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61
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eHam Forums / Amplifiers / RE: Driving Solid State vs. Tube amps
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on: August 06, 2012, 02:18:41 PM
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Do: Apply 100% drive and tune plate/load for maximum output and then reduce drive until you get the desired 70% output power. In other words, tune the amp according to the mfgs specifications and then reduce the drive to get the desired reduced output.
I do not buy into this as there is little margin for error with some amps. I always start with reduced drive, get it close, increase drive and then re-tune. Then when tuned I reduce/set drive to desired output. A lot of 811 amp tubes have bit the dust with full power "cold" tunes. (cold meaning amp not tuned for current band) I don't buy into this either, but when I had a tube amp I would tune it for max power and then increase the loading slightly until the power output dropped a few watts, not 70%. |
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62
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eHam Forums / Antennas and Towers and more / RE: 160-40 - am I missing out not using these bands?
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on: August 03, 2012, 10:42:33 AM
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If you are on central time you probably are too far west to take advantage of DX on 40 before 8 PM. Same thing can be said for 80, and of course forget 160 at this time of the year. I'm on the east coast and have no problem working into EU in late afternoon/evening with a 2 element wire beam on 40. In the fall I hear EU from about 2 PM EST on 40 and evenings on 80. I've noticed lately that EU comes in quite well on 17. As long as 17 propagates that is my favorite band with 40 being second.
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65
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eHam Forums / Amplifiers / RE: ALS-600 load faults
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on: July 31, 2012, 10:59:47 AM
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if it still does this into a dummy load then you are either overdriving the amp (too much power or spike) or the alc is not working/adjusted correctly. If all ese fails I would call Ameritron to get some answers. I had one of those amps for a couple of years and found that mine was a little touchy when the antenna SWR exceeded 1.5:1. With a solid state amp it's mandatory that the ALC be connected to the exciter and adjusted in accordance with the manual.
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66
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eHam Forums / Antennas and Towers and more / RE: Dipole antenna - build or buy
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on: July 27, 2012, 09:18:19 AM
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I want to build a combination 40m and 20m dipole or a 80m, 40m and 20m combination dipole and I must be blind as I cannot find any designs for these.
Length cannot be more than around 90ft, I would like it much lower if I can do it.
Are there any or should I just buy a Windom or ZS6BKW from a manufacture? Any ideas?
thanks Nick
Nick: if your intention is to feed the antenna with 50 ohm coax, a trap dipole or fan dipole may be in order. However, if you only have 90 feet to play with, a trap dipole would be the best option. You can buy the trap dipole kits from Unidalla, or just buy the traps from them and use your own wire, as someone else also pointed out. Ron, W4VR |
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67
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eHam Forums / Amplifiers / RE: When did FCC change PEP?
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on: July 27, 2012, 09:10:29 AM
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BTW, I had a daily sked with the original WX2S, Tom, before he passed away of a heart attack. Thanks for the BTW. Although I never met the man, I've included a small memorial for him on my QSL card and added him to the National SK Archive: http://www.silentkeyhq.com/main.php4?p=bin/NSKALookup.php4&call=WX2S . Perhaps you have some additional info to share. - Steve (WX2S.) Thanks for posting the obituary. I really don't have anything to add. You did a fine job in tracking down the essentials. Ron, W4VR |
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69
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eHam Forums / Antennas and Towers and more / RE: Vertical or Horizontal?
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on: July 23, 2012, 01:36:12 PM
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Considering your location and those ridges around you, a dipole may be a better way to go. The problem I've had with roof-mounted verticals is that if you run more than 100 watts you start interfering with home entertainment equipment. About the only band I use a vertical anymore is on 160 meters to get the lower takeoff angle.
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70
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eHam Forums / Amplifiers / RE: How to choose a linear.....
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on: July 23, 2012, 01:30:43 PM
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The AL-80B is not a bad choice if you can find one that was assembled correctly. MFJ has had quality control problems, but I understand they are doing something to improve that. You can buy an ALS-600 for the same price, but you won't get quite as much power out as you will with the 80B. I had the ALS-600 for a couple of years and never had a problem with it at 500 watts output. If you have an external tuner a solid state amp is the way to go. Whatever you do, buy something new so you won't have to replace the tubes right away. There are lots of folks out there that are very hard on amplifier tubes, trying to squeeze out that last watt.
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73
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eHam Forums / Amplifiers / RE: When did FCC change PEP?
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on: July 15, 2012, 08:34:15 AM
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Those old power limits were based on input power (plate current times plate voltage). Now it's based on power output. The only ones that were severely impacted by this change were the AM'ers; they are limited to 375 watts output unmodulated carrier. BTW, I had a daily sked with the original WX2S, Tom, before he passed away of a heart attack.
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74
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eHam Forums / Elmers / RE: Multiple antenna tuners
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on: July 12, 2012, 10:09:04 AM
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Can't you turn off the auto tuner in the amp if you want to use an external tuner with a larger matching range? Also, not a good idea to turn on the auto tuner in the exciter when you're driving that particular amp. I use the Icom PW1 and the auto tuner in the amp can be turned on or placed in the bypass mode.
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