Re: TR7 recommission stalls.
Hi Craig?
Sounds,like a plan.
Going to check those pin numbers again.
Will let you know tommorrow, what thevpins have on them.
Seem to remember 19/21 were 40 mhz.
Kind regards?
Mike
G3ZCC
?
|
Re: TR7 recommission stalls.
Hi Mike-
?
I just spent the last two weeks inside the PBT board before finding my issue. Per the alignment procedure, do you:
?
- Have 40MHz on pin 19??
- Have 53.695 MHz on pin 17?
- Have 5.645MHz on pin 40?
I do have a supposedly working PBT board arriving here next week that I bought from eBay, which I no longer need. Consider that for worst case.?
--
Craig/W8CS
Greenville, SC
|
? Tom
Thanks for your help, I did as you noted and adjusted R17, now it? reads 1900V LV no load and 2700V HV? no load, a little high on the HV but unless you think there is another issue I'm happy.
Now the funny thing is about 4 days ago that was the first thing I did, that is adjust R17 using the method you noted. However I first turned it a little to the right and then a little to the left and really did not see a change on the meter so I went in another direction, but it worked this time turning the amp off and adjusting just a little bit at at time. The first time I saw movement on the meter but I turned it in the wrong direction, so with about 4 times turning the amp on to read the meter and off to make the adjustment making certain the bleeders drained of any existing voltage I kept moving it little by little, then I had to move it back just a bit.
I'll tell you seeing that tiny adjustment is difficult, using a flashlight you have to get at the right angle or the light just reflects back into your eyes.
Thanks for your HELP Tom very much.
73 Tim
WB8UHZ
On Saturday, January 11, 2025 at 09:32:51 AM EST, amfone via groups.io <amfone20000@...> wrote:
OK Tom thanks for the advice I will do so, very much appreciated. I have the amp apart now I'll do so today.
Tim,?
If you¡¯re sure the meter itself is ok then tweak the pot to see if you can increase the reading on the L7 meter.?
Use a non conductive tool.
To be safe give it small adjustments with the amp off and
make sure the plate ¡°Ep button is pushed in¡± plate voltage meter is
reading ¡°0¡± (Capacitors discharged) before adjusting.?
You want to move it in the direction of ¡°More¡± resistance
(Wiper in the direction of the ground side) as one side is directly
grounded.?
CCW looking at the back of the amp.?
Then turn the amp on and check the reading.
Repeat as necessary.?
Tom
On Friday, January 10, 2025 at 06:15:43 PM EST, Thomas W9TAB via groups.io <electron@...> wrote:
Tim,?
If you¡¯re sure the meter itself is ok then tweak the pot to see if you can increase the reading on the L7 meter.?
Use a non conductive tool.
To be safe give it small adjustments with the amp off and make sure the plate ¡°Ep button is pushed in¡± plate voltage meter is reading ¡°0¡± (Capacitors discharged) before adjusting.?
You want to move it in the direction of ¡°More¡± resistance (Wiper in the direction of the ground side) as one side is directly grounded.?
CCW looking at the back of the amp.?
Then turn the amp on and check the reading.
Repeat as necessary.?
Tom
On Jan 10, 2025, at 4:49?PM, amfone via groups.io <amfone20000@...> wrote:
?
Tom I have two L7's and one L4B so I did not use anything to measure it against other than the meter on the other two amps, both of which read the proper voltage. I also used two different supplies as I have four all which
I have rebuilt. Using two different supplies the one L7 I'm working on read low in the LV and HV position. The other two amps with the same supplies read correctly.
73 Tim
WB8UHZ
On Friday, January 10, 2025 at 05:44:23 PM EST, Thomas W9TAB via groups.io <electron@...> wrote:
Tim,
What did you use to measure it with to compare against the meter in the amp??
Color TV HV probe, HV probe with DVM etc.?
I use a Fluke 80k-40 with a Fluke 87 DVM in my shop.?
Tom?
On Jan 10, 2025, at 11:33?AM, Evan via groups.io <k9sqg@...> wrote:
?
I typically see 1800 volts and 2500 volts BUT that is for my specific line voltage! ?Low line voltage results in low readings.
Tom
The B+ voltage is reading about 1500 to 1600 on the LV reading no load and about 2200 to 2300 on HV? no load. I took it out of line to work on it and can't give accurate numbers at this time but suffice to say it reads low.
I did not do the other adjustments.
