[AMRadio] AM IARU Bandplan


Brett Gazdzinski Brett.Gazdzinski at verizon.net
Thu Mar 11 19:01:46 EST 2010


That is about 600 watts carrier out at 70% efficiency, and modulated 100% 
would be about 2400 watts pep. The 250 TH will be running at 263 watts 
dissipation!

My 813 rig runs about the same, 2000 volts at 400 ma for 560 watts carrier 
at 70% efficiency, although something must be off as the meters show 600 
watts out, and 700 seems no problem.

My pep meter only goes up to 2000 watts, so I have no idea what the peak 
power is.

Brett
N2DTS


----- Original Message ----- 
From: "rbethman" <rbethman at comcast.net>
To: "Discussion of AM Radio in the Amateur Service" 
<amradio at mailman.qth.net>
Cc: "D. Chester" <k4kyv at charter.net>
Sent: Thursday, March 11, 2010 12:55 AM
Subject: Re: [AMRadio] AM IARU Bandplan


Don,

The first issue, the BC-610sw were designed and spec'd to run at 100V AC.

Mine rune at the currently available 125 to 127 VAC  that is supplied.

This places voltages ABOVE those listed in the TMs.

Therefore, when one looks at the voltage difference, this will carry
through as higher voltages throughout.  This is the primary problem in
the voltage in the PA circuit.  I automatically get a 1.1554154, (etc  -
irrational number repetitive in ad-nauseum, Increase in all the
transmitter voltages.

This is now putting 2309VDC on the plate of the 250TH.  The plate
current dips at about 380mA.

My method of measuring PEP out to the antenna is the "newer" Bird Peak
reading wattmeter.

It was a few months out of calibration.  I had gotten 1 1500W slug.  I
pinned it to the right EVERY time I keyed up and talked.  Iordered two
more slugs, a 2000W and a 2500W.

I saw that I could pin the meter against the right hand stop with the
2500W slug.

I've tried the Heathkit HVDC Probe.  It unfortunately gooes up to 40KV.
Even bypassing ONE of the precision however megohm resistors only got me
to a 20KVDC max scale.  I do KNOW that I am getting over 2000VDC on the
final.

( have tried to keep the equipment within limits.

The audio chain has a 400 Cycles to 2500 cycles range.  This transformer
from the first speech amplifier to the pair of 2A3s, and is amplified
and fed to the pair of 100THs folowed by the modulation transformer.
The applied to the PA, a 250TH.

I run a Kenwood SM-220 station monitor, along with the BP-8 panadaptor
option.  I even feed the R-390A IF or the SP-600 IF into the BP-8.  Its
inputs are at 455Khz.  Each receiver is either in the 8Kc position in
the case of the R-390A, or the 13KIc position for the SP-600.

I hope I made clear what is being done.

Bob - NoDGN



On 3/10/2010 11:41 PM, D. Chester wrote:
>> I have enough of a time keeping the BEASTs reined in at 1500W PEP.  If I
>> set the microphone resting current at the specified in the TM at 40ma,
>> the darn thing WILL hit 2500W PEP.
>>
>>
>> Bob - N0DGN
>>
>
> Bob, what are you using to measure your PEP?
>
> All the stock BC-610's I ever worked on back in the 60's and 70's would 
> just
> about make 100% on positive modulation peaks before flat-topping. This is
> inherent to the factory design because of the modulation transformer
> step-down turns ratio.  If the 610 is run according to the TM's 
> instructions
> (also saving the 250TH from premature failure), you run 2000v on the final
> at 250 milliamps for 500 watts DC input.  This optimistically gives about
> 350 watts carrier out, based on the (optimistic) assumption of 70%
> efficiency. No way that stock BC-610 could even make 1500 watts peak 
> power,
> let alone 2500 watts.
>
> That's why the FeeCee deleted the requirement that hams have "accurate
> instruments" to measure power when they changed over to the p.e.p.
> bullshi'ite.  As stated in their own Report and Order, they knew it would 
> be
> unrealistic to expect the average hammy hambone to be able to accurately
> measure power output with commonly-used instruments and typical hammy
> technical knowledge (and remember, that was during the era when the 
> average
> amateur radio operator was still expected to actually know something about
> what was inside his "box" and how it worked).
>
> > From what I constantly hear over the air, to-day's hams seem about 
> > equally
> obsessed with two things: peak power and SWR. Both are way overblown 
> beyond
> their actual significance.  I suspect a lot of hams have an inflated idea 
> of
> how much power they are actually running, using a typical el-cheapo hammy
> hambone wattmeter, combined with grand delusions of "Strap".
>
> Don k4kyv
> _______________________________________________________________
>
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-- 
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|               AM Amateur Radio Operator    NØDGN                 |
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| Bob Bethman                \\\|///     " The absence of a danger |
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