[UK-CONTEST] Amplifier Advice ACOM 2000's

[David]

Ian

I agree with you also about RX performance. I would not like to be running a
FT857 in a major contest (I use one in the car) its close in performance is
terrible makes a perfect transmission a wide one due to its inadequate
dynamic range. Many RXs in use are of similar inadequate performance to the
FT817/FT857/897 series in a strong signal environment. Even the FT1000MP has
inadequate close in dynamic range and in RTTY and CW contests I used to hear
phantom signals created by intermodulation products of multiple contest
signals.

It is for this reason that a significant number of major contesters now use
the Elecraft K3. If you hear a wide signal on a K3 it is the TX that is the
problem. Also the K3 PA IMD is around -40dB below PEP at 100 watts and lower
at 40-50 watts. Most popular rigs are -30dB or worse.

The cause of wide signals using FSK is inadequate filtering of the TX
signal. 

73 David

-----Original Message-----
From: uk-contest-bounces at contesting.com
[mailto:uk-contest-bounces at contesting.com] On Behalf Of Ian White GM3SEK
Sent: 26 January 2012 10:17
To: uk-contest at contesting.com
Subject: Re: [UK-CONTEST] Amplifier Advice ACOM 2000's

Christopher Plummer wrote:
>please don't run kilowatts BECAUSE YOU (think) YOU CAN, the rest of us 
>don't appreciate the sidebands and spatter.

How strange to say that about RTTY contests, because RTTY is a
constant-level mode where any "sidebands and splatter" are guaranteed
*not* to have been generated in the amplifier!

The transceiver, the amplifier, the antenna and the propagation can all
increase the levels of "sidebands and splatter" that other people hear...
but somehow, only one of those gets the blame.

The large majority of amplifiers that require only 30-50W drive create no
higher levels of far-out IMD than the barefoot transceiver at 100W (and I do
mean absolute levels). Many stations are actually *less* noticeable
elsewhere on the band when using an amplifier.

Of course the main signal is louder when using an amplifier; but (and how
often do we need to say this?) being loud is not a crime.


-- 

73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek
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