Elecraft › [QRO]

KPA-500 Question

Classic

List

Threaded

13 messages Options

Fred Maas

KPA-500 Question

something I don't see in the specs of the KPA500, and I wonder if possible ....

the ability to have the KPA500 remember which antenna to associate with which band, and appropriately switch a remote electronic antenna relay. Automatic amplifier band switching is of limited usefulness unless the appropriate antenna is selected automatically at the same time.

Possible or not?

TNX,

73, Fred - kt5x

K2 # 0700

K3 # 0144

aka W5YA / qrp

aka WS0TA / SOTA
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

Don Wilhelm-4

Re: KPA-500 Question

Fred,

I would think the KPA500 would be using the same antenna system as is
being used by the K3.
If that is the case, any automated antenna selection system that was
used by the K3 would also be used when the KPA500 is in-line. So I fail
to understand why that additional capability needs to be in the KPA500.
I see only an antenna input and an antenna output on the KPA500, unlike
the KAT3 or the KAT500 to be available later which have 2 antenna outputs.

73,
Don W3FPR

On 7/10/2011 9:35 AM, Fred Maas wrote:

> something I don't see in the specs of the KPA500, and I wonder if possible ....
>
> the ability to have the KPA500 remember which antenna to associate with which band, and appropriately switch a remote electronic antenna relay. Automatic amplifier band switching is of limited usefulness unless the appropriate antenna is selected automatically at the same time.
>
> Possible or not?
>
> TNX,
>
> 73, Fred - kt5x
>

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

K2GN

Re: KPA-500 Question

You guys lost me.
The KPA500 has one input and one output. If you want to use a particular
antenna on it, it must be routed to the KPA500 by the K3. It's a one to one
deal.
I'm hoping the KAT500 can select from more than 2 outputs.

Larry/K2GN - http://k2gn.com
K-Line - K3 S/N - 3278 P3 S/N - 51 KPA-500 - S/N 27

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Don Wilhelm
Sent: Sunday, July 10, 2011 9:56 AM
To: Fred Maas
Cc: [hidden email]
Subject: Re: [Elecraft] KPA-500 Question

Fred,

I would think the KPA500 would be using the same antenna system as is
being used by the K3.
If that is the case, any automated antenna selection system that was
used by the K3 would also be used when the KPA500 is in-line. So I fail
to understand why that additional capability needs to be in the KPA500.
I see only an antenna input and an antenna output on the KPA500, unlike
the KAT3 or the KAT500 to be available later which have 2 antenna outputs.

73,
Don W3FPR

On 7/10/2011 9:35 AM, Fred Maas wrote:
> something I don't see in the specs of the KPA500, and I wonder if possible
....
>
> the ability to have the KPA500 remember which antenna to associate with
which band, and appropriately switch a remote electronic antenna relay.
Automatic amplifier band switching is of limited usefulness unless the
appropriate antenna is selected automatically at the same time.
>
> Possible or not?
>
> TNX,
>
> 73, Fred - kt5x
>
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

Dick Dievendorff

Re: KPA-500 Question

In reply to this post by Fred Maas

Fred:

The KPA500 doesn't have antenna selection, automatic or otherwise. It has
one input SO-239 connector for the transceiver and one SO-239 connector for
the amplifier output.

One way to approach this, used by many, is to use the K3 band change lines
on its accessory connector to control an external antenna switch. Band
decoders are available with varying degrees of capability (and cost) from
Elecraft (KRC2), Unified Microsystems (BCD-10) , Top Ten Devices (BD-Y-SD)
, microHAM (Station Master and an earlier Band Decoder) , Array Solutions
(several, their current is called the BandMaster III), and others.

The Unified Microsystems BCD-10, perhaps augmented with its HSD-9 High Side
Driver Board, is among the most affordable of these.

Each of the choices has some characteristic that makes it an attractive
solution if it fits your overall station. Some have manual override. Some
provide visual indicators to show the selected antenna.

