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K1 question...

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Thomas R. Hauff

K1 question...

Hi y'all!

I have noted that most of the posts in the elecraft reflector are about the
K3. I hope this isn't out of line.

I bought a K1 awhile back because it was billed as a great first-time
builder's kit. As one of those first-time builders, I suppose I'd agree,
but I've run into a few rather basic questions and I'm undoubtedly driving
Gary up the wall with them. I'm a rank beginner on all things electronic I'm
afraid. He's set me the task of building an RF probe (which I'm getting to)
and told me to get a signal generator as well.

I need to do the signal tracing the manual suggests (Appendix E, p5) and
wanted to build the signal generator shown in schematic on that page. I have
the KFL1-4 board with 17, 20, 30 and 40 meters and am only hearing signals
on the 40 meter band. I thought I'd build the signal generator with a switch
to change between crystals.

I'm looking for some advice:

I have one power supply (a Samlex SEC-1235M) and I guess I'll need another
power source for the signal generator. As I looked at the Samlex site
(http://www.universal-radio.com/CATALOG/hamps.html), I saw both linear and
switching power supplies. Does it matter which kind I get? Any other
suggestions for inexpensive options?

I suppose I'll stop with one question for now.

Thanks hams!

Tom (WB7RTE)

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Dave KQ3T

Re: K1 question...

Hi Tom,

Both varieties will produce the DC voltages you need (as would a few
batteries). For your purposes, the differences between the two types may
not matter.

Linear power supplies use a conventional transformer to convert line
voltage (117vac) to a lower voltage (typically 15-18vac), which is then
rectified by diodes, filtered by capacitors and (usually) controlled by
a voltage regulator to 13-14 volts DC. Unfortunately, as the current
goes up, the size of the transformer (which usually contains an iron
core) goes up as well; a 20 amp 12V linear power supply might weigh 15
lbs or more.

Switching power supplies generate a high frequency AC voltage, which
does away with the need for the heavy transformer. So switching supplies
tend to be lighter than linear supplies for the given amount of current
produced. The disadvantage is that the high frequency AC can, in poor
designed/shielded supplies, generate "hash" that can be heard in your
receiver.

QST has tested a number of switching power supplies recently, you might
check to see if the supplies you're considering have been evaluated.

73,
Dave KQ3T

Thomas R. Hauff wrote:

> Hi y'all!
>
> I have noted that most of the posts in the elecraft reflector are about the
> K3. I hope this isn't out of line.
>
> I bought a K1 awhile back because it was billed as a great first-time
> builder's kit. As one of those first-time builders, I suppose I'd agree,
> but I've run into a few rather basic questions and I'm undoubtedly driving
> Gary up the wall with them. I'm a rank beginner on all things electronic I'm
> afraid. He's set me the task of building an RF probe (which I'm getting to)
> and told me to get a signal generator as well.
>
> I need to do the signal tracing the manual suggests (Appendix E, p5) and
> wanted to build the signal generator shown in schematic on that page. I have
> the KFL1-4 board with 17, 20, 30 and 40 meters and am only hearing signals
> on the 40 meter band. I thought I'd build the signal generator with a switch
> to change between crystals.
>
> I'm looking for some advice:
>
>
>
> I have one power supply (a Samlex SEC-1235M) and I guess I'll need another
> power source for the signal generator. As I looked at the Samlex site
> (http://www.universal-radio.com/CATALOG/hamps.html), I saw both linear and
> switching power supplies. Does it matter which kind I get? Any other
> suggestions for inexpensive options?
>
>
>
> I suppose I'll stop with one question for now.
>
> Thanks hams!
>
>
>
> Tom (WB7RTE)
>
>

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Don Wilhelm-4

Re: K1 question...

In reply to this post by Thomas R. Hauff

Tom,

Yes, K1 questions are welcome here - after all, it is an "Elecraft"
reflector, not a "K3" reflector. The relative newness and the
popularity of the K3 does make the bulk of the traffic K3 related. For
that reason, many on the reflector want us to remember to put K1, K2,
K3, etc. in the subject line so their email sorters can deposit the
posts into the appropriate folder.

Switching the crystals on your signal generator is a good idea, although
I have that generator wired up "ugly style" on a piece of copper clad
board, and I used a strip of 3 'machine pin' sockets (like in a DIP
socket) as a crystal socket, so I can plug in any variety of crystals
for whatever band I need - easier than a dedicated switch IMHO.

There is no reason that oscillator cannot be powered from a 9 volt
battery, or a regulated 9 to 12 volt 'wall-wart' (most are *not*
regulated) - it takes very little current - certainly less expensive
than a separate power supply, and more portable. Since your current
power supply has a 35 amp ICS, 30 amp Continuous rating, it has plenty
of reserve current, you should be able to use that supply for the
oscillator as well as the K1 - in fact that supply will easily run most
100 watt class transceivers. BTW - there is no reason the oscillator
has to look 'pretty', it just has to work (and hold itself together
during use). Many QRP friends and I build things of that nature in an
Altoids tin - it can hold both the oscillator and the battery.

Switching power supplies are lightweight, and many are excellent - but
some do have RF emissions high enough to be bothersome in a ham station
- check the ARRL reviews if you want data on any particular one
(assuming they have reviewed that one). Normally linear supplies are
noise-free, but transformers are heavy, so a high current supply may be
quite weighty. I have an Astron RS-35A (rated 35 amps ICS) that powers
everything in the hamshack and lives on the floor under the desk. If
you are just beginning, you may want to get a DC power distribution
system (I like the ones with Anderson Powerpole connectors - like the
"Rigrunners") rather than an additional power supply, you will likely be
adding additional transceivers and accessories as time goes on, and one
power supply can possibly serve them all if you can distribute the power.

For your K1 problem - yes the strong oscillator signal will likely help
you. The most common problem encountered in tuning the K1 is getting
the pre-mixer bandpass filters aligned correctly. You must peak 30
meters before peaking 40 meters, and similarly, peak 17 (or 15) meters
before peaking 20 meters. Failure to follow that sequence will cause
all kinds of frustration. The trimmer capacitors will normally be set
close to the center position - if you do not find a peak near the center
setting, there is a problem to be found (like an extra turn on the
toroids). When counting toroid turns, count the number of times the
wire passes through the center - a straight wire through the center of a
core is one turn, and a full wrap around the core is 2 turns.

73,
Don W3FPR

Thomas R. Hauff wrote: