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Robert Klaus
Posted on Sunday, July 06, 2003 - 1:37 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Has anybody had any luck using a common availiable 11M amp. on 6M without any modifications or very little? I mess around on 6M SSB 50.125, but all the amp.s for 6M start at close to $400.00! Any suggestions would be great I know the circuits are similar. My FT-620B I use is really the same as any 11 radio for example. It even has a 1306/07 Driver/Final just tuned for 6M. Thanks.......
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Znut
Posted on Sunday, July 06, 2003 - 3:41 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Klaus,

I have used a Shooting Star(two SD 1446's with a little AB1 bias) on 6 with some success but had 2 major problems. It is hard to drive it just right with my 5054DX. SD 1446 transistors are very happy at 50 mhz(that is where they were designed to operate) and with 5 or 10 watts they are doing most of what they can do. My radio kicks out more than that with the RF power just cracked open a tiny bit. Which brings me to the other problem. The chitter-chattering relay. The station receiving can't hear the first syllable of each word because the gain is so much with the amp on those first syllables are way down. When I can I am going to get another one and modify it to key with the mic on the radio. I would also like to put a trimmer cap on the output side of the transistors to fine tune it for 6.

Take a look at this PDF and notice how similar the impedance characteristics are at 30 and 50mhz.

Yes the transistor is designed to operate class C but they do very well with some bias.

http://us.st.com/stonline/books/pdf/docs/2805.pdf

The good part is, these so-called 250 amps offer much bang for the buck.
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738
Posted on Monday, July 07, 2003 - 4:12 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Thanks for the info. keep me posted. I have a FT-620B it does about 16-20W pep I'm sure I could adjust it down some. The relay chatter sounds like a problem to work out. 6M amp.s are heavy on the wallet close to $400 to start! BTW my old Yasue has 11 meter Driver/Final 1306/07 I have been able to do so much to it because it's basically a 70's CB! Anyway let me know if you get anywhere I don't have $400.00 for a amp but could afford a 11m 250 or 350 type amp.
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Gage
Posted on Monday, July 07, 2003 - 9:53 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Robert I have an old Kris Boomer,on the back it has a sticker that shows 10/6meters.I've used it on 11meters and works good.Only used the amp on 11meters.I run a ft-847 so it would not do me a bit of good to hook the amp up.Hope that helps you out a little.
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Znut
Posted on Monday, July 07, 2003 - 11:25 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

738,

Grab one and give it a try. Make sure it is one of those which have AB1 bias added if you plan to use it on SSB. Hey, until you modify it for direct keying on SSB you could always use it for FM or any other mode which will keep the relay engaged, like SSTV, AM, or CW(if you TX slow enough, I guess.)

Did you check out the specs on the transistors? Be careful whilst shopping for an amp like this. Many so-called "250's" also have MRF 455's and one even has 2SC2290's which is the little brother to the 2SC2879. The 2879 will operate at 50mhz but has WAY different input/output impedances between 27 and 50mhz. I don't know how well the 2290 works on 6M. If you are in doubt, post a question here on the forum as to which transistor a particular amp uses and if it is biased AB.

I probably won't be too much help but there are many knowledgeable techs and forum members here who will be.

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