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K1 KAT1 SWR Adjustment

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crstrode

K1 KAT1 SWR Adjustment

My new K1 is working great!

However, the SWR indications appear to be a bit low.

For example, I have a ground mounted vertical antenna (Hy-Gain 18-HT Hy-Tower) with lots of radials. The SWR as indicated by the K1 is 1.0:1, which does not appear to be correct. My trusty MFJ 249 tells me the SWR on this antenna is closer to 1.5:1, as I would expect.

If I connect a non-inductive dummy load of 100 or 25 ohms, the indicated SWR is closer to 1.5:1 instead of the expected 2.0:1.

When adjusting C9 for the lowest possible voltage, the instructions tell me to set the power out to 5.0 watts, however the manual does not tell me to increase power from the 1.5 watts nominal tuning output level to the full 5.0 watts.

Should I enter TUNE mode, then tap to increase output power to 5.0 watts as I make the C9 adjustment?

Carl Strode
WA7CS

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Don Wilhelm-4

Re: K1 KAT1 SWR Adjustment

Carl,

The main reason for the reflected circuitry in the KAT1 is to monitor
for the lowest SWR during a TUNE operation. For that purpose, it is not
necessary that the indication is accurate.

If you wish to calibrate the SWR indication, check the C9 balance
setting first - connect a known good 50 ohm non-reactive load (the
Elecraft DL1 is good) If you do not know for certain about your dummy
load, measure it with an antenna analyzer. If it is anything other than
a pure 50 ohms resistive, you may still achieve a null, but the bridge
will be balanced at the impedance of your actual load and not
necessarily 50 ohms resistive.
Next, calibrate the forward power, and lastly, calibrate the SWR
indication (by adjusting only the trimpot) using a resistive load which
produces a known SWR, such as a 100 ohm (SWR=2.0) or a 75 ohm load
(SWR=1.5).

The power level is not critical to any of these adjustments, but it may
be easier to see the null at 5 watts than at 1.5 watts. If you want to
do it at 5 watts, adjust first at lower power and then make quick, but
small, adjustments at the higher power.

73,
Don W3FPR

Strode, Carl R wrote:

> My new K1 is working great!
>
> However, the SWR indications appear to be a bit low.
>
> For example, I have a ground mounted vertical antenna (Hy-Gain 18-HT Hy-Tower) with lots of radials. The SWR as indicated by the K1 is 1.0:1, which does not appear to be correct. My trusty MFJ 249 tells me the SWR on this antenna is closer to 1.5:1, as I would expect.
>
> If I connect a non-inductive dummy load of 100 or 25 ohms, the indicated SWR is closer to 1.5:1 instead of the expected 2.0:1.
>
> When adjusting C9 for the lowest possible voltage, the instructions tell me to set the power out to 5.0 watts, however the manual does not tell me to increase power from the 1.5 watts nominal tuning output level to the full 5.0 watts.
>
> Should I enter TUNE mode, then tap to increase output power to 5.0 watts as I make the C9 adjustment?
>
>
>

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crstrode

RE: K1 KAT1 SWR Adjustment

Don, thanks so much for the reply.

My dummy load is one I cooked up for my K2 SWR adjustment. It consists of some 50 ohm precision film type resistors bolted to an aluminum heat sink. I can't recall who gave me the idea, and suggested the actual resistors to use, but it may have been you.

I have four of them all presently connected in a series parallel arrangement for a load very very close to 50 ohms. My antenna analyzer says it's essentially flat.

I do have one question. You say the third step is to adjust the "trimpot" with the known SWR dummy loads. Are you referring to R2, or C9?

If it is R2 that you are talking about, I've given that a shot already. I ended up returning it to the setting as specified in the KAT1 manual.

I was worried that smoke and flames might come shooting out.

When I adjusted it for a better SWR indication it was about 180-degrees out of rotation (i.e. the manual says to adjust R1, and visually set R2 to match the rotation of R1).

Carl Strode
WA7CS

[hidden email]

-----Original Message-----
From: Don Wilhelm [mailto:[hidden email]]
Sent: Tuesday, January 29, 2008 12:02 PM
To: Strode, Carl R
Cc: '[hidden email]'
Subject: Re: [Elecraft] K1 KAT1 SWR Adjustment

Carl,

The main reason for the reflected circuitry in the KAT1 is to monitor for the lowest SWR during a TUNE operation. For that purpose, it is not necessary that the indication is accurate.

If you wish to calibrate the SWR indication, check the C9 balance setting first - connect a known good 50 ohm non-reactive load (the Elecraft DL1 is good) If you do not know for certain about your dummy load, measure it with an antenna analyzer. If it is anything other than a pure 50 ohms resistive, you may still achieve a null, but the bridge will be balanced at the impedance of your actual load and not necessarily 50 ohms resistive.
Next, calibrate the forward power, and lastly, calibrate the SWR indication (by adjusting only the trimpot) using a resistive load which produces a known SWR, such as a 100 ohm (SWR=2.0) or a 75 ohm load (SWR=1.5).

The power level is not critical to any of these adjustments, but it may be easier to see the null at 5 watts than at 1.5 watts. If you want to do it at 5 watts, adjust first at lower power and then make quick, but small, adjustments at the higher power.

73,
Don W3FPR

Strode, Carl R wrote:

Don Wilhelm-4

Re: K1 KAT1 SWR Adjustment

Carl,

Yes, I may have been the one to suggest those resistors for a dummy load
- if you used the 50 ohm ones, they should be flat up to 200 MHz or more
depending on your physical implementation - short leads and such.

Yes, adjust R2 to indicate the correct SWR - no smoke will happen - but
do that as the last step.
The C9 adjustment must be done first, and once that is correct, do not
touch it again or you will have to do everything all over.

If you want to use your 25 ohm and 100 ohm resistors to indicate a
better setting for C9, then connect them alternately (use *short* leads)
to the antenna jack - you are looking for the SWR indication to be the
*same* for both (ignore the actual SWR amount, just adjust C9 slightly
until they both read the same). After that, go back to the 50 ohm load
and set the trimmer resistor for forward power, and lastly use either
your 25 or 100 ohm load and set the SWR = 2.0, then call it done. On
the KAT2 and KAT1, it is not uncommon for the final adjustment of the
reflected trimmer resistor to be quite different than the setting for
the FWD trimmer - it just happens to be that way. As I indicated in my
previous note, the actual SWR means nothing to the tuner itself, it
merrily searches for the minimum SWR - and minimum SWR is a better
indication of correct tuning than any actual SWR value.

73,
Don W3FPR

Strode, Carl R wrote:

