Re: [Elecraft] KAT500 Attenuator
I think the only thing that is for sure is that this is very poorly documented. The schematic shows two resistors, the assembly manual shows one, and the correct value of the one (by my measurement) is unknown. Whether or not it is, or isn't, used is another unknown. It seems to me that Elecraft could comment on this and clear this up, but that hasn't been forthcoming. Silence isn't always golden. Wes N7WS On 12/15/2021 3:52 PM, Al Lorona wrote: Have we, in fact, established that this attenuator is enabled at any point of the tune cycle? Because if not, then we're all spun up for nothing. Is it reasonable to believe that the attenuator was one of those design elements that might have been deemed necessary at one time but then the designers changed their mind for the finished product? I think so. The mysterious R7 may have been left off of the final circuit board precisely to cause such a bad mismatch that it would be obvious to operator, software, or both, and so that corrective action could be taken. Al W6LX/4 __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KAT500 Attenuator
" Have we, in fact, established that this attenuator is enabled at any point of the tune cycle? Because if not, then we're all spun up for nothing." KAT500 Serial Command Reference Revised 8/18/2021 firmware version 02.00 says: "ATTN Enable Attenuator GET format: ATTN; SET/RESPONSE format: ATTN0; (disabled) or ATTN1; (enabled). Selects relay K22, which switches in an attenuator resistor. It may take a few milliseconds after issuing an ATTNx; setter before the relay changes. Firmware releases the attenuator if it detects power high enough to damage to the attenuator. Firmware normally inserts the attenuator during “full search tune” to present a more consistent load to a transceiver during tune operations. The attenuator is disabled if the tune power is too low with the attenuator in place." This version was released so the document was compatible with firmware 2.05 changes. As I have said earlier in this thread I see no evidence that ATTN changes state during a "full search tune". We are left with an attenuator design change that no one seems to understand and documentation that may not be correct. Whether that is "spun up for nothing" probably depends on one's perspective. Andy, k3wyc __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KAT500 Attenuator
Have we, in fact, established that this attenuator is enabled at any point of the tune cycle? Because if not, then we're all spun up for nothing. Is it reasonable to believe that the attenuator was one of those design elements that might have been deemed necessary at one time but then the designers changed their mind for the finished product? I think so. The mysterious R7 may have been left off of the final circuit board precisely to cause such a bad mismatch that it would be obvious to operator, software, or both, and so that corrective action could be taken. Al W6LX/4 __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KAT500 Attenuator
"I took the cover off mine and verified that the shunt resistor was missing and the series one measured 228 ohm. Clearly, if this is dynamically switched while seeking a match the poor exciter is going to be totally confused. " The list and private replies I have seen seem to show the attenuator with both resistors presents a reasonable match to the exciter. The attenuator with R7 removed presents a horrible match to the exciter. With the single resistor attenuator active my TS-590S load is so bad that it folds back to very lower power output, far too low for the tuner to continue the tune cycle, so it would then switch out the attenuator. However, I don't see any sign that the attenuator is ever switched in circuit on my KAT500. I have only recently added ATTN to my monitoring and recording so I have no data from firmware 1.75 or earlier. If I get bored I may load 1.75 to see if I can detect attenuator activation. Andy, k3wyc __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KAT500 Attenuator
I took the cover off mine and verified that the shunt resistor was missing and
the series one measured 228 ohm. Clearly, if this is dynamically switched while
seeking a match the poor exciter is going to be totally confused. The
attenuator should have been implemented with two 30 ohm resistors in the first
place. What motivated them to remove one is a mystery.
The fact that mine appears to have changed value says to me, that while clever,
the use of the bottom panel for a heat sink is problematic. I suspect this is
also the case in the K3/K3S LPA where there are a lot of FET failures.
Wes N7WS
On 12/12/2021 8:48 PM, Bob McGraw wrote:
Just went through different antenna configurations and bands. Using the KAT500
Utility, selecting the ATTENUATOR and then TUNE on my K3S shows a SWR of 1.5:1
and when the ATTENUATOR is not selected the SWR shows 1.1:1. An external
SWR/PWR meter in the line between the radio and KAT500 shows the same values.
In receive mode, I hear a relay click when selecting the ATTENUATOR and again
when de-selecting the ATTENUATOR. Also noted the RX signal drop about ~3 dB
{maybe less} when the ATTENUATOR is selected.
