Anyone have experience using a single Comant CI-121 to feed to COM
radios with the Comant CI-601 diplexor?

And, anyone have experience feeding a GPS and COM with the Comant
CI-2480 antenna?

I have 3 antennas on the roof of the fuselage (COM1, COM2, GPS). It's
going into the paint shop soon, so now's a good time to consider
minimizing the clutter up there.

On 3 Jun 2004 18:22:59 -0700, (Dave) wrote:

>Anyone have experience using a single Comant CI-121 to feed to COM
>radios with the Comant CI-601 diplexor?
>
>And, anyone have experience feeding a GPS and COM with the Comant
>CI-2480 antenna?
>
>I have 3 antennas on the roof of the fuselage (COM1, COM2, GPS). It's
>going into the paint shop soon, so now's a good time to consider
>minimizing the clutter up there.

I don't have specific experience of any of the diplexors but I have
been involved with antennas and splitters in broadcasting etc.

What I can say is everything added in series with an antenna will have
some loss. If you split COM into two there will be a small loss, in
addition if the antenna fails you've lost both COM.

Similar logic follows with the GPS. The losses are likely to be small
but maximum range could be reduced slightly.

Having said that we have an existing NAV antenna which now feeds NAV1,
NAV2 and Glideslope. All work well but NAV1 always picks up a signal
before NAV2 and the DME (separate antenna) frequently gives distance
before either NAV signal is usable.


David

Piper Warrior G-BHJO
Scotland, UK

E-mail (Remove Space after pilot): pilot

David > wrote in message >...
> On 3 Jun 2004 18:22:59 -0700, (Dave) wrote:

So how do you keep the transmit power of one comm from blowing up
the receiver in the other one? Seems like it would take a circulator
that would weigh about as much as your battery!!

I did install a COMANT combination GPS and COMM broadband antenna.
One position takes care of both.

Getting the required isolation wasn't that hard... they had already
understood the problem very well.

Bill Hale

>
> >Anyone have experience using a single Comant CI-121 to feed to COM
> >radios with the Comant CI-601 diplexor?
> >
> >And, anyone have experience feeding a GPS and COM with the Comant
> >CI-2480 antenna?
> >
> >I have 3 antennas on the roof of the fuselage (COM1, COM2, GPS). It's
> >going into the paint shop soon, so now's a good time to consider
> >minimizing the clutter up there.
>
>

On 4 Jun 2004 15:46:51 -0700, (Bill Hale) wrote:

>David > wrote in message >...
>> On 3 Jun 2004 18:22:59 -0700, (Dave) wrote:
>
>So how do you keep the transmit power of one comm from blowing up
>the receiver in the other one? Seems like it would take a circulator
>that would weigh about as much as your battery!!
>

I would avoid using two COM on the same antenna but it can be done.
I can't remember the number of wavelengths but I'm sure you could make
a co-axial combining filter.
Imagine a rectangle made with co-axial cable.
Put the two COM at diagonally opposite corners.
Put the antenna at one of the other corners and a balancing load at
the other.
The two COM need to have a 180° phase shift so signals cancel
It's all too messy and two antennas are much more efficient.

>I did install a COMANT combination GPS and COMM broadband antenna.
>One position takes care of both.
>
>Getting the required isolation wasn't that hard... they had already
>understood the problem very well.
>
>Bill Hale
>
>>
>> >Anyone have experience using a single Comant CI-121 to feed to COM
>> >radios with the Comant CI-601 diplexor?
>> >
>> >And, anyone have experience feeding a GPS and COM with the Comant
>> >CI-2480 antenna?
>> >
>> >I have 3 antennas on the roof of the fuselage (COM1, COM2, GPS). It's
>> >going into the paint shop soon, so now's a good time to consider
>> >minimizing the clutter up there.
>>
>>


David

E-mail (Remove Space after pilot): pilot

shared these priceless pearls of wisdom:

>
->I would avoid using two COM on the same antenna but it can be done.
->I can't remember the number of wavelengths but I'm sure you could make
->a co-axial combining filter.
->Imagine a rectangle made with co-axial cable.
->Put the two COM at diagonally opposite corners.
->Put the antenna at one of the other corners and a balancing load at
->the other.
->The two COM need to have a 180° phase shift so signals cancel
->It's all too messy and two antennas are much more efficient.

If you use this bozo's scheme to put two coms on one antenna, can I buy the
crispy fried remains for spare parts?


->
->>I did install a COMANT combination GPS and COMM broadband antenna.
->>One position takes care of both.
->>
->>Getting the required isolation wasn't that hard... they had already
->>understood the problem very well.

No problem. Getting isolation between 127 MHz. and 1575 MHz. isn't too
difficult. Getting isolation between 127 MHz. and 126 MHz. is a crystal bitch
without a lot of folderol.

Jim


Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

On Fri, 18 Jun 2004 13:09:37 -0700, Jim Weir > wrote:


>shared these priceless pearls of wisdom:
>
>>
>->I would avoid using two COM on the same antenna but it can be done.
>->I can't remember the number of wavelengths but I'm sure you could make
>->a co-axial combining filter.
>->Imagine a rectangle made with co-axial cable.
>->Put the two COM at diagonally opposite corners.
>->Put the antenna at one of the other corners and a balancing load at
>->the other.
>->The two COM need to have a 180° phase shift so signals cancel
>->It's all too messy and two antennas are much more efficient.
>
>If you use this bozo's scheme to put two coms on one antenna, can I buy the
>crispy fried remains for spare parts?
>
>
>->
>->>I did install a COMANT combination GPS and COMM broadband antenna.
>->>One position takes care of both.
>->>
>->>Getting the required isolation wasn't that hard... they had already
>->>understood the problem very well.
>
>No problem. Getting isolation between 127 MHz. and 1575 MHz. isn't too
>difficult. Getting isolation between 127 MHz. and 126 MHz. is a crystal bitch
>without a lot of folderol.
>
>Jim
>
>
>Jim Weir (A&P/IA, CFI, & other good alphabet soup)
>VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
>http://www.rst-engr.com

The last time you disagreed with me you found that Bird Power meters
did not read as you thought! So before you start getting rude read my
first line of my reply ("I would avoid using two COM on the same
antenna but it can be done"). I did not say it was sensible. I did say
"It's all too messy and two antennas are much more efficient".

As for isolation between 126MHz & 127 MHz you must know it can also be
done with filters. They may be expensive and heavy but it can be done.
Amateur repeaters using 0.6MHz on 145MHz is common using one antenna.
Before you complain I know these are only used on one frequency as
I've built and operated a repeater for years.

Let's leave it there...!