Keyboard Shortcuts
ctrl + shift + ? :
Show all keyboard shortcuts
ctrl + g :
Navigate to a group
ctrl + shift + f :
Find
ctrl + / :
Quick actions
esc to dismiss
Likes
Search
Rich tells us how to Ram 300+ A through a 40 A breaker.
|
pentalab
--- In ham_amplifiers@..., R L Measures <r@...> wrote:
Ohm's Law. The calc. peak mains current was c. 300A. The measured result was 1200v- pk into 50-ohms on SSB. ### 1200 V pk equates to 14,396 watts pep output into a 50 ohm load....14,395.65 /.63 = 22,850 w dc input. Primary VA = 22,850 x 1.22 = 27,877 va 27,877 /240v = 116.155 A .... not including fil xfmr, blower etc. Peak current is aprx 375A with big wire and a big C filter... every 8.3 msecs. ### Rich... tell us how you take a steady state plate and grid current meter readings..... with out blowing ur under rated 40 A house breaker ???? IE: a dead cxr... for just 3-6 seconds... just long enough to measure grid/plate current + fil V, loaded plate V, etc. Forget the fil v/ plate v...... focus on just the plate + grid current. ### If u just pulse tune it...and talk...fine... I do too. Unless both ur plate/grid meter's are peak reading types.... I can't see how it's done. ### IMO.. the entire system should be configured to at least handle a 4-7 second dead cxr.... without blowing breakers, melting coax, frying tank coils etc. ### For a 8170/8171.... I'd use a 100A breaker... and a bare min of 2 ga wire... and considering the 300-400A peak current draw every 8.3 msec..... 3 x 000 CU is the real ticket.... regardless of length. ### BTW... what's the CCS rating of the SB-220's plate xfmr ??? I heard it was 1200 va. Now Rich has stated it's only 600Va. I'm sure the smaller SB-200 is 600 va CCS. ### Will a SB-220 stock... in good condition, on low plate V...be capable of delivering 600W CCS RTTY ??? If so... the plate xfmr would have to be a 1200 va unit. Later... Jim VE7RF R L Measures, AG6K, 805.386.3734 |
|
On Nov 19, 2006, at 10:28 PM, pentalab wrote:
--- In ham_amplifiers@..., R L Measures <r@...> wrote:CorrectOhm's Law. The calc. peak mains current was c. 300A. The ..14,395.65 /.63 = 22,850 w dc input.My guess is that the efficiency was closer to 60%. Primary VA = 22,850Only if one assumes that the filter-C stores zero Joules in the 70% interim between 30pps, 30% duty-cycle tuning pulses. . .... notThe mains ESR was measured at 0.079¦¸, add 200' of #4 Cu. Xfmr pri. R = 0.075¦¸, sec R = 12¦¸, and the turns ratio is 240/3000 = 12.5. I came up c. 300A-pk - which could have been in the ballpark since my wife could hear the wires vibrate in the attic when I tuned the sucker up. For designed-for-SSB amplifiers, I don't. The plate/anode current meter is used only to adj. ZSAC. During speech, it probably indicated c. 1/3 of the anode current, or perhaps 1.3 A. . . After adjusting for zero grid-current and 0.5A of ZSAC, and tuning-loading for the specified screen-current I was done with meter readings. The next step was optional -- to measure peak-V into 50-ohms with an oscilloscope and a HV multiplier probe. .... with out blowing ur under rated 40 AWith an amplifier that was designed for SSB-only, only a dead-head would use a dead-carrier. Easy: grid current is zero, ZSAC is whatever is specified, with a 30% duty-cycle tuning-pulser, multiply the screen-current reading by 3.3. For example, normal screen-current is 120ma, so when the meter peaks at 36mA with the Tune-C control, the 8170 or 8171 is ready for use. To have been able to go on the A0 trip would have required a HV transformer that weighed and cost triple, plus the added cost of 200' of #2 Cu. The total cost for the Plywood Box 8170 project was $1200, not counting the 200' of #4 Cu for the 240v 50a outlet. For RTTY, this makes sense, but for SSB, it's greenbacks flushed down the crapper. It's not speced, Jim, but the core dimensions figure out to c. 550w. Now Rich has stated it's onlyI have no idea, Jim. Continuous broadcasting is something I have zero interest in. later ...R L Measures, AG6K, 805.386.3734 r@..., rlm@..., www.somis.org |
|
Robert B. Bonner
You guys are killing me.
toggle quoted message
Show quoted text
BOB DD -----Original Message-----
From: ham_amplifiers@... [mailto:ham_amplifiers@...] On Behalf Of pentalab Sent: Monday, November 20, 2006 12:29 AM To: ham_amplifiers@... Subject: [ham_amplifiers] Rich tells us how to Ram 300+ A through a 40 A breaker. --- In ham_amplifiers@..., R L Measures <r@...> wrote: Ohm's Law. The calc. peak mains current was c. 300A. The measured result was 1200v- pk into 50-ohms on SSB. ### 1200 V pk equates to 14,396 watts pep output into a 50 ohm load....14,395.65 /.63 = 22,850 w dc input. Primary VA = 22,850 x 1.22 = 27,877 va 27,877 /240v = 116.155 A .... not including fil xfmr, blower etc. Peak current is aprx 375A with big wire and a big C filter... every 8.3 msecs. ### Rich... tell us how you take a steady state plate and grid current meter readings..... with out blowing ur under rated 40 A house breaker ???? IE: a dead cxr... for just 3-6 seconds... just long enough to measure grid/plate current + fil V, loaded plate V, etc. Forget the fil v/ plate v...... focus on just the plate + grid current. ### If u just pulse tune it...and talk...fine... I do too. Unless both ur plate/grid meter's are peak reading types.... I can't see how it's done. ### IMO.. the entire system should be configured to at least handle a 4-7 second dead cxr.... without blowing breakers, melting coax, frying tank coils etc. ### For a 8170/8171.... I'd use a 100A breaker... and a bare min of 2 ga wire... and considering the 300-400A peak current draw every 8.3 msec..... 3 x 000 CU is the real ticket.... regardless of length. ### BTW... what's the CCS rating of the SB-220's plate xfmr ??? I heard it was 1200 va. Now Rich has stated it's only 600Va. I'm sure the smaller SB-200 is 600 va CCS. ### Will a SB-220 stock... in good condition, on low plate V...be capable of delivering 600W CCS RTTY ??? If so... the plate xfmr would have to be a 1200 va unit. Later... Jim VE7RF R L Measures, AG6K, 805.386.3734 Yahoo! Groups Links |
to navigate to use esc to dismiss