Thanks Tim
On Thursday, January 9, 2025 at 09:35:48 PM EST, Thomas W9TAB via groups.io <electron@...> wrote:
Tim
I missed your response on an earlier post, how far off is the B+ voltage? (Measured vs indicated)?
How did the Grid / Plate current calibrations turn out??
(Verifying a 100% working meter)?
Tom W9TAB?
On Jan 9, 2025, at 5:08?PM, amfone via groups.io <amfone20000@...> wrote:
?
Tom I opened up the L7 today and the 2.2 meg resistors 8 of them rather than reading 17.6 Megs are actually reading 16.66 Meg. or just less than 5% off. Not sure if that is the problem perhaps? R17 is the issue, R17 is 10K and adjustable any
idea of where to get that little thing?
If you think I'm wrong on the dropping resistors and the effect they would have on the proper voltage reading let me know please.
Thanks 73 Tim
WB8UHZ
On Wednesday, January 8, 2025 at 11:19:24 AM EST, amfone via groups.io <amfone20000@...> wrote:
Thank you Thomas yes these are carbon style resistors that Drake used back in the day and over time they age, take in moisture etc. and change in value I'm hoping that is the issue as I purchased new resistors from Mouser.
Thank you
Tim
On Wednesday, January 8, 2025 at 09:43:20 AM EST, Thomas W9TAB via groups.io <electron@...> wrote:
Tim,
Carbon composition resistors typically increase in value over time due to absorbing moisture.?
That is the reason the voltage divider network resistance has increased causing the voltage to read low.?
Military spec publications identified this a long time ago and Allen Bradley recommended taking the resistors and putting them in an oven at 150F for 5 days to return them to spec.?
Naturally in your case it makes more sense to just replace them if you cannot adjust it with the potentiometer, after all, that¡¯s why it¡¯s there. ?
On Jan 7, 2025, at 10:47?PM, amfone via groups.io <amfone20000@...> wrote:
?
OK sorry for the mistake I used the term in reference to the meter not reading correctly.
73 Tim
WB8UHZ
On Tuesday, January 7, 2025 at 10:55:56 PM EST, Jim Shorney via groups.io <jimnu0c@...> wrote:
OK but please stop calling them shunts. They are series voltage dropping resistors. The only shunt is the pot. A shunt is a resistance across the meter terminals to increase the current value needed for a full scale reading.
On Wed, 8 Jan 2025 03:38:34 +0000 (UTC)
"amfone via groups.io" <amfone20000@...> wrote:
>? Jim thanks for your help regarding the location and the voltage requirements of the shunts.
--
73
-Jim
NU0C
|
Jim accurately describes the manner in which IMD is typically tested and reported ¡ª i.e., when two close-in signals produce an IMD product that exceeds the noise floor.? But it seems to me that the IMD inherent in just about any amplifier will actually raise
the noise floor, because any noise within the passband is causing some low-level IMD products that also appear within the passband.??
So the noise floor might be said to consist of two components, which we'll call Original Noise and IMD Noise.? When we reduce the RF gain, we're reducing the Signal and the Original Noise by the same amount, but reducing the IMD Noise faster, because of the
1:3 ratio between the Original Noise and the IMD Noise.
If we're considering just the noise floor of the receiver circuitry, this effect would be pretty small.? But if we consider band noise as a component of the Original Noise,? and consider how the IMD products of that band noise contribute to what we're calling
IMD Noise, the effect may not be so small, particularly on the low bands where most of us experience a lot of noise.? In this case, turning down the rf gain could make a noticeable contribution to the S/N ratio.? I think this is why Bob Heil's video is able
to show a marked increase in readability of an 80-meter QSO by turning down the rf gain.
Thoughts welcome.
Art Delibert, KB3FJO
toggle quoted message
Show quoted text
Jim, IMD? (3rd order intercept is calculated)? is easily measured on any RX.? On the Drake tube gear, like R4B / R4C, it was never outstanding to begin with.? The problem is the 2nd mixer, it doesn't have any dynamic range to begin with.? Rob Sherwood's
'fix' for that was the various roofing xtal filters....which work superb.? The roofing filters? will eliminate or partially eliminate? one of the 2 x offending? signals.....and bye bye IMD resulting from them.?
?
?On my yaesu FT-1000D? ?and also my FT-1000MP-MKV, after doing the W8JI noise blanker mod ( blanker is not totally shut off when switched off),? I can't find any IMD.? ?I need 2 x signals, both 50 db > S9, and 2khz apart,? to produce an IMD product equal
to the noise floor....and that's on the bench.? ?That's just not happening with any ant connected.? My noise floor is S2? to S8, depending on the band.? ?Ok, now any IMD is well below my noise floor...so it's a non issue, since I can't hear it.??
IF you reduce the RF gain a bunch..... the agc threshold INCREASES ........ and any IMD from 2 x loud, closely spaced signals will be BELOW the agc threshold.? ?So yeah, if u had zero band noise, and 2 x super loud, closely spaced signals on RX,? and could
actually? hear IMD, it will VANISH? if the RF gain is turned down.? ? It will also vanish if you insert some attenuation in the RX path.? ?The IMD will drop off at triple the value of the inserted attenuation.??
Jim? VE7RF
|
Good evening everyone.
The Tr7 has stopped working.
I have traced it to the PBT/REFERENCE board.
Have it fitted to extenders, all oscillators working fine except the 8.050, which does not appear to be working at all.
I think the manual has a typo on the number of the coils.1101?
I have also tried testing this by draping both the frequency counter and a gc rx listening on the frequency..
Manual not too clear (just my luck).
Anyone have any ideas?
Thanks in advance.
Mike
G3ZCC
?
|
Anyone interested in this memorabilia box 9x7x4 ? ? 
? Doug ?
|
Jim, IMD? (3rd order intercept is calculated)? is easily measured on any RX.? On the Drake tube gear, like R4B / R4C, it was never outstanding to begin with.? The problem is the 2nd mixer, it doesn't have any dynamic range to begin with.? Rob Sherwood's 'fix' for that was the various roofing xtal filters....which work superb.? The roofing filters? will eliminate or partially eliminate? one of the 2 x offending? signals.....and bye bye IMD resulting from them.?
?
?On my yaesu FT-1000D? ?and also my FT-1000MP-MKV, after doing the W8JI noise blanker mod ( blanker is not totally shut off when switched off),? I can't find any IMD.? ?I need 2 x signals, both 50 db > S9, and 2khz apart,? to produce an IMD product equal to the noise floor....and that's on the bench.? ?That's just not happening with any ant connected.? My noise floor is S2? to S8, depending on the band.? ?Ok, now any IMD is well below my noise floor...so it's a non issue, since I can't hear it.??
IF you reduce the RF gain a bunch..... the agc threshold INCREASES ........ and any IMD from 2 x loud, closely spaced signals will be BELOW the agc threshold.? ?So yeah, if u had zero band noise, and 2 x super loud, closely spaced signals on RX,? and could actually? hear IMD, it will VANISH? if the RF gain is turned down.? ? It will also vanish if you insert some attenuation in the RX path.? ?The IMD will drop off at triple the value of the inserted attenuation.??
Jim? VE7RF
|
Harbach PM-400 / L7 and bleeders
I'm looking for things in the shack that may need attention.
I bought this L7 in 2020 and noticed that one of the huge bleeder resistors was open.? I replaced it and noticed, like we all do, that the L7PS turns into a great room heater with those resistors in the circuit.? The amp was working before I reconnected the resistor amd I know that the 3W bleeders on the board are probably enough.? I know that these room-heaters are part of the ALC circuit.
I am also considering doing the bias change with the diodes (I do wish someone had a schematic of this, as I prefer seeing what I'm doing.
I've looked through past posts and don't see anything that matches, though I remember seeing discussions...
Any insights?
Steve Wedge, W1ES
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
|
I was looking forward to an explanation. We ask a simple question, "does the path have a heart?" Sometimes the path does not.
On Saturday, January 11, 2025 at 09:25:42 AM EST, Jim Shorney via groups.io <jimnu0c@...> wrote:
Now you are just being argumentative. It sounds like you are saying that intermodulation distortion behaves differently in your RX. Fine. I will leave it up to you to educate yourself with technical journals and Google searches. Then you can measure your own RX with a low distortion signal generator and a capable spectrum analyzer. Have fun.
