Thanks for the clarification, and link, Ian. I was just being a bit careful
in case I stepped on anyones copyright.
Thanks also for the clarification about what was being measured and its
effects on other people using the band. However, as a mainly VHF/UHF user,
it does worry me that we go to a lot of trouble to get the best receivers
that we can, but sometimes forget the effects of our transmitters... One of
the reasons I bought a KX3 was to use it to transvert to VHF and UHF bands,
so I am concerned about "Brand F" as Ian refers to them. It makes me very
glad I did not go back down that route, but on the other hand, my receivers
may have to cope with the transmitter outputs from other people who are
using that make of transceiver to transvert onto the VHF/UHF bands. I've
even heard of people considering EME using transverters fed by 'Brand F'
transceivers..
On 23cm the signals can be very loud, often approaching S9(9) +40dB. In
fact, the beacon with the signals detectable out several kHz either side of
the main transmission, *was* many dB over S9 here a few days ago. Signal
paths were so good I worked three Polish stations using just 10W and a 39
element Yagi getting reports of 559 from one who was 1500km from here. On
UHF bands many people do try to give realistic reports of how strong the
signals really are. He was using 150W to a similar Yagi/Uda, so if he'd used
a dish (not uncommon on 23cm) then he might well have approached +40dB over
9. These conditions are not that uncommon on the higher UHF and SHF bands.
I to have a PA capable of 150W, so when I eventually fire that up I will
certainly be much stronger than +40dB to many of my neighbours, and not so
close neighbours, on 23cm and, eventually, 13cm as well.
So, "good enough" on HF may turn into "only just acceptable" at times on
other bands.
I don't think that this KX3 user should go back to sleep just yet...
Dave (G0DJA)
----- Original Message -----
From: "Ian White" <gm3...@ifwtech.co.uk>
To: "'Dave'" <d...@g0dja.co.uk>; "'Elecraft Reflector'"
<elecraft@mailman.qth.net>
Sent: Saturday, December 21, 2013 9:41 AM
Subject: RE: [Elecraft] Transmitter performance
To help make this discussion clearer, there is no problem about
referencing the original article [1]. The author, SM5BSZ, has published
it on his website for everyone to see, because this topic of wideband
noise from transmitters needs to be much more widely known.
<http://www.sm5bsz.com/dynrange/dubus313.pdf>
Dave's concern is that high-level TX noise sidebands can cause problems
to other band users. HF operators never notice this problem because TX
noise is buried beneath other band noise; but it can be a very real
problem on VHF and microwaves where the background noise levels are
extremely low but signals can sometimes be much stronger than on HF.
This places extreme demands on dynamic range - not only in the receiver
(which we hear a hear a lot about) but also in the transmitter.
The KX3 qualifies as 'good enough' because its transmitter noise
sidebands are unlikely to affect anyone else's noise floor unless the
main signal is stronger than S9+40dB... and the K3 is another 20dB
better than that.
Bottom line: Elecraft users can go back to sleep :-)
[1] For full disclosure, I am a volunteer editor for DUBUS magazine
(www.dubus.org). Copyright of articles published in DUBUS remains with
the original authors, so they are free to publish in other media as
well.
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