| Author |
Message |
    
Johhn
Intermediate Member
Username: Johhn
Post Number: 169
Registered: 8-2007
| | Posted on Friday, March 19, 2010 - 12:35 pm: | 
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Can you Mod an Amp from A.M. to F.M. |
Tech237
Moderator
Username: Tech237
Post Number: 1318
Registered: 4-2004
| | Posted on Friday, March 19, 2010 - 2:02 pm: |
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Can it be done - Yes. Is it worth doing - probably not. To do so requires changing the way the amplifier is biased, and this may entail more work than the amp is worth.
AM amps usually run as Class A because this Class produce the linear signal needed for this type of operation. The disadvantage is that this Class are the LEAST efficient of amplifiers - usually around 50%.
FM amplifiers usually run in Class AB or sometimes (rarely) Class C because the slight amplitude non-linearity created by these amps can be tolerated,as the amplitude is not as important as the frequency changes. The Class AB amp generally runs around 50% efficiency, while the Class C can be as high as 80%.
What changes the amps class of operation?? Simple the point in the input cycle that the Amp stops amplifying that signal. A Class A amp conducts for the full 360 degrees of the input signal, a Class AB between 180 and 359 degrees, and a Class C for less than 180 degrees. It is this time, that the input signal is basically "ignored" that creates the amplitudal non-linearity on the output from the amp.
Sorry Johhn, if this answer went deeper than a simple yes/no, but I wanted to give you some idea why I don't recommend changing an amp unless you are absolutely sure of what you are doing.
Tech237
N7AUS
God only made some many perfect head, on the rest he put hair.
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Patzerozero
Senior Member
Username: Patzerozero
Post Number: 4835
Registered: 7-2004
| | Posted on Friday, March 19, 2010 - 2:17 pm: |
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what amp? and what radio do you plan on using it with?
most of the 'custom' class 'C' amps already work as well as they are going to on FM anyway. my davemade box won't work with my magnum 257 on 10m SSB at all, but i've used a texas star dx500 & dx667 on 10m SSB and 'experimented' on 10m FM with 'no complaints'. |
Johhn
Intermediate Member
Username: Johhn
Post Number: 170
Registered: 8-2007
| | Posted on Friday, March 19, 2010 - 6:16 pm: |
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My Yaesu 7800,Just F.M. Too Reach A distent-
Repeter..147.0000 mhz. With a Palomar 250 |
2ec837
Intermediate Member
Username: 2ec837
Post Number: 143
Registered: 12-2001
| | Posted on Friday, March 19, 2010 - 9:19 pm: |
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Your palomar will not work on VHF!!! |
Johhn
Intermediate Member
Username: Johhn
Post Number: 171
Registered: 8-2007
| | Posted on Saturday, March 20, 2010 - 8:22 am: |
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Yes You are correct ,,It won't work ..
Can one mod This Amp ..Change The amp
too operate on VHF?? |
Tech237
Moderator
Username: Tech237
Post Number: 1323
Registered: 4-2004
| | Posted on Thursday, March 25, 2010 - 12:34 pm: |
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NO... No ... No...
Tech237
N7AUS
God only made some many perfect head, on the rest he put hair.
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