Base Amp For A 257hp

[Captain Kilowatt]

I really hate these threads and shoulda kept out of it. Everyone knows someone who runs a 100w radio into a 1 pill, into a 2 pill, into a 4 pill that works perfectly. And honestly if you spend your money you can run the dog shit out of it for all I care, but bad advice on a new purchase is just bad advise.


The spec sheet from Toshiba or XForce?

The Toshiba spec sheet says 10w pep max drive and with anything above 4w the linearity starts to drop off badly. Anything above 100-120w pep out and the IMD starts to creep way up above -24dB down. You're talking about 40w pep drive per pill on the 2 pill, and 20w pep drive per pill on the 4 pill. Now these tests are ran at 12.5vdc and most people are running at least 14vdc, but the principle is the same.

If you look at the XForce specs, the 2 pill will key 100w with a 5w input which is 13dB and pretty typical. However, it also says 120w peak drive will produce 400 peak out and that's only 5dB! The 4 pill says 10w carrier in produces 400w out, which again is 13dB and is expected. Peak drive is 240w with 1000w out and we're back down to 6dB.

Carl can say anything he likes, but he didn't make the transistor.


I don't know that Carl ever worked for Dave, but that's here nor there.


SSB doesn't have a carrier.


2-4w peaking 80w is waaay over modulated. So you've got an over modulated radio producing harmonics, and gain compression producing IMD and the whole setup makes way more heat than needed. The difference in 600w and 400w is less than 2dB plus a lot less heat and garbage.

I'm sticking to my guns, an 80w radio into an 8 pill or maybe even a 6 pill would be the better choice in transistor amplifiers. But the best option would be to use tubes that are capable of taking that drive while remaining linear.

I don't see a single thing in this post that I disagree with. Most people don't know the difference between "it works" and "it works like it should" when it comes to running amps. The 11m CB crowd is the ONLY place where 80 watts into a pair of 2879's will work well, stay cool, and not interfere with neighbors. It's also the only radio service where users and their golden screwdriver "techs" know more about the limits of the transistors that they use than the manufacturers of the transistors. Makes me want to give up everything else I have and go back to CB wit a one pill modulator driving a two pill driving a four pill into an 8 pill. Man!! I should be king of the hill with that setup.

 

[tba02]

Fixing that for you - "Man!! I should be king of the PILL with that setup."

 

[Crusher]

LOL @Captain Kilowatt , I know of a few guys running a cobra 29 into a 4 pill into an 8 pill. Yes it does happen.

 

[BammBamm]

Looks like I poked a stick in a hornets nest here. I like the sounds of the SB200 but finding one seems difficult. I mainly run SSB and clarity is my major goal here, No I don't run my 257 wide open into my TS and actually I haven't been using it lately as either I have no conditions or when I do have them I find I don't need the amp. I had another member PM me and ask a good question that I am now considering which was why not sell the TS and invest the new amp money into a good ham radio base station and get my ticket. As he stated I could always listen with the new radio until I pass the test and I do have a nieghbor with his license that is willing to help me set up a ham station but he is against my freebanding ways.

 

[GnG8d]

I had another member PM me and ask a good question that I am now considering which was why not sell the TS and invest the new amp money into a good ham radio base station and get my ticket. As he stated I could always listen with the new radio until I pass the test and I do have a nieghbor with his license that is willing to help me set up a ham station but he is against my freebanding ways.

If you plan on getting your ticket someday anyway, that sounds like a grand idea.

 

[binrat]

BammBamm,
I think you will find there is a lot of converted ham guys kicking around. Check here for radios http://www.kwarc.org/swapshop/index.htm
I recently seen a TS-50 for less than $375.
Start getting out to hamfests, but beware. Some people want the same price for their stuff as if it was NOS.

 

[AudioShockwav]

Got to agree.
I used to have a 400-12HD built by Xforce.
Some will disagree, but the power supply you will get in the Amp is not worth it.
Unless something has changed, they run a unregulated supply, couple of transformers, 4 x 50 amp fwb rectifiers on a small heat sink, and a BIG filter cap to try to cope with smoothing everything out.
The first worst thing you can do to it is turn it on.
Really.
The supply comes on and that big cap looks like a dead short as the transformers and rectifiers pour out everything they can into it to charge it.
That is hard on stuff. That big thump when you "flip the big switch" makes the rectifiers cry out for mercy.
They call them B Bias, it is a very basic and can not cope with the wild voltage swings from the unregulated supply bouncing around at insane drive levels.
They swamp the crap out of the input, they are not very efficient and that is why you can drive the snot out of them.
If Toshiba 2879`s were not over built like they were, this stuff would not have become so popular but that transistor can take abuse, and everyone got used to seeing them run at 20+ volts in class c but the signal will be full of garbage.


If you just buy the mobile, you are getting a "better" deal ( cough cough)
Really you are still better off with Tubes if you want to go the Amp route, and even better off if you make sure that your antenna system is the best it can be in your current location.
I know everyone gets tired of hearing it, the work the world on 100 watts,but I have a AL 811 amp sitting in my laundry room covered up because I feel I do just fine with the 100 watts out of my rig at home.

73
Jeff

 

[GnG8d]

If Toshiba 2879`s were not over built like they were, this stuff would not have become so popular but that transistor can take abuse, and everyone got used to seeing them run at 20+ volts in class c but the signal will be full of garbage.

Not to mention the new breed of 2sc2879. The DIE is not going to take the abuse of the Toshiba, so people might want to start running within spec now to save on the wallet later.

 

[9C1Driver]

The magnum 257hp can drive a 2 pill amp that is setup to take the pep wattage. I have a magnaforce 350hd and it worked quite well with the magnum 257hp, I now am running an older but new style TNT 600hd with toshiba 2879's and the magnum 257hp as a base. It gets great reports! And the only thing That gets warm is the rfx75, which I have a fan on that keeps it ice cold. Read the spec sheet and you will see that 60-80 watts isn't too much pep for these amps. Just make sure that you have a good VSWR reading before adding the 4 pill as it will cause issues if not. I use the TNT 600hd every so often and it doesn't bother a thing in my house or any Of the neighbors as I have asked already. As for a new amp I woul really consider looking at the Dave Made amp line as well as the xforce. JMO, but to be honest most, If not most newer designs were copied from the original Dave made amps. All the guys that used to work for the old Dave made company started their own thing and the rest is history lol. Anyway, you can use a 4 pill amp with that radio, just be careful and watch the carrier on ssb, use the mic gain and set it at about 1/2 way for ssb use wit the rf power turned all the way up. For am with the 4 pill I keep my dead key around 2-4 watts and pep is 80 watts. I don't really look at the watt meter for numbers, more to check VSWR, but I have seen around 600-750 watts on ssb with the magnum 257hp and the TNT 600hd using a radio shack meter. This is just my expirience, hope it helps. God bless.

I do love the TnT line of amplifiers and as long as they are still tough with the new DEI finals they should still be great amplifiers. I would also say a TnT 350 would handle more drive better then a TS350. I just wanted to show that a TS350 will make 75-100 % of it's capable wattage with 18 watts PEP or less. A local here ran an Omegaforce HP into a TnT600 and that mobile rocked. As I recall he got about the same peak numbers you are seeing with yours. Cheers.

 

[222DBFL]

I agree, I try not to use my amp unless it's necessary , which isn't too often. I need to spend some more time with my antenna system as well. Not that it's bad, it's just not what I want. Current antenna was given to me. It's an old one and will soon be replaced with something much better. But I do agree, a tube amp would seem like the best bet. JMO. God bless