Posted by
S55M on
Apr 09, 2005; 9:34pm
URL: http://elecraft.85.s1.nabble.com/Elecraft-XV144-and-XV50-TX-Noise-and-birdie-tp376803p376808.html
Hello!
I have made some measurments, but not with XV series transverters but with
"Javornik" 144/14MHz IF.
I compared Ft1KMP and K2 driving the same transverter and observed the
noise (not birdies) 20KHz away from the carier.
The K2+TRV increased noise some 7 to 10dB more than FT1KMP+TRV at same power
output (+43dBm).But K2 has less "splatters" as Ft1KMP.
And about birdies (the "milion" of tiny ones)...most of them are generated
on KSB2 SSB board interacting between PIC clock signal and SSB audio
path,mostly in Q1.
I have made some shielding and bring them down for some 10dB but this is not
most "brilliant" solution.
http://www.s55m.com/teh/images/ksb2.jpgI have tried to moove Q1 on the bottom side of PCB but no improovment.
I also noticed the "drifting condor" but i have no idea where it comes from
:( .
You are lucky to use 28MHz IF ,so You are free of 14.361MHz "beacon".
For the general phase noise of K2 on TX i still wait for some solution
either from designers or maybe from good friend of mine
Robi-S53WW.
73's
S55M-Adi
P.S.
Here are my measurment of K2 RX compared to FT1KMP and TS930S
http://www.s55m.com/teh/K2930MP.jpgand
http://www.s55m.com/teh/RXPN.gif----- Original Message -----
From: "Ken G3WCS" <
[hidden email]>
To: <
[hidden email]>
Sent: Saturday, April 09, 2005 12:33 PM
Subject: [Elecraft] Elecraft XV144 and XV50 - TX Noise and birdie
> Hello all,
>
> A few months back I put together the XV144 and XV50 transverters. Both
> work fine but following some comments from very local stations I decided
> to make one or two checks.
>
> I am comparing these tranverters with my own original 144Mhz transverter
> which I built about 15 years ago.
>
> With no input to either transverter but with the input terminated at 50
> ohm and with a resonant antenna connected, listening on another receiver
> with an antenna connected reveals quite a high hiss or mixing noise when
> the PTT line is operated. This happens on both the 50 and 144 Mhz
> transverters. If I operate the PTT line of my old home brew transverter
> there is no such noise or if any it is very much reduced. I am sure the
> hiss (phase/mixer noise) is many db down on the normal output level but
> it is nevertheless much greater than my original home made unit.
>
> Secondly, and somewhat more worrying is a drifting birdie that both the
> XV50 and the XV144 produce. Once again I know these are many db down on
> the normal output but the 144 Mhz birdie is of sufficient strength that
> a station 15 miles away heard it whilst trying to work an EME QSO. It
> drifted across the frequency he was using. On my particular transverters
> these birdies occur at about 50.130 Mhz on the XV50 and about 144.140
> Mhz. They seem to drift LF during TX and at a rate of about 10 Khz in 5
> minutes.
>
> I wonder if anyone else has made any observations and come up with a
> cure. I all other aspects the transverters are excellent and totally
> stable. Indeed, the 144 Mhz version is fitted with a crystal oven.
>
> I know there was a thread on here a month or two back regarding phase
> noise being heard by stations within a 20 Km radius during high levels
> of 144 Mhz activity.
>
> Has anyone else got any more comments or observations to make. I know
> that my observations are not exactly 'scientific' but there are made by
> comparison with a different transverter which does not exhibit these
> problems. During all these tests the transverters have had their inputs
> and outputs correctly terminated with no 28 Mhz drive source connected.
>
> Sorry for the long waffle. Any comments most welcome.
>
>
> Best 73,
>
>
> Ken G3WCS.
> --
>
> Ken G3WCS
> IO83rh : Cheshire : NW England
> (+44) (0)870 765 1632 (home)
> (+44) (0)7733 400 950 (mobile & sms)
>
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