Thanks Skipp025!
I have an old Lampkin service monitor and I've been tuning the
duplexer by using my handheld as a receiver with the Lampkin as the
generator. It just doesn't have enough oomph for proper tuning of the
reject portion of 2 cans in series.... So I'm working "somewhere" in
the notch... not good enough. I'll be looking for use of a proper
service monitor, and probably keep using the MSR2000 unit -- it fits
my installation better than the Wacom.
On Dec 20, 2007, at 6:09 PM, skipp025 wrote:
> > Cort Buffington <[EMAIL PROTECTED]> wrote:
> > Repeater Builders,
> > I pose to you all a question. I have two UHF duplexers, both 4
> > cavity pass-reject. One is a Wacom (the ubiquitous 3U rackmount
> > guy) and the other is from a Motorola MSR2000.
>
> Both very fine units for what they are.
>
> > I have really poor equipment, and don't necessarily "trust"
> > manufacturer specs. Anybody have an opinion on which one is
> > better, or pros and cons to each?
>
> Nothing bad to say about each one...
>
> > The rest of the RF equipment are Hamtronics T304 and R305
> > and a Mirage D-1010-RN. The T304 is "throttled" back so
> > that the Mirage is making about 55-60W. I'm currently running
> > on the MSR2000 duplexer, not tuned as well as it could be.
> > Some desense, and some is probably curable with better tuning
> > of the duplexer,
>
> Nat's-a$$ alignment of the duplexer including the notch positions
> will make a large difference in the overall system performance.
>
> > helical preselector on the front end, etc.
>
> Depends on how the helical pre-selector is constructed. Some designs
> have active included active preamplifiers and some are straight
> forward filters, which are "only so helpful".
>
> > But so far, I'm finding the additional receiver sensitivity
> > (over say a Mitrek/MSR or Micor) is far out-weighing the desense
> > 73 DE N0MJS
> > Cort
>
> Most of the current Hamtronics Receivers are red-hot in the
> sensitivity department, pretty fair in the 3rd order intercept
> performance and "fair" in the "blocking" performance spec.
>
> The elephant in the room is the 60 watt output PA and the
> relatively unprotected receiver front end.
>
> A complete/proper duplexer alignment will be the most bang for
> your buck. In specific you need to ensure the duplexer band-reject
> notch frequencies are properly spaced.
>
> A non-technical broad statement regarding duplexer notch and
> band-pass operation. Relative to the grand scheme of things more
> relative performance is often gained with strong/deep notch-out
> performance (of the unwanted other frequency) versus band-pass
> only (of the desired frequency).
>
> Folks with modest resources often adjust band-pass, band-reject
> duplexers using the max power into a watt meter/load method.
> Much system performance is lost when the reject-notch tuning
> is discounted or ignored for lack of proper test equipment.
>
> Unless you know for sure someone has properly aligned the duplexer
> notch (band-reject) positions you can and should assume they
> are not exactly in the best possible position.
>
> Once again... the duplexer reject notch adjustment is another
> one of the few repeater performance "free lunch" items, which
> should not be ignored. Because there are only a few "free lunch"
> items on the menu.
>
> cheers,
> s.
>
>
>
Yahoo! Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/Repeater-Builder/
<*> Your email settings:
Individual Email | Traditional
<*> To change settings online go to:
http://groups.yahoo.com/group/Repeater-Builder/join
(Yahoo! ID required)
<*> To change settings via email:
mailto:[EMAIL PROTECTED]
mailto:[EMAIL PROTECTED]
<*> To unsubscribe from this group, send an email to:
[EMAIL PROTECTED]
<*> Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/
