[mdmars_members] Re: Cascade Repeater

  • From: R HENDRICKSON <w3dtn@xxxxxxxxxxx>
  • To: mdmars_members@xxxxxxxxxxxxx
  • Date: Tue, 6 Oct 2009 14:29:25 -0700 (PDT)

The Duplexer at Cascade is a standard Motorola 4-can High-Band unit.  To set 
the reject notches on each can, you have to slide the coupling links back and 
forth to find the null, then set them in place with a thumbnut.  Unfortunately, 
these duplexers have a reputation of not holding the notch very well when 
subjected to any mechanical vibration or other motion.  Just flexing the 
mounting frame can cause the notch to change.  What I think happened to the 
duplexer tuning is that when the repeater was being carried in Wayne's pick-up 
truck, the vibration caused the duplexer tuning to get off.  It appears to me 
that the repeater now has a desense problem, possibly due to the duplexer notch 
tuning being out of alignment.
 I have the equipment needed to go retune it on site.  I have also just 
finished tuning an old Sinclair 4-cavity duplexer.  It has pretty good numbers 
- 86 dB rejection, and just 1.8 dB insertion loss on the transmit side, and 0.6 
dB loss on the receive side.  So we can replace the Motorola duplexer with the 
Sinclair unit - there is room inside the cabinet for the larger Sinclair unit.
However, if you can "acquire" a better, more stable, unit, let's go for it!  Or 
perhaps the entire repeater could be used to replace the current machine in 
Thanks for watching out for us!
73,  Gary  W3DTN/AAR3EY

--- On Tue, 10/6/09, pudgeforrester@xxxxxxxxxxxxx 
<pudgeforrester@xxxxxxxxxxxxx> wrote:

From: pudgeforrester@xxxxxxxxxxxxx <pudgeforrester@xxxxxxxxxxxxx>
Subject: [mdmars_members] Re: Cascade Repeater
To: mdmars_members@xxxxxxxxxxxxx
Date: Tuesday, October 6, 2009, 2:10 PM

Confidential please.
What duplexer does the Cascade repeater have in it?  I just took a GE Mastr II 
out of service at Wheeling CAP and it has a DB products 4 can duplexer in it.  
I'm quietly "setting" on that repeater in hopes it can be recrystaled and used 
for MARS in the future.
God bless,


Other related posts: