Thanks, guys, a good topic and one that always seems to come up. And
it sparks more questions and comments, of course.
The cable length issue is a brother to "if you don't like your VSWR,
change the point along the transmission line where you're measuring
it." By changing the length of the line, we're creating a transmission
line transformer (a good thing) but we're limited by its length (not so
good). It seems to me the mentioned circulator/isolator at the output
of the xmtr is a better fix, as reflections coming back from the
duplexer is absorbed by the circulator's load, the xmtr is generally
happy, and we're no longer limited where we can put things in a rack or
elsewhere.
For amateurs, coming up with usable VHF circulators seems to be
difficult and usually expensive, and coax always seems to be cheaper.
Has anyone had luck finding a source for reasonbly priced VHF
circulators, or success in rolling their own?
Also, I noted in the pamphlet Kevin referenced that the unused duplexer
port was left open (Figs. 1 & 2). I guess if the isolation is already
greater than the load's return loss, it doesn't matter, at least at the
reject frequency. But it seems to me one could possibly create problems
for oneself by not terminating the unused open port. Just a thought.
Maybe I work better knowing there's a load there. ;-)
Your comments, please.
73, Russ WB8ZCC
On 8/5/2010 10:19 AM, Doug Hutchison wrote:
Hi Kevin and all who responded to my question.
Thank you, good info in the link provided by Kevin along with other
interