>
>Buckshots usually appear the first milliseconds before the ALC in a
>transmitter reduces the gain. Have been heard from many transceivers
>barefoot in the past and has nothing to do with the linearity of the DAF
>linear. So, maybe this was the cause of Norms bad signal not the DAF?
Norm's signal was not bad after he put fixed volts on the screens and
stopped running grid current to the 4cx250Bs.
>
>Maybe he had to insert an attenuator beetween the transmitter and exciter to
>reduce the effects of his , maybe, variable load? If I remember right a
>dummyload was used in later versions at the input of the DAF for the same
>reason?
>
>The DAF has been used very much in the past when most hams were very much
>technically minded and had to build much of their SSB gear themselfs. They
>were much more critical of the quality of their SSB signals then now and
>gave honest reports and really cared for a clean signal. Many hams monitored
>their signals on instruments and understood was inside their rigs. If the
>DAF had been as bad as some of you guys say, it would never become popular,
>thats for sure.
>
>I think it is very foolish to consider the DAF to be bad because just one
>guy called Norm had a bad signal.
All of the DAFs I heard produced more doo-doo than conventional
amplifiers.
I have never heard a conventional grid-driven linear amplifiier that was
linear at more than virtually zero grid current. However, I have heard
some grid-driven amplifiers that had a stiff,not-regulated screen-supply
that produced ok results. .
cheers, Hans
>----------
>>Från: nospam4me@juno.com
>>Till: amps@contesting.com
>>Ämne: [AMPS] daf on-air amplifier testing
>>Datum: mån 27 dec 1999 06.20
>>
>
>>
>>[snip]
>>>From: Colin
>>>...I do not know that the G2DAF design is good or bad, and I would
>>>not use it on the air without testing, what I am objecting to is the
>>>thought process and testing procedures of Rich. They are flawed.
>>
>>how..?
>>
>>>His assertions and conclusions may be correct - but not for all the
>>>reasons stated.
>>
>>Let me tell you about my testing procedures for Norm's DAF
>>amplifier. During a casual conversation with a weak, out of state
>>mobile on 7255 lsb, very heavy spectral buckshot from an operator in
>>conversation on 7258 lsb would cover the mobile's signal.
>>A quick dial up the band would find Norm as the source of the
>>buckshot among the 10 or so other operators. After Norm turned
>>the amplifier off, I could resume my conversation with the mobile 3KHz
>>down the band.
>>I've not been bothered by Norms amplifier in some time now, probably
>>because I've since learned it'd been modified to use a fixed screen
>>potential.
>>In case it was never mentioned, Norms amplifier used dual 4cx250s. I
>>have a copy of the screen control circuit he used. Quite the interesting
>>animal.
>>
>>>And, I do find it somewhat disheartening to have a design from a
>>>respected tube engineer (G2DAF) rejected because it
>>>is misunderstood and as a result of a flawed investigation.
>>
>>Provide me with evidence the daf circuit operates within reasonable
>>values,
>>I'll consider using it. So far the applied example on 7258 could be heard
>>
>>quite well down 3KHz, far above the operators using tubes with handles
>>in their amplifiers.
>>Since the screens were fixed, the buckshot went away.
>>
>>cheers
>>skipp
- Rich..., 805.386.3734, www.vcnet.com/measures.
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