OT: question re: antenna/rig swtich

[Greg Buhyoff]

Group,

This is off topic and I would deeply appreciate any responses to be
sent to me off list.  I am posting here because I respect the
knowledge and experience of the people who are members of this
reflector.

This may sound stupid but I have not had experience with this before,
so I ask before I do something stupid.

I use an external antenna switch mounted on the outside wall of my
house to switch in one of six antennas and have a single coax line
coming into the radio room.   I now have four separate radio stations,
2 K3s and two other radios, all set up differently for different types
and modes of operation.  All have amps in line that can be used when
needed -- one a KW and the others 750w output.  Currently I manually
attach the output coax for the station I want to use to the coax lead
coming into the house from the external switch.  A pain.

I want to be able to simply use a manual switch to select the station
that would connect to the external antenna switch coax lead into the
radio room.  I would then use the manual antenna switch to select the
station and the remote controller to select the antenna.  I was
looking at the Alpha Delta manual switch with four switched ports and
a common and then would connect the common to the coax lead coming
from the external antenna switch (DX Engineering) and then each output
coax from each of four stations to the four ports on the Alpha Delta
and then could switch stations via the Alpha Delta manual switch (all
ports not selected go to ground) and, obviously, then select my
antennas as I have been doing using my remote antenna switch.

Again, this sounds stupid, but I have not had to do this before and
always used manual "antenna" switches to simply select antennas.  My
question is this:

Given the Alpha Delta manual switch has  >60dB port isolation -- is
this isolation good enough that I can use the this manual switch to
select stations even though each of the  stations has the capability
delivering up to 1 KW output?  I don't want to blow out the front ends
of the radios connected to this manual switch.

I appreciate any answers that can be sent on to me.  I know this
sounds stupid, but I have been a ham since 1958 and simply have not
had or needed to do this.  I now have four great stations that I
carefully put together as part of a "plan" when I retired and I don't
want to do something stupid at this point.  I have done plenty of
stupid things in the past and more will happen, but I thought I could
simply ask a question here with hopes someone can allay my fears of
using such a switching setup or educate me in those things I don't
understand or did not think of.

Thanks so very much and 73,
Greg K2UM
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[daleputnam]

Hi Greg,

  I have that arrangement here, with dual switching.. I don't run the amount of power you do, but have tested the isolation... of the switches, and am concerned about the amount of power that is allowed into the rx of the unused stations... I cured part of that with the grounded when not in use switch for the antenna switch... now I believe I need similar on the station switch...

 


--... ...--
Dale - WC7S in Wy







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[Don Wilhelm-4]

Greg,

Theory says you should not have any problem.  With 60 dB isolation and
1000 watts, there may be as much as 1 mW at the input of each receiver -
that is 223.6 mV, which is a large signal, but still within the power
handling capability of most receivers.

In the practical world, if there are any leakage paths *around* the
switch or coupling between the coax lines, then even though the switch
itself provides 60 dB isolation, the system isolation may be much lower
- just how much depends on your setup.

You could set it up and test at lower power - tune the other radios to
the transmit frequency and see what the S-meters tell you.

73,
Don W3FPR

Greg Buhyoff wrote:

> Group,
>
> This is off topic and I would deeply appreciate any responses to be
> sent to me off list.  I am posting here because I respect the
> knowledge and experience of the people who are members of this
> reflector.
>
> This may sound stupid but I have not had experience with this before,
> so I ask before I do something stupid.
>
> I use an external antenna switch mounted on the outside wall of my
> house to switch in one of six antennas and have a single coax line
> coming into the radio room.   I now have four separate radio stations,
> 2 K3s and two other radios, all set up differently for different types
> and modes of operation.  All have amps in line that can be used when
> needed -- one a KW and the others 750w output.  Currently I manually
> attach the output coax for the station I want to use to the coax lead
> coming into the house from the external switch.  A pain.
>
> I want to be able to simply use a manual switch to select the station
> that would connect to the external antenna switch coax lead into the
> radio room.  I would then use the manual antenna switch to select the
> station and the remote controller to select the antenna.  I was
> looking at the Alpha Delta manual switch with four switched ports and
> a common and then would connect the common to the coax lead coming
> from the external antenna switch (DX Engineering) and then each output
> coax from each of four stations to the four ports on the Alpha Delta
> and then could switch stations via the Alpha Delta manual switch (all
> ports not selected go to ground) and, obviously, then select my
> antennas as I have been doing using my remote antenna switch.
>
> Again, this sounds stupid, but I have not had to do this before and
> always used manual "antenna" switches to simply select antennas.  My
> question is this:
>
> Given the Alpha Delta manual switch has  >60dB port isolation -- is
> this isolation good enough that I can use the this manual switch to
> select stations even though each of the  stations has the capability
> delivering up to 1 KW output?  I don't want to blow out the front ends
> of the radios connected to this manual switch.
>
> I appreciate any answers that can be sent on to me.  I know this
> sounds stupid, but I have been a ham since 1958 and simply have not
> had or needed to do this.  I now have four great stations that I
> carefully put together as part of a "plan" when I retired and I don't
> want to do something stupid at this point.  I have done plenty of
> stupid things in the past and more will happen, but I thought I could
> simply ask a question here with hopes someone can allay my fears of
> using such a switching setup or educate me in those things I don't
> understand or did not think of.
>
> Thanks so very much and 73,
> Greg K2UM
>  
>

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[Julius Fazekas n2wn]

Hi Greg,

This might be a good question to post on the contest reflector. Stations like KC1XX, K1TTT, W3LPL, etc all deal with such issues with their Multi-Multi stations.

I like Alpha Delta switches and don't think you'll have a problem with them. You could look for Bird switches with higher power ratings (on the surplus market or I think RF Engineering carries them). Transfer relays may be another option...

73,
Julius

Greg Buhyoff wrote

Group,

This is off topic and I would deeply appreciate any responses to be
sent to me off list.  I am posting here because I respect the
knowledge and experience of the people who are members of this
reflector.

This may sound stupid but I have not had experience with this before,
so I ask before I do something stupid.

I use an external antenna switch mounted on the outside wall of my
house to switch in one of six antennas and have a single coax line
coming into the radio room.   I now have four separate radio stations,
2 K3s and two other radios, all set up differently for different types
and modes of operation.  All have amps in line that can be used when
needed -- one a KW and the others 750w output.  Currently I manually
attach the output coax for the station I want to use to the coax lead
coming into the house from the external switch.  A pain.

I want to be able to simply use a manual switch to select the station
that would connect to the external antenna switch coax lead into the
radio room.  I would then use the manual antenna switch to select the
station and the remote controller to select the antenna.  I was
looking at the Alpha Delta manual switch with four switched ports and
a common and then would connect the common to the coax lead coming
from the external antenna switch (DX Engineering) and then each output
coax from each of four stations to the four ports on the Alpha Delta
and then could switch stations via the Alpha Delta manual switch (all
ports not selected go to ground) and, obviously, then select my
antennas as I have been doing using my remote antenna switch.

Again, this sounds stupid, but I have not had to do this before and
always used manual "antenna" switches to simply select antennas.  My
question is this:

Given the Alpha Delta manual switch has  >60dB port isolation -- is
this isolation good enough that I can use the this manual switch to
select stations even though each of the  stations has the capability
delivering up to 1 KW output?  I don't want to blow out the front ends
of the radios connected to this manual switch.

I appreciate any answers that can be sent on to me.  I know this
sounds stupid, but I have been a ham since 1958 and simply have not
had or needed to do this.  I now have four great stations that I
carefully put together as part of a "plan" when I retired and I don't
want to do something stupid at this point.  I have done plenty of
stupid things in the past and more will happen, but I thought I could
simply ask a question here with hopes someone can allay my fears of
using such a switching setup or educate me in those things I don't
understand or did not think of.

Thanks so very much and 73,
Greg K2UM
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[Erwin Haynes]

I had the very set-up you are considering building - also using the 4 position Alpha Delta switch. I am now converting back to a modified manual set-up.

Why? the Alpha Delta switch developed a fault -- if you open it up you will find that the mechanism is a thin strip of metal which is pressed to make contact with each respective contact of the 4 positions as you move the knob into the next detent.

It seems the metal strip was mounted by the manufacturer "not centered", so that after only after a short period of usage (2 months after installing a new unit) the contact made to the 2 positions on one side of the switch were poor or even intermittent.

It cost me shipping my K-3 back to Aptos both ways and repair costs - and Elecraft was very nice to me on repair costs, even though this was clearly my fault.

So, as a matter of QTH operating philosophy, I have now purchased a MFJ coax patch panel, have labeled all inlets and outlets of the panel and each piece of coax in my QTH on both ends -- and have designed and made copies of a check list which I use each time I re-configure. Perhaps overboard -- but it was an expensive lesson learned.

FWIW.

Regards,
 Erwin
KI4TBD
Canton, GA, USA
"Join the DARC side! Deutscher Amateur Radio Club!"

Greg Buhyoff wrote:

> Group,
>
> This is off topic and I would deeply appreciate any responses to be
> sent to me off list.  I am posting here because I respect the
> knowledge and experience of the people who are members of this
> reflector.
>
> This may sound stupid but I have not had experience with this before,
> so I ask before I do something stupid.
>
> I use an external antenna switch mounted on the outside wall of my
> house to switch in one of six antennas and have a single coax line
> coming into the radio room.  I now have four separate radio stations,
> 2 K3s and two other radios, all set up differently for different types
> and modes of operation.  All have amps in line that can be used when
> needed -- one a KW and the others 750w output.  Currently I manually
> attach the output coax for the station I want to use to the coax lead
> coming into the house from the external switch.  A pain.
>
> I want to be able to simply use a manual switch to select the station
> that would connect to the external antenna switch coax lead into the
> radio room.  I would then use the manual antenna switch to select the
> station and the remote controller to select the antenna.  I was
> looking at the Alpha Delta manual switch with four switched ports and
> a common and then would connect the common to the coax lead coming
> from the external antenna switch (DX Engineering) and then each output
> coax from each of four stations to the four ports on the Alpha Delta
> and then could switch stations via the Alpha Delta manual switch (all
> ports not selected go to ground) and, obviously, then select my
> antennas as I have been doing using my remote antenna switch.
>
> Again, this sounds stupid, but I have not had to do this before and
> always used manual "antenna" switches to simply select antennas.  My
> question is this:
>
> Given the Alpha Delta manual switch has  >60dB port isolation -- is
> this isolation good enough that I can use the this manual switch to
> select stations even though each of the  stations has the capability
> delivering up to 1 KW output?  I don't want to blow out the front ends
> of the radios connected to this manual switch.
>
> I appreciate any answers that can be sent on to me.  I know this
> sounds stupid, but I have been a ham since 1958 and simply have not
> had or needed to do this.  I now have four great stations that I
> carefully put together as part of a "plan" when I retired and I don't
> want to do something stupid at this point.  I have done plenty of
> stupid things in the past and more will happen, but I thought I could
> simply ask a question here with hopes someone can allay my fears of
> using such a switching setup or educate me in those things I don't
> understand or did not think of.
>
> Thanks so very much and 73,
> Greg K2UM
> 
>

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[Rick Dettinger-3]

Don,

Does it matter if the rigs not in use are turned off?  I assumed that  
they would have more immunity to overload if the unused rig was not  
turned on.  The Alpha Delta instructions says the switches are meant  
to be used for switching multi antennas and one rig or multi  
receivers.  They do not mention multi transceivers.  I use two  
transceivers with one antenna but I removed the protection plug  
(Arcplug) as I wasn't sure if that was the reason they didn't  
recommend the switch for multi transceivers.  But I always leave the  
unused rig turned off.  No problem so far but I only run 100 watts  
maximum.