> Don, thanks so much for the reply.
>
> My dummy load is one I cooked up for my K2 SWR adjustment. It consists of some 50 ohm precision film type resistors bolted to an aluminum heat sink. I can't recall who gave me the idea, and suggested the actual resistors to use, but it may have been you.
>
> I have four of them all presently connected in a series parallel arrangement for a load very very close to 50 ohms. My antenna analyzer says it's essentially flat.
>
>
> I do have one question. You say the third step is to adjust the "trimpot" with the known SWR dummy loads. Are you referring to R2, or C9?
>
> If it is R2 that you are talking about, I've given that a shot already. I ended up returning it to the setting as specified in the KAT1 manual.
>
> I was worried that smoke and flames might come shooting out.
>
> When I adjusted it for a better SWR indication it was about 180-degrees out of rotation (i.e. the manual says to adjust R1, and visually set R2 to match the rotation of R1).
>
>
> Carl Strode
> WA7CS
>
> [hidden email]
>
> -----Original Message-----
> From: Don Wilhelm [mailto:[hidden email]]
> Sent: Tuesday, January 29, 2008 12:02 PM
> To: Strode, Carl R
> Cc: '[hidden email]'
> Subject: Re: [Elecraft] K1 KAT1 SWR Adjustment
>
> Carl,
>
> The main reason for the reflected circuitry in the KAT1 is to monitor for the lowest SWR during a TUNE operation. For that purpose, it is not necessary that the indication is accurate.
>
> If you wish to calibrate the SWR indication, check the C9 balance setting first - connect a known good 50 ohm non-reactive load (the Elecraft DL1 is good) If you do not know for certain about your dummy load, measure it with an antenna analyzer. If it is anything other than a pure 50 ohms resistive, you may still achieve a null, but the bridge will be balanced at the impedance of your actual load and not necessarily 50 ohms resistive.
> Next, calibrate the forward power, and lastly, calibrate the SWR indication (by adjusting only the trimpot) using a resistive load which produces a known SWR, such as a 100 ohm (SWR=2.0) or a 75 ohm load (SWR=1.5).
>
> The power level is not critical to any of these adjustments, but it may be easier to see the null at 5 watts than at 1.5 watts. If you want to do it at 5 watts, adjust first at lower power and then make quick, but small, adjustments at the higher power.
>
> 73,
> Don W3FPR
>
> Strode, Carl R wrote:
>
>> My new K1 is working great!
>>
>> However, the SWR indications appear to be a bit low.
>>
>> For example, I have a ground mounted vertical antenna (Hy-Gain 18-HT Hy-Tower) with lots of radials. The SWR as indicated by the K1 is 1.0:1, which does not appear to be correct. My trusty MFJ 249 tells me the SWR on this antenna is closer to 1.5:1, as I would expect.
>>
>> If I connect a non-inductive dummy load of 100 or 25 ohms, the indicated SWR is closer to 1.5:1 instead of the expected 2.0:1.
>>
>> When adjusting C9 for the lowest possible voltage, the instructions tell me to set the power out to 5.0 watts, however the manual does not tell me to increase power from the 1.5 watts nominal tuning output level to the full 5.0 watts.
>>
>> Should I enter TUNE mode, then tap to increase output power to 5.0 watts as I make the C9 adjustment?
>>
>>
>>
>>
>
>
>

crstrode

FW: K1 KAT1 SWR Adjustment

In reply to this post by crstrode

If the KAT1 merely tunes for the lowest voltage as developed at TP1, then does the KAT1 really use the <1.2:1 criteria to initiate an attempt at finding a good match?

Page #11 of the Rev. C KAT1 manual says:

"If the match is already very good (< 1.2:1), the tuner's L and C settings will not be changed."

Without adjustment of R2, how does the KAT1 know the difference between a good match and a bad match?

Of course, once the tuning process is started, the lowest voltage at TP-1 indicates the best match (assuming C9 was adjusted with a valid load).

Geez - my feeble brain is suffering from SWR overload.

Carl Strode
WA7CS

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Don Wilhelm-4

Re: K1 KAT1 SWR Adjustment

In reply to this post by Don Wilhelm-4

Carl,
:-) Don't worry about it - it does work.
Actually the KAT1 (and other Elecraft tuners) do a comparison of the
forward and reflected power in the microprocessor in the tuner. It is
the main K2 microprocessor that displays the SWR.

The way I read that statement in the manual the tuner determines that
the match is sufficiently low (and that will always be less than 1.2:1)
- it may be mush less, and usually is. But that is a way of explaining
that a match of 1.2:1 *is* a good match. Many hams get all bent out of
shape if the match is anything greater than 1.0:1 (you have likely heard
them on the air and in private discussions). It becomes a game of "My
SWR is better than your SWR!", and the discussion goes on and on. In
reality the loss from a 1.5:1 or even a 2:1 SWR is not that great at HF
- when you get up to VHF and UHF, it becomes much more significant. I
don't try to prune my antennas any more than is necessary, and I am
happy with 1.5 or less with no greater than 2.0:1 at the band edges - I
don't normally use a tuner, and that works out just fine for me - the
transceiver loads just fine.

