PA3DUV escribi:
> > ## A few months back.... I bought a Fluke "Mini 62" IR point and
> > shoot thermonter..
.. comes with a built in laser pointer.... and can
> > be switched from C to F as well. Works slick.... and will
> > give instant readings onto one LCD display
>
> 2 weeks ago I checked out my twin GU84B tetrode amp with
that.
>
> Running 6 kW on 7 MHz into the R&S dummyload I found the following hot
> spots:
>
> The connection between tubular wound 20 meter coil and the lead to the
> toroidal 40/80/160 meter coil
How are these connections made?. Mechanically wrapped and then soldered?,
with maybe siver solder?.
Best regards
Guillermo - LU8EYW.
P.S.: curious to know how one do at those power levels.
>
> The coil section on the INSIDE of the toroid
>
> The connection from the coil to the bandswitch
>
> The hottest point was the coil section INSIDE the toroid, 200C + was
> measured
>
> The DC blocking caps (2 in parallel) remained remarkable cool, no
> significabt temperature rise.
>
> The anode coolers went up to 95C
>
> The 10-20-30 meter tank coil section went up to 130C
>
> I'll post some pictures of the actual
measurement when I'm back home.
>
> Cheers from YMM, Alberta,
> Dick, PA3DUV
>
>
>
>
> ----- Original Message -----
> *From:* pentalab jim.thomson@
telus.com>
> *To:*
ham_amplifiers@yahoogroups.com> ham_amplifiers@
yahoogroups.
com>
> *Sent:* Thursday, October 05, 2006 10:45 PM
> *Subject:* [ham_amplifiers] Re: Tank eff......WAS 3 - phase HV supply
>
> --- In
ham_amplifiers@yahoogroups.com> ham_amplifiers@
yahoogroups.
com>, "PA3DUV" wrote:
> >
> > Hey guys,
> >
> > don't make a
fuss about the last killowatt :-))))))))))
))))))
> >
> > Cheers, Dick
> > PA3DUV
> >
> >
> > ----- Original Message -----
> > From: Peter Voelpel
> > To:
ham_amplifiers@yahoogroups.com> ham_amplifiers@
yahoogroups.
com>
> > Sent: Wednesday, October 04, 2006 10:29 PM
> > Subject: RE: [ham_amplifiers] Re: 3 - phase HV supply
> >
> >
> > Sorry,
> >
> >
> > Indeed, for 25KW out one needs 45KVA, but only in class B.
> > 67% efficiency is a bit high in class AB, it will be around 63%
> minus loss in the pi-network.
> > Some of the output in a GG amp is coming from the driver, so
> efficiency is NOT= output*100%/
input power...
>
> ### How
come all the tetrode fellows always say that ?? We
> carefully measured the eff on this latest 6000A7 linear... and
> got 67%. Now granted... the wattmeter slug could be a little
> high... the plate current + HV meter's could be a little low...
> skewing the results.
>
> ### Figure maybe 1% loss in the tank circuit... from the coil.
> And more like almost 2% on 10m.[ 1-2% of the power output]
> The kicker is.... on 10m...all that tank coil heat is being dumped
> into just 2 x turns..... vs less heat being dumped into the
> ENTIRE coil (or a portion of it)... on the lower bands.
>
> ### In various tests I have done... one would think that on say a
> 20-10m coil.... that when on say 15m.... that the adjacent
> unused portion of the coil would heatsink the used portion.....
.
> it sorta does... poorly. It ends up the used portion will get
> hot... the unused portion [next
turn over] runs barely warm... go
> figure.
>
> ### BTW.... most Vac caps have an unloaded Q of around 5000....
> compared to a typ tank coil of 100-300. IMO... most of the tank
> losses are going to be in the tank coil... interconnecting
> straps.... bandswitch contacts, etc.
>
> ### You need very very few watts to heat up a tank coil....esp
> hollow tubing. With solid material... like say 8 ga wire
> [used on the L4B 2 x 3-500Z] used on 80/40m.. or say solid 6
> ga wire used on some 20m coils.... it just takes longer to heat
> up..... the flipside is... with any solid material.... it takes a
> helluva lot longer to cool down.... cuz of the the stored up heat
> inside a bigger thermal mass.
