Ok, so here's the deal
I'm running a high power UHF repeater that transmits on 442.675 (60
watts out of duplexer). As part of the same system, there is a link
receiver on 434.xxx. The link receiver is being de-sensed by the repeater xmtr
(I'm guestimating around 6 dB or so). While I
Just split the duplexer and you one half of it into your receive line.
Tune it up to pass your 434.xxx channel, then fight with the rejection
for your 442.675 channel. You should see 60+ dB of reject. (HINT - one
most of those duplexers (if I remember right), there is an adjustable
cap down
Ken,
If your T1500 cavity is the loop type such that the SO239's are closer
to the tuning screw, you can set the pass to 434.xxx and the reject to
442.675, but might have to move the stationary knob to the outer
position to get greater than a 5Mhz split. Rejecting that way is only
effective
Thanks for the replies folks - some good ideas.
I should have clarified that the spare T-1500 cavities I have are BP
only. And my plan is to use it as a suck-out (notch) filter. That is
why I was talking about using a T in line with the receive line.
Ken
At 09:28 AM 4/1/2010, KT9AC wrote:
I have a 40W UHF test machine running with two narrowband GM300's and a
1507 with no desense. Wondering what link radios your looking at (can
reply privately if you want).
---Believe it or not it's a MastrII Exec
Ken
On 4/1/2010 12:40 PM, Ken Arck wrote:
Thanks for the replies folks - some good ideas.
I should have clarified that the spare T-1500 cavities I have are BP
only. And my plan is to use it as a suck-out (notch) filter. That is
why I was talking about using a T in line with the receive line.
I sat back and waited for all the responses, and you're on the right track.
I've done this using band pass cavities on both UHF and VHF.
The only error is that you should not terminate the cavity with a 50 ohm
load. You will be able to see the difference (terminated, then
unterminated),
Remove one of the coupling loops and replace it with a metal hole
plug, the cavity will then turn into a notch.
Place either 1/4 electrical wavelength cable or 1/2 wavelength between
the Tee and the cavity if you desire a high pass or low pass peak to
the notch.
On Thu, Apr 1, 2010 at 9:40 AM,
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