Re: [Drakelist] Drake 1A Progress
Although that's how it is addressed in the articles, it's not just an audio problem. Jim, let's take this off-line and we can bring K9YC into the discussion. Thanks. Paul, W9AC ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Drake 1A Progress
On Thu, 27 Jan 2011 21:09:38 -0500, Paul Christensen wrote: >The Pin 1 problem discussed by Muncy and Brown refers to the incorrect use >of audio shielding when the cable shielding bypasses the equipment chassis >and relies only upon circuit ground. Audio is just ELF RF. :) >The inclusion of the coaxial braid onto the SO-239 has no relevancy in and >of itself to the Pin 1 audio problem. Although that's how it is addressed in the articles, it's not just an audio problem. When is a ground not a ground? Where do induced currents on the outside of the coax shield go? What can they couple to along the way? What sort of lumped impedances are in series? No need to bring Mil-spec into the discussion, we're talking Drakes here. 73 -Jim -- Ham Radio NU0C Lincoln, Nebraska, U.S.S.A. TR7/RV7/R7A/L7, TR6/RV6, T4XC/R4C/L4B, NCL2000, SB104A, R390A, GT550A/RV550A, HyGain 3750, IBM PS/2 - all vintage, all the time! "Give a man a URL, and he will learn for an hour; teach him to Google, and he will learn for a lifetime." HyGain 3750 User's Group - http://groups.yahoo.com/group/HyGain_3750/ http://incolor.inetnebr.com/jshorney http://www.nebraskaghosts.org ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Drake 1A Progress
It's all part of the same big picture. The Pin 1 problem discussed by Muncy and Brown refers to the incorrect use of audio shielding when the cable shielding bypasses the equipment chassis and relies only upon circuit ground. I'm discussing RF shield connectivity -- not audio. Moreover, I am not advocating the abandonment of the chassis for the SO-239. Rather, the chassis should not be the basis of the only RF ground return from the SO-239. Mil-Spec equipment not only makes use of the chassis ground but also brings the RF coax shield all the way to the chassis connector. The better equipment manufacturers (e.g., Mil-Spec) do not rely on a path of sheet metal, screws, and other hardware to ensure a low impedance RF path -- only to have that pathway deteriorate with time in less than ideal operating environments. The inclusion of the coaxial braid onto the SO-239 has no relevancy in and of itself to the Pin 1 audio problem. Paul, W9AC ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Drake 1A Progress
On Thu, 27 Jan 2011 20:24:38 -0500, Paul Christensen wrote: >> There are very good reasons for the chassis to function as a ground >> return. Do >> a Google search on "the pin 1 problem". > >This is very different than the "PIN 1" problem addressed by Jim, K9YC and >others. It's all part of the same big picture. 73 -Jim -- Ham Radio NU0C Lincoln, Nebraska, U.S.S.A. TR7/RV7/R7A/L7, TR6/RV6, T4XC/R4C/L4B, NCL2000, SB104A, R390A, GT550A/RV550A, HyGain 3750, IBM PS/2 - all vintage, all the time! "Give a man a URL, and he will learn for an hour; teach him to Google, and he will learn for a lifetime." HyGain 3750 User's Group - http://groups.yahoo.com/group/HyGain_3750/ http://incolor.inetnebr.com/jshorney http://www.nebraskaghosts.org ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Drake 1A Progress
There are very good reasons for the chassis to function as a ground return. Do a Google search on "the pin 1 problem". This is very different than the "PIN 1" problem addressed by Jim, K9YC and others. Paul, W9AC - Original Message - From: "Jim Shorney" To: Sent: Thursday, January 27, 2011 8:11 PM Subject: Re: [Drakelist] Drake 1A Progress On Thu, 27 Jan 2011 17:52:42 -0500, Paul Christensen wrote: I have never been a believer in allowing the chassis to function as an RF ground return, especially on SO-239 connectors. Those connectors really need their own reliable return path to a solid circuit ground point. Not sure how that practice started or when... 73 -Jim -- Ham Radio NU0C Lincoln, Nebraska, U.S.S.A. TR7/RV7/R7A/L7, TR6/RV6, T4XC/R4C/L4B, NCL2000, SB104A, R390A, GT550A/RV550A, HyGain 3750, IBM PS/2 - all vintage, all the time! "Give a man a URL, and he will learn for an hour; teach him to Google, and he will learn for a lifetime." HyGain 3750 User's Group - http://groups.yahoo.com/group/HyGain_3750/ http://incolor.inetnebr.com/jshorney http://www.nebraskaghosts.org ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Drakelist Digest, Thanks to all on the light bulb issue.