73
Rick Dettinger   K7MW


On Mar 5, 2009, at 5:52 AM, Don Wilhelm wrote:

> Greg,
>
> Theory says you should not have any problem.  With 60 dB isolation and
> 1000 watts, there may be as much as 1 mW at the input of each  
> receiver -
> that is 223.6 mV, which is a large signal, but still within the power
> handling capability of most receivers.
>
> In the practical world, if there are any leakage paths *around* the
> switch or coupling between the coax lines, then even though the switch
> itself provides 60 dB isolation, the system isolation may be much  
> lower
> - just how much depends on your setup.
>
> You could set it up and test at lower power - tune the other radios to
> the transmit frequency and see what the S-meters tell you.
>
> 73,
> Don W3FPR
>

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[Don Wilhelm-4]

Rick,

I do not believe it makes much difference whether the rigs not in use
are turned on or off.  Any damage would occur in the preamp or mixer
stages in most cases, and the devices are sitting there with their
inputs connected whether power is on or off, but there also may be some
T/R switching arrangement in a transceiver ahead of the receiver front
end devices - it would be difficult to predict just how the unbiased
diodes (power off) would respond if the signal were large enough - it
would depend on the design.
We do know that the K2 will tolerate 0.14 Vrms of input signal without
damage - that is the signal level that is used for Receive Signal
Tracing if one is to match the RF Probe values listed as 'expected'.  I
also know that my K2 will stand a 1 volt input signal without damage
(that has happened several times) - but I don't know what the upper
limit is and don't want to try a destructive test.

So, the real answer is either "it all depends" or "I don't know".

73,
Don W3FPR

Rick Dettinger wrote:

> Don,
>
> Does it matter if the rigs not in use are turned off?  I assumed that  
> they would have more immunity to overload if the unused rig was not  
> turned on.  The Alpha Delta instructions says the switches are meant  
> to be used for switching multi antennas and one rig or multi  
> receivers.  They do not mention multi transceivers.  I use two  
> transceivers with one antenna but I removed the protection plug  
> (Arcplug) as I wasn't sure if that was the reason they didn't  
> recommend the switch for multi transceivers.  But I always leave the  
> unused rig turned off.  No problem so far but I only run 100 watts  
> maximum.
>
> 73
> Rick Dettinger   K7MW
>
>
> On Mar 5, 2009, at 5:52 AM, Don Wilhelm wrote:
>
>  
>> Greg,
>>
>> Theory says you should not have any problem.  With 60 dB isolation and
>> 1000 watts, there may be as much as 1 mW at the input of each  
>> receiver -
>> that is 223.6 mV, which is a large signal, but still within the power
>> handling capability of most receivers.
>>
>> In the practical world, if there are any leakage paths *around* the
>> switch or coupling between the coax lines, then even though the switch
>> itself provides 60 dB isolation, the system isolation may be much  
>> lower
>> - just how much depends on your setup.
>>
>> You could set it up and test at lower power - tune the other radios to
>> the transmit frequency and see what the S-meters tell you.
>>
>> 73,
>> Don W3FPR
>>
>>    
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[KC9QQ]

You may want to check out the products from TopTen.  They are a little pricey, but they are what are used by many of the Multi-Multi contest stations to share six antennas with 6 high power operator stations.  I just purchased one of their A/B switches to switch a single antenna between my K2 and Pro III.  It provides 80 db isolation and uses interlocked relays to avoid the possibility of a relay failure allowing power to allow transmitter power to flow back into the rig not being used.  

If you look at the application note one their site, it shows a setup very similar to what you describe.

Here is the link to the site:  http://www.qth.com/topten/abss.htm 

Fred, KC9QQ

Greg Buhyoff wrote

Group,

This is off topic and I would deeply appreciate any responses to be
sent to me off list.  I am posting here because I respect the
knowledge and experience of the people who are members of this
reflector.

This may sound stupid but I have not had experience with this before,
so I ask before I do something stupid.

I use an external antenna switch mounted on the outside wall of my
house to switch in one of six antennas and have a single coax line
coming into the radio room.   I now have four separate radio stations,
2 K3s and two other radios, all set up differently for different types
and modes of operation.  All have amps in line that can be used when
needed -- one a KW and the others 750w output.  Currently I manually
attach the output coax for the station I want to use to the coax lead
coming into the house from the external switch.  A pain.

I want to be able to simply use a manual switch to select the station
that would connect to the external antenna switch coax lead into the
radio room.  I would then use the manual antenna switch to select the
station and the remote controller to select the antenna.......