? Since I operate also operate
CW, I usually rubber band one of my bugs to one side when
operating phone on either mode. You'll hear the T/R relay
click when you first close the circuit, but it releases
just as fast.
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Mark N2DMI
joe braswell
Gary WB6OGD
David
Marcus PY2PLL
Jim Shorney