On Thu, 27 Jan 2011 13:09:40 EST, fjmel...@aol.com wrote: >Thanks to everyone for their replies on the light bulb issue. I will look >further into the thermistor application. I was concerned about the statement >about the power supply regulation when using a thermistor. Any additional >comments about that issue. I don't want to create any additional problems by >trying to solve this one. I don't think it's an issue if the NTC is properly sized. I installed one from a PC power supply in my AC-4, and didn't notice any problems - although I didn't take any actual measurements. Also, my PS-7, but there it's rather a moot point since it is a regulated supply. For the truly concerned, a time-delay relay circuit can be devised to bypass the NTC after a few seconds. 73 -Jim -- Ham Radio NU0C Lincoln, Nebraska, U.S.S.A. TR7/RV7/R7A/L7, TR6/RV6, T4XC/R4C/L4B, NCL2000, SB104A, R390A, GT550A/RV550A, HyGain 3750, IBM PS/2 - all vintage, all the time! "Give a man a URL, and he will learn for an hour; teach him to Google, and he will learn for a lifetime." HyGain 3750 User's Group - http://groups.yahoo.com/group/HyGain_3750/ http://incolor.inetnebr.com/jshorney http://www.nebraskaghosts.org ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Drake 1A Progress
On Thu, 27 Jan 2011 17:52:42 -0500, Paul Christensen wrote: >I have never been a believer in allowing the chassis to function as an RF >ground return, especially on SO-239 connectors. Those connectors really >need their own reliable return path to a solid circuit ground point. Not >sure how that practice started or when... There are very good reasons for the chassis to function as a ground return. Do a Google search on "the pin 1 problem". 73 -Jim -- Ham Radio NU0C Lincoln, Nebraska, U.S.S.A. TR7/RV7/R7A/L7, TR6/RV6, T4XC/R4C/L4B, NCL2000, SB104A, R390A, GT550A/RV550A, HyGain 3750, IBM PS/2 - all vintage, all the time! "Give a man a URL, and he will learn for an hour; teach him to Google, and he will learn for a lifetime." HyGain 3750 User's Group - http://groups.yahoo.com/group/HyGain_3750/ http://incolor.inetnebr.com/jshorney http://www.nebraskaghosts.org ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Drakelist Digest, Vol 31, Issue 45
- Original Message - From: "TC Dailey" To: Sent: Thursday, January 27, 2011 2:58 PM Subject: Re: [Drakelist] Drakelist Digest, Vol 31, Issue 45 Speaking of the AC-4 - Anybody used one of the "upgrade" boards on a NON STANDARD AC-4? Story I get is that there are different versions of them, and the "inventor" refuses to supply adequate information on the various versions - I got the thing in, but it was no Heathkit - rather an "invent it as you go" sort of thing. Tom - Denver By "inventor" do you mean the Heathkit Shop kit or the AC-4? If the upgrade kit I found that assembling the board was a breeze and the instructions for that part reasonably good. However when installing the thing I found the wiring in my AC-4 was not as described in the kit instruction. I was able to figure out what to do but I think the insructions left a lot to be desired. Too much effort on warning about HV and not enough on procedure and either drawings of pictures. All that said the kit works fine and is probably a good idea since it uses currently available parts and not special can capacitors although the latter are probably available on special order. BTW, the bias circuit is exactly the same as the original, no additional protection in case it fails. Probably that would require some sort of fairly rapidly acting crow-bar on the HV and screens or at least the screen voltage to shut down the final in the event of bias failure. I suspect this would not be difficult to do these days but probably overkill for this rig. -- Richard Knoppow Los Angeles WB6KBL dickb...@ix.netcom.com ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Drakelist Digest, Vol 31, Issue 45
So far as I am aware, there are only two 'versions' of the AC-4. One has a 120/240 AC switch capability, the other does not. There are a couple of capacitor value changes, but the basic supply is the same. There are also at least two versions of the AC-3 supply, one with a choke in the LV filter and one with a resistor. What is 'non-standard' about your AC-4?? 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line and TR-4/C Service Supplement CDs TC Dailey wrote: Speaking of the AC-4 - Anybody used one of the "upgrade" boards on a NON STANDARD AC-4? Story I get is that there are different versions of them, and the "inventor" refuses to supply adequate information on the various versions - I got the thing in, but it was no Heathkit - rather an "invent it as you go" sort of thing. Tom - Denver ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Drakelist Digest, Vol 31, Issue 45
