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K2 #4913 160m issue?

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Ken Bessler-2

K2 #4913 160m issue?

My VFO range on 160m is 1330-1941. The rig stops tuning
outside this range. I didn't notice it until tonight because I rarely
tune outside of 1800-1900.

At first I suspected the 80/160m bandpass inductors which I
never readjusted after I installed the 160m module. I didn't do
that because I was getting full power into a dummy load across
both bands with L3/L4 peaked for 80m only.

Might this be another clue? My VFO won't tune above 4.104,
either. All the other bands seem fine.

I just tweaked L3/L4 for a good compromise of power on *both*
bands but I still can't get the VFO to cover all of 160m.

Help?

Ken KG0WX
K2 #4913
(Firmware 204p)

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Don Wilhelm-3

RE: K2 #4913 160m issue?

Ken,

It is the VCO - not the bandpass filters. The VCO will stop changing
frequency when the voltage at the left end of R30 goes much above 7.7 volts
and becomes unstable below 1 volt.

It would appear that you need to re-investigate the entire VCO range
adjustment and adjust L30 to get everything within range on all bands. See
the VCO alignment section of the manual (page 61 in the Rev F manual).

If you cannot get 160 meters within range C75 may be at the lower edge of
its tolerance, a small padder capacitor can often be added across C75 to
bring things in line.

73,
Don W3FPR

> -----Original Message-----
>
> My VFO range on 160m is 1330-1941. The rig stops tuning
> outside this range. I didn't notice it until tonight because I rarely
> tune outside of 1800-1900.
>
> At first I suspected the 80/160m bandpass inductors which I
> never readjusted after I installed the 160m module. I didn't do
> that because I was getting full power into a dummy load across
> both bands with L3/L4 peaked for 80m only.
>
> Might this be another clue? My VFO won't tune above 4.104,
> either. All the other bands seem fine.
>
> I just tweaked L3/L4 for a good compromise of power on *both*
> bands but I still can't get the VFO to cover all of 160m.
>
>

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Ken Bessler-2

Re: K2 #4913 160m issue?

----- Original Message -----
From: "W3FPR - Don Wilhelm" <[hidden email]>
To: "Ken Bessler" <[hidden email]>; "Elecraft Main Group"
<[hidden email]>
Sent: Wednesday, July 20, 2005 8:15 AM
Subject: RE: [Elecraft] K2 #4913 160m issue?

> Ken,
>
> It is the VCO - not the bandpass filters. The VCO will stop changing
> frequency when the voltage at the left end of R30 goes much above 7.7
> volts
> and becomes unstable below 1 volt.
>
> It would appear that you need to re-investigate the entire VCO range
> adjustment and adjust L30 to get everything within range on all bands.
> See
> the VCO alignment section of the manual (page 61 in the Rev F manual).
>
> If you cannot get 160 meters within range C75 may be at the lower edge of
> its tolerance, a small padder capacitor can often be added across C75 to
> bring things in line.
>
> 73,
> Don W3FPR

Bingo! I actually woke up last night with that idea but I decided
to wait until I heard from the list before messing around.

2000 kc was 8.89v and all my values that I had written down
in the manual were off.

I found I had to make a compromise between 2000 (7.3v) and
3500 (1.83v) when tweaking L30 but all the other bands were
well in range.

The only changes to the rig since I first did the VCO alignment
are the addition of the KAT2, KIO2 and K160RX. Could adding
the 160m module be the culprit? My guess is yes but I could
not find anything in the 160 manual talking about re-aligning the
VCO after installing the module.

Maybe a good candidate for an errata sheet?

Thanks for the help, Don!

Ken
--
Just my 2¢... 73 es gd dx de Ken KGØWX
Grid EM17ip, Flying Pigs #-1055
Proud builder & owner of Elecraft K2 #4913

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Don Wilhelm-3

RE: K2 #4913 160m issue?

Ken,

I really can't underatand why adding only C75 to the circuit (the only
change to the VCO for 160 meters) would throw off your prior adjustments, so
you might want to look for something else.

Actually the only thing I can think of right now is the possibility that T5
is mounted a bit loose and something (your hand maybe) shifted the turns on
T5 slightly - stranger things have happened.

73,
Don W3FPR

> -----Original Message-----
>
> > Ken,
> >
> > It is the VCO - not the bandpass filters. The VCO will stop changing
> > frequency when the voltage at the left end of R30 goes much above 7.7
> > volts
> > and becomes unstable below 1 volt.
> >
> > It would appear that you need to re-investigate the entire VCO range
> > adjustment and adjust L30 to get everything within range on all bands.
> > See
> > the VCO alignment section of the manual (page 61 in the Rev F manual).
> >
> > If you cannot get 160 meters within range C75 may be at the
> lower edge of
> > its tolerance, a small padder capacitor can often be added across C75 to
> > bring things in line.
> >
> > 73,
> > Don W3FPR
>
> Bingo! I actually woke up last night with that idea but I decided
> to wait until I heard from the list before messing around.
>
> 2000 kc was 8.89v and all my values that I had written down
> in the manual were off.
>
> I found I had to make a compromise between 2000 (7.3v) and
> 3500 (1.83v) when tweaking L30 but all the other bands were
> well in range.
>
> The only changes to the rig since I first did the VCO alignment
> are the addition of the KAT2, KIO2 and K160RX. Could adding
> the 160m module be the culprit? My guess is yes but I could
> not find anything in the 160 manual talking about re-aligning the
> VCO after installing the module.
>
> Maybe a good candidate for an errata sheet?
>
> Thanks for the help, Don!
>
> Ken
> --
>