It's also possible to roll your own, it can be a simple one IC project for
the decoder chip plus whatever transistors you need to drive your chosen
relays.

The K3's band change lines go from its back panel accessory connector to the
band decoder. The decoder controls an antenna switch (a number of relays)
that switches one RF input line to any of N antennas. The list of antenna
switch manufacturers is long and includes microHAM, Top Ten Devices, and
Array Solutions.

Some multiple-radio stations use a pair of band decoders, one per
transceiver, and a 2 x N antenna switch that allows either radio to use any
antenna, and keeps both radios from selecting the same antenna. I use an
Array Solutions "SixPak" for this. There are other newer products.

The Antenna1 output of the K3 goes to the KPA500 transceiver in. The KPA500
output goes to the antenna switch common. The antennas connect to the
antenna switch.

If you're building a multi-radio station with antennas anywhere near one
another, you'd want to add some band pass filters, also automatically
switched, between the K3s and their amplifier(s), to protect the receivers
from the other transmitter(s).

And we call this hobby "wireless"...

Some amplifiers have a couple of antenna outputs. Ours doesn't. Whatever
number of antenna connectors we chose, other than one, would be too few for
some and too many for many.

73 de Dick, K6KR

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Fred Maas
Sent: Sunday, July 10, 2011 6:36 AM
To: [hidden email]
Subject: [Elecraft] KPA-500 Question

something I don't see in the specs of the KPA500, and I wonder if possible
....

the ability to have the KPA500 remember which antenna to associate with
which band, and appropriately switch a remote electronic antenna relay.
Automatic amplifier band switching is of limited usefulness unless the
appropriate antenna is selected automatically at the same time.

Possible or not?

TNX,

73, Fred - kt5x

K2 # 0700

K3 # 0144

aka W5YA / qrp

aka WS0TA / SOTA
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

N5GE

Re: KPA-500 Question

In reply to this post by Fred Maas

I've been using a KRC2 for a couple of years. It's an easy build and easy to
set up.

I've never had a problem with it.

73,
Tom
Amateur Radio Operator N5GE
ARRL Lifetime Member
QCWA Lifetime Member

On Sun, 10 Jul 2011 07:35:40 -0600, "Fred Maas" <[hidden email]> wrote:

>something I don't see in the specs of the KPA500, and I wonder if possible ....
>
>the ability to have the KPA500 remember which antenna to associate with which band, and appropriately switch a remote electronic antenna relay. Automatic amplifier band switching is of limited usefulness unless the appropriate antenna is selected automatically at the same time.
>
>Possible or not?
[snip]

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

Amateur Radio Operator N5GE

Fred Maas

Re: KPA-500 Question

In reply to this post by Dick Dievendorff

Thanks for reply. That is what I thought.

I am not familiar with the various outboard devices to which you refer (as
have never needed them). I am not suggesting that the KPA500 needs
additional antenna outputs though that is one way to do it. That would
constritute an internal antenna switch. The KPA500 represents many upgrades
from my 1980's amplifier so I am surprised that my 80's amp has a capability
that the KPA500 doesn't.

The band data information from the K3 goes to the KPA500 to tell it what
band it is to be on. Are you saying this can be paralleled safely and also
instruct another device? I would think such might not be compatible and a
risky thing to do.

In my set up (with an old Yaesu FL-7000) the band data information from the
K3 goes to the FL7000 to tell it which band to be on. The FL7000 then
associates one of four antenna positions with a band, this is changeable at
any time and then remembered, and outputs relay control to a remote antenna
switch. If the remote switch is not in use, the "antenna" which is
associated by band is irrelevant. I am surprised that the KPA500 does not
have this capability standard and built in with the outboard remote antenna
relay being an option. Without this, band changing is not, in fact,
automatic.