I did notice initially when selecting the ATTENUATOR it seemed to be
inconsistent in results for a few times. I figure this is some issue with
relay contacts. Once exercised 3 or 4 times, no further strange operation
was observed.
Don't have a clue if the resistors in question are installed or not.
I recall that certain ICOM tuners insert an attenuator on the input when
running the tune routine. This is said to provide a constant impedance/load
to the transmitter while the tuner runs through its range of L and C values.
This of course is for a radio that folds back power when the SWR is >3:1 or so.
73
Bob, K4TAX
On 12/12/2021 7:24 PM, elecraft-requ...@mailman.qth.net wrote:
Message: 4
Date: Fri, 10 Dec 2021 13:30:16 +
From: Andy Durbin
To:"elecraft@mailman.qth.net"
Subject: [Elecraft] KAT500 Attenuator
Message-ID:
Content-Type: text/plain; charset="iso-8859-1"
KAT500 has an input attenuator that may, under certain conditions, be
activated during a full search tune. Page 1 rev C of the KAT500 schematic
shows the attenuator is a divider consisting of R6 and R7 which are both 39
ohm. My KAT500 serial number 2609 does not have R7 fitted and R7 is shown as
not populated in Figure 17 of KAT500 User's Manual Rev C6.
The removal of R7 changes the potential divider into a simple series resistor
and my measurements show my KAT500 presents a very poor match to my TS-590
exciter when the attenuator is active. In this example the KAT500 was in
bypass and connected to a nominal 50 ohm dummy load. The impedance presented
to my TS-590 by KAT500 was measured with an LP-100A:
Att Out: R 48.1, X 2.4, Pwr 4.48, SWR 1.06
Att In: R 22.3, X 162.6, Pwr 0.55, SWR 9.98
Do other KAT500 owners see similar results? (Attenuator can be switched
in/out with KAT500 utility)
Can someone please explain why the attenuator was changed.
Thanks and 73,
Andy k3wyc
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[Elecraft] KAT500 Attenuator
Just went through different antenna configurations and bands. Using the
KAT500 Utility, selecting the ATTENUATOR and then TUNE on my K3S shows a
SWR of 1.5:1 and when the ATTENUATOR is not selected the SWR shows
1.1:1. An external SWR/PWR meter in the line between the radio and
KAT500 shows the same values.
In receive mode, I hear a relay click when selecting the ATTENUATOR and
again when de-selecting the ATTENUATOR. Also noted the RX signal drop
about ~3 dB {maybe less} when the ATTENUATOR is selected.
I did notice initially when selecting the ATTENUATOR it seemed to be
inconsistent in results for a few times. I figure this is some issue
with relay contacts. Once exercised 3 or 4 times, no further strange
operation was observed.
Don't have a clue if the resistors in question are installed or not.
I recall that certain ICOM tuners insert an attenuator on the input when
running the tune routine. This is said to provide a constant
impedance/load to the transmitter while the tuner runs through its range
of L and C values. This of course is for a radio that folds back power
when the SWR is >3:1 or so.
73
Bob, K4TAX
On 12/12/2021 7:24 PM, elecraft-requ...@mailman.qth.net wrote:
Message: 4
Date: Fri, 10 Dec 2021 13:30:16 +
From: Andy Durbin
To:"elecraft@mailman.qth.net"
Subject: [Elecraft] KAT500 Attenuator
Message-ID:
Content-Type: text/plain; charset="iso-8859-1"
KAT500 has an input attenuator that may, under certain conditions, be activated
during a full search tune. Page 1 rev C of the KAT500 schematic shows the
attenuator is a divider consisting of R6 and R7 which are both 39 ohm. My
KAT500 serial number 2609 does not have R7 fitted and R7 is shown as not
populated in Figure 17 of KAT500 User's Manual Rev C6.
The removal of R7 changes the potential divider into a simple series resistor
and my measurements show my KAT500 presents a very poor match to my TS-590
exciter when the attenuator is active. In this example the KAT500 was in
bypass and connected to a nominal 50 ohm dummy load. The impedance presented
to my TS-590 by KAT500 was measured with an LP-100A:
Att Out: R 48.1, X 2.4, Pwr 4.48, SWR 1.06
Att In: R 22.3, X 162.6, Pwr 0.55, SWR 9.98
Do other KAT500 owners see similar results? (Attenuator can be switched in/out
with KAT500 utility)
Can someone please explain why the attenuator was changed.
Thanks and 73,
Andy k3wyc
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Re: [Elecraft] KAT500 Attenuator
Guys, I'm not about to remove all of the cables to look but using my iPhone camera it looks like I have S/N 1418, which I kit-built. My R7 is AWOL and R6 measures about 228 Ohm. Looks like Elecraft needs to explain. Wes N7WS On 12/10/2021 8:25 AM, Andy Durbin wrote: Hi Lyn, Thanks for your report. Your KAT500 is a later serial than mine so I doubt R7 is fitted. (Mine was a kit build and I don't know if factory units are in the same serial number series) I don't know the source of my Rev C schematics. I received some of my KAT500/KPA500 from Elecraft support and some by an internet search. I assume there must be a later version that documents the elimination of R7. 73, Andy, k3wyc __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KAT500 Attenuator
Hi Lyn, Thanks for your report. Your KAT500 is a later serial than mine so I doubt R7 is fitted. (Mine was a kit build and I don't know if factory units are in the same serial number series) I don't know the source of my Rev C schematics. I received some of my KAT500/KPA500 from Elecraft support and some by an internet search. I assume there must be a later version that documents the elimination of R7. 73, Andy, k3wyc __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KAT500 Attenuator
Andy - My KAT500 (s/n 2916) behaves pretty much the same way. I don't know if R7 is present, but tuning into my normal antenna produces these results: Man/Auto (doesn't matter): Att Out = SWR 1.00 "" " " Att IN = SWR 99.99 My guess is that the KAT500 cannot get a strong enough signal to tune properly with the Attenuator IN. Interestingly, when it was new, it did not have that problem. Perhaps R7 has failed. 73 Lyn, W0LEN PS - Where did you find KAT500 rev C schematics? Thx. -Original Message- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Andy Durbin Sent: Friday, December 10, 2021 7:30 AM To: elecraft@mailman.qth.net Subject: [Elecraft] KAT500 Attenuator KAT500 has an input attenuator that may, under certain conditions, be activated during a full search tune. Page 1 rev C of the KAT500 schematic shows the attenuator is a divider consisting of R6 and R7 which are both 39 ohm. My KAT500 serial number 2609 does not have R7 fitted and R7 is shown as not populated in Figure 17 of KAT500 User's Manual Rev C6. The removal of R7 changes the potential divider into a simple series resistor and my measurements show my KAT500 presents a very poor match to my TS-590 exciter when the attenuator is active. In this example the KAT500 was in bypass and connected to a nominal 50 ohm dummy load. The impedance presented to my TS-590 by KAT500 was measured with an LP-100A: Att Out: R 48.1, X 2.4, Pwr 4.48, SWR 1.06 Att In: R 22.3, X 162.6, Pwr 0.55, SWR 9.98 Do other KAT500 owners see similar results? (Attenuator can be switched in/out with KAT500 utility) Can someone please explain why the attenuator was changed. Thanks and 73, Andy k3wyc __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to l...@lnainc.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
[Elecraft] KAT500 Attenuator
KAT500 has an input attenuator that may, under certain conditions, be activated during a full search tune. Page 1 rev C of the KAT500 schematic shows the attenuator is a divider consisting of R6 and R7 which are both 39 ohm. My KAT500 serial number 2609 does not have R7 fitted and R7 is shown as not populated in Figure 17 of KAT500 User's Manual Rev C6. The removal of R7 changes the potential divider into a simple series resistor and my measurements show my KAT500 presents a very poor match to my TS-590 exciter when the attenuator is active. In this example the KAT500 was in bypass and connected to a nominal 50 ohm dummy load. The impedance presented to my TS-590 by KAT500 was measured with an LP-100A: Att Out: R 48.1, X 2.4, Pwr 4.48, SWR 1.06 Att In: R 22.3, X 162.6, Pwr 0.55, SWR 9.98 Do other KAT500 owners see similar results? (Attenuator can be switched in/out with KAT500 utility) Can someone please explain why the attenuator was changed. Thanks and 73, Andy k3wyc __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
