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Elecraft XV144 and XV50 - TX Noise and birdie

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Ken G3WCS

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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S55M

Re: Elecraft XV144 and XV50 - TX Noise and birdie

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.jpg
I 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.jpg
and
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)
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com

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S55M

Re: Elecraft XV144 and XV50 - TX Noise and birdie

In reply to this post by Ken G3WCS

And here are some things to read about K2+XV144!
I think something went wrong with measured K2 or XV144 but this are the
results and Henning comments:

http://www.df9ic.de/tech/trxtest/trxtest.html

Some comments from Eric, Wayne or others is Wellcome!

S55M Adi

----- 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

Don Wilhelm-3

RE: Elecraft XV144 and XV50 - TX Noise and birdie

Adi,

No comment on the numbers they produced, but from Henning's comments about
the K2 - "worst receiver", "ridiculously high AGC threshold" and his stated
dislike of the variable crystal IF filter indicate to me that he either has
a strong bias against the K2s features or has it adjusted improperly.
Unfortunately, there was no data presented without the transverter, so it is
difficult to judge whether or not the K2 used was properly adjusted. ARRL
test lab results indicate the base K2 has a very good receiver.

73,
Don W3FPR

> -----Original Message-----
>
> And here are some things to read about K2+XV144!
> I think something went wrong with measured K2 or XV144 but this are the
> results and Henning comments:
>
> http://www.df9ic.de/tech/trxtest/trxtest.html
>
>
>
> Some comments from Eric, Wayne or others is Wellcome!
>
> S55M Adi
>
>

DW Harms

RE: Elecraft XV144 and XV50 - TX Noise and birdie

Hi all,

If the K2 has positive IIP3 specifications on 28 MHz which I think it has
(though the measurements I have seen were all conducted on 14 MHz...), then
it is hard to believe the measurements of DF9IC are reflecting the true
situation.
The XV144 uses a TUF-1H which is a 17 dBm mixer, the frontend is made up of
devices with positive IIP3 specs, so -26,4 dBm is really impossible!
I suppose something went wrong in these measurements and that can happen, we
are humans after all. But I hope DF9IC will redo that test!

The only thing that I am convinced of, is that the phase-noise of the K2 can
be improved and that it will bring significant improvement. I totally agree
with Robert S53WW on that one. Of course, -124 dBc at 10 kHz is not bad but
it must be possible to improve it to the level of the Ten Tec OMNI VI+ (-138
dBc/Hz at 10 kHZ)....
Another point of improvement may be the bandfilters in the 28 MHz section.
They are the same types that are used on the lower bands and their in-band
and out-band selectivity on 28 is a point of concern.

Best 73, Dick PA2DW

K2 #3892 plus DEM 28-144 ECK transvertor to 2m (never measured yet hi!)

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S55M

Re: Elecraft XV144 and XV50 - TX Noise and birdie

Hello K2ers!

I just written an email to Henning regarding his results and told him, that
should be a great gesture if he can add a note to his site where is clearly
written, that something was wrong with measured K2 or XV144.
I hope he will do it.

73's
Adi
----- Original Message -----
From: "Dick Harms PA2DW" <[hidden email]>
To: <[hidden email]>; "'S55M'" <[hidden email]>; "'Ken G3WCS'"
<[hidden email]>; <[hidden email]>
Sent: Sunday, April 10, 2005 6:15 PM
Subject: RE: [Elecraft] Elecraft XV144 and XV50 - TX Noise and birdie

> Hi all,
>
> If the K2 has positive IIP3 specifications on 28 MHz which I think it has
> (though the measurements I have seen were all conducted on 14 MHz...),
then
> it is hard to believe the measurements of DF9IC are reflecting the true
> situation.
> The XV144 uses a TUF-1H which is a 17 dBm mixer, the frontend is made up
of
> devices with positive IIP3 specs, so -26,4 dBm is really impossible!
> I suppose something went wrong in these measurements and that can happen,
we
> are humans after all. But I hope DF9IC will redo that test!
>
> The only thing that I am convinced of, is that the phase-noise of the K2
can
> be improved and that it will bring significant improvement. I totally
agree
> with Robert S53WW on that one. Of course, -124 dBc at 10 kHz is not bad
but
> it must be possible to improve it to the level of the Ten Tec OMNI VI+
(-138
> dBc/Hz at 10 kHZ)....
> Another point of improvement may be the bandfilters in the 28 MHz section.
> They are the same types that are used on the lower bands and their in-band
> and out-band selectivity on 28 is a point of concern.
>
> Best 73, Dick PA2DW
>
> K2 #3892 plus DEM 28-144 ECK transvertor to 2m (never measured yet hi!)
>

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