Hi Marv, Gee, that feed forward correction method sounds like something that would be ideal for the FT-1000D. As you said, it could be later moved from rig to rig too. So far all I've seen on the web
Feed-forward correction is a very powerful, but somewhat involved distorsion reduction technique. For more information, and some worked examples, see chapter 13 "Ultra-low distorsion power amplifiers
Hi Tom, First, I've never seen a feed forward correction system implemented for HF so, I can't point you to any done circuits. It may be because it's a futile undertaking. I don't know of any amateur
Karl-Arne, OK on the caution needed regarding obtaining these high IMD numbers. Good advice, OM. I would say that the level of distortion I heard when listening to the 5mW level coming out of the FT-
I called some ham friends looking for 4CX-350's drivers for the tetrode linear project. One of the guys has some 8560A's, with sockets, heatsinks, etc. that I can swap some stuff for. These are the c
The STC data for 4CX250B gives typical values for class AB1: 2kV anode, 350V screen, 100mA Iq. 2 tone Po 325W pep, IMD3 -30dBc, IMD5 -50dBc. Same IMD at 1500V anode, 225W pep out. The power levels me
That's the info I needed, Steve! -30 db IMD at 300+ watts. Yes, as you said, the 8560's [4CX-250's] will be used as class A voltage drivers putting out barely a watt or two, and 30 volts of swing. Th
Those figures are too good for a 4cx250B. They are probably referencing to pep. Looking in the (older version) "care and feeding of power grid tubes" they show the 4CX250B at 348 watts pep output to
Gary, Yes, I've read that too, but then I've read the opposite.. That statement above would make my question about using a chain of GG tubes running at 1/10th reduced ratings a poor idea. I'm a litt
The data sheet is explicit in specifying the levels as relative to each tone. In my experience, STC brand 4CX250s do come close to this. There's a scanned version at www.g8wrb.org It's ok to referenc
I think it's important to consider the difference between the class AB biassing that we are all used to in our amplifiers, and true class A which is usually reserved for specialist ultra-linear requi
Yes I see you are right Steve. I don't know where I got it from that changing one tone would give those parameters. Must of had a bad dream. I do remember that receivers always have the characteristi
tubes" is located? http://www.cpii.com/eimac/eiapps.htm The link to "Son of C&F" is at the top of the page. Also see the links to many of our other favorite topics. -- 73 from Ian GM3SEK 'In Practice
Yes - although IMD5 (or higher order) is rarely significant with class A amps running low IMD3. Very! It's a whole new world where driver stages are much bigger than you think they need to be. Say yo
Reminds me of a certain K5 station asking a European moonbouncer: "Whaddya runnin'?" "A 4CX250 --" "Geez, whaddya drivin' with THET?" (It wasn't K5GW, but Gerald will know the voice :-) -- 73 from Ia
Very interesting comments. It certainly IS an eye opener when you see what each driver plate dissipation needs to be for an all class A chain. But an easy way to maintain high IMD figures. I'm consid
Please disregard my question below: "Would there be a major disadvantage to running the whole tetrode chain in GG with standard voltages on the grid and screen? It seems it would be much easier to ta
Just to keep the reflector updated with info... I received a few private emails regarding using a chain of hi mu GG tubes in cascade. The general consensus is that it was not a very good idea. One re
A few thoughts covering several recent posts: Stability with tetrode amps should not be a problem if you use ceramic tubes with the proper bases. More than anything, I think it's the lead length in g
For VHF and UHF amplifiers, I found this to be true, but for HF ones, to my surprise, things blew. As I see it, whereas lanky glass-tubes can have VHF parasites, compact ceramic ones can have UHF par