It doesn't say anywhere that I can see, even though it does specify 6kHz @
-26dB for ISB, and 9kHz at -26dB for DSB AM. I asked -- I'll let you know what
I find out.
Joe,
N3JI
"R.Measures" <r@somis.org> wrote:
On Aug 25, 2004, at 6:56 AM, Joe Isabella wrote:
> I take that to mean 650W PEP, 50% duty cycle for 10 mins. To equate
> that to AM, 650W PEP is about
> 150W carrier. But since you have a 150W carrier 100% of the time,
> does that require further
> derating?? All I know is that the TL-922 or SB 220 would do 300W
> carrier AM (or about 1200W PEP)
> for a "normal" AM transmission. I added the auxiliary cooling to my
> Kenwood to keep things cooler
> in the power supply since the fan pulls air mainly over the tubes and
> did little for the supply.
> I would add the extra fan and start at 150W carrier and see how it
> does for a while. if all is
> well (and I'm sure it will be), take it to 200W carrier. If that's
> okay, go to 250W, then 300W.
> I would guess that you'll be fine running it at 300W -- it's beyond
> that that I started having
> problems (PS got too hot).
>
> BTW, read your QRZ bio -- glad you're getting into AM. I run ESSB as
> well and find AM even
> better!! Seems that if the League's proposal of 3kHz wide SSB goes
> through, there won't be any
> other place to run extended audio!! Let's see how it goes...
Joe -- 3kHz wide at how many db down?
>
> Joe,
> N3JI
>
> --- Ed Briggs wrote:
>
>> I contacted the manufacturer on a related topic some time back. Their
>> official response (contained in the manual) is for keydown operation,
>> 650W
>> max, 50% duty cycle, 10 minutes max transmission time (as you know
>> from the
>> manual)
>>
>> I inquired how to derate this for a longer transmission time (say 30
>> minutes). I speculated that since when operating bias is applied (no
>> rf
>> drive) the amp idles at appx 160 ma yielding a dissipation of 450w,
>> representing just under 50% of the combined dissipation of the two
>> tubes,
>> and I asked, is it 'safe' to let the two tubes run with at this level
>> of
>> dissipation for 30 minutes (the key is up after all).
>>
>> They responded " In theory 450 watts should be safe for key down
>> operation
>> but we could not guarantee the tubes would survive this operation."
>>
>> How does this apply to your AM question. The manufacturer seems to
>> have
>> some reservations about cooling at 450w steady state so, although I'm
>> not
>> sure whether they mean 450 w output or 450 w dissipation (possibly the
>> same).
>>
>> Others on this reflector may be able to use this data point from the
>> manufacturer to predict.
>>
>> Ed
>>
>> ----- Original Message -----
>> From: "Rob Atkinson, K5UJ"
>> To:
>> Sent: Tuesday, August 24, 2004 10:13 AM
>> Subject: [Amps] Centurion cooling improvement ideas for AM service
>>
>>
>>> Hi folks,
>>>
>>> I am the owner of a 3 year old Ten Tec Centurion amp. This unit
>>> employs
>> two
>>> 3-500ZGs on an elevated socket platform in the rear right side of the
>>> cabinet (when facing the front panel). On the rear left side is the
>>> h.v.
>>> power supply with a Dahl model 422 transformer which delivers 3.2 kv
>> (around
>>> 2.9 under load) to the plates. Between the p.s. and rf deck is a rf
>> shield
>>> running down the middle of the chassis. A square hole is cut in this
>>> between the tubes and p.s. and over that is mounted a Bi-Sonic tube
>>> axial
>>> muffin fan, model 4E-115-S21, sleeve bearing, 115 v. 220 ma 20 w.
>>> 2200 RPM
>>> moving 82 CFM. The fan is on the tube side of the shield, and draws
>>> air
>> in
>>> through the left side of the cabinet, over the p.s. and exhausts it
>>> horizontally over the h.v. plate choke and tubes, including the pins
>>> and
>>> anode heat sinks, which are the flat type extending out
>>> horizontally. As
>>> most of you know, this has become the standard cooling method for
>>> these
>>> tubes in amateur amps since Heathkit began using it for the SB220.
>>>
>>> This cooling is adequate for low duty cycle modes for which the
>>> Centurion
>>> was designed, but I would like to use mine for brief transmissions
>>> (5 to
>> 10
>>> minutes or less) of dsb carrier AM running a carrier of 200 to 250
>>> watts.
>> I
>>> have done this for a couple of minutes and the amp gets pretty darn
>>> hot.
>> I
>>> would therefore like to boost cooling so as to avoid seal failure.
>>> Increased noise is not a problem for me.
>>>
>>> Bi-Sonic manufactures a fan that is identical to the stock fan but at
>> higher
>>> rpm, and 20 more ma, 22 w. and 105 CFM, around a 25% improvement over
>> stock.
>>> Is this an increase worth pursuing? Another possibility would be
>>> to add
>> a
>>> fan to the external surface of the cabinet over the grill on the
>>> right
>> side
>>> of the rf deck to speed up the draw of air to the right, out of the
>> cabinet.
>>> Again, is this an improvement, and would it be worth pursuing?
>>>
>>>
>>>
>>> Overall, :
>>> A. Are these mods necessary
>>> B. Are there any comments on these methods
>>> C. Perhaps most important, is operating this amp on AM beyond its
>> efficiency
>>> and heat dissipation design capability and should I keep it for SSB
>>> and
>> CW,
>>> and look for something with higher plate voltage and/or tubes with
>>> higher
>>> plate dissipation / more cooling?
>>>
>>> Tnx,
>>>
>>> Rob Atkinson
>>> K5UJ
>>>
>>> p.s. to save you time and trouble, please no comments to run a plate
>>> modulated boat anchor.
>>>
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>
>
>
>
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Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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