[Elecraft] Transmitter performance

[Dave]

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" <gm3sek at ifwtech.co.uk>
To: "'Dave'" <dave at g0dja.co.uk>; "'Elecraft Reflector'" 
<elecraft at 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.
>