[drakelist] T-4 Reciter question - neutralization in general
[EMAIL PROTECTED] made an utterance to the drakelist gang -- hi, I got my early xmas presents yesterday, an R-4 and T-4 reciter (I think the T-4 serial is 106 or something low like that). The 6JB6 tubes were pretty soft - around 70 watts when gain cranked fully CW on 40 meters. The long story made short is I pulled the old 6JB6 tubes out and replaced them with what appear to be new sylvania. I don't think they're matched because the design of the plate is slightly different. They're both 6JB6 Sylvania but look a little different inside. I followed the procedure in the manual to neutralize them at 28.8mc with a nice bird dummy load. I got them neutralized fairly quickly with max output at the bottom of the dip on 10 meters. I don't remember exactly what the final power out was, but I think it was around 90 watts. Now the meat and potatoes of the question - on 40 meters the bottom of the dip is not max output - the bottom of the dip is about 5 to 10 watts less than max output. Did I make a mistake? I never run 10 meters so optimized operation on 10 meters isn't doing me any good. The 10 watts that I'm losing by running at the bottom of the dip on 40 meters doesn't bother me either - I just wonder if I missed a step or if this is typical behavior? Thanks! -- 73 Jason N1SU http://n1su.com/ -- Submissions:drakelist@www.zerobeat.net Unsubscribe:[EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost:[EMAIL PROTECTED] - help in body of message Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net --
[drakelist] R-4 R-4B S meter question
[EMAIL PROTECTED] made an utterance to the drakelist gang -- R-4 question... I followed the S meter / AGC recalibration procedure to the letter for both my R-4 and R-4B. The thing I noticed that is different is that the R-4 has very little S meter movement for weak signals where the R-4B will show movement for weak ones - but strong signals that are S9 will read S9 on both units - broadcast stations that are +20dB show as +20 on both. It's the weak ones that show up as S2 or S3 on the R-4B that don't move the needle at all on the R-4. Weird. Thanks -- 73 Jason N1SU http://n1su.com/ -- Submissions:drakelist@www.zerobeat.net Unsubscribe:[EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost:[EMAIL PROTECTED] - help in body of message Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net --
Re: [drakelist] reduced bias on T-4XB
Garey Barrell [EMAIL PROTECTED] made an utterance to the drakelist gang -- Jason - I think this is your question!... The tank circuit of a transmitter is essentially a matching network to match the high impedance of the tube plate circuit to the low impedance of an antenna feedline.The plate circuit impedance is approximately equal to the plate voltage divided by the plate current, or approximately 2000 ohms. A typical antenna feedline is 50 ohms, so you need a transformation ratio of about 40. Adjusting the TUNE and LOAD controls tunes the network for a match between these two impedances. The network's job is to couple the RF energy from the plate circuit to the feedline. When the network is tuned, (plate current dipped,) the maximum amount of RF generated is being transferred to the antenna. When the match is NOT correct, (plate current NOT dipped,) the network isn't transferring RF efficiently, the tubes are attempting to drive a mismatched load, and have to dissipate the wasted power as heat. Any time the plate current is NOT dipped, indicating the match is not correct, any additional plate current must be dissipated by the tube plates as heat. Hopefully this isn't too convoluted to follow... 73, Garey - K4OAH Chicago [EMAIL PROTECTED] wrote: On Wed, 30 Nov 2005, Garey Barrell wrote: I ran three 4 Lines on autostart RTTY. They ran 24/7, and often made transmissions in excess of 30 minutes, AT FULL POWER. In this service, the finals lasted a little over two years, typically, with end of life defined as 100W output on 20M. This piqued my curiosity again - Let's say you're running your T-4XB at full power for 30 minutes at a time at 300mA and the plate is perfectly dipped. All is good. But if the plate isn't dipped at 300mA and would be at 240mA if dipped properly there would be 60mA of current wasted as heat running at 300mA. But it's still 300mA, whether resonant and dipped at 300mA or splattering at 300mA - the thing i'm wondering is if the tubes are suffering more at 300mA undipped or if the life expectancy the same as 300mA dipped perfectly, being paced at a rate of current (heat) travelling through the metal. And I suppose the other question is what is a plate dip anyway - can I think of it as if the tank circuit is sucking the power out of the tube or is it best to think of the tank circuit as a valve that passes the power when at resonance, and the current increases as the RF power output is backed up and can't get out? Sorry for the rudimentary questions but I can't find this online anywhere and don't have an old ARRL handbook that explains it. thanks -- 73 Jason N1SU http://n1su.com/ -- Submissions:drakelist@www.zerobeat.net Unsubscribe:[EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost:[EMAIL PROTECTED] - help in body of message Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net --