>
> ### On a related subject.... if I remember correctly, in
> Eimac's .. "care and feeding" for thermal properties..
. copper
> was ... '1.0' and aluminium was '.57' IE:
aluminium
> doesn't conduct heat worth banana's... compared to copper !
> Steel, and stainless steel is a LOT worse.......
.. just
> something to keep in mind.
>
> ## A few months back.... I bought a Fluke "Mini 62" IR point and
> shoot thermonter..
.. comes with a built in laser pointer.... and can
> be switched from C to F as well. Works slick.... and will
> give instant readings onto one LCD display ... and a 2nd
> display will always hold the peak highest temp. [both backlit to
> boot] By holding the trigger down solid... and moving the
> laser pointer about slowly... or quickly.... you can find hot
> spots all over the place ! You can see quickly where you are
> leaking heat from the outside of a home.... measure exhaust
> manifold temps, xfmr's... tank coils... find where ur attic is
> not insulated properly [heat radiating down from a ceiling... in
> just one
spot], and doz's of other uses..... like measuring
> exhaust air temp from a linear... Air conditioning problems in the
> home or car. This Fluke 62 goes from below freezing
> [instant temp readings of ur fridge/deep freezer] to something
> like 900 deg F. It will easily differentiate between one part of
> a tank coil.... and another portion... just a few mm away. A
> great bargain for around $100.00 Shop around.
>
> ### IMO.... since a huge portion of the drive power on a GG linear
> [ in this case, 640w of the 800 w of drive used] appears in the
> output.... I'd consider that ... "free extra eff".
>
> ### In any event... anode dissipation is REDUCED... if apparent
> eff is UP.
>
> ## DC plate input - power out = anode diss. What am I
> supposed to do.... subtract the drive power... from the power
> output 1st.... THEN calculate plate diss ??? Nobody is about
>
to do that.... so why bother subtracting the drive power from the
> output, to cal eff ?
>
> ### I tried several experiments by varying the loaded tank Q on
> various bands... and also varying the loaded tank Q on the tuned
> input network. Now Rauch will tell you tank Q makes no diff..
> and is not important...
. and a loaded Q of "22" is just fine.....
> fact is loaded Q on a tank circuit DOES make a big
> difference. A loaded Q of around 3.3 for a tuned input is fine
> [this would equate to Q =2 doing it Rich's way]. A loaded Q
> of 10-12 [new method] [ 8-10 old method] is ample for the high
> power PI output. You start running a Q of 12-22 [new
> method].... you can easily see, and measure effects asap. The
> circulating currents skyrocket... tank coils + bandswitch / roller
> inductor conacts heat up.... eff DROPS, amp tuning becomes narrow
> banded... requiring more
frequent tune ups, when u qsy etc.
>
> ### On a tuned input.... I tried a Q of 5.... eff drops..esp on
> the higher bands. We used bird line sections on both the
> input/output of the tuned input circuit [consisted of 2 x
> broadcast variables + a tapped 4 uh coilt] output through the 2nd
> line section... then into a 50 ohm load was 150-160w . By
> INcreasing the small coil's uh tap... just a tiny bit.....
> lowering the Q.... and power out of the tuned input... shot up to
> 195 w.
>
> ### with too high a Q on a tuned input... we could actually get
> the 5/32 " solid copper 4uh coil good and warm on the high
> bands 20-17-15m.
>
> ### IF the tuned input is NOT done correctly...
.. it will kill
> ur eff.. real fast. Locating the C2 tuned input variable cap
> closer to the tube socket/ and/or installing a small 100 pf NPO
> doorknob next to the socket..[ in
effect moving a portion of C2
> closer to the socket] will improve the eff on the higher bands.
>
> ### I'd say we may well be arguing semantics here.... but I'd
> say it's just one more advantage of GG amps.... better apparent
> eff... and slightly lower plate diss.
>
> Later... Jim VE7RF
>
> > 73
> > Peter
> >
>
>
