[Boatanchors] 120 - 240vac and output

[Gary Schafer]

Sometimes it's nice to have information police. It is good for 
entertainment value if nothing else. :>)

I wonder what the transfer curves look like for 3-500Z's in an SB200? I 
believe that was the amplifier being discussed. Maybe there are transfer 
curves for the filaments too? I believe that was being discussed.

The 2X and 4X is a way to get in the ball park with differences as there 
is 2X the current in a 120 volt circuit from what there is in a 240 volt 
circuit and there is 2X the voltage step up in the HV transformer in a 
120 volt circuit compared to a 240 volt circuit for a given amount of 
power. If we know the primary voltage drop on the 120 volt mains we can 
figure what it is on 240 volts without too much trouble. Much easier 
than trying to figure out what the resistance of the mains in your house 
all the way back to the pole just so you can use I squared R to 
calculate. Vic is on the mark here.

This was I thought more of a generic discussion on 120 Volts verses 240 
volts and how it affects voltage drop. We did not get into transformer 
losses either which play in the problem.

Part of the discussion was about tube life on 120 verses 240 volts. I 
assumed that arose from the question of filament voltage-- so my simple 
answer about that.

As far as signal strength doubling with 4 times the power, that can be 
correct. It all depends on what your perspective is on what double the 
signal strength is. If it is one of 2X the power then 3 db of course 
would be correct. If it is one of 2X the voltage then 6 db or 4X the 
power would be correct. Without qualifying your statements you are no 
more correct than Ray was.

It is not always necessary to write reams of information to answer a 
question. It can always be elaborated to death and no one wants to read 
it anymore.

However you do add another perspective which I would think is of value too.

Happy thanksgiving,
Gary K4FMX



Ron wrote:
> Sometimes I sit and read these posts and just shake my head.
> The one great thing about the internet is that information can be 
> available to a great number of people quickly.  The worst thing is that 
> the wrong information can be passed just as easily.
> 
> I made no comment during the 2x 4x discussion but now with the 4 times 
> your power to double your signal strength .....well ...that's enough.
> 
> Primary loss is calculated from I *2 x R not 2x or 4x.  In this case I 
> is doubled and 2 squared is 4 so for this specific case , 4x is correct 
> ......but losses are from the square of the current.  All the 
> assumptions so far assume that the secondary side or the high voltage 
> transformer acts as a resistive linear load and that is not so.  Take a 
> look at the  transfer curves for a 3-500z  and you will see what 
> currents it draws 2KV compared to 2.2 or 2.4KV. Current drawn in the 
> secondary is reflected to the primary .  When you work this problem , 
> you work it from the secondary back to the primary ...not primary to 
> secondary.
> 
> As far as the 4x power to double signal strength ...it ain't so.  
> Doubling signal strength will add 3 dB to your signal strength.  I 
> suppose if your signal is 1/2 S unit then adding 3dB would double it but 
> when your signal strength is S7 , doubling your power gives you a signal 
> of S7.5 as an S unit is 6 dB.
> I'll agree about the extra 200 watts ....it won't make a difference.
> 
> Come on guys, if your going to post information , remember that a lot of 
> fellows will read your stuff and then pass it on.
> I can't tell you how many guys will sit and argue a point about some 
> information gleaned from some post they read a week or two years ago 
> that was just wrong.
> ---
> Ron
> 
> 
> 
> 
> Ray Friess wrote:
> 
>> What Vic says is true....   AND another thing to remember along with 
>> it is that that extra
>> 200 watt difference is not going to make a BIT of difference in your 
>> signal strength.   The
>> receiving station wouldnt be able to tell the difference in your 
>> signal if you went from 1000
>> watts to 1200 watts.    In fact, the scientific fact is that in order 
>> to DOUBLE  your signal
>> strength.. you have to FOUR TIMES your power..    so adding an 
>> additional 200 watts to a
>> 1000 watt signal is not going to make a bit of difference.... even in 
>> the worst of QRM or
>> band conditions....
>>
>>
>> Vic Rosenthal wrote:
>>
>>> Gary Schafer wrote:
>>>
>>>> Think about this for a minute and you should be able to figure it 
>>>> out yourself. The only thing that changes in the amp whether it is 
>>>> run on 120 or 240 is the primary configuration of the transformer. 
>>>> The rest of the amp knows nothing of the difference. Filament 
>>>> voltage is the same and plate voltage is the same.
>>>>
>>>> With a however here, The plate voltage may be a little better 
>>>> regulated (may not drop quite as much) because of a little less 
>>>> voltage drop on the house wiring on 240 volts. 
>>>
>>>
>>>
>>>
>>> But keep in mind that the reduction in plate voltage due to primary 
>>> voltage drop will be FOUR TIMES greater on 120V than 240V.  The 
>>> primary voltage drop will be twice as great, since the current is 
>>> double (given the same wire size, etc.). Since the transformer will 
>>> need to multiply the voltage 2X more, the drop will be 4X what it 
>>> was.  If you have a 120V circuit using no. 8 wire going directly to 
>>> the service entrance, the effect will be much smaller; but most 120v 
>>> circuits are not like this.
>>>
>>> This explains why people say they get 1200 watts with 240 V and only 
>>> 1000 watts on 120, for example.
>>>
>>
>> _______________________________________________
>> Boatanchors mailing list
>> Boatanchors at mailman.qth.net
>> http://mailman.qth.net/mailman/listinfo/boatanchors
>> ** List Administrator - Duane Fischer, W8DBF/W9WZE **   ** For 
>> Assistance: dfischer at usol.com **         $$ For vintage radio info, 
>> see the HCI web site $$      http://www.w9wze.org  
>>
> 
> 
>