[Boatanchors] 120 - 240vac and output
Ray Friess
rayfri at highstream.net
Fri Nov 26 19:19:18 EST 2004
HI HI... well, it all comes down to what the bard said... "the
sound, the fury... signifying nothing"
Gary Schafer wrote:
> Well Ray, now that you have defined what you mean by "doubling the
> signal strength" I have to say that is a very liberal S meter you are
> dealing with there!
>
> That may be so on some S meters. But that would make the calibration
> of the S meter just a little over 1 DB per S unit!
>
> By the way the difference between 1000 watts and 1200 watts is about
> .8 db. So on that S meter with 1 DB per S unit, you could see 1 S unit
> difference in that change of power.
>
> The old standard was 6 DB per S unit. That would make the meter go up
> by 1 S unit if you increased your power by 4 times.
>
> Unfortunately most receivers are not set up to that standard today.
> Some are a little over 1 DB per S unit on the low end of the scale to
> around 5 DB or so per S unit as you approach S9. There are a few that
> conform to the 6 DB per S unit standard.
>
> So you really can't go much by what someone tells you they read on an
> S meter when you increase your power.
>
> But what you can count on is that if you double your power your signal
> will increase by 3 DB. If you double it again it will increase another
> 3 DB. So increasing it by 4 times gains you 6 DB. On a real S meter
> that would be 1 S unit.
>
> I am not sure what you were getting at when you said the other guy
> would notice a difference only if you were running into a 9 db gain beam?
> It sounds like you are saying that there will be a greater difference
> in your signal strength when increasing from 1000 watts to 1200 watts
> if you are feeding that beam verses feeding a no gain antenna like a
> dipole?
>
> If that is what you mean, then that is not correct. If you had a 9 db
> gain antenna and you double your power from say 100 watts to 200
> watts, that is still a 3 db increase in signal strength on that same
> antenna. Increasing power by 3 db again to 400 watts gives you a 6 db
> increase over the 100 watts you first had. 1 S unit again.
>
> It always takes 2 times the power to increase signal strength by 3 db.
> No matter how much gain you have in the antenna or anywhere else.
>
> Now if you are saying that that extra 200 watts from 1000 watts to
> 1200 watts may make a difference in poor signal conditions, I would
> agree with you. If you are almost readable with 1000 watts, 1200 watts
> may be enough difference to be heard but not by much. It would be
> almost immeasurable at the other end. Well, the difference is .8 db
> between 1000 watts and 1200 watts. If someone has a 1 db per S unit
> meter then he will probably see the difference.
>
> 73
> Gary K4FMX
>
>
>
> Ray Friess wrote:
>
>> The 4x power to double signal strength that I was referring to was
>> the power output of the
>> transmitter or linear.. In other words, if I want to double the
>> S meter reading on the other
>> guys receiver from, say, S 4 to about S 9, and I am running 100
>> watts .... then I generally need
>> to go to 400 watts to get double that reading on his S meter.
>> Again, increasing my power
>> output from my linear from 1000 watts up to 1200 watts is not going
>> to make me one bit strong
>> in the other guys receiver or his S meter.... GENERALLY.
>> I say generally because if I am running that extra 200 watts into
>> a beam with a 9 db gain...
>> while he wont see a doubling of my signal strength over 1000 watts
>> into that same beam, he may
>> see an S unit difference, which can make the difference between a
>> contact or no contact...
>> especially in a pileup.... Still, to me it wouldnt be worth the
>> worry or extra effort to run 220
>> into my shack just for my linears. I would, and do, use 115....
>>
>>
>>
>> Gary Schafer wrote:
>>
>>> 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.
>>>>>>
>>>>>
>>>>> _______________________________________________
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>>>>> ** 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
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>>
>>>
>>
>>
>>
>
>
>
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