73, Fred

> Fred:
>
> The KPA500 doesn't have antenna selection, automatic or otherwise. It has
> one input SO-239 connector for the transceiver and one SO-239 connector
> for
> the amplifier output.
>
> One way to approach this, used by many, is to use the K3 band change lines
> on its accessory connector to control an external antenna switch. Band
> decoders are available with varying degrees of capability (and cost) from
> Elecraft (KRC2), Unified Microsystems (BCD-10) , Top Ten Devices
> (BD-Y-SD)
> , microHAM (Station Master and an earlier Band Decoder) , Array Solutions
> (several, their current is called the BandMaster III), and others.
>
> The Unified Microsystems BCD-10, perhaps augmented with its HSD-9 High
> Side
> Driver Board, is among the most affordable of these.
>
> Each of the choices has some characteristic that makes it an attractive
> solution if it fits your overall station. Some have manual override. Some
> provide visual indicators to show the selected antenna.
>
> It's also possible to roll your own, it can be a simple one IC project
> for
> the decoder chip plus whatever transistors you need to drive your chosen
> relays.
>
> The K3's band change lines go from its back panel accessory connector to
> the
> band decoder. The decoder controls an antenna switch (a number of relays)
> that switches one RF input line to any of N antennas. The list of antenna
> switch manufacturers is long and includes microHAM, Top Ten Devices, and
> Array Solutions.
>
> Some multiple-radio stations use a pair of band decoders, one per
> transceiver, and a 2 x N antenna switch that allows either radio to use
> any
> antenna, and keeps both radios from selecting the same antenna. I use an
> Array Solutions "SixPak" for this. There are other newer products.
>
> The Antenna1 output of the K3 goes to the KPA500 transceiver in. The
> KPA500
> output goes to the antenna switch common. The antennas connect to the
> antenna switch.
>
> If you're building a multi-radio station with antennas anywhere near one
> another, you'd want to add some band pass filters, also automatically
> switched, between the K3s and their amplifier(s), to protect the receivers
> from the other transmitter(s).
>
> And we call this hobby "wireless"...
>
> Some amplifiers have a couple of antenna outputs. Ours doesn't. Whatever
> number of antenna connectors we chose, other than one, would be too few
> for
> some and too many for many.
>
> 73 de Dick, K6KR
>

Edward R Cole

Re: KPA-500 Question

In reply to this post by Fred Maas

Something to remember is that your coax switching needs to handle
high-power. If it is rated at 500w it will likely fail; go for at
least a kilowatt. Manual multi-position switches are common. But
using coax relays is an option if you need fast switching for contesting, etc.

Just remember not to switch "hot". That means not when the KPA-500
is transmitting. This will cause arcs, pitting of contacts, possible
failure of the output devices in the amp.

I recently had an experience running 1250w at 144-MHz where a coax
relay overheated and melted the movable contact shorting it out and
causing extreme anode and grid current on my 8877. The relay was
rated for 1200w at 150-MHz. It was not "hot-switched" as it is
controlled by a sequencer. None the less the contact got so hot that
is folded 180-degrees back on itself so that it contacted ground in
the coaxial cavity of the switch. It is being replaced with a coax
switch rated for 3kW. Oh the 8877 is probably OK as it can handle
2500w for short durations.
http://www.kl7uw.com/Switch-001_1.jpg

So not all manufacturers are equal - check the rating of switches
used for QRO. Ratings are all for low SWR and derate when SWR
climbs! Also often overlooked is insertion loss in relays (more
significant as freq. rises into VHF/UHF). I find the simple
open-frame coax bypass switches that are used in most commercial amps
are not low loss or flat SWR. My 6m Mirage presents a 1.4 SWR to the
K3 when its in bypass and I have a 50-ohm termination on the
amp. Power loss is about 1w (of the 8w output of the K3/10). That
is about 0.6 dB. Typical loss of VHF coax relays is 0.05 dB No one
would confuse a Mirage with "quality", of course.

The simple fool-proof switch is to connect cables manually.
--------------------------------------
Message: 41
Date: Sun, 10 Jul 2011 07:58:47 -0700
From: "Dick Dievendorff" <[hidden email]>
Subject: Re: [Elecraft] KPA-500 Question
To: "'Fred Maas'" <[hidden email]>
Cc: [hidden email]
===snipped====
The Antenna1 output of the K3 goes to the KPA500 transceiver in. The KPA500
output goes to the antenna switch common. The antennas connect to the
antenna switch.
=============
Some amplifiers have a couple of antenna outputs. Ours doesn't. Whatever
number of antenna connectors we chose, other than one, would be too few for
some and too many for many.

73 de Dick, K6KR

73, Ed - KL7UW, WD2XSH/45
======================================
BP40IQ 500 KHz - 10-GHz www.kl7uw.com
EME: 50-1.1kw?, 144-1.4kw, 432-100w, 1296-60w, 3400-?
DUBUS Magazine USA Rep [hidden email]
======================================

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

Dick Dievendorff

Re: KPA-500 Question

In reply to this post by Fred Maas

Yes, the band data lines can be paralleled to the KPA500 and another antenna
switching device. The KPA500 order page offers an optional accessory cable
kit for use with the K3 (KPAK3AUX) that contains of a cable and a "Y"
connector for the AUX connector for just such a purpose.

The advantage of doing it this way, rather than having the amplifier
involved in antenna selection, is that automated antenna switching is
available whether the KPA500 is on or off.

Band changing with antenna selection can indeed be made automatic. It
requires a little more hardware than the K3 and KPA500. We don't offer a
band decoder of our own, but we work well with the many decoders that are
already on the market.

There are a lot of possibilities when one considers antenna switching
arrangements. If we offered a 4-position switch, someone would need 6 or 8
or 10. There are a good number of options available from a number of fine
manufacturers and there have been a number of construction articles in the
amateur literature. I'd look first to the NCJ archives if you want to "roll
your own".

73 de Dick, K6KR

-----Original Message-----
From: Fred Maas [mailto:[hidden email]]
Sent: Sunday, July 10, 2011 11:26 AM
To: Dick Dievendorff
Cc: [hidden email]
Subject: Re: [Elecraft] KPA-500 Question

Thanks for reply. That is what I thought.

I am not familiar with the various outboard devices to which you refer (as
have never needed them). I am not suggesting that the KPA500 needs
additional antenna outputs though that is one way to do it. That would
constritute an internal antenna switch. The KPA500 represents many upgrades
from my 1980's amplifier so I am surprised that my 80's amp has a capability
that the KPA500 doesn't.

The band data information from the K3 goes to the KPA500 to tell it what
band it is to be on. Are you saying this can be paralleled safely and also
instruct another device? I would think such might not be compatible and a
risky thing to do.

In my set up (with an old Yaesu FL-7000) the band data information from the
K3 goes to the FL7000 to tell it which band to be on. The FL7000 then
associates one of four antenna positions with a band, this is changeable at
any time and then remembered, and outputs relay control to a remote antenna
switch. If the remote switch is not in use, the "antenna" which is
associated by band is irrelevant. I am surprised that the KPA500 does not
have this capability standard and built in with the outboard remote antenna
relay being an option. Without this, band changing is not, in fact,
automatic.

73, Fred

> Fred:
>
> The KPA500 doesn't have antenna selection, automatic or otherwise. It
> has one input SO-239 connector for the transceiver and one SO-239
> connector for the amplifier output.
>
> One way to approach this, used by many, is to use the K3 band change
> lines on its accessory connector to control an external antenna
> switch. Band decoders are available with varying degrees of
> capability (and cost) from Elecraft (KRC2), Unified Microsystems
> (BCD-10) , Top Ten Devices
> (BD-Y-SD)
> , microHAM (Station Master and an earlier Band Decoder) , Array
> Solutions (several, their current is called the BandMaster III), and

others.