On Sat, 11 Jan 2025 13:29:54 +0000 (UTC) "Joseph K7CBR via groups.io" <k7cbr@...> wrote: >? No, that demo you linked would NOT account for observations on my own hardware at a 250hz, 500hz, or even 2.8khz bandwidth as far as "internally generated noise". That has to do with showing the mess in crowded band conditions. I do know that radio hardware have internal distortion, this is not a secret. > The demo you linked to, shows a span of 10MHz, 1MHz/div. Your link does not account for internal IMD in the passband of my receiver at the settings I asked about. He demonstrated IMD of his transmitter. The receiver mixing scheme and inter-stage bias class (through to AF) does factor into this, yet I wanted you to explain clearly and coherently what you mean, and how this is significant enough to be a consideration to our audible perception? In the link video, if I park my R4C (it wont park at 1GHz), and have my 600Hz roofing filter in line, cascading through my 250Hz filter, listening to CW, I wont hear those other signals. > So please explain so we can all get onto the same page. Explain and show how you are measuring this so I can do the same. Thanks > > Joseph > >? ? On Friday, January 10, 2025 at 08:19:05 PM EST, Jim Shorney via groups.io <jimnu0c@...> wrote:? >? >? > There is a demonstration given by a fellow in the link I posted in message /g/DRAKE-RADIO/message/81833 . > > However it is common knowledge that IMD products change at a faster rate than the fundamentals. Given that there is no such thing as a perfect amplifier your radio has some degree of internally generated distortion products. > > On Fri, 10 Jan 2025 23:08:06 +0000 (UTC) > "Joseph K7CBR via groups.io" <k7cbr@...> wrote: > > >? OK. Just so we are on the same page, I need you to show me how you are measuring all this so I can too can see the empirical evidence and be convinced that this indeed is as critical as you say it is in the 2.1 to 2.8khz pass-band of my device? I can't weigh in on this until you explain and show me how you measured all this. > > Joseph > > > >? ? On Friday, January 10, 2025 at 05:38:21 PM EST, Jim Shorney via groups.io <jimnu0c@...> wrote:? > >? > >? > > And you are missing my point. Reducing the RF gain makes internally generated IMD products decrease faster than the desired signal. Which is entirely on topic for the usage of the RF Gain control. ACG attack distortion and IMD are certainly related but AGC is not the sole cause of internally generated IMD. > > > > On Fri, 10 Jan 2025 15:47:44 +0000 (UTC) > > "Joseph K7CBR via groups.io" <k7cbr@...> wrote: > >? > > >? have you been checked for rabies? lol* read my whole note from 7:07AM ET. AGC/RF gain was my topic. I shall leave Drake IMD issues to manufacturers and other ops to try and conquer. Im running a 52 year old set of boxes. Run them as clean as I can (xmit/rcv). full stop... > > > > > > *asking this, could get me banned for life... hope not yet its A-OK... > > > Joseph > > > > > >? ? On Friday, January 10, 2025 at 07:53:48 AM EST, Jim Shorney via groups.io <jimnu0c@...> wrote:? > > >? > > >? > > > That is one aspect of the issue. Every amplifier has IMD whether gain controlled or not. It is a question of how much. It may be very little or it may be a lot but each stage contributes to the total. > > > > > > On Fri, 10 Jan 2025 12:05:42 +0000 (UTC) > > > "Joseph K7CBR via groups.io" <k7cbr@...> wrote: > > >?? > > > >? AGC attack distortion is the actual problem. Decreasing RF gain on low bands where the noise level remains high is what we are talking about??? > > > > > >?? > > > > > >? > > > -- 73 -Jim NU0C
|
Re: Using the PLJ-6LED digital display with the R4C
On Fri, Jan 10, 2025 at 12:39 PM, Mark - WB0IQK wrote:
?
There is no problem on 10-15? mtrs. They act just like 160-20.? I have two 'C' lines and both act the same. You might try ditching the coupling cap and see what results you get. I've done that before and it seemed to work OK.?
?
I've been testing the readout in an external housing, coax connected to the INJ jack on the R4C? Right now I have no coupling cap at all and still having problems on 15 and 10.? I haven't paid any attention to the capacitance of the connecting coax, but I probably should.? May have some old RG-62 around here somewhere and I think that has fairly low capacitance per foot.? I wonder if you've ever measured the signal voltage you see at the counter input on each band?
?
73, Floyd - K8AC
|
OK Tom thanks for the advice I will do so, very much appreciated. I have the amp apart now I'll do so today.
Tim,?
If you¡¯re sure the meter itself is ok then tweak the pot to see if you can increase the reading on the L7 meter.?
Use a non conductive tool.
To be safe give it small adjustments with the amp off and
make sure the plate ¡°Ep button is pushed in¡± plate voltage meter is
reading ¡°0¡± (Capacitors discharged) before adjusting.?
