Elecraft

K3: Using a K3 to route antenna signals to external devices...

Classic

List

Threaded

14 messages Options

NK7Z

K3: Using a K3 to route antenna signals to external devices...

A few months ago someone asked how to move the antenna signal coming in
on the main antenna connector of a K3 to an external SDR via some
connector in the rear of the K3.

The answer indicated connecting the SDR antenna to some connector in the
rear of the radio, and pressing some number of front panel keys to route
the signals from the antenna to the SDR...

Can someone point me at that post, or tell me how this is accomplished?
The RF Signal flow on the K3 has always eluded me.

Also, is the output from the K3 at zero or close to zero when
transmitting? i.e. is it safe for the SDR?

--
73s and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Technical Specialist
ARRL Volunteer Examiner
ARRL OOC for Oregon
______________________________________________________________
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

Joe Subich, W4TV-4

Re: K3: Using a K3 to route antenna signals to external devices...

> The answer indicated connecting the SDR antenna to some connector in
> the rear of the radio, and pressing some number of front panel keys
> to route the signals from the antenna to the SDR...
Connect a splitter, input to the RX Ant Out jack, one output to the
RX ANT IN jack and the other output to the Antenna input of your SDR.

Press the RX ANT button to activate the RX ANTENNA Out/RX ANT IN path.

> Also, is the output from the K3 at zero or close to zero when
> transmitting? i.e. is it safe for the SDR?

Yes, the RX ANT Out/IN path is on the receive side of the T/R switch.
There is no RF (or only leakage) present in transmit.

73,

... Joe, W4TV

On 2019-04-08 4:06 PM, Dave Cole (NK7Z) wrote:

> A few months ago someone asked how to move the antenna signal coming in
> on the main antenna connector of a K3 to an external SDR via some
> connector in the rear of the K3.
>
> The answer indicated connecting the SDR antenna to some connector in the
> rear of the radio, and pressing some number of front panel keys to route
> the signals from the antenna to the SDR...
>
> Can someone point me at that post, or tell me how this is accomplished?
> The RF Signal flow on the K3 has always eluded me.
>
> Also, is the output from the K3 at zero or close to zero when
> transmitting? i.e. is it safe for the SDR?
>

______________________________________________________________
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

Re: K3: Using a K3 to route antenna signals to external devices...

In reply to this post by NK7Z

Dave,

Look for a post by Bob McGraw.

In brief, it takes a TEE adapter and 2 short pieces of coax. Put the
adapter between the 2 pieces of coax, and then connect one coax to ANT
OUT and the other to ANT IN. The SDR is connected to the TEE adapter.

To get output to the SDR, you must set the K3 for the RX ANT.

If you are not interested in a multi-band input to the SDR, but only the
K3 IF (for a panadapter application), then you can simply connect the
SDR to the K3 IF OUT and set the SDR to tune 8.215MHz.

In both cases, the SDR will be protected during transmit.

73,
Don W3FPR

On 4/8/2019 4:06 PM, Dave Cole (NK7Z) wrote:
> A few months ago someone asked how to move the antenna signal coming in
> on the main antenna connector of a K3 to an external SDR via some
> connector in the rear of the K3.
>
> The answer indicated connecting the SDR antenna to some connector in the
> rear of the radio, and pressing some number of front panel keys to route
> the signals from the antenna to the SDR...
>
______________________________________________________________
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

Bob McGraw - K4TAX

Re: K3: Using a K3 to route antenna signals to external devices...

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

I agree with Joe in the procedure. As to using or the need for a
"splitter", I don't find the input impedance of the SDR Play/RSP1 to be
anywhere near 50 ohms. In fact it is much higher. Thus the result
of using a simple BNC "T" does not load the signal of the main
receiver. If your SDR receiver does present a 50 ohm input, then you
can expect to loose about 3 dB of received signal.

And correct, the SDR will be protected when one is transmitting.

73

Bob, K4TAX

On 4/8/2019 3:22 PM, Joe Subich, W4TV wrote:

>
>
>> The answer indicated connecting the SDR antenna to some connector in
>> the rear of the radio, and pressing some number of front panel keys
>> to route the signals from the antenna to the SDR...
> Connect a splitter, input to the RX Ant Out jack, one output to the
> RX ANT IN jack and the other output to the Antenna input of your SDR.
>
> Press the RX ANT button to activate the RX ANTENNA Out/RX ANT IN path.
>
> > Also, is the output from the K3 at zero or close to zero when
> > transmitting? i.e. is it safe for the SDR?
>
> Yes, the RX ANT Out/IN path is on the receive side of the T/R switch.
> There is no RF (or only leakage) present in transmit.
>
> 73,
>
> ... Joe, W4TV
>

NK7Z

Re: K3: Using a K3 to route antenna signals to external devices...

Thank you gents! Now to uppack my KPA500 which came back from support
today...

73s and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Technical Specialist
ARRL Volunteer Examiner
ARRL OOC for Oregon

On 4/8/19 1:31 PM, Bob McGraw K4TAX wrote:

> I agree with Joe in the procedure.   As to using or the need for a
> "splitter", I don't find the input impedance of the SDR Play/RSP1 to be
> anywhere near 50 ohms. In fact it is much higher.    Thus the result
> of using a simple BNC "T" does not load the signal of the main
> receiver. If your SDR receiver does present a 50 ohm input, then you
> can expect to loose about 3 dB of received signal.
>
> And correct, the SDR will be protected when one is transmitting.
>
> 73
>
> Bob, K4TAX
>
>
> On 4/8/2019 3:22 PM, Joe Subich, W4TV wrote:
>>
>>
>>> The answer indicated connecting the SDR antenna to some connector in
>>> the rear of the radio, and pressing some number of front panel keys
>>> to route the signals from the antenna to the SDR...
>> Connect a splitter, input to the RX Ant Out jack, one output to the
>> RX ANT IN jack and the other output to the Antenna input of your SDR.
>>
>> Press the RX ANT button to activate the RX ANTENNA Out/RX ANT IN path.
>>
>> > Also, is the output from the K3 at zero or close to zero when
>> > transmitting? i.e. is it safe for the SDR?
>>
>> Yes, the RX ANT Out/IN path is on the receive side of the T/R switch.
>> There is no RF (or only leakage) present in transmit.
>>
>> 73,
>>
>>    ... Joe, W4TV
>>
>
> ______________________________________________________________
> 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

Joe Subich, W4TV-4

Re: K3: Using a K3 to route antenna signals to external devices...

In reply to this post by Bob McGraw - K4TAX

On 2019-04-08 4:31 PM, Bob McGraw K4TAX wrote:

> I don't find the input impedance of the SDR Play/RSP1 to be
> anywhere near 50 ohms. In fact it is much higher. Thus the result
> of using a simple BNC "T" does not load the signal of the main
> receiver.

However, since the K3 receiver is relatively close to 50 Ohms, it
*WILL* load the input of SDRs with high input impedance - to the
extent that the SDR *can* lose 10 dB or more of sensitivity. The
splitter works to protect the sensitivity of *BOTH* receivers -
if that were not the case why do you think Wayne bothered to include
a splitter in the design for the KRX3!

73,

... Joe, W4TV

On 2019-04-08 4:31 PM, Bob McGraw K4TAX wrote:

Jim Brown-10

Re: K3: Using a K3 to route antenna signals to external devices...

I don't understand the math behind this. The 50 ohm input Z of the K3
terminates the transmission line. The SDR sees whatever voltage is
across the K3 input. More to the point, why does it matter? In most
real world stations, especially below VHF, noise from the antenna is
sufficiently greater than circuit noise that circuit noise doesn't
matter. A ratio of 13 dB satisfies this condition.

73, Jim K9YC

On 4/8/2019 2:15 PM, Joe Subich, W4TV wrote:
> However, since the K3 receiver is relatively close to 50 Ohms, it
> *WILL* load the input of SDRs with high input impedance - to the
> extent that the SDR *can* lose 10 dB or more of sensitivity.

______________________________________________________________
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

Martin Sole-3

Re: K3: Using a K3 to route antenna signals to external devices...

In reply to this post by NK7Z

I've been playing with this sort of setup recently. I have a K3 with a
KXV3 and an SDRPlay RSP1. For my usage I find that theP3 is a better
option and when I want the display on the PC I have the RSP1 connected
to the P3 IF Out and use the software set to accommodate it is working
at a fixed IF.