Bottom line is that the approximate setting (for those who do not have
the capability to set the SWR accurately) is good enough for the tuner
to do its job.

73,
Don W3FPR

Strode, Carl R wrote:

> If the KAT1 merely tunes for the lowest voltage as developed at TP1, then does the KAT1 really use the <1.2:1 criteria to initiate an attempt at finding a good match?
>
> Page #11 of the Rev. C KAT1 manual says:
>
> "If the match is already very good (< 1.2:1), the tuner's L and C settings will not be changed."
>
>
> Without adjustment of R2, how does the KAT1 know the difference between a good match and a bad match?
>
> Of course, once the tuning process is started, the lowest voltage at TP-1 indicates the best match (assuming C9 was adjusted with a valid load).
>
> Geez - my feeble brain is suffering from SWR overload.
>
> Carl Strode
> WA7CS
>
> [hidden email]
>
> -----Original Message-----
> From: [hidden email] [mailto:[hidden email]] On Behalf Of Don Wilhelm
> Sent: Tuesday, January 29, 2008 1:09 PM
> To: '[hidden email]'
> Subject: Re: [Elecraft] K1 KAT1 SWR Adjustment
>
> Carl,
>
> Yes, I may have been the one to suggest those resistors for a dummy load
> - if you used the 50 ohm ones, they should be flat up to 200 MHz or more depending on your physical implementation - short leads and such.
>
> Yes, adjust R2 to indicate the correct SWR - no smoke will happen - but do that as the last step.
> The C9 adjustment must be done first, and once that is correct, do not touch it again or you will have to do everything all over.
>
> If you want to use your 25 ohm and 100 ohm resistors to indicate a better setting for C9, then connect them alternately (use *short* leads) to the antenna jack - you are looking for the SWR indication to be the
> *same* for both (ignore the actual SWR amount, just adjust C9 slightly until they both read the same). After that, go back to the 50 ohm load and set the trimmer resistor for forward power, and lastly use either your 25 or 100 ohm load and set the SWR = 2.0, then call it done. On the KAT2 and KAT1, it is not uncommon for the final adjustment of the reflected trimmer resistor to be quite different than the setting for the FWD trimmer - it just happens to be that way. As I indicated in my previous note, the actual SWR means nothing to the tuner itself, it merrily searches for the minimum SWR - and minimum SWR is a better indication of correct tuning than any actual SWR value.
>
> 73,
> Don W3FPR
>
>
>
>

crstrode

RE: SWR Adjustment (Don't Worry about it)

Don thanks for reinforcing the "Don't worry about it" part.

I fiddled around with the KAT1 adjustments last evening with all sorts of dummy loads, RF probes, wattmeters, other rigs, antenna analyzers, etc.

The most valuable bit of awareness I came away with was that each method of measurement produced a significantly different result. Coax lengths, number of connections, different test equipment, physical layout, etc, injected a lot of variables that are very difficult to quantify.

The very last thing I did was to compare the indicated output power and SWR from my K1 to the K2 indications when connected to the same known load via a Bird Wattmeter. Neither rig will display exactly 2.0:1 SWR into a known good flat 100 and 25 ohm load.

On the K2, a 1.7 to 1.8 was the best I could get for both loads. Adjusting the KAT1 R2 to maximum came into the ballpark - not spot-on, but at least on the same team.

With the KAT1, I figgered that as long as the C9 null was done properly, adjusting R2 for max indicated SWR will get me into the "Don't worry about it" Zone.

One interesting thing I did notice was that after dashing thru the menus, entering TUNE, adjusting CLS, CLP, output level, etc, the K1 microprocessor appeared to become discombobulated from time to time. A momentary power-down always cleared the cobwebs and got it back to normal.

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