>
> The Unified Microsystems BCD-10, perhaps augmented with its HSD-9 High
> Side Driver Board, is among the most affordable of these.
>
> Each of the choices has some characteristic that makes it an
> attractive solution if it fits your overall station. Some have manual
> override. Some provide visual indicators to show the selected antenna.
>
> It's also possible to roll your own, it can be a simple one IC
> project for the decoder chip plus whatever transistors you need to
> drive your chosen relays.
>
> The K3's band change lines go from its back panel accessory connector
> to the band decoder. The decoder controls an antenna switch (a number
> of relays) that switches one RF input line to any of N antennas. The
> list of antenna switch manufacturers is long and includes microHAM,
> Top Ten Devices, and Array Solutions.
>
> Some multiple-radio stations use a pair of band decoders, one per
> transceiver, and a 2 x N antenna switch that allows either radio to
> use any antenna, and keeps both radios from selecting the same
> antenna. I use an Array Solutions "SixPak" for this. There are other
> newer products.
>
> The Antenna1 output of the K3 goes to the KPA500 transceiver in. The
> KPA500
> output goes to the antenna switch common. The antennas connect to the
> antenna switch.
>
> If you're building a multi-radio station with antennas anywhere near
> one another, you'd want to add some band pass filters, also
> automatically switched, between the K3s and their amplifier(s), to
> protect the receivers from the other transmitter(s).
>
> And we call this hobby "wireless"...
>
> Some amplifiers have a couple of antenna outputs. Ours doesn't.
> Whatever number of antenna connectors we chose, other than one, would
> be too few for some and too many for many.
>
> 73 de Dick, K6KR
>

Dick Dievendorff

Re: KPA-500 Question

Oops!

We don't offer an antenna switch.

Sorry, Jack!

73 de Dick, K6KR

-----Original Message-----
From: Willard Myers [mailto:[hidden email]]
Sent: Sunday, July 10, 2011 12:10 PM
To: Dick Dievendorff
Subject: Re: [Elecraft] KPA-500 Question

On 2011.07.10, at 15:02, Dick Dievendorff wrote:

> Band changing with antenna selection can indeed be made automatic. It
> requires a little more hardware than the K3 and KPA500. We don't offer
> a band decoder of our own, but we work well with the many decoders
> that are already on the market.

Umm, the KRC2 is an excellent band decoder.

Bill, K1GQ

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

Don Wilhelm-4

Re: KPA-500 Question

In reply to this post by Fred Maas

Fred and all,

As Dick's post stated, the K3 band data outputs can be paralleled with
the KPA500 lines.
The KPA500 has internal protection diodes to isolate it from external
band decoders that might damage the KPA500 band data input circuits.

The only "catch" is that currently the K3 has internal pullup resistors
to 5 volts on the band data outputs. If the band decoder devices have
their own pullup resistors (especially those who pullup to +12 volts),
the K3 and/or the band decoder may have problems because of differences
in the supply voltage to the pullups, and the cure is to add series
diodes (with the cathode end toward the K3) to the inputs of the band
data decoder. The diodes prevent current from the external decoder's
pullup resistors from flowing into the K3.

The KRC2 used with the K3 avoids this situation since it uses the AUXBUS
signal to determine which band the K3 is on.