What do you mean "non standard AC-4" ? You mean like an AC-3 ? I've done two AC-3's, and I did have some puzzlement, had to refer to the schematic to make sure what I was doing made sense, color coding on some of the wires was not as expected, etc.. But not THAT difficult. Heck, if you're going to muck with 700VDC you better oughta be comfortable with schematics and test equipment etc. The "Heathkit" part of the supplier's name refers to the initial kits he did, which were for HEATHKIT radios, so that's where the name comes from. Chuck, K1OM On Thu, Jan 27, 2011 at 5:58 PM, TC Dailey wrote: > Speaking of the AC-4 - Anybody used one of the "upgrade" boards on a NON > STANDARD AC-4? > > Story I get is that there are different versions of them, and the > "inventor" refuses to supply adequate information on the various versions - > I got the thing in, but it was no Heathkit - rather an "invent it as you go" > sort of thing. > > Tom - Denver > > ___ > Drakelist mailing list > Drakelist@zerobeat.net > http://mailman.zerobeat.net/mailman/listinfo/drakelist > ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Drakelist Digest, Vol 31, Issue 45
Speaking of the AC-4 - Anybody used one of the "upgrade" boards on a NON STANDARD AC-4? Story I get is that there are different versions of them, and the "inventor" refuses to supply adequate information on the various versions - I got the thing in, but it was no Heathkit - rather an "invent it as you go" sort of thing. Tom - Denver ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
[Drakelist] Drake 1A Progress
Been diagnosing somewhat low sensitivity on my Drake 1A. I think I reported here that I replaced all suspect paper caps with metalized Polypropylene "yellow jacket" types. I saw no improvement with the new caps. In a nutshell, loss of gain was affected by the severe drift of two 33K carbon-composition resistors, one on the screen of V2, the other on the screen of V4. Both resistors drifted up to about 105K. I replaced both with 1/2W carbon film types and wow, what a difference! Now, I need to use that darned 30dB attenuator even on the high bands! Proper screen voltage is an absolute must in the early RF and IF stages in order to extract required gain. I can now think of a few other boatanchors of mine that likely need the same treatment. Other resistors, (including other values of screen resistors on the other tubes) are off a bit as expected since the set is 50 years old, but for some reason the 33K resistors drifted way out there. So, I highly recommend that 1A owners check those values to determine if they've drifted. Had another quirk: As I rotated the antenna trim, I noticed that Rx sensitivity would change if I gently pushed the control. I noticed that the ground frame of the air cap trimmer is connected to a small copper mounting plate. That plate is connected to yet another plate, and that plate is connected to the chassis, relying only on the hardware to make for a low impedance connection to circuit ground. Rather than fight the copper and hardware corrosion, I noticed that the trim cap has an unused solder tab on its ground frame. Easy fix: Just bring the tab down and solder it the mid plate. I then soldered the mid plate to the copper chassis. Problem gone. Sure makes soldering easy when the chassis parts are all copper! I have never been a believer in allowing the chassis to function as an RF ground return, especially on SO-239 connectors. Those connectors really need their own reliable return path to a solid circuit ground point. Not sure how that practice started or when... Darn, I almost forgot how easy it is to troubleshoot VT receivers since so many parts are unterminated at the VT. Unlike solid-state circuits, few parts require removal of one end. That greatly accelerates the troubleshooting process. Also, I am going to add a 110V Zener diode at the VFO's 105VDC B+ line. The current limiting resistor is already there going back to the +105V rail. My utility AC lines voltage runs high at 125V so using a Variac, I dropped the AC line voltage down to see where I achieved 105VDC. It occurs about 110VAC. I'm doing this to help stabilize the VFO by better regulating B+. The 105V supply rail from the PS only goes to the VFO, although it's part of a resistive divider feeding B+ to other tubes. I doubt it will help too much as other circuit factors likely mask any improvement, but it does seem like the right thing to do. About a year ago, I purchased a couple inrush limiters from Electric Radio Magazine. They do a nice job of bringing back high utility voltage down to about 115V where this equipment really belongs. I could add the same circuit to the receivers, but the external solution is non-invasive and probably helps to preserve the value of the 1A. Paul, W9AC ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Drakelist Digest, Thanks to all on the light bulb issue.
