On Saturday, March 14, 2015 at 5:07:37 AM UTC-4, Jeff wrote:
On 14/03/2015 01:48, Channel Jumper wrote:
Tom W3TDH;836715 Wrote:
I am looking for recommendations for a dual band antenna that will serve
two separate radios. The reason that I want to use a single antenna is
that I have a limited number of mounting points for antennas. At
present it will be hard for SWMBO; as in Rumpole's spouse, She Who Must
Be Obeyed; to tolerate the use of both our home's gable ends and the
chimney being used to support antennas. I am planning to replace my
Diamond X-30 with a triband vertical for Six, Two, and .7 Meters. The
chimney will then support a rotor aimed Two and .7 Meter beam. The
second gable end will support the Two meter / Seventy Centimeter dual
band vertical that I am asking for help in selecting.

One radio will be a two meter packet node which will be used as a
Winlink Radio Message Server. The other radio will be a UHF D-STAR
hotspot. I am willing to pay what is needed to to get the best antenna
for this application but I don't want to waste money ineffectively. So
the two meter radio will be in the 144 MHz portion of the band and I
don't yet actually know were the D-STAR hotspot will be run. I have a
DCI filter and diplexer to keep the two radios from actually knowing of
each others existence. Since a hotspot is not supposed to be a terribly
wide area installation I would imagine that I do not want an extremely
high gain antenna but I am perfectly open to be reeducated on that. The
difficulty is that I would guess that the Radio Message Server / Packet
would benefit from as much horizontal gain as can be achieved. I have a
home brewed collinear two meter J-Pole that has been a good performer on
two meters and presents a low SWR on 440 MHz. I have yet to master
antenna modeling but I would imagine; given all the warnings I have read
on line; that it has poor radiation pattern on UHF. Is it likely to be
too poor a performer for a hot spot on UHF?

I really am asking because I want to know. I am not looking for
encouragement to do something that will be ineffective. Thank you in
advance for any help you may be willing to offer.

--
Tom Horne W3TDH

Tom,
You have too many of the same band antenna's concentrated in one place.
No matter how hard you try, they aren't going to play nice with each
other.
I read 14 posts and no one gave an even close right answer to your
question.
The answer is that you need to construct a tower, no less than 100',
near your house in order to even try to do what you wish to do.
Even then, you will need feet of separation vertically in order to get
the antenna's to play nice with each other.
Your SWR is going to be all messed up, because you have too many of the
same antenna's in the same proximity.

The only good 6 / 2 / 70 cm antenna that I could recommend would be the
Diamond v2000. This is the only antenna that I am aware of that has a
decent amount of gain - if you want to call it that, along with being
semi resonant on all three bands.

What you are doing is back-feeding everything that you transmit back
into the receive of the front ends of all of the radios in your shack
when any one radio transmits. Unless it is in your budget to replace
all those radios on a semi annual schedule, you will eventually
experience that each of those transceivers will eventually become deaf.

I have seen filters promoted in QST that allows two operators on two
different bands to share a beam antenna with two transceivers, as long
as each transceiver stays on it's band it is ok.

But there is a hell of a difference between 20 meters - 14 MHz - CW and
40 meters Phone.

Even though 70 cm is not a harmonic of 2m, and even though there is a
heck of a disparity between 440 MHz and 146 MHZ there is always going to
be problems when dealing with FM, and Digital modes.

I have to take your wife's side on this one!

Tell your club to go out and buy an acre of ground and put up a
transmitter and a tower and put their packet and their D-Star crap on
their tower, and then you can tune to their tower frequency if you so
choose. You are killing not only all of your transceivers by what you
are trying to do, but you are diminishing the range at which you
yourself can operate...

If you can hear other repeaters / more than 20 miles away though all of
that RF noise you have created, you will be lucky..

It doesn't matter if the radios are all turned on or off, as long as
they are connected to the coax / antenna, they are still going to
experience front end overload.


What a complete load of hog wash!!

A dual band antenna and the DCI filter/diplexer will work just fine.
The DCI filter provides bandpass characteristics on both 2 & 70 and then
provides a single output. The filters provide more than adequate
isolation between radios to stop any damage for reasonable power levels.

You almost certainly will be able to hear the harmonics from the 2m tx
on 70 but the level will not cause any damage.

By the way Channel Jumper 70cms IS a harmonic of 2m, perhaps time to
brush up on your 3 times table.

Jeff



On Saturday, March 14, 2015 at 5:07:37 AM UTC-4, Jeff wrote:
On 14/03/2015 01:48, Channel Jumper wrote:
Tom W3TDH;836715 Wrote:
I am looking for recommendations for a dual band antenna that will serve
two separate radios. The reason that I want to use a single antenna is
that I have a limited number of mounting points for antennas. At
present it will be hard for SWMBO; as in Rumpole's spouse, She Who Must
Be Obeyed; to tolerate the use of both our home's gable ends and the
chimney being used to support antennas. I am planning to replace my
Diamond X-30 with a triband vertical for Six, Two, and .7 Meters. The
chimney will then support a rotor aimed Two and .7 Meter beam. The
second gable end will support the Two meter / Seventy Centimeter dual
band vertical that I am asking for help in selecting.

