3 X 146.925 - 2 X 147.225 = 146.325 (the input frequency of one of the repeaters)
3 X 147.225 - 2 X 146.925 = 147.828 (The input frequency of the other repeater)
Because the PL tone of both repeaters rides on the intermod products, it will keep both repeaters keyed up.
These 2 repeaters cannot co-exist without some serious filtering. Even then, the close physical spacing of the antennas may still be a problem for filters. The best fix would be to change the frequency of one of the repeaters.
73, Joe, K1ike
At 03:50 PM 4/18/2004, you wrote:
Message: 6
Date: Sun, 18 Apr 2004 18:04:23 -0000
From: "Michael Singewald N1PLH" <[EMAIL PROTECTED]>
Subject: Is there a relationship between 147.225 and 146.925?
There are two machines on the same tower on these frequencies with
one antenna about 20 feet directly over the other. Each machine is
putting out about 30 - 50 watts. Each machine plays fine by itself,
but as soon as the other tranmitter comes up the problems begin.
Each machine has a different PL required to key up (67 and 77). If
someone unkeys on 146.925 while 147.225 is keyed, the 925 which
encodes a pl seems to get into itself and the 225. The 925
transmitter also causes the same problem on the 225 receiver.
These two are fine as long as the other is not keyed at the same
time. Someone in the group has said that there is a harmonic causing
this and those two repeaters just cannot be co located. I admit I
don't know much about this, but how can a harmonic be causing this if
they are both on VHF? I would think that mixing might possibly be
responsible for this. The BpBr duplexers were just tuned so I don't
think they are the problem. The SWR is flat on both machines as
well. Also, both repeaters are new (1 Hamtronics, 1 Kendecom).
How can I determine if the problem is mixing? If it is mixing, how
can we fix it? Would a "crystal filter" on the receiver help?
Neither of these machines are mine, so I am trying to gather info for
the two affected groups, so thank you for any advice!
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