73,
Don W3FPR

On 7/10/2011 2:25 PM, Fred Maas wrote:

> Thanks for reply. That is what I thought.
>
> I am not familiar with the various outboard devices to which you refer (as
> have never needed them). I am not suggesting that the KPA500 needs
> additional antenna outputs though that is one way to do it. That would
> constritute an internal antenna switch. The KPA500 represents many upgrades
> from my 1980's amplifier so I am surprised that my 80's amp has a capability
> that the KPA500 doesn't.
>
> The band data information from the K3 goes to the KPA500 to tell it what
> band it is to be on. Are you saying this can be paralleled safely and also
> instruct another device? I would think such might not be compatible and a
> risky thing to do.
>
> In my set up (with an old Yaesu FL-7000) the band data information from the
> K3 goes to the FL7000 to tell it which band to be on. The FL7000 then
> associates one of four antenna positions with a band, this is changeable at
> any time and then remembered, and outputs relay control to a remote antenna
> switch. If the remote switch is not in use, the "antenna" which is
> associated by band is irrelevant. I am surprised that the KPA500 does not
> have this capability standard and built in with the outboard remote antenna
> relay being an option. Without this, band changing is not, in fact,
> automatic.
>
> 73, Fred
>

Joe Subich, W4TV-4

Re: KPA-500 Question

> If the band decoder devices have their own pullup resistors
> (especially those who pullup to +12 volts), the K3 and/or the band
> decoder may have problems because of differences in the supply
> voltage to the pullups, and the cure is to add series diodes (with
> the cathode end toward the K3) to the inputs of the band data
> decoder.

Series diodes to devices with +12V pull-ups will not solve the issue
of "mixed" pull-up voltages. The K3 will still see the higher of
the pull-up voltages (+5 in the K3, +5 in the KPA-500, +12 or +13.8
in the "foreign" band decoder). The real issue occurs when the
pull up resistor in the "foreign" device is too small and the K3
can not sink the resulting current - or if the "foreign" decoder
uses low power CMOS inputs which requires a low state voltage
below 0.3V!

> The KRC2 used with the K3 avoids this situation since it uses the
> AUXBUS signal to determine which band the K3 is on.

microHAM Station Master also avoids this situation since it uses
the K3/P3 CAT bus (and provides an alternate CAT interface) for
its band data.

73,

... Joe Subich, W4TV
microHAM America, LLC.
http://www.microHAM-USA.com
http://groups.yahoo.com/group/microHAM

On 7/10/2011 3:19 PM, Don Wilhelm wrote:

> Fred and all,
>
> As Dick's post stated, the K3 band data outputs can be paralleled with
> the KPA500 lines.
> The KPA500 has internal protection diodes to isolate it from external
> band decoders that might damage the KPA500 band data input circuits.
>
> The only "catch" is that currently the K3 has internal pullup resistors
> to 5 volts on the band data outputs. If the band decoder devices have
> their own pullup resistors (especially those who pullup to +12 volts),
> the K3 and/or the band decoder may have problems because of differences
> in the supply voltage to the pullups, and the cure is to add series
> diodes (with the cathode end toward the K3) to the inputs of the band
> data decoder. The diodes prevent current from the external decoder's
> pullup resistors from flowing into the K3.
>
> The KRC2 used with the K3 avoids this situation since it uses the AUXBUS
> signal to determine which band the K3 is on.
>
> 73,
> Don W3FPR
>
> On 7/10/2011 2:25 PM, Fred Maas wrote:
>> Thanks for reply. That is what I thought.
>>
>> I am not familiar with the various outboard devices to which you refer (as
>> have never needed them). I am not suggesting that the KPA500 needs
>> additional antenna outputs though that is one way to do it. That would
>> constritute an internal antenna switch. The KPA500 represents many upgrades
>> from my 1980's amplifier so I am surprised that my 80's amp has a capability
>> that the KPA500 doesn't.
>>
>> The band data information from the K3 goes to the KPA500 to tell it what
>> band it is to be on. Are you saying this can be paralleled safely and also
>> instruct another device? I would think such might not be compatible and a
>> risky thing to do.
>>
>> In my set up (with an old Yaesu FL-7000) the band data information from the
>> K3 goes to the FL7000 to tell it which band to be on. The FL7000 then
>> associates one of four antenna positions with a band, this is changeable at
>> any time and then remembered, and outputs relay control to a remote antenna
>> switch. If the remote switch is not in use, the "antenna" which is
>> associated by band is irrelevant. I am surprised that the KPA500 does not
>> have this capability standard and built in with the outboard remote antenna
>> relay being an option. Without this, band changing is not, in fact,
>> automatic.
>>
>> 73, Fred
>>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

