In article ,
"Ralph Mowery" wrote:

"Tom W3TDH" wrote in message
...
I am going to declare myself lost on this one so please be patient. I had
though I had addressed these issues when I said I was using a DCI Dual
Band Filter and Diplexer. Is the DCI combination filter and diplexer
insufficient to protect the two radios from each other? DCI claimed it
would be. The model number is DCI-146-444-DX-DB. The web sight were it
is listed is
http://www.dci.ca/?Section=Products&SubSection=Amateur. If I need to add
Duplexers it is practical to do because the mobile ones available used are
manageable money. If there is a real chance for damage in the event .of
simultaneous transmission then I will need to add circulators and dummy
loads to the output of both radios. That will end up being a little
pricy.


That DCI should be plenty to protect the two rigs. You may have a desense
on the 440 receiver if it on a near 3 rd harmonic of the 144 transmiter. It
won't be enough to cause any damage, just enough to block the 440 receiver.

I agree that you are not likely to damage a radio. The common duplexer
(or triplexer) is often used to connect a single multi-band antenna to
multiple connectors of a multi-band radio, which is essentially multiple
radios in a single package. The difference between this and what you
are planning, is that the multi-band radio is usually not used for
simultaneous reception and transmission. Or at least you would accept
some desensitization if it occurred.

You can choose frequencies such that the third harmonic of the Two Meter
frequency is not in the IF passband of the 440 receiver, but you are
likely have overloading of the receiver's broad front end. (You may
also have some overloading of the Two Meter radio due to the amount of
power involved.)

That said, go ahead and try it. It may work well enough to meet your
needs. If it does not work out, the alternative is a "real" repeater.

One advantage of a repeater, is that local users can hear each other.
With your Hot Spot, local users are talking simplex.

73,
Fred
K4DII