My major concern, based on my actual measurements, is that operating a
power amp of this type and design at reduced to significantly reduced
power nets very poor efficiency. In fact, my KPA500 at certain power
levels below 500 watts will actually have higher heat dissipation than
if operated at rated power. With this known, we all understand that heat
is one of the most detrimental factors regarding solid state circuits
and components. I find many instances where hams operate at lower
power with the thinking "it will save my tubes or transistors, etc."
Based on measurements, this thinking is far from accurate. I refer it
to "old ham lore".
As to operating on 60M, the US power limit is 100 watts ERP (Effective
Radiated Power) with reference to a 1/2 wave dipole. Unless one actually
knows the loss and gain of the antenna system, just operating at 150 to
200 watts is a blind shot in the dark. Do you know the gain or loss of a
specific antenna? Loss in a feedline is relatively easy to determine.
Gain or loss in the antenna is quite a challenging project. Of course
who is going to know? That is not important. But what is important,
one must be thoughtful of others, those that do operate within legal
power limits. Just because you can, is no sign you should do so. It
just isn't the ham radio way. The methodology is different for 30M
where the PEP is 200 watts. Add a 6 dB gain antenna and one has 800
watts ERP. 60M is not like that.
Perhaps the regulations should be re-written such that legal limit power
is 1500 watts ERP in place of 1500 watts PEP. That certainly would put
all folks on a level playing field. After all, FM broadcast and TV
stations power is sated in ERP values. I go back to changes when AM
power was defined as 1 Kw DC input to the final stage. That was changed
to a power of 1500 watts PEP. With AM that equates to a carrier of 375
watts modulated 100% for 1500 watts PEP.
While electricity may be cheap, the abuse and failure of solid state
devices operating at high temperature is not cheap. Just something to
think about.
73
Bob, K4TAX
----------------------------------------------------------------------
Message: 1
Date: Tue, 24 Dec 2024 21:17:55 +0000 (UTC)
From: Wilber Bandemer <bandem...@aol.com>
To: "elecraft@mailman.qth.net" <elecraft@mailman.qth.net>
Subject: [Elecraft] KPA 500 Power Amp.
Message-ID: <1476882602.6827589.1735075075...@mail.yahoo.com>
Content-Type: text/plain; charset=UTF-8
KPA 500 will not transmits on 60 meters. Please tell me what is wrong and what
should I do to fixed this problem?73Wilber AB5WW
------------------------------
Message: 2
Date: Tue, 24 Dec 2024 13:32:23 -0800
From: jerry <je...@tr2.com>
To: Wilber Bandemer <bandem...@aol.com>
Cc: elecraft@mailman.qth.net
Subject: Re: [Elecraft] KPA 500 Power Amp.
Message-ID: <b69f1bd595b09352c8ff823dfa70b...@tr2.com>
Content-Type: text/plain; charset=US-ASCII; format=flowed
Why use it on 60M? Legal limit is 100W ERP on that band.
- Jerry, KF6VB
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com
