WA6HYQ Just a question. What benefit is there to drive an FL2100B with a Viking II. The Viking II will run 100 watts plate modulated AM, which is equal to 400 watts peak envelope power. At most you may get 250 watts out of the Yaesu running it hard, it does not have a heavy supply which equals 1000 watts peak envelope power. That equates to a 3.5 db difference at the receive end, just or a half an S-unit. If you run it any less then that you will not note a difference. 73 Tim
________________________________ From: "[email protected]" <[email protected]> To: [email protected] Cc: [email protected]; Peter Hoon <[email protected]>; [email protected] Sent: Wed, December 30, 2009 8:20:03 AM Subject: Re: [Drakelist] How to Lower T4XC Drive To Linear Amp During SSB? On my AM station I drive a Yaesu FL2100B with a Johnson Viking-II. So I don't have to throttle the transmitter back to 10 watts from 100, I place a T connector in series between the transmitter and amplifier, from the center of the T I place a 100 watt dummy load which works great! John, WA6HYQ Curt Nixon <[email protected] t> To Sent by: Peter Hoon <[email protected]> drakelist-bounces cc @zerobeat.net [email protected] Subject Re: [Drakelist] How to Lower T4XC 12/29/2009 06:28 Drive To Linear Amp During SSB? AM Please respond to [email protected] t GM Peter: IMHO, you need a pad between the Tx and amp. You're asking the T4 to really throttle back and in doing so with the gain pot, other things begin to change, not just the output power. I run a similar setup here with a grid driven AMP from a T4x.. I have a three dB Tee attenuator in a small box mounted in the line going into the amp. You need to make sure this gets bypassed when in receive, so either building it into the amp or using an external t/r relay is required. Use non-reactive resistors and remeber that these need to dissipate all the power you are losing. Another way is to use one of the monolithic attenuators available. they are easily found on epay and are very reasonable. they need to be mounted on a heat sink but are reliable and no-fuss and come in a variety of losses. Hope this helps, Curt KU8L Peter Hoon wrote: > Am having difficulty running our Drake T4XC into a QRO Technologies DX > 2500 Linear Amp. > > Here is a description of the problem, things we've tried so far, and > an appeal for your ideas and input. > > The DX 2500 amp requires very little drive. Preferably, we want to > run 500 to 800 watts PEP out of the amp to our loop at this 9,000 foot > above sea level Rocky Mountain ridge QTH. Have neighbors on both > sides, and so far we all get along. That would mean about 9 to 18 > watts SSB PEP (40 and 80 meters) out from the T4XC into the DX 2500 amp. > > Listeners say our best T4XC speech in SSB running barefoot is with > T4XC gain set at the 11:00 AM position (with a Drake desk mike). But > then, when we turn on our amp, we have way too much drive, the amp > tubes' screen current is exceeded on voice peaks, and the DX 2500 > protection circuit puts it into the fault mode, thus turning off the amp. > > Here are solutions we have tried: > > Yes, we have looked at the SWR the amp sees going into the tuner for > the loop. We are able to get virtually a perfect match, with no > reactance, and zero reflected watts. > > Have tried injecting ALC from the T4XC into the DX 2500 (from the jack > on the AC4). With the T4XC gain set at the 11:00 AM position, the > T4XC sends about -8 volts max on SSB voice peaks. The DX 2500 can > handle up to -20 volts of ALC. We still cannot get the ALC pot on the > front panel of the DX 2500 to sufficiently limit drive on voice peaks. > Perhaps with more practice and tweaking, we can find the correct ALC > pot setting. But so far no cigar. > > Tried completely closing the load control (full counter clockwise) on > the T4XC to reduce drive. But it only reduces drive to 60 watts CW in > tune mode, still far too much drive PEP in SSB. Even with plate > re-dipping with the changed load control, am concerned about possible > spurious products when the load capacitor in the T4XC is not at resonance. > > Tried reducing the T4XC gain control to the 9:00 AM position. But > fellows say our speech lacks the "presence" it has when running > barefoot with gain at 11:00 AM position. > > Suspect the basic problem is that the T4XC gain control does limit CW > power output in Tune and CW, but controls speech amplifier gain (but > not PEP output power) in the SSB mode. > > Please suggest ideas to try. > > One idea that could be worth trying is to mount a separate pot at the > rear of the T4XC (in an empty hole) that would limit cathode current > to the 12BY7A driver, when in the SSB mode. A SPST switch could > "short" out this pot when not wanted. There may also be a way of > placing a rear chassis mounted pot at the proper place on one of the > 12AX7A speech amp sections during SSB that would limit T4XC PEP output. > > Thanks. > > Peter > VE1CHS/0 > Nederland, Colorado > > > ------------------------------------------------------------------------ > > _______________________________________________ > Drakelist mailing list > [email protected] > http://mailman.zerobeat.net/mailman/listinfo/drakelist > _______________________________________________ Drakelist mailing list [email protected] http://mailman.zerobeat.net/mailman/listinfo/drakelist _______________________________________________ Drakelist mailing list [email protected] http://mailman.zerobeat.net/mailman/listinfo/drakelist
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