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Terry Schieler

Re: 6 Meters

Ron, AC7AC wrote:

I can't speak for the engineering or product decisions that went into
offering 6 meters with the K3, but for an excellent low-noise 6 meter
capability Elecraft does offer the XV50 transverter which is well integrated
into the K3 and K2 rigs offering direct frequency readout, all of the
capabilities of the base K3 (or K2), and the 6 meter band becomes part of
the band selection just like the HF bands.

The XV144, 222 and 432 round out the same capability, letting you cycle
through bands using the K2 or K3 bandswitch from 160 through 70 cm with one
rig, and each of the VHF/UHF transverters has a low-noise high-performance
receive front end designed specifically for that band.

As Wayne's often mentioned here, the advanced up-conversion design of the K3
is superior for HF but makes incorporating VHF a real challenge. Using an XV
transverter specifically designed for each VHF band keeps the K3 (or K2)
operating as a tunable I.F. in the HF (28 MHz) range.

Ron AC7AC

Hi Ron,

I posted a number of months back asking if I would be better off using my
existing XV50 6 meter transverter with my K3 than the internal K3 receiver.
Someone from Elecraft replied that there would be no real benefit to doing
this. Can't recall who, but it convinced me to put my XV50 up for sale.

Terry, W0FM
K3/100 #474

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wayne burdick

Re: 6 Meters

Administrator

Terry Schieler wrote:

> I posted a number of months back asking if I would be better off using
> my
> existing XV50 6 meter transverter with my K3 than the internal K3
> receiver.
> Someone from Elecraft replied that there would be no real benefit to
> doing
> this. Can't recall who, but it convinced me to put my XV50 up for
> sale.

It was me.

The XV-50 might provide an advantage if:

- you already had your station set up with multiple XV-series
transverters

- you had HF antennas connected to both ANT1 and ANT2, and thus
need to use a transverter in order to take advantage of a
special 6-m antenna

- you already have an XV-50, need the lower NF it provides on 6 m,
and you'd rather not outfit your K3 with a PR6 preamp (and KXV3 I/O
board)

73,
Wayne
N6KR

---

http://www.elecraft.com

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Terry Schieler

Re: 6 Meters & XV3

Hi Wayne,

Good points. You had also mentioned the need for an amp if I wanted more TX
power than the XV50 provides. Another good point.

But, if I decide to keep my XV50 will you make me a black metal chassis
housing with white lettering so that it will match my K-3? :o)

Thanks and best to all in Aptos!

Terry, W0FM

-----Original Message-----
From: wayne burdick [mailto:[hidden email]]
Sent: Monday, January 26, 2009 11:21 AM
To: Terry Schieler
Cc: [hidden email]; 'Ron D'Eau Claire'
Subject: Re: 6 Meters

Terry Schieler wrote:

> I posted a number of months back asking if I would be better off using
> my
> existing XV50 6 meter transverter with my K3 than the internal K3
> receiver.
> Someone from Elecraft replied that there would be no real benefit to
> doing
> this. Can't recall who, but it convinced me to put my XV50 up for
> sale.

It was me.

The XV-50 might provide an advantage if:

- you already had your station set up with multiple XV-series
transverters

- you had HF antennas connected to both ANT1 and ANT2, and thus
need to use a transverter in order to take advantage of a
special 6-m antenna

- you already have an XV-50, need the lower NF it provides on 6 m,
and you'd rather not outfit your K3 with a PR6 preamp (and KXV3 I/O
board)

73,
Wayne
N6KR

---

http://www.elecraft.com

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Julian, G4ILO

Re: TX IMD

In reply to this post by Greg - AB7R

Gregory Fischer wrote

Not doubting your TX IMD report in PSK. But I typically see ~-32dB IMD when
checking PSK at 50W.

You are probably right to doubt it. Such a difference made me try a test again, on a different band. I got a different set of results. Probably it is better to use a dummy load when testing the TX. The IMD Meter is designed to be used off-air (hence when TXing into an antenna) but it would appear that other factors can affect the readings. This needs further investigation.

Julian, G4ILO. K2 #392 K3 #222 KX3 #110
* G4ILO's Shack - http://www.g4ilo.com
* KComm - http://www.g4ilo.com/kcomm.html
* KTune - http://www.g4ilo.com/ktune.html

Geoffrey Mackenzie-Kennedy

Re: TX IMD

In reply to this post by David Cutter

David,

Sorry for being slow to reply.

You wrote:

> Is there a "sweet spot" to which one can adjust the power output for
> minimum IMD,

In general terms the short answer is that there might be. If the two tone
signal driving an amplifier under test is very 'clean' in terms of odd order
IMD products, the ratio between the amplitude of each odd order product
generated by the amplifier and the desired tones should gradually decrease
as power output increases if the amplifier is 'well behaved', the limit
being near and below compression. In practice some amplifiers are not well
'behaved' which can result in either an increase or decrease from the
expected amplitude of odd order IMD products as the power output is
increased. Please note that any misbehaviour of the third order products vs
power output can be quite different from any misbehaviour of the fifth,
seventh, ninth etc.

If the two tone signal from the driver is not squeaky 'clean' then it will
of course influence the outcome, which is one reason why in Type Approval
specifications for commercial use SSB transmitters used to transmit speech,
the two tone input interface is the mike connector, also the audio line
input if the latter exists.

> if so, how would you do it easily? I presume you would need another rx
> or spectrum analyser.

My choice is to use a spectrum analyser because all significant odd order
products can be seen simultaneously while varying the transmitter's power
output. Situations do arise for example in which the third order products
might dip at some power output but the fifths increase. A receiver can be
used, but because only one product can be watched at a time the task becomes
tedious. The input applied to a spectrum analyser or receiver must be of
such a level that neither is overloaded.

> And I bet it changes with antenna reflections, ie from one end of the band
> to the other.

How much will depend on the design of the amplifier and the load presented.
One approach used is to specify the load VSWR limits between which the
transmitter's performance must meet the power output, IMD, spurious output
requirements and so on, usually using a 50 +j0 load as the reference.

Be assured that I am strongly opposed to any move to introduce any form of
mandatory specifications covering equipment used in the Amateur Service in
addition to those that already exist.

73,
Geoff
GM4ESD

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Alan Bloom

Re: TX IMD

In reply to this post by Julian, G4ILO

One factor that affects IMD is power supply voltage variation under
load. The standard PS cable that comes with the K3 drops several tenths
of a volt at max power. Add that to power supply regulation and
internal voltage drop in the K.

On my unit, the voltage reading on the K3 display goes from 13.5V to
12.4V when I press the key on CW. (100W, 14 MHz) I could easily see
that being the limiting factor in transmit IMD performance on SSB.

Al N1AL

On Mon, 2009-01-26 at 10:19, Julian, G4ILO wrote:

>
> Gregory Fischer wrote:
> >
> > Not doubting your TX IMD report in PSK. But I typically see ~-32dB IMD
> > when
> > checking PSK at 50W.
> >
> You are probably right to doubt it. Such a difference made me try a test
> again, on a different band. I got a different set of results. Probably it is
> better to use a dummy load when testing the TX. The IMD Meter is designed to
> be used off-air (hence when TXing into an antenna) but it would appear that
> other factors can affect the readings. This needs further investigation.
>
> -----
> Julian, G4ILO. K2 #392 K3 #222.
> http://www.g4ilo.com/ G4ILO's Shack http://www.ham-directory.com/ Ham
> Directory http://www.g4ilo.com/kcomm.html KComm for Elecraft K2 and K3

Joe Subich, W4TV-4

Re: TX IMD

In reply to this post by Dave Hachadorian

Unfortunately neither the Toshiba or ASI datasheets for the
2SC2782 used in the KPA3 provide any IMD specifications.
Unlike the information available for the 2SC2879.

The 2SC2879 has a distinct "sweet spot" at 60 Watts output
with 12.5V and 100 mA idle current. A push pull pair of
2SC2879 (e.g., FT-990) would be expected to produce -38dB
IMD at 120 watts at the collector (100 W from the LPF) with
8 - 10 W of drive and Vcc 12.5V at 28 MHz. Note that the
2SC2879 is also rated for -24dB IMD at 100 Watts per device
(or 200 W PEP from a pair) ... there is no such specification
for the 2SC2782.

I haven't been able to find IMD data on the low level devices
for either the FT-990 (2SC2166 predriver, 2SC3133 drivers) or
K3 (RD06HHF1 predriver, RD15HVF1 drivers). However, I am a
bit concerned that the K3 predriver is only rated for 30 MHz
operation!

73,

... Joe, W4TV

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Dave
> Hachadorian
> Sent: Monday, January 26, 2009 11:42 AM
> To: Elecraft reflector
> Subject: Re: [Elecraft] TX IMD
>
>
> There is something that has been puzzling me for the last 17 years.
>
> In November of 1991, QST reviewed the Yaesu FT-990, which
> used a 13.8 vdc PA. Worst case measured 3rd order IMD
> was -38 dB, 5th order was -47 dB. This measurement was at
> 100 watts output. The review is available on ARRL's
> members-only web site.
>
> ARRL had this comment, "It's refreshing to see that it's
> possible to make a 100-W MF/HF radio with low voltage finals
> AND such low-distortion transmitter performance".
>
> As far as I know, no ham 13.8 volt radio has even come close
> to this TX IMD performance ever since. Looking at the 990
> PA, there's a 2sc2166 predriver, a pair of 2sc3133
> drivers, and a pair of 2sc2879 finals, all npn transistors,
> nothing exotic.
>
> So what was Yaesu's secret, and why hasn't anyone else even
> come close?
>
> Dave Hachadorian, K6LL
> Yuma, AZ
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> .
>
> _______________________________________________
> Elecraft mailing list
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Jay Bromley

Re: TX IMD

In reply to this post by Julian, G4ILO

HI Julian and Greg,
I see some difference in measured IMD in various software using the same
equipment. I also notice a difference in going narrow on receive. Of
coarse the transmitter's IMD isn't changing, but the the recorded result.
Still useful for testing as long as you compare apples to apples.

73 de jay/w5jay..

> Gregory Fischer wrote:
>>
>> Not doubting your TX IMD report in PSK. But I typically see ~-32dB IMD
>> when
>> checking PSK at 50W.
>>
> You are probably right to doubt it. Such a difference made me try a test
> again, on a different band. I got a different set of results. Probably it
> is
> better to use a dummy load when testing the TX. The IMD Meter is designed
> to
> be used off-air (hence when TXing into an antenna) but it would appear
> that
> other factors can affect the readings. This needs further investigation.
>
> -----
> Julian, G4ILO. K2 #392 K3 #222.
> http://www.g4ilo.com/ G4ILO's Shack http://www.ham-directory.com/ Ham
> Directory http://www.g4ilo.com/kcomm.html KComm for Elecraft K2 and K3
> --
> View this message in context:
> http://n2.nabble.com/6-Meters-tp2213777p2219621.html
> Sent from the Elecraft mailing list archive at Nabble.com.
>
> _______________________________________________
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P.B. Christensen

Re: TX IMD

In reply to this post by Jan Erik Holm

> "One factor that affects IMD is power supply voltage variation under
load. The standard PS cable that comes with the K3 drops several tenths
of a volt at max power. Add that to power supply regulation and
internal voltage drop in the K."

In addition to lowering the AWG size, I am using a Lambda linear supply with
remote Hi-Z sensing terminals (A pair of #12 AWG for supply, and #22AWG for
sense).

The PS detects the IR drop at the load, then compensates for the duration of
the IR sag back at the PS. It works quite well for CW and PSK, although I
have not performed any tests to measure the Lambda's response time to the
supply line IR drop. So, the sensing lines may or may not be keeping up
with the instantaneous sag in order to be of any benefit in SSB TX mode.

Paul, W9AC

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Greg - AB7R

Re: TX IMD

In reply to this post by Jay Bromley

Thanks Jay. I tend to not go by what IMD is reported by softare as there
are other factors involved the effect the resulting displayed IMD. The
KK7UQ IMD meters is measuring it at the source.

Tnx
Greg

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]]On Behalf Of Jay Bromley
Sent: Monday, January 26, 2009 3:58 PM
To: Julian, G4ILO; [hidden email]
Subject: Re: [Elecraft] TX IMD

HI Julian and Greg,
I see some difference in measured IMD in various software using the same
equipment. I also notice a difference in going narrow on receive. Of
coarse the transmitter's IMD isn't changing, but the the recorded result.
Still useful for testing as long as you compare apples to apples.

73 de jay/w5jay..

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Robert Friess

Re: TX IMD

In reply to this post by Joe Subich, W4TV-4

The RD06HHF1 used in the Low Power Amplifier in the K3 is NOT rated
to only 30 MHz. It does carry a specification for 6 watts power
output and 16dB gain at 30 MHz, perhaps for services at 27 MHz, but
further down the data sheet are S parameters all the way to 1000 MHz
indicating a much wider range of useful operation. The RD06HHF1 as
used in the K3 operates at an output power of only about 1 watt.
Furthermore, when the K3 is equipped with the 100 watt KPA3, the low
power amplifier operates at about 5 watts output. At this level the
contribution to total IMD is negligible.

