Hi All, I need to come up with a CLEAN 50W-70W IPA to drive my newly built 6 meter 8877. I have 20W available from a DownEast 50-28 transverter. An older N4NTA 6M kit using a single MRF-492 (10W to 1
BTW, Used as an IPA: Is it possible to clean up the N4LTA 6M MRF-492 brick by idling it at several amps (instead of 100ma) - closer to class A1 and adding some negative feedback via an emitter resist
Hi Marv, Your idea about using a 4CX350J IPA is interesting. I suppose it would have to be VERY physically close to the 8877 or the RF negative feedback will have phase shift problems. ie, It will no
Hi Clay, Not sure if this happens as soon as you throw the HV switch or not... but: Start with a "conquer and divide" technique. With plug unplugged and unit off, with an ohmmeter that can read diode
Hi Clay, That's good - you've made some progress and eliminated 1/2 of the rig. I take it you have no good 3-500Z spares to try. If not, I wouldn't worry about blowing anything up by popping fuses. P
Oliver, You may know the following info already, but just in case... just setting the drive power at an arbitrary level is not a good idea for several reasons... Lets say the final tubes are getting
Hi All, I'm planning to build up a 75M monoband amplifier that has at least -45db to -50db 3rd order IMD using heavy RF negative feedback. 10MW in, 1500W out. I wanted to get opinions here what other
Thanks for all the replies! cheezz... I got close to 15 private ones and they're still coming in - really appreciate the ideas, guys. Please excuse me if I don't answer them all... K5GZ [good whiskey
Yes, Gerald, I thought about the DC bias variation too... the fact it would be swinging under ssb modulation... and thought that was not a good thing unless the tube was run in class A. This is class
Correction: It was pointed out to me that the cathode resistor for negative feedback is to be used only for a grid driven [grounded cathode] amplifier to generate degenerative [negative] feedback. In
Thanks for the replies. Let's address a few comments. I'm trying to get the right direction to follow, then do some serious, focused study in the right areas. One comment: Why bother to get better li
I like BOTH suggestions, Gary! Having the input link phase reversable opens the door for GG driving GG experiments. For the GG input drive NFB resistor, what value would you try for an 8877 input? It
Hi Marv! Now THAT'S the kind of info I've been looking for, OM. OK on using the 'J' tube versions and the TRW class A chips. I imagine the J's are harder to find used. I went to a site that has a CA5
That's more valuable info, Marv - Tnx again! A few follow up questions: If I tap off the FT-1000D 10mW low level point, can I run a long ~ 20' coax cable to the amplifier CA2XX module's input, or wil
Hi Gary, Tnx for the IMD measurement info. Sounds easy enough. Actually I've been doing a similar thing, but using a recorded voice to play thru the rig and measure the bandwidth and levels. I will m
Marv, Just as a note on your Hughes sample amplifier URL below.... I see no negative DC bias on either the 4CX-250 nor the 4X10. Strange that it's not there. Bias is OK on the 6146. Would appropriate
Thank you Marv. You da man! That answers a lot. I'll ask you just a few more, please, and then let you be... :-) I've got a few of 4-400A's, sockets and chimneys here. I was hoping to substitute one
Hi Marv, Well, you've given me a lot to think about. I'll look for cleaner drivers than the 6146 and 4-400A. You make a good point about not giving up IMD in that lower level area, if there is an eas
Aw, you guys are brutal! Here's what I REALLY look like: http://home.comcast.net/~k1jj/wsb/media/254120/site1050.jpg Marv, OK on the FT-1000D feed forward info. Interesting alternative. Though, chang
Hi Peter, Yes, that's an interesting tube line up. I'm kinda leaning that way. That's a great way to provide voltage for both the final's screen and driver's plates. One regulated supply - I like it.