Thanks!
Yes, a string of short pulses and a pep output meter is the right method
tuning up an amplifier. For a grounded grid linear, tune for maximum output
and increase loading a bit beyond that and try to keep the manufactures
recommended relationship beetween anode and grid current. The grid current
is also a good indicator of proper loading. The average anode voltage will
then be very often nearly the same as in actual service when you have
condenser input in your power supply. Nowadays you do not need the ALC cable
as you can , in the latest rigs, adjust the proper drive power via the menu.
On a crowded band your ham neighbors will love you more if you then adjust
your microphone gain so that you just get a flicker of ALC indication at the
rigs instrument. You will still get max pep output but sometimes less "
buckshots " close to the frequency.
Hej daa / Hans SM5KI
----------
>Från: measures <measures@vcnet.com>
>Till: "Hans Goldschmidt" <sm5ki@algonet.se>, "AMPS" <amps@contesting.com>
>Ämne: Re: SV: [AMPS] feedback sought: Ameritron AL-80
>Datum: lör 30 okt 1999 16.36
>
>
>>
>>Hej all:
>>
>>I have in front of me an EIMAC data sheet of the 3-500Z ( 6-1-77) and HAM
>>RADIO (1/77 ) - an article by W6SAI called "intermittent voice operation " (
>>EIMAC publication AS 40 ) . The 3-500Z is said to deliver 890 watts of
>>useful watts ( does this include output circuitry losses?? ) at 3500
>>volts/400 mA and 40 dB 3rd order products. The 8873 ( inside same as 8875
>>and 8874 ), mentioned in the HAM RADIO article, has a 350 mA maximum anode
>>current. Still, EIMAC, in IVS service,allows 500 mA ( in short tune ups
>
>? very short. According to the specs, the max. on time for 500mA is
>50-milliSeconds. In other words, you must use a tuning pulser for
>tune-up.
>
>>and
>>SSB modulation peak current ) with still low 35 dB 3rd order distorsion
>>products. The 8874 family has been been pushed to this limit in this IVS way
>>in many amplifiers by HENRY, HEATHKIT, ALPHA with little problems in normal
>>use. I also have seen many amplifiers using 8873 and 8874 after many years
>>service still delivering almost full power with no harm and still almost
>>normal distorsion products. Even when using PEP in cw service. My old HENRY
>>using a pair of 8873s, nowadays used by a guy in cw contests, still works
>>fine. It all depends on the operator, of course - the way he tunes up his
>>amplifier and using it. RTTY, FM and long tune-ups is of course not possible
>>in this IVS service unless you have a thick wallet,hi!
>
>? Indeed Hans. For a photo of what happened to some 8874 (oxide)
>cathodes that were driven beyond this rating, see photos in ''Parasitics
>Revisited'' in the Sept and Oct. 1990 issues of *QST*. However,
>overdrive does not shorten the life of thoriated tungsten cathodes.
>
>
>>----------
>>>FrÂn: measures <measures@vcnet.com>
>>>Till: "AMPS" <amps@contesting.com>
>>>?mne: Re: [AMPS] feedback sought: Ameritron AL-80
>>>Datum: l?r 30 okt 1999 07.27
>>>
>>
>>>
>>>>
>>>>Your mileage may vary, but from my own experience:
>>>>
>>>>I have owned all three: AL-80, SB1000, and AL80B. They all showed >850
>>>>watts carrier into non-radiating (HA!) loads when measured with Bird 43 and
>>>>2500H slug. They worked very well and, in my not so humble opinion, were
>>>>great bangs for the bux. .....
>>>
>>>Obtaining such power from a single 3-500Z at this anode supply voltage
>>>requires driving the tube to more than its Eimac and Amperex rating
>>>of400mA max.. The result is increased splatter in SSB service. The
>>>designer of this amplifier (Mr. Tom Rauch) claimed that he had a letter
>>>from Eimac that increased the anode current rating to more than 500mA.
>>>He never produced the letter.
>>>- cheers
>>>>
>>>>At 02:27 PM 10/29/1999 -0700, Joe wrote:
>>>>>
>>>>>Hi,
>>>>>I have come across an original Ameritron AL-80
>>>>>amplifier. This is not the AL-80A or AL-80B. Runs a
>>>>>single 3-500Z.
>>>>>
>>>>
>>>>73 from NS1Z, FN44rn
>>>>
>>>>John Wilcox
>>>>871 Route 120
>>>>Rumford, ME 04276-3836
>>>>
>>>>fon: 207-364-2246
>>>>
>>>>--
>>>>FAQ on WWW: http://www.contesting.com/ampsfaq.html
>>>>Submissions: amps@contesting.com
>>>>Administrative requests: amps-REQUEST@contesting.com
>>>>Problems: owner-amps@contesting.com
>>>>Search: http://www.contesting.com/km9p/search.htm
>>>>
>>>
>>>
>>>- Rich..., 805.386.3734, www.vcnet.com/measures.
>>>
>>>
>>>--
>>>FAQ on WWW: http://www.contesting.com/ampsfaq.html
>>>Submissions: amps@contesting.com
>>>Administrative requests: amps-REQUEST@contesting.com
>>>Problems: owner-amps@contesting.com
>>>Search: http://www.contesting.com/km9p/search.htm
>>>
>>>
>>
>>--
>>FAQ on WWW: http://www.contesting.com/ampsfaq.html
>>Submissions: amps@contesting.com
>>Administrative requests: amps-REQUEST@contesting.com
>>Problems: owner-amps@contesting.com
>>Search: http://www.contesting.com/km9p/search.htm
>>
>
>
>- Rich..., 805.386.3734, www.vcnet.com/measures.
>
>
>--
>FAQ on WWW: http://www.contesting.com/ampsfaq.html
>Submissions: amps@contesting.com
>Administrative requests: amps-REQUEST@contesting.com
>Problems: owner-amps@contesting.com
>Search: http://www.contesting.com/km9p/search.htm
>
>
--
FAQ on WWW: http://www.contesting.com/ampsfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|