Fred, I have used thermistors numerous times, the most recent being installation in the primary winding of a filament transformer on my Drake L4B linear. I've noticed no adverse effects in this application having measure the filament voltage in standby and operate/transmit. Some critical instances might have a slight drop in regulation due to the added primary circuit resistance but I'd imagine that it would be minimal in most cases. As a side note, proceed with caution when buying a "step start" circuit, box, etc. One product I know of (I own two) claims the device is a surge protector and step-start for 220 v that I use on my linears. Yes, it does provide a "slow" turn on BUT in the best of cases, for 1/4 to 1/2 of an AC cycle. Trust me, the caps haven't charged and the filaments haven't warmed in that short period of time. Manufacturer rep agreed with me but said "...it does afford some degree of inrush protection." The key word is what is meant by degree, hi hi. 73, Evan -Original Message- From: fjmel...@aol.com To: drakelist@zerobeat.net Sent: Thu, Jan 27, 2011 1:09 pm Subject: Re: [Drakelist] Drakelist Digest, Thanks to all on the light bulb issue. Thanks to everyone for their replies on the light bulb issue. I will look further into the thermistor application. I was concerned about the statement about the power supply regulation when using a thermistor. Any additional comments about that issue. I don't want to create any additional problems by trying to solve this one. Thanks 73 de Fred WD8ADG ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Question about the 9MC filters
Darryl - That's what I get for being in a hurry. Seems to be happening more often these days! :-) You are correct, you can only do one filter at a time. You can use the dial skirt as a reference, i.e., turn on the CAL, and tune to zero beat. Set the dial skirt to "0". THEN tune through the calibrator in either filter position and you can see the approximately 2-1/2 kHz marks on either side where the S-Meter reads near maximum and with a drop to noise on either side. Then turn OFF the calibrator, and with the dial set to "0", switch between USB and LSB, listening for 'similar' noise pitch in either position. If they are not the same, then tweak C130 slightly one way or the other until they are. Again, they won't sound identical, but not 'bassy' or 'hissy' on either. Yes, the drop to the 'valley' between the two filters will only be about 20-30 dB due to the skirt slope of the filters. You can see this in the diagram of the filter response mentioned earlier. What we are attempting to do here is get the CO at the right place to be between the passbands, NOT necessarily in that maximum notch position. The Balanced Modulator will take care of the additional attenuation of the carrier. So, sorry for the confusion on my part. Hopefully the above will clear it up and 'un-traumatize' you!!! :-) 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line and TR-4/C Service Supplement CDs kb8bku wrote: Garey, Thanks for the explaination! I have never heard this double hump when tuning the calibrator signal in any of my Drakes (TR-3, TR-4, 4A-line twins). I assume the null that you describe tuning through is the BFO frequency, between the two filter passbands. But it would seem to me that you would only have one passband filter active at a time (depending on the selected sideband), and so no null in the middle(between the two), but rather the signal would just fall off on either side of the single (LSB or USB) passband. This is more what I think I hear from my radios. I must be missing something or perhaps I am misunderstanding your explaination. Or perhaps I have some work to do! I can switch sidebands while tuning and get close to what you describe, but my dip in the middle is only about 20dB, not all the way to noise. KB8BKU, Darryl in Dayton On Jan 25, 2011, at 11:12 PM, Garey Barrell wrote: Kevin - A scope can be used, although I find it easier to just listen to the receiver. Think of the two filter passbands as the letter "M" as depicted on Page 29 of the TR-4 Manual. The goal is to adjust C130 so that it sits in the valley between the two filters. If you turn on the CALibrator and tune through it in either direction in receive mode, you'll see the S-Meter go from noise level up to 10 over S-9 or so for a couple of kHz, then down to noise again, back up