I tried connecting the RSP1 with a tee piece and two short pieces of
coax to have a separately tunable third receiver but found a lot of
unwanted responses on the SDR receivers display. Although I did not
investigate very far, switching back to the much more acceptable P3 IF
out technique in short order, I can only presume leakage from the K3 is
the cause.

It could be that I had things 'set wrong' so please feel free to comment
but although an impedance matching splitter might not be a necessity it
seems to me at least that some sort of buffer ahead of the SDR might
well be.

Martin, HS0ZED

On 09/04/2019 03:06, Dave Cole (NK7Z) wrote:

> A few months ago someone asked how to move the antenna signal coming
> in on the main antenna connector of a K3 to an external SDR via some
> connector in the rear of the K3.
>
> The answer indicated connecting the SDR antenna to some connector in
> the rear of the radio, and pressing some number of front panel keys to
> route the signals from the antenna to the SDR...
>
> Can someone point me at that post, or tell me how this is
> accomplished? The RF Signal flow on the K3 has always eluded me.
>
> Also, is the output from the K3 at zero or close to zero when
> transmitting? i.e. is it safe for the SDR?
>

Don Wilhelm

Re: K3: Using a K3 to route antenna signals to external devices...

Martin,

Connecting the SDR to the ANT OUT/ANT IN jacks allows the SDR to see the
enitire spectrum of the K3 antenna below the cutoff of the Low Pass filters.
Thaqt is apt to pick up any responses that are within the range of the
SDR tuning, and if there are spurs coming from your antenna (which have
nothing to do with the K3) then they will be seen.

Using the K3 (or P3) IF OUT will restrict the bandwidth to that near the
K3 IF and may not show you those spurs - which are likely coming from
devices throughout your house and your neighborhood.

73,
Don W3FPR

On 4/8/2019 10:24 PM, Martin Sole wrote:

> I've been playing with this sort of setup recently. I have a K3 with a
> KXV3 and an SDRPlay RSP1. For my usage I find that theP3 is a better
> option and when I want the display on the PC I have the RSP1 connected
> to the P3 IF Out and use the software set to accommodate it is working
> at a fixed IF.
>
> I tried connecting the RSP1 with a tee piece and two short pieces of
> coax to have a separately tunable third receiver but found a lot of
> unwanted responses on the SDR receivers display. Although I did not
> investigate very far, switching back to the much more acceptable P3 IF
> out technique in short order, I can only presume leakage from the K3 is
> the cause.
>
> It could be that I had things 'set wrong' so please feel free to comment
> but although an impedance matching splitter might not be a necessity it
> seems to me at least that some sort of buffer ahead of the SDR might
> well be.
>
> Martin, HS0ZED
>
>
> On 09/04/2019 03:06, Dave Cole (NK7Z) wrote:
>> A few months ago someone asked how to move the antenna signal coming
>> in on the main antenna connector of a K3 to an external SDR via some
>> connector in the rear of the K3.
>>
>> The answer indicated connecting the SDR antenna to some connector in
>> the rear of the radio, and pressing some number of front panel keys to
>> route the signals from the antenna to the SDR...
>>
>> Can someone point me at that post, or tell me how this is
>> accomplished? The RF Signal flow on the K3 has always eluded me.
>>
>> Also, is the output from the K3 at zero or close to zero when
>> transmitting? i.e. is it safe for the SDR?
>>
>
> ______________________________________________________________
> 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
>

Sverre Holm (LA3ZA)

Re: K3: Using a K3 to route antenna signals to external devices...

In reply to this post by Don Wilhelm

But what if there is a PR6-10 preamp in this path. Where should the
splitter/TEE-adapter be in that case?

>In brief, it takes a TEE adapter and 2 short pieces of coax. Put the
>adapter between the 2 pieces of coax, and then connect one coax to ANT
>OUT and the other to ANT IN.

