[Amps] Price per Watt Conversation

[Carl]

OTOH spikes and overcurrent was a primary cause for mercury vapor rectifier 
failures  and since the 1N5408 and 6A10 arrived I havent heard of a 
failure.....which doesnt mean they havent....

Carl


----- Original Message ----- 
From: "Roger (K8RI)" <k8ri at rogerhalstead.com>
To: <amps at contesting.com>
Sent: Sunday, April 23, 2017 3:04 AM
Subject: Re: [Amps] Price per Watt Conversation


> 75.6% efficiency shows the devices are biased deep into class C, not 
> pulsed. Linear should be 60 to 65%. With 4 devices running 1500 to 2500 
> PEP total out the heat and junction temperatures should not be a problem. 
> Even linear / digital at 1500 shouldn't be a problem as they are running 
> less than 400W per device..
> These appear to me to be a major step in the right direction. OTOH we 
> should not forget that a tiny (short duration) voltage spike can take out 
> a SS device, while tubes are relatively forgiving. Very forgiving when 
> compared to SS devices
>
> 73, Roger (K8RI)
>
> On 4/23/2017 2:21 AM, Roger (K8RI) wrote:
>> On the parallel, PP, the convention has been PP, parallel. Each unit runs 
>> two devices, PP with the outputs into a combiner..  Those new 65 Volt 
>> devices,
>> http://www.richardsonrfpd.com/Pages/Product-Details.aspx?productId=1241241 
>> rated at 1800 watts ea (one page lists Max as 2KW Carrier) at $250 ea. 4 
>> would be $1,000 and only 375W per device. Less than a quarter of their 
>> ratings which should require far fewer efforts at the most efficient 
>> cooling per device.
>> Actually with 4 of these, 3 KW out is still less than 50% leaving them 
>> running well away from the  "1% knee"
>>
>> NOTE the base, rather than being insulated is the source, so the copper 
>> spreader would be at 65 VDC
>>
>> Running at those levels would require less protective circuitry and an 
>> ability to handle higher SWR.  Of course, with that much overhead there 
>> would be those who would want every watt they could get out of it even 
>> though the circuits were optimized for the legal limit, or relatively 
>> close to it.
>>
>> With 4 devices at $1,000, we are very close to the cost of tubes capable 
>> of running any mode at the legal limit.  Even at the 1800 W limit we're 
>> looking at 7200 Max which 4 devices should do on SSB.  How ever you look 
>> at it these new LDMOS are capable of working the legal limit from 160 
>> through 440 although the LP filters could get kinda messy, but ALL bands 
>> with one amp! Now there's something to think about.  OTOH the layout for 
>> HF and low VHF wold probably be a problem at high VHF and UHF.
>>
>> 73, Roger (K8RI)
>>
>> On 4/22/2017 10:08 PM, Jim Thomson wrote:
>>> Date: Sat, 22 Apr 2017 16:53:50 +0000 (UTC)
>>> From: Catherine James <catherine.james at att.net>
>>> To: <amps at contesting.com>, Manfred Mornhinweg <manfred at ludens.cl>
>>> Subject: Re: [Amps] Price per Watt Conversation
>>>
>>> Manfred,
>>>
>>>     So would it be better to use 4 or or more devices with somewhat 
>>> lower ratings for linear operation?
>>>
>>>     Is there a cheaper option to use simpler heat sinks that don't have 
>>> to be carefully machine, but push them less hard by spreading the power 
>>> over a larger number of devices?  What's the practical upper limit of 
>>> devices that could be used before creating other design problems?
>>>
>>> 73,
>>> Cathy
>>> N5WVR
>>>
>>>
>>> ##  why not use   4  x  BLF188XR    or    4 x MRFX1K80H ? Is it even 
>>> possible to use 2 x devices in parallel in each half of a push-pull 
>>> amplifier ?    If it is possible, then the heat could be extracted  over 
>>> 4 x devices.
>>> The TX imd, with 4 x devices run at 1.5 kw, on paper, should be good, 
>>> since each device is running at 375 w pep output.   Toss in 
>>> pre-distortion, and IMD could be reduced further.
>>>
>>> _______________________________________________
>>> Amps mailing list
>>> Amps at contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
>>
>>
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