--

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

N7US

Re: KPA-500 Question

In reply to this post by Dick Dievendorff

A benefit of Elecraft's not including multiple antenna outputs in the KPA500
is being able to price it lower and not forcing customers to buy a
capability that they don't need. The Alpha 9500 has a sophisticated
4-antenna output capability, but that adds to the price whether it's needed
or not.

Jim N7US

-----Original Message-----

Yes, the band data lines can be paralleled to the KPA500 and another antenna
switching device. The KPA500 order page offers an optional accessory cable
kit for use with the K3 (KPAK3AUX) that contains of a cable and a "Y"
connector for the AUX connector for just such a purpose.

The advantage of doing it this way, rather than having the amplifier
involved in antenna selection, is that automated antenna switching is
available whether the KPA500 is on or off.

Band changing with antenna selection can indeed be made automatic. It
requires a little more hardware than the K3 and KPA500. We don't offer a
band decoder of our own, but we work well with the many decoders that are
already on the market.

There are a lot of possibilities when one considers antenna switching
arrangements. If we offered a 4-position switch, someone would need 6 or 8
or 10. There are a good number of options available from a number of fine
manufacturers and there have been a number of construction articles in the
amateur literature. I'd look first to the NCJ archives if you want to "roll
your own".

73 de Dick, K6KR

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

Don Wilhelm-4

Re: KPA-500 Question

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

Joe is correct that the diodes will not prevent the K3 drivers from
seeing the higher voltages from an external band decoder, and if the
voltage is higher than the 5 volt level that the K3 resistors are tied
too, current will flow through the two pullup resistors. The real cure
is to remove the pullup resistors from the K3 (that can be done, the
driver chip is still open drain).

The K3 driver is not likely to be damaged - the driver IC is a
TPIC6C595, and its data sheet says the voltage can be as high as 33
volts and the open drains can sink as much as 100 ma. continuously
(although I would suggest a safety factor of up to 50%).

To restate - the problem is current through the two pullup resistors
(which are powered from two different power sources, and can best be
cured by removing the pullup resistors from the K3.

Elecraft added the pullup resistors some time ago so users would not
have to add pullup resistors to those band decoders that did not have
them, but since then we face this situation with those band decoders
that do have pullup resistors installed.

73,
Don W3FPR

On 7/10/2011 3:47 PM, Joe Subich, W4TV wrote:

>
>
>> If the band decoder devices have their own pullup resistors
>> (especially those who pullup to +12 volts), the K3 and/or the band
>> decoder may have problems because of differences in the supply
>> voltage to the pullups, and the cure is to add series diodes (with
>> the cathode end toward the K3) to the inputs of the band data
>> decoder.
>
> Series diodes to devices with +12V pull-ups will not solve the issue
> of "mixed" pull-up voltages. The K3 will still see the higher of
> the pull-up voltages (+5 in the K3, +5 in the KPA-500, +12 or +13.8
> in the "foreign" band decoder). The real issue occurs when the
> pull up resistor in the "foreign" device is too small and the K3
> can not sink the resulting current - or if the "foreign" decoder
> uses low power CMOS inputs which requires a low state voltage
> below 0.3V!
>
>> The KRC2 used with the K3 avoids this situation since it uses the
>> AUXBUS signal to determine which band the K3 is on.
>
> microHAM Station Master also avoids this situation since it uses
> the K3/P3 CAT bus (and provides an alternate CAT interface) for
> its band data.
>
> 73,
>
> ... Joe Subich, W4TV
> microHAM America, LLC.
> http://www.microHAM-USA.com
> http://groups.yahoo.com/group/microHAM
>