-----
Sverre, LA3ZA

K2 #2198, K3 #3391,
LA3ZA Blog: http://la3za.blogspot.com,
LA3ZA Unofficial Guide to K2 modifications: http://la3za.blogspot.com/p/la3za-unofficial-guide-to-elecraft-k2.html
--
Sent from: http://elecraft.365791.n2.nabble.com/
______________________________________________________________
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

Sverre, LA3ZA

K2 #2198, K3 #3391,
LA3ZA Blog: http://la3za.blogspot.com,
LA3ZA Unofficial Guide to K2 modifications: http://la3za.blogspot.com/p/la3za-unofficial-guide-to-elecraft-k2.html

Joe Subich, W4TV-4

Re: K3: Using a K3 to route antenna signals to external devices...

After the PR6/PR10 to gain the benefit of the PR6/PR10 for
the SDR as well as the K3/KRX3 receiver(s).

73,

... Joe, W4TV

On 2019-04-09 6:48 AM, Sverre Holm (LA3ZA) wrote:

> But what if there is a PR6-10 preamp in this path. Where should the
> splitter/TEE-adapter be in that case?
>
>> In brief, it takes a TEE adapter and 2 short pieces of coax. Put the
>> adapter between the 2 pieces of coax, and then connect one coax to ANT
>> OUT and the other to ANT IN.
>
>
>
> -----
> Sverre, LA3ZA
>
> K2 #2198, K3 #3391,
> LA3ZA Blog: http://la3za.blogspot.com,
> LA3ZA Unofficial Guide to K2 modifications: http://la3za.blogspot.com/p/la3za-unofficial-guide-to-elecraft-k2.html

Sverre Holm (LA3ZA)

Re: K3: Using a K3 to route antenna signals to external devices...

Thanks, Joe.

Works nicely and saved me the cost of something like the MFJ-1708B-SDR SDR
RF sensing T/R switch!

-----
Sverre, LA3ZA

K2 #2198, K3 #3391,
LA3ZA Blog: http://la3za.blogspot.com,
LA3ZA Unofficial Guide to K2 modifications: http://la3za.blogspot.com/p/la3za-unofficial-guide-to-elecraft-k2.html
--
Sent from: http://elecraft.365791.n2.nabble.com/
______________________________________________________________
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

Sverre, LA3ZA

K2 #2198, K3 #3391,
LA3ZA Blog: http://la3za.blogspot.com,
LA3ZA Unofficial Guide to K2 modifications: http://la3za.blogspot.com/p/la3za-unofficial-guide-to-elecraft-k2.html

Don Wilhelm

Re: K3: Using a K3 to route antenna signals to external devices...

In reply to this post by Sverre Holm (LA3ZA)

Sverre,

That answer depends ---
If you want to connect the SDR directly to the antenna, put the TEE
between the ANT OUT and the preamp.
OTOH, if you want to have the preamp in-line for the SDR input, put the
TEE between the preamp output and the ANT IN connector.

If you chose to use the preamp with the SDR, you may have to do some
work on the powering and activation of the preamp.

73,
Don W3FPR

On 4/9/2019 6:48 AM, Sverre Holm (LA3ZA) wrote:
> But what if there is a PR6-10 preamp in this path. Where should the
> splitter/TEE-adapter be in that case?
>
>> In brief, it takes a TEE adapter and 2 short pieces of coax. Put the
>> adapter between the 2 pieces of coax, and then connect one coax to ANT
>> OUT and the other to ANT IN.
>
>
______________________________________________________________
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

Sverre Holm (LA3ZA)

Re: K3: Using a K3 to route antenna signals to external devices...

Doug,

Yes, thanks, you're right. I have the preamp set up to be active for the
higher bands 12, 10, and 6 m, and in the bypass position otherwise. I use
this to connect an old shortwave receiver (not an SDR) to my main antenna,
so I guess it doesn't hurt for it with the extra gain. But I'll try both
configurations, both before and after the preamp.

-----
Sverre, LA3ZA

K2 #2198, K3 #3391,
LA3ZA Blog: http://la3za.blogspot.com,
LA3ZA Unofficial Guide to K2 modifications: http://la3za.blogspot.com/p/la3za-unofficial-guide-to-elecraft-k2.html
--
Sent from: http://elecraft.365791.n2.nabble.com/
______________________________________________________________
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

Sverre, LA3ZA

K2 #2198, K3 #3391,
LA3ZA Blog: http://la3za.blogspot.com,
LA3ZA Unofficial Guide to K2 modifications: http://la3za.blogspot.com/p/la3za-unofficial-guide-to-elecraft-k2.html