73,
Bob, N6CM

On Mon, Jan 26, 2009 at 1:14 PM, Joe Subich, W4TV <[hidden email]> wrote:

>
> Unfortunately neither the Toshiba or ASI datasheets for the
> 2SC2782 used in the KPA3 provide any IMD specifications.
> Unlike the information available for the 2SC2879.
>
> The 2SC2879 has a distinct "sweet spot" at 60 Watts output
> with 12.5V and 100 mA idle current. A push pull pair of
> 2SC2879 (e.g., FT-990) would be expected to produce -38dB
> IMD at 120 watts at the collector (100 W from the LPF) with
> 8 - 10 W of drive and Vcc 12.5V at 28 MHz. Note that the
> 2SC2879 is also rated for -24dB IMD at 100 Watts per device
> (or 200 W PEP from a pair) ... there is no such specification
> for the 2SC2782.
>
> I haven't been able to find IMD data on the low level devices
> for either the FT-990 (2SC2166 predriver, 2SC3133 drivers) or
> K3 (RD06HHF1 predriver, RD15HVF1 drivers). However, I am a
> bit concerned that the K3 predriver is only rated for 30 MHz
> operation!
>
> 73,
>
> ... Joe, W4TV
>
>
>
>
> > -----Original Message-----
> > From: [hidden email]
> > [mailto:[hidden email]] On Behalf Of Dave
> > Hachadorian
> > Sent: Monday, January 26, 2009 11:42 AM
> > To: Elecraft reflector
> > Subject: Re: [Elecraft] TX IMD
> >
> >
> > There is something that has been puzzling me for the last 17 years.
> >
> > In November of 1991, QST reviewed the Yaesu FT-990, which
> > used a 13.8 vdc PA. Worst case measured 3rd order IMD
> > was -38 dB, 5th order was -47 dB. This measurement was at
> > 100 watts output. The review is available on ARRL's
> > members-only web site.
> >
> > ARRL had this comment, "It's refreshing to see that it's
> > possible to make a 100-W MF/HF radio with low voltage finals
> > AND such low-distortion transmitter performance".
> >
> > As far as I know, no ham 13.8 volt radio has even come close
> > to this TX IMD performance ever since. Looking at the 990
> > PA, there's a 2sc2166 predriver, a pair of 2sc3133
> > drivers, and a pair of 2sc2879 finals, all npn transistors,
> > nothing exotic.
> >
> > So what was Yaesu's secret, and why hasn't anyone else even
> > come close?
> >
> > Dave Hachadorian, K6LL
> > Yuma, AZ
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > .
> >
> > _______________________________________________
> > Elecraft mailing list
> > Post to: [hidden email]
> > You must be a subscriber to post to the list.
> > Subscriber Info (Addr. Change, sub, unsub etc.):
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> >
> > Help: http://mailman.qth.net/subscribers.htm
> > Elecraft web page: http://www.elecraft.com
>
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>

Jan Erik Holm

Re: TX IMD

In reply to this post by Alan Bloom

Yes of course, "however" this cable is supplied by Elecraft
and is part of the "high performance" kit.
My own PS has a 0.06V drop RX > TX and that is good enough!

/ SM2EKM
-----------
Alan Bloom wrote:

> One factor that affects IMD is power supply voltage variation under
> load. The standard PS cable that comes with the K3 drops several tenths
> of a volt at max power. Add that to power supply regulation and
> internal voltage drop in the K.
>
> On my unit, the voltage reading on the K3 display goes from 13.5V to
> 12.4V when I press the key on CW. (100W, 14 MHz) I could easily see
> that being the limiting factor in transmit IMD performance on SSB.
>
> Al N1AL
>
>
> On Mon, 2009-01-26 at 10:19, Julian, G4ILO wrote:
>> Gregory Fischer wrote:
>>> Not doubting your TX IMD report in PSK. But I typically see ~-32dB IMD
>>> when
>>> checking PSK at 50W.
>>>
>> You are probably right to doubt it. Such a difference made me try a test
>> again, on a different band. I got a different set of results. Probably it is
>> better to use a dummy load when testing the TX. The IMD Meter is designed to
>> be used off-air (hence when TXing into an antenna) but it would appear that
>> other factors can affect the readings. This needs further investigation.
>>
>> -----
>> Julian, G4ILO. K2 #392 K3 #222.
>> http://www.g4ilo.com/ G4ILO's Shack http://www.ham-directory.com/ Ham
>> Directory http://www.g4ilo.com/kcomm.html KComm for Elecraft K2 and K3
>
>