to 10 over S-9 for a couple of kHz, and then back down to noise level. If you get this pattern, then C130 is close. Fine adjustment is to listen to the receiver noise (no antenna, high band, no signals) and switch back and forth between USB and LSB. The 'pitch' of sound should be similar in both positions. If one sounds low or 'bassy' and the other side sounds high and 'hissy', then adjust C130 slightly until they sound about the same. They will NOT sound EXACTLY the same due to anomalies in the filter passbands, but they should sound similar. Just in case you are 'really' asking about nulling the Carrier in the Balanced Modulator, in this case you can clip the ground lead of the scope to the chassis and then just lay the probe tip near the Driver tube socket. Set the SIDEBAND switch to "X", key the transmitter in X-CW with the GAIN at full CCW, and adjust C127 and R85 for MINIMUM signal. Again, it's easier to listen on an external receiver if you have one available, and do the above, adjusting for minimum signal in the receiver. 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line and TR-4/C Service Supplement CDs Kevin Elliott wrote: I have been reading all of the posts in the new Drake archive and the old Drake archive trying to learn as much as I can about my TR4. To you old pros this will be a rookie question, but I am of the belief that if you don't ask you don't learn. Okay I have read where it has been said that you can use a couple of different ways to set C130 correctly. One being use a digital receiver and listening for the matching null and the one that I want to ask about is using a scope to adjust them. Where will the scope probe be connected to read this information or is it indirectly connected with a loop of wire around the oscillator tube to see the nulls. I got the Great service CD and I love it and will be going through it and digesting all I can. Thanks Kevin _ KG0MN ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobea
Re: [Drakelist] Drakelist Digest, Thanks to all on the light bulb issue.
Thanks to everyone for their replies on the light bulb issue. I will look further into the thermistor application. I was concerned about the statement about the power supply regulation when using a thermistor. Any additional comments about that issue. I don't want to create any additional problems by trying to solve this one. Thanks 73 de Fred WD8ADG ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Question about the 9MC filters
Garey, Thanks for the explaination! I have never heard this double hump when tuning the calibrator signal in any of my Drakes (TR-3, TR-4, 4A-line twins). I assume the null that you describe tuning through is the BFO frequency, between the two filter passbands. But it would seem to me that you would only have one passband filter active at a time (depending on the selected sideband), and so no null in the middle(between the two), but rather the signal would just fall off on either side of the single (LSB or USB) passband. This is more what I think I hear from my radios. I must be missing something or perhaps I am misunderstanding your explaination. Or perhaps I have some work to do! I can switch sidebands while tuning and get close to what you describe, but my dip in the middle is only about 20dB, not all the way to noise. KB8BKU, Darryl in Dayton On Jan 25, 2011, at 11:12 PM, Garey Barrell wrote: > Kevin - > > A scope can be used, although I find it easier to just listen to the receiver. > > Think of the two filter passbands as the letter "M" as depicted on Page 29 of > the TR-4 Manual. The goal is to adjust C130 so that it sits in the valley > between the two filters. If you turn on the CALibrator and tune through it > in either direction in receive mode, you'll see the S-Meter go from noise > level up to 10 over S-9 or so for a couple of kHz, then down to noise again, > back up to 10 over S-9 for a couple of kHz, and then back down to noise > level. If you get this pattern, then C130 is close. Fine adjustment is to > listen to the receiver noise (no antenna, high band, no signals) and switch > back and forth between USB and LSB. The 'pitch' of sound should be similar > in both positions. If one sounds low or 'bassy' and the other side sounds > high and 'hissy', then adjust C130 slightly until they sound about the same. > They will NOT sound EXACTLY the same due to anomalies in