One radio will be a two meter packet node which will be used as a
Winlink Radio Message Server. The other radio will be a UHF D-STAR
hotspot. I am willing to pay what is needed to to get the best antenna
for this application but I don't want to waste money ineffectively. So
the two meter radio will be in the 144 MHz portion of the band and I
don't yet actually know were the D-STAR hotspot will be run. I have a
DCI filter and diplexer to keep the two radios from actually knowing of
each others existence. Since a hotspot is not supposed to be a terribly
wide area installation I would imagine that I do not want an extremely
high gain antenna but I am perfectly open to be reeducated on that. The
difficulty is that I would guess that the Radio Message Server / Packet
would benefit from as much horizontal gain as can be achieved. I have a
home brewed collinear two meter J-Pole that has been a good performer on
two meters and presents a low SWR on 440 MHz. I have yet to master
antenna modeling but I would imagine; given all the warnings I have read
on line; that it has poor radiation pattern on UHF. Is it likely to be
too poor a performer for a hot spot on UHF?

I really am asking because I want to know. I am not looking for
encouragement to do something that will be ineffective. Thank you in
advance for any help you may be willing to offer.

--
Tom Horne W3TDH

Tom,
You have too many of the same band antenna's concentrated in one place.
No matter how hard you try, they aren't going to play nice with each
other.
I read 14 posts and no one gave an even close right answer to your
question.
The answer is that you need to construct a tower, no less than 100',
near your house in order to even try to do what you wish to do.
Even then, you will need feet of separation vertically in order to get
the antenna's to play nice with each other.
Your SWR is going to be all messed up, because you have too many of the
same antenna's in the same proximity.

The only good 6 / 2 / 70 cm antenna that I could recommend would be the
Diamond v2000. This is the only antenna that I am aware of that has a
decent amount of gain - if you want to call it that, along with being
semi resonant on all three bands.

What you are doing is back-feeding everything that you transmit back
into the receive of the front ends of all of the radios in your shack
when any one radio transmits. Unless it is in your budget to replace
all those radios on a semi annual schedule, you will eventually
experience that each of those transceivers will eventually become deaf.

I have seen filters promoted in QST that allows two operators on two
different bands to share a beam antenna with two transceivers, as long
as each transceiver stays on it's band it is ok.

But there is a hell of a difference between 20 meters - 14 MHz - CW and
40 meters Phone.

Even though 70 cm is not a harmonic of 2m, and even though there is a
heck of a disparity between 440 MHz and 146 MHZ there is always going to
be problems when dealing with FM, and Digital modes.

I have to take your wife's side on this one!

Tell your club to go out and buy an acre of ground and put up a
transmitter and a tower and put their packet and their D-Star crap on
their tower, and then you can tune to their tower frequency if you so
choose. You are killing not only all of your transceivers by what you
are trying to do, but you are diminishing the range at which you
yourself can operate...

If you can hear other repeaters / more than 20 miles away though all of
that RF noise you have created, you will be lucky..

It doesn't matter if the radios are all turned on or off, as long as
they are connected to the coax / antenna, they are still going to
experience front end overload.


What a complete load of hog wash!!

A dual band antenna and the DCI filter/diplexer will work just fine.
The DCI filter provides bandpass characteristics on both 2 & 70 and then
provides a single output. The filters provide more than adequate
isolation between radios to stop any damage for reasonable power levels.

You almost certainly will be able to hear the harmonics from the 2m tx
on 70 but the level will not cause any damage.

By the way Channel Jumper 70cms IS a harmonic of 2m, perhaps time to
brush up on your 3 times table.

Jeff

Jeff

May I ask that you cool your jets a little. Please turn off the afterburners and stick to the questions that I'm asking. I don't want to be a focus of a flame war. I came here in the hope of getting good information and the task of sorting out conflicting advice is so much easier if I don't need to also filter out gratuitous feuding.

Your version of what is possible is attractive because it allows me to do what I want to do to support my clubs D-STAR project and provide a training resource for the ARES Hospital Emergency Net staff to become competent with Winlink.

I realize that there are some Hams that despise Winlink and all other automated store and forward systems. I will be doing everything I can to avoid interference to other Amateurs but since we are using this to support hospitals under emergency conditions I think that everyone can just suck it up and bare with the emergency traffic and whatever inconvenience it may generate. b

Would you please advise if the third harmonic issue is likely to be serious enough to require the use of a low pass filter between the two meter transceiver and the Diplexer/Band Pass Filter when using separate transmitters?

--
Tom Horne W3TDH