[AMRadio] Mod Transformer Available


John E. Coleman (ARS WA5BXO) wa5bxo2005 at pctechref.com
Wed Sep 28 09:34:45 EDT 2005


Hi Jim:
	Don't know what happened to Don's message it did get muddled up!  
	But here is another.  
	If the XFMR is to work into 5500 ohms and the final current is to be
no more than 200 ma (0.2A) then the voltage on the final can't be more than
1100 volts.  (E = I * R). DC input power to the final would only be 220
Watts.  It will obviously work well under these conditions but what a large
XFMR for only 110 watts of audio.  You could double the voltage to 2200
volts and unload the final to keep the current at 200 ma this would give you
440 watts DC input power.  But now the load is 11000 ohms.  The XFMR will
probably work OK into this higher Z but how will it effect the frequency
response.  Raising the voltage to 4400 volts and keeping the current down to
200 ma will give you 880 watts DC input to the final.  This XFMR is rated
for over 1000 watts of audio so it would have no trouble modulating this 880
watts DC but now the load Z is 22000 ohms.  Now were talking some serious
changes in Z for what the XFMR is stated to work into.  I wonder what that
does to the frequency response and coupling efficiency.   Plus the
insulation would need to with stand at least 8800 Volts Peak for 100%
modulation.  
	I think you can see that it is not possible to match all of the
rating of the XFMR at once.  Something has to be worded incorrectly about
this XFMR.  Perhaps it was never designed to have any current through it's
secondary and was required to have a large choke to by pass the most of the
current.  But you cannot design a 1000 WATT TRANSMITTER with only 200 ma max
current through the secondary of this XFMR and maintain 5500 ohms load Z
without a modulation reactor of some sort shunting it. 

-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of James M. Walker
Sent: Tuesday, September 27, 2005 8:59 PM
To: Discussion of AM Radio
Subject: Re: [AMRadio] Mod Transformer Available

Well,
I guess I am still confused, Sigh but I am going to drop the request
clarification, as the clarification seems to be muddled!
Jim
WB2FCN







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