The EU 4-400A is QB4-1100 or QY4-400, atleast when
made by Philips.
73 SM2EKM
----------
Karl-Arne Markström wrote:
> "Amperex 8179, which may be similar to the 4-400"
>
> The 8179 or QB5/2000 is actually more of an European 4-1000A.
>
> It has comparable plate voltage and plate dissipation ratings, and is
> specified for
> linear amplifier service.
>
> 73/
>
> Karl-Arne
> SM0AOM
>
> ----- Original Message -----
> From: "k7fm" <k7fm@teleport.com>
> To: <amps@contesting.com>
> Sent: Tuesday, January 10, 2006 5:24 AM
> Subject: [Amps] Components Causing Distortion in Amplifiers
>
>
>
>>Someone asked whether components such as capacitors can cause distortion in
>>linear amplifiers. Somehow the e-mail got side-tracked, but I have some
>>comments in response. The response is not quite on point, but raises some
>>interesting points.
>>
>>The comments are not mine, but those of W2LPC and WA2PDI, both who worked
>>for Amperex at the time they wrote the article. The article was published
>>in 73 Magazine in May of 1963. The article is entitled "Low Distortion All
>>Band Linear Kilowatt" and described about the design of an amplifier using a
>>Amperex 8179, which may be similar to the 4-400. They mentioned all of the
>>normal things, such as regulated screen and bias - but let them finish the
>>story:
>>
>>"When the amplifier was first constructed, the distortion was found to be
>>quite bad (about -30 db). This was caused largely by the fact that the
>>current meters and the circuit breaker coils in the negative leads of the
>>power supplies were not bypassed for audio frequencies, causing an audio
>>voltage to be superimposed on the power suply voltages. By bypassing the
>>meters and circuit breakers coils with electrolyticcapacitors, the
>>distortion was decreased considerably.
>>
>>The distortion was decreased still further by leaving the unused turns on
>>the plate tank coil unshorted when switching from band to band, instead of
>>shorting them as was done when the amplifier was first constructed.
>>
>>The 8179 data sheet states that the tube must be operated in a vertical
>>position only. During testing, the amplifier was operated on its side and
>>it was noted that the distortion figures became slightly degraded, probably
>>caused by misalignment of the control and screen grids due to sagging of the
>>elements when the tube is operated on its side."
>>
>>Later in the article, they summarized design considerations for a low
>>distortion amplifier. In summary, they are:
>>1. Any impedance in series with the power supplies must be bypassed for
>>audio as well as rf.
>>2. In grounded grid operation, second harmonics of the driver must be
>>suppressed, normally with a tuned input.
>>3. The screen and control grid power supplies should be well regulated.
>>4. The excited distortion should be at least 20 db better than the
>>amplifier in order not to increase the amplifier distortion by more than 1
>>db. If extra drive power is available reisistive swamping is advised for
>>grounded grid operation.
>>5. The plate tank coil should be progressive opened instead of shorted when
>>changing bands.
>>
>>I brought up these points a number of years ago and someone told me I was
>>nuts for saying that shorting out the turns would affect distortion. Well,
>>I am not saying that - two employees who worked for Amperex said it.
>>The inference is that they had a spectrum analyzer and hard data to support
>>their statements - but I do not know. Perhaps they were janitors and just
>>made it up.
>>
>>I mentioned it, because if Tom is designing the perfect amplifier he at
>>least ought to have the input, and it can be tested easily enough.
>>
>>73, Colin K7FM
>>
>>_______________________________________________
>>Amps mailing list
>>Amps@contesting.com
>>http://lists.contesting.com/mailman/listinfo/amps
>>
>>
>>--
>>No virus found in this incoming message.
>>Checked by AVG Free Edition.
>>Version: 7.1.371 / Virus Database: 267.14.16/224 - Release Date: 2006-01-09
>>
>>
>
>
>
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|