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palomar 250ld or 450ld ?
- Thread starter cbgus
- Start date
Depends. The Palomar name has been stamped on so many amplifiers over the years. You will want one of the blue face class AB Palomars if you can find one. The black face versions with 1446 finals are low end light duty class C amplifiers.
There are many considerations, base or mobile, SSB or AM talking, what radio/'s do you plan on running, how big a power supply, and how much do you want to spend.
There are many considerations, base or mobile, SSB or AM talking, what radio/'s do you plan on running, how big a power supply, and how much do you want to spend.
go with the bigger one,you can always turn it down,you cant turn up if its all the way up,hehe 73 de JW
thanks for answering, I think I will buy the model 450ld,
These amplifiers operate in am and ssb?
saying the price?
Palomar FET 450 LD Export Ham Radio Mosfet Linear Amplifier
These amplifiers operate in am and ssb?
saying the price?
Palomar FET 450 LD Export Ham Radio Mosfet Linear Amplifier
might want to check and see if it truly is class ab,, another member here just purchased one of these same amps and said it sounded very bad on ssb,, i think he sent it back for a refund, you will have to do a search for the post, it wasnt too long ago, maybe a few weeks
If it is a mosfet amp, chances are it is linear. That is one good thing about moving away from the BJTs (bipolar transistors). With the MOSFET design it is easier for them to just make it operate at least somewhat linear.
I have seen the older Palomar amplifiers that were stamped AB1 (which is ridiculous because in AB-1 the one refers to the way a *TUBE* is operating not a transistor, so it should read AB if in fact it really is but we won't get into that here) that were actually class C.
I have even seen some that had all of the parts there and in operation for AB mode operation but had the bias grounded out on the input transformers which made the amplifier a class C. They did this on a lot of the black faced, gold faced, and even blue faced Palomar amps because when they built them to design, they did have intentions to make them class AB, but they would do into self oscillation due to no negative feedback, poor RF bypassing and some other issues, so rather than fix the issues, it was easier just to ground out the bias supply through a piece of wire wrapped around a piece of ferrite creating a choke (kind of) and effectively making it class C. In class C you could get away with these issues, because the gain was lowered and you could get away with these design flaws. The correct fix was to undo the class C conversion, add negative feedback, make a few fixes and convert it to AB back to where it was supposed to be.
Not to get on a rant, but I figured I would give some history.
When the MOSFET designs came along, some were good, some OK, and some looked like bad science projects. It's hard to tell what you are getting without knowing what you are looking at...
However, the good news is, that because of the way a MOSFET operates, they kind of (the builders) had to get with the program more often than not, and had to in a lot of cases build a real linear amplifier. Not to say that the linearity is great, or IMD is great from one of these creations, but it's a lot better than what was out there before.
I may be a bit biased (no pun intended) but if it were me, I would say go with a Texas Star 350. I like them because they are mote linear than a lot of what is out there, better components, low impedance source for the bias supply which means better linearity.
But to your original question, the 250 or the 450? .. depends on your drive levels. If you go with the 450 and underdrive it, and let it just cruise along, you won't be pushing the 250 hard and overheat it, distort, go into compression, etc.
I have seen the older Palomar amplifiers that were stamped AB1 (which is ridiculous because in AB-1 the one refers to the way a *TUBE* is operating not a transistor, so it should read AB if in fact it really is but we won't get into that here) that were actually class C.
I have even seen some that had all of the parts there and in operation for AB mode operation but had the bias grounded out on the input transformers which made the amplifier a class C. They did this on a lot of the black faced, gold faced, and even blue faced Palomar amps because when they built them to design, they did have intentions to make them class AB, but they would do into self oscillation due to no negative feedback, poor RF bypassing and some other issues, so rather than fix the issues, it was easier just to ground out the bias supply through a piece of wire wrapped around a piece of ferrite creating a choke (kind of) and effectively making it class C. In class C you could get away with these issues, because the gain was lowered and you could get away with these design flaws. The correct fix was to undo the class C conversion, add negative feedback, make a few fixes and convert it to AB back to where it was supposed to be.
Not to get on a rant, but I figured I would give some history.
When the MOSFET designs came along, some were good, some OK, and some looked like bad science projects. It's hard to tell what you are getting without knowing what you are looking at...
However, the good news is, that because of the way a MOSFET operates, they kind of (the builders) had to get with the program more often than not, and had to in a lot of cases build a real linear amplifier. Not to say that the linearity is great, or IMD is great from one of these creations, but it's a lot better than what was out there before.
I may be a bit biased (no pun intended) but if it were me, I would say go with a Texas Star 350. I like them because they are mote linear than a lot of what is out there, better components, low impedance source for the bias supply which means better linearity.
But to your original question, the 250 or the 450? .. depends on your drive levels. If you go with the 450 and underdrive it, and let it just cruise along, you won't be pushing the 250 hard and overheat it, distort, go into compression, etc.
Thank you very much for your comment, it was very interesting. I will seek information from the Texas Star. My input power would be 5 to 10w, would be enough for the Texas Star?
Check out H&Y electronics, they have a web site..give them a call. The only place I would not recommend is GI Joe's radio electronics. The reason is I had a friend order from them..they don't provide tracking info..very slow to ship, paid for 3 day shipping and got ground a week and a half later with no resolution on the shipping charge, and they drop ship from ohio somewhere.
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