the filter > passbands, but they should sound similar. > > Just in case you are 'really' asking about nulling the Carrier in the > Balanced Modulator, in this case you can clip the ground lead of the scope to > the chassis and then just lay the probe tip near the Driver tube socket. Set > the SIDEBAND switch to "X", key the transmitter in X-CW with the GAIN at full > CCW, and adjust C127 and R85 for MINIMUM signal. Again, it's easier to > listen on an external receiver if you have one available, and do the above, > adjusting for minimum signal in the receiver. > > 73, Garey - K4OAH > Glen Allen, VA > > Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line > and TR-4/C Service Supplement CDs > > > > Kevin Elliott wrote: >> I have been reading all of the posts in the new Drake archive and the old >> Drake archive trying to learn as much as I can about my TR4. To you old >> pros this will be a rookie question, but I am of the belief that if you >> don't ask you don't learn. Okay I have read where it has been said that you >> can use a couple of different ways to set C130 correctly. One being use a >> digital receiver and listening for the matching null and the one that I want >> to ask about is using a scope to adjust them. Where will the scope probe be >> connected to read this information or is it indirectly connected with a loop >> of wire around the oscillator tube to see the nulls. >> I got the Great service CD and I love it and will be going through it and >> digesting all I can. >> Thanks >> Kevin _ KG0MN >> >> > > ___ > Drakelist mailing list > Drakelist@zerobeat.net > http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Question about the 9MC filters
On Jan 25, 2011, at 11:12 PM, Garey Barrell wrote: > Kevin - > > A scope can be used, although I find it easier to just listen to the receiver. > > Think of the two filter passbands as the letter "M" as depicted on Page 29 of > the TR-4 Manual. The goal is to adjust C130 so that it sits in the valley > between the two filters. If you turn on the CALibrator and tune through it > in either direction in receive mode, you'll see the S-Meter go from noise > level up to 10 over S-9 or so for a couple of kHz, then down to noise again, > back up to 10 over S-9 for a couple of kHz, and then back down to noise > level. If you get this pattern, then C130 is close. Fine adjustment is to > listen to the receiver noise (no antenna, high band, no signals) and switch > back and forth between USB and LSB. The 'pitch' of sound should be similar > in both positions. If one sounds low or 'bassy' and the other side sounds > high and 'hissy', then adjust C130 slightly until they sound about the same. > They will NOT sound EXACTLY the same due to anomalies in the filter > passbands, but they should sound similar. > > Just in case you are 'really' asking about nulling the Carrier in the > Balanced Modulator, in this case you can clip the ground lead of the scope to > the chassis and then just lay the probe tip near the Driver tube socket. Set > the SIDEBAND switch to "X", key the transmitter in X-CW with the GAIN at full > CCW, and adjust C127 and R85 for MINIMUM signal. Again, it's easier to > listen on an external receiver if you have one available, and do the above, > adjusting for minimum signal in the receiver. > > 73, Garey - K4OAH > Glen Allen, VA > > Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line > and TR-4/C Service Supplement CDs > > > > Kevin Elliott wrote: >> I have been reading all of the posts in the new Drake archive and the old >> Drake archive trying to learn as much as I can about my TR4. To you old >> pros this will be a rookie question, but I am of the belief that if you >> don't ask you don't learn. Okay I have read where it has been said that you >> can use a couple of different ways to set C130 correctly. One being use a >> digital receiver and listening for the matching null and the one that I want >> to ask about is using a scope to adjust them. Where will the scope probe be >> connected to read this information or is it indirectly connected with a loop >> of wire around the oscillator tube to see the nulls. >> I got the Great service CD and I love it and will be going through it and >> digesting all I can. >> Thanks >> Kevin _ KG0MN >> >> > > ___ > Drakelist mailing list > Drakelist@zerobeat.net > http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
