>This is enough Dave, lets not start it all over again!
>Thanks Will, K6NDV
>
Dave/Mike ? made some valid points, Will. Please see below.
>-----Original Message-----
>From: owner-amps@contesting.com [mailto:owner-amps@contesting.com]On
>Behalf Of Wt8r@aol.com
>Sent: Saturday, July 21, 2001 9:54 AM
>To: na9d@speakeasy.net; amps@contesting.com
>Subject: Re: [AMPS] Setting the record straight--Dick Ehrhorn
>
>
>
>In a message dated 7/21/01 11:34:47 AM Eastern Daylight Time,
>na9d@speakeasy.net writes:
>
>>
>> on 7/18/01 12:03 PM, 2 at 2@vc.net wrote:
>>
>> >
>> > /\ Designing an unconditionally-stable HF/MF amplifier is more
>difficult
>> > than designing a stable amplifier for VHF. Although I have heard
>> > reports thereof, I have never seen parasitic damage in a VHF or UHF
>> > amplifier.
>>
>> I gotta throw my 2 cents in on this one because this statement is just not
>> completely accurate.
>
>Two cents is more than your statement is worth, because you don't know
>whether Rich has heard reports thereof nor do you know whether he has seen
>parasitic damage in a VHR or UHF amplifier as he states. He says that he
>has not, so one might conclude that you are calling him a liar.
>
/\ liar is a bit strong.
>> Building a stable amplifier that has high gain becomes increasingly
>> difficult the higher ones goes in frequency. Things such as layout issues,
>> bypassing and genuine parasitics become critical. When I say "genuine
>> parasitics" I don't mean the kind Rich talks about. I am talking about
>the
>> inherent, real world, stray inductances and capacitances in components.
>
>Please explain the difference between "genuine parasitics" and Measure's
>parasitics" since you are so well versed in theory.
>
/\ the last part of this sentence is (beginning with "since") detracts
from the impact. Understating works way better than overstating.
>> Rich's statement could argued to be correct only because generally we hams
>> build our HF/MF amplifiers to be pretty broad banded in their coverage.
>> Sure we may have different tuned circuits for different bands, but the
>> amplifier in general covers a very large percentage bandwidth. For
>> simplicity's sake let's say the HF band is from 1 to 30 MHz, centered at 15
>> MHz (I know it starts higher than 1 MHz). An amp designed to cover this
>> basically is designed for nearly 200% bandwidth! (Percentage bandwidth is
>> defined as the total bandwidth covered divided by the center frequency *
>> 100). Our bandwidth is 30MHz - 1 MHZ = 29 MHz. %BW = (29/15)*100 which is
>> approximately 200%.
>>
>The above statement is ludicrous and shows how well you understand radio
>theory.
>
/\ and mathematics. Remove "is ludicrous and" - and you have a better
torpedo.
>> That's significant and that's what makes designing plate chokes, suppressor
>> chokes, etc. a real art.
>>
>> Now take a UHF amplifier design at 435 MHz. Even if we wanted to cover the
>> entire 70cm band from 420 to 450 MHz, we only have a percentage bandwidth
of
>> 6.8%! Yet no one designs the UHF amplifiers to have even that much
>> bandwidth. It would be rather difficult. Amazing, how we are covering
>> approximately the same total bandwidth - 30 MHz.
>>
>> A UHF amplifier with the same bandwidth as our HF amp would literally cover
>> from nearly DC to 900 MHz!
>>
>> My point is we have to compare apples to apples. An HF amp with a
bandwidth
>> of 6.8% would be MUCH easier to stabilize than a UHF amplifier with 6.8%
>> bandwidth.
>
>Your comparison is apples to lemons. Does your wunderkin 4-1000A amplifier
>which you built using clever techniques, operate on the following frequencies
>in YOUR stated bandwidth: 4-6.99 Mhz, 7.3-13.99 MHz, 14.3-20.99 MHz and
>21.5-27.99 MHz?
>>
>> Rich's statement as blanket fact is just not true.
>
>Not only are your statements untrue, some might call them unintelligent.
>
/\ ditto
- R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.
end
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