You want to move it in the direction of ¡°More¡± resistance
(Wiper in the direction of the ground side) as one side is directly
grounded.?
CCW looking at the back of the amp.?
Then turn the amp on and check the reading.
Repeat as necessary.?
Tom
On Friday, January 10, 2025 at 06:15:43 PM EST, Thomas W9TAB via groups.io <electron@...> wrote:
Tim,?
If you¡¯re sure the meter itself is ok then tweak the pot to see if you can increase the reading on the L7 meter.?
Use a non conductive tool.
To be safe give it small adjustments with the amp off and make sure the plate ¡°Ep button is pushed in¡± plate voltage meter is reading ¡°0¡± (Capacitors discharged) before adjusting.?
You want to move it in the direction of ¡°More¡± resistance (Wiper in the direction of the ground side) as one side is directly grounded.?
CCW looking at the back of the amp.?
Then turn the amp on and check the reading.
Repeat as necessary.?
Tom
On Jan 10, 2025, at 4:49?PM, amfone via groups.io <amfone20000@...> wrote:
?
Tom I have two L7's and one L4B so I did not use anything to measure it against other than the meter on the other two amps, both of which read the proper voltage. I also used two different supplies as I have four all which
I have rebuilt. Using two different supplies the one L7 I'm working on read low in the LV and HV position. The other two amps with the same supplies read correctly.
73 Tim
WB8UHZ
On Friday, January 10, 2025 at 05:44:23 PM EST, Thomas W9TAB via groups.io <electron@...> wrote:
Tim,
What did you use to measure it with to compare against the meter in the amp??
Color TV HV probe, HV probe with DVM etc.?
I use a Fluke 80k-40 with a Fluke 87 DVM in my shop.?
Tom?
On Jan 10, 2025, at 11:33?AM, Evan via groups.io <k9sqg@...> wrote:
?
I typically see 1800 volts and 2500 volts BUT that is for my specific line voltage! ?Low line voltage results in low readings.
Tom
The B+ voltage is reading about 1500 to 1600 on the LV reading no load and about 2200 to 2300 on HV? no load. I took it out of line to work on it and can't give accurate numbers at this time but suffice to say it reads low.
I did not do the other adjustments.
Thanks Tim
On Thursday, January 9, 2025 at 09:35:48 PM EST, Thomas W9TAB via groups.io <electron@...> wrote:
Tim
I missed your response on an earlier post, how far off is the B+ voltage? (Measured vs indicated)?
How did the Grid / Plate current calibrations turn out??
(Verifying a 100% working meter)?
Tom W9TAB?
On Jan 9, 2025, at 5:08?PM, amfone via groups.io <amfone20000@...> wrote:
?
Tom I opened up the L7 today and the 2.2 meg resistors 8 of them rather than reading 17.6 Megs are actually reading 16.66 Meg. or just less than 5% off. Not sure if that is the problem perhaps? R17 is the issue, R17 is 10K and adjustable any
idea of where to get that little thing?
If you think I'm wrong on the dropping resistors and the effect they would have on the proper voltage reading let me know please.
Thanks 73 Tim
WB8UHZ
On Wednesday, January 8, 2025 at 11:19:24 AM EST, amfone via groups.io <amfone20000@...> wrote:
Thank you Thomas yes these are carbon style resistors that Drake used back in the day and over time they age, take in moisture etc. and change in value I'm hoping that is the issue as I purchased new resistors from Mouser.
Thank you
Tim
On Wednesday, January 8, 2025 at 09:43:20 AM EST, Thomas W9TAB via groups.io <electron@...> wrote:
Tim,
Carbon composition resistors typically increase in value over time due to absorbing moisture.?
That is the reason the voltage divider network resistance has increased causing the voltage to read low.?
Military spec publications identified this a long time ago and Allen Bradley recommended taking the resistors and putting them in an oven at 150F for 5 days to return them to spec.?
Naturally in your case it makes more sense to just replace them if you cannot adjust it with the potentiometer, after all, that¡¯s why it¡¯s there. ?
On Jan 7, 2025, at 10:47?PM, amfone via groups.io <amfone20000@...> wrote:
?
OK sorry for the mistake I used the term in reference to the meter not reading correctly.