Re: [drakelist] reduced bias on T-4XB
[EMAIL PROTECTED] made an utterance to the drakelist gang -- On Wed, 30 Nov 2005, Garey Barrell wrote: I ran three 4 Lines on autostart RTTY. They ran 24/7, and often made transmissions in excess of 30 minutes, AT FULL POWER. In this service, the finals lasted a little over two years, typically, with end of life defined as 100W output on 20M. This piqued my curiosity again - Let's say you're running your T-4XB at full power for 30 minutes at a time at 300mA and the plate is perfectly dipped. All is good. But if the plate isn't dipped at 300mA and would be at 240mA if dipped properly there would be 60mA of current wasted as heat running at 300mA. But it's still 300mA, whether resonant and dipped at 300mA or splattering at 300mA - the thing i'm wondering is if the tubes are suffering more at 300mA undipped or if the life expectancy the same as 300mA dipped perfectly, being paced at a rate of current (heat) travelling through the metal. And I suppose the other question is what is a plate dip anyway - can I think of it as if the tank circuit is sucking the power out of the tube or is it best to think of the tank circuit as a valve that passes the power when at resonance, and the current increases as the RF power output is backed up and can't get out? Sorry for the rudimentary questions but I can't find this online anywhere and don't have an old ARRL handbook that explains it. thanks -- 73 Jason N1SU http://n1su.com/ -- Submissions:drakelist@www.zerobeat.net Unsubscribe:[EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost:[EMAIL PROTECTED] - help in body of message Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net --
Re: [drakelist] Tr-4 problem again
F3WT [EMAIL PROTECTED] made an utterance to the drakelist gang -- Thank you , Bob! 73 and season's greetings to all. Pierre - F3WT Le 21 déc. 05 à 00:36, Robert Donnell a écrit : I feel like the two-filters in the transceivers was a continuation of the theme of the 2A/2B receivers, where changing sidebands was actually moving the filter response, with respect to the BFO. You've all probably seen some of the rigs from other makers, with a single filter and analog VFO. When you changed sidebands, you had to either use a different tuning mark, or recalibrate against the 100 kHz crystal, to account for the carrier being shifted about 3 kHz between upper sideband and lower sideband. With Drake rigs this was not necessary, since the carrier oscillator stayed put. The first Drake transceiver I owned was a TR-3, and I felt like the dual filters gave the radio an upscale flavor, in addition to the potential for improved frequency stability in the local oscillator, because the only time it changed frequency was when it was shifted into the passband for CW transmission. Shifting the carrier frequency instead of using (and switching) a second crystal was undoubtedly a cost saving measure, probably to offset the cost of a second filter, and perhaps to save from having to build potentially less-reliable or less-stable real-time crystal switching. Also, shifting the VFO, to compensate for shifting the carrier oscillator, would have been virtually impossible to make track over the full range of the VFO, without having a second slug-tuned inductor to either swap between, for sideband changes, or to offset the VFO the proper amount at all points in the tuning range, when the alternate sideband was selected. That sounds like my idea of a technician's nightmare. I'm betting just getting one slug-tuned inductor to track a 12% frequency range change with linear frequency change vs. slug insertion was not trivial to learn how to do. In any event, I thought the dual-filter arrangement more elegant than the alternative. 73, Bob, KD7NM -- Original Message -- From: F3WT [EMAIL PROTECTED] Date: Tue, 20 Dec 2005 22:26:05 +0100 F3WT [EMAIL PROTECTED] made an utterance to the drakelist gang - - Hi Garey, Very clear explanation below! I have a related question I was wondering about for a while: Why were TR4s - and others by he way - designed with 2 sideband filters and 1 Xtal ( 9MHz ) rather than todays set of 1 sidebandfilter and 2 Xtals (SSB) or 3 including CW? Was it a problem then shifting VFO without loosing stability? 73, Pierre - F3WT Sent via the WebMail system at webmail.pioneernet.net -- Submissions:drakelist@www.zerobeat.net Unsubscribe:[EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost:[EMAIL PROTECTED] - help in body of message Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net --
