[mdmars_members] Re: Cascade Repeater

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

Pudge,
 
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 
DC.  
 
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



Jim,
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,

Pudge


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