73 Tim
WB8UHZ
On Tuesday, January 7, 2025 at 10:55:56 PM EST, Jim Shorney via groups.io <jimnu0c@...> wrote:
OK but please stop calling them shunts. They are series voltage dropping resistors. The only shunt is the pot. A shunt is a resistance across the meter terminals to increase the current value needed for a full scale reading.
On Wed, 8 Jan 2025 03:38:34 +0000 (UTC)
"amfone via groups.io" <amfone20000@...> wrote:
>? Jim thanks for your help regarding the location and the voltage requirements of the shunts.
--
73
-Jim
NU0C
|
Now you are just being argumentative. It sounds like you are saying that intermodulation distortion behaves differently in your RX. Fine. I will leave it up to you to educate yourself with technical journals and Google searches. Then you can measure your own RX with a low distortion signal generator and a capable spectrum analyzer. Have fun. On Sat, 11 Jan 2025 13:29:54 +0000 (UTC) "Joseph K7CBR via groups.io" <k7cbr@...> wrote: No, that demo you linked would NOT account for observations on my own hardware at a 250hz, 500hz, or even 2.8khz bandwidth as far as "internally generated noise". That has to do with showing the mess in crowded band conditions. I do know that radio hardware have internal distortion, this is not a secret.
The demo you linked to, shows a span of 10MHz, 1MHz/div. Your link does not account for internal IMD in the passband of my receiver at the settings I asked about. He demonstrated IMD of his transmitter. The receiver mixing scheme and inter-stage bias class (through to AF) does factor into this, yet I wanted you to explain clearly and coherently what you mean, and how this is significant enough to be a consideration to our audible perception? In the link video, if I park my R4C (it wont park at 1GHz), and have my 600Hz roofing filter in line, cascading through my 250Hz filter, listening to CW, I wont hear those other signals.
So please explain so we can all get onto the same page. Explain and show how you are measuring this so I can do the same. Thanks
Joseph
On Friday, January 10, 2025 at 08:19:05 PM EST, Jim Shorney via groups.io <jimnu0c@...> wrote:
There is a demonstration given by a fellow in the link I posted in message /g/DRAKE-RADIO/message/81833 .
However it is common knowledge that IMD products change at a faster rate than the fundamentals. Given that there is no such thing as a perfect amplifier your radio has some degree of internally generated distortion products.
On Fri, 10 Jan 2025 23:08:06 +0000 (UTC)
"Joseph K7CBR via groups.io" <k7cbr@...> wrote:
? OK. Just so we are on the same page, I need you to show me how you are measuring all this so I can too can see the empirical evidence and be convinced that this indeed is as critical as you say it is in the 2.1 to 2.8khz pass-band of my device? I can't weigh in on this until you explain and show me how you measured all this.
Joseph
? ? On Friday, January 10, 2025 at 05:38:21 PM EST, Jim Shorney via groups.io <jimnu0c@...> wrote:?
?
?
And you are missing my point. Reducing the RF gain makes internally generated IMD products decrease faster than the desired signal. Which is entirely on topic for the usage of the RF Gain control. ACG attack distortion and IMD are certainly related but AGC is not the sole cause of internally generated IMD.
On Fri, 10 Jan 2025 15:47:44 +0000 (UTC)
"Joseph K7CBR via groups.io" <k7cbr@...> wrote:
? have you been checked for rabies? lol* read my whole note from 7:07AM ET. AGC/RF gain was my topic. I shall leave Drake IMD issues to manufacturers and other ops to try and conquer. Im running a 52 year old set of boxes. Run them as clean as I can (xmit/rcv). full stop...
*asking this, could get me banned for life... hope not yet its A-OK...
Joseph
? ? On Friday, January 10, 2025 at 07:53:48 AM EST, Jim Shorney via groups.io <jimnu0c@...> wrote:?
?
?
That is one aspect of the issue. Every amplifier has IMD whether gain controlled or not. It is a question of how much. It may be very little or it may be a lot but each stage contributes to the total.
On Fri, 10 Jan 2025 12:05:42 +0000 (UTC)
"Joseph K7CBR via groups.io" <k7cbr@...> wrote:
?
? AGC attack distortion is the actual problem. Decreasing RF gain on low bands where the noise level remains high is what we are talking about?? ?
-- 73 -Jim NU0C
|
I agree with Jim on the relay, I eliminated the cut off bias scheme on my L7.?
toggle quoted message
Show quoted text
On Jan 11, 2025, at 1:35?AM, Jim VE7RF via groups.io <jim.thom@...> wrote:
?
check the TR relay thoroughly.....esp the center pole.? Mine had the center pole contacts burnt right off after years of use.... tnx to drakes fubar idea of cut off bias, etc.??
|
No, that demo you linked would NOT account for observations on my own hardware at a 250hz, 500hz, or even 2.8khz bandwidth as far as "internally generated noise". That has to do with showing the mess in crowded band conditions. I do know that radio hardware have internal distortion, this is not a secret.
The demo you linked to, shows a span of 10MHz, 1MHz/div. Your link does not account for internal IMD in the passband of my receiver at the settings I asked about. He demonstrated IMD of his transmitter. The receiver mixing scheme and inter-stage bias class (through to AF) does factor into this, yet I wanted you to explain clearly and coherently what you mean, and how this is significant enough to be a consideration to our audible perception? In the link video, if I park my R4C (it wont park at 1GHz), and have my 600Hz roofing filter in line, cascading through my 250Hz filter, listening to CW, I wont hear those other signals.
So please explain so we can all get onto the same page. Explain and show how you are measuring this so I can do the same. Thanks
Joseph
On Friday, January 10, 2025 at 08:19:05 PM EST, Jim Shorney via groups.io <jimnu0c@...> wrote:
There is a demonstration given by a fellow in the link I posted in message /g/DRAKE-RADIO/message/81833 . However it is common knowledge that IMD products change at a faster rate than the fundamentals. Given that there is no such thing as a perfect amplifier your radio has some degree of internally generated distortion products.
On Fri, 10 Jan 2025 23:08:06 +0000 (UTC)
"Joseph K7CBR via groups.io" <k7cbr@...> wrote:
>? OK. Just so we are on the same page, I need you to show me how you are measuring all this so I can too can see the empirical evidence and be convinced that this indeed is as critical as you say it is in the 2.1 to 2.8khz pass-band of my device? I can't weigh in on this until you explain and show me how you measured all this.
> Joseph
>
>? ? On Friday, January 10, 2025 at 05:38:21 PM EST, Jim Shorney via groups.io <jimnu0c@...> wrote:?
>?
>?
> And you are missing my point. Reducing the RF gain makes internally generated IMD products decrease faster than the desired signal. Which is entirely on topic for the usage of the RF Gain control. ACG attack distortion and IMD are certainly related but AGC is not the sole cause of internally generated IMD.
>
> On Fri, 10 Jan 2025 15:47:44 +0000 (UTC)
> "Joseph K7CBR via groups.io" <k7cbr@...> wrote:
>
> >? have you been checked for rabies? lol* read my whole note from 7:07AM ET. AGC/RF gain was my topic. I shall leave Drake IMD issues to manufacturers and other ops to try and conquer. Im running a 52 year old set of boxes. Run them as clean as I can (xmit/rcv). full stop...
> >
> > *asking this, could get me banned for life... hope not yet its A-OK...
> > Joseph
> >
> >? ? On Friday, January 10, 2025 at 07:53:48 AM EST, Jim Shorney via groups.io <jimnu0c@...> wrote:?
> >?
> >?
> > That is one aspect of the issue. Every amplifier has IMD whether gain controlled or not. It is a question of how much. It may be very little or it may be a lot but each stage contributes to the total.
> >
> > On Fri, 10 Jan 2025 12:05:42 +0000 (UTC)
> > "Joseph K7CBR via groups.io" <k7cbr@...> wrote:
> >?
> > >? AGC attack distortion is the actual problem. Decreasing RF gain on low bands where the noise level remains high is what we are talking about??
> >
> >?
>
>
>
--
73
-Jim
NU0C
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check the TR relay thoroughly.....esp the center pole.? Mine had the center pole contacts burnt right off after years of use.... tnx to drakes fubar idea of cut off bias, etc.??
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On Fri, Jan 10, 2025 at 10:21 PM, Roger KW4EMF wrote:
<I've looked at several internet posts about checking the 500z's with a multimeter. If I understand this correctly. Two of the pins are the filament and three of them are grids. What should the readings look like when <checking them with the ohm meter? The tubes are out of course.?
<Thanks
?
Pins? 1+5 are the cathode...and will read zero ohms, or close to it.??
Pins 2+3+4? ?are all tied internally to the grid.? You will see zero ohms between any of the grid pins.?
And u will read a wide open? between cathode and grid.
Grid to cathode shorts are not uncommon, but that never happens till the fil is lit.? A good eimac 3-500Z will hi-pot test 5 kv between grid and cathode/fil .? ?A chinese? 3-500Z will hi-pot test 1 kv? between? grid and cathode.?
U need to go through every inch of that amp.? 1400 watts on 20m..and only 400 watts on? 40+80m is indicative? of either a bandswitch problem / coil tapping issue, on the kw output side, or a tuned unput bandswitch problem, or tuned inputs.? ?and now u are down to 400 watts on 20m.?
You can also pull one tube out...and test with remaining tube, and vice versa.? ?It could also be an issue with one or both sockets.? ? It's a simple amp, in its basic form it's a pi tuned input and pi tuned output.? Metering,? B+, fil V, and a tr relay.?
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Subwoofers are mostly for below about 100 hz so there should be plenty of low end for SSB which seldom goes much below about 300 hz. The smoothness can really make a difference. Even though the interference is still there it is not as noticeable. There is more to a good speaker than just its frequency range.
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On 1/10/2025 4:08 PM, jerry-KF6VB wrote: The recent discussion of communication speakers inspired me.? I remembered I have a set of Boston Acoustics surround sound boxes salted away in the closet.
? I just brought one down, hooked it up.? I was worried that without its subwoofer, it wouldn't have
enough lows.? I needn't have.? All the SSB voices have that "FM sound". Actually, I think there's
too much lows.
? But it's very smooth.? Definitely a cut above the typical communications speaker.
???????????????????? - Jerry, KF6VB
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
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There is a demonstration given by a fellow in the link I posted in message /g/DRAKE-RADIO/message/81833 . However it is common knowledge that IMD products change at a faster rate than the fundamentals. Given that there is no such thing as a perfect amplifier your radio has some degree of internally generated distortion products. On Fri, 10 Jan 2025 23:08:06 +0000 (UTC) "Joseph K7CBR via groups.io" <k7cbr@...> wrote: OK. Just so we are on the same page, I need you to show me how you are measuring all this so I can too can see the empirical evidence and be convinced that this indeed is as critical as you say it is in the 2.1 to 2.8khz pass-band of my device? I can't weigh in on this until you explain and show me how you measured all this.
Joseph
On Friday, January 10, 2025 at 05:38:21 PM EST, Jim Shorney via groups.io <jimnu0c@...> wrote:
And you are missing my point. Reducing the RF gain makes internally generated IMD products decrease faster than the desired signal. Which is entirely on topic for the usage of the RF Gain control. ACG attack distortion and IMD are certainly related but AGC is not the sole cause of internally generated IMD.
On Fri, 10 Jan 2025 15:47:44 +0000 (UTC)
"Joseph K7CBR via groups.io" <k7cbr@...> wrote:
? have you been checked for rabies? lol* read my whole note from 7:07AM ET. AGC/RF gain was my topic. I shall leave Drake IMD issues to manufacturers and other ops to try and conquer. Im running a 52 year old set of boxes. Run them as clean as I can (xmit/rcv). full stop...
*asking this, could get me banned for life... hope not yet its A-OK...
Joseph
? ? On Friday, January 10, 2025 at 07:53:48 AM EST, Jim Shorney via groups.io <jimnu0c@...> wrote:?
?
?
That is one aspect of the issue. Every amplifier has IMD whether gain controlled or not. It is a question of how much. It may be very little or it may be a lot but each stage contributes to the total.
On Fri, 10 Jan 2025 12:05:42 +0000 (UTC)
"Joseph K7CBR via groups.io" <k7cbr@...> wrote:
? AGC attack distortion is the actual problem. Decreasing RF gain on low bands where the noise level remains high is what we are talking about?
-- 73 -Jim NU0C
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This rig is still available.? I have it listed on flee-bay at us$429.? Looking for reasonable offers.
?
Also have the MS-4 and PS-4 that matches the rig if interested.
?
Thanks all!
?
Wayne
?
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The recent discussion of communication speakers inspired me. I remembered I have a set of Boston Acoustics surround sound boxes salted away in the closet.
I just brought one down, hooked it up. I was worried that without its subwoofer, it wouldn't have
enough lows. I needn't have. All the SSB voices have that "FM sound". Actually, I think there's
too much lows.
But it's very smooth. Definitely a cut above the typical communications speaker.
- Jerry, KF6VB
|
Mike Davidsohn G3ZCC
Craig W8CS
Floyd - K8AC
Jim Shorney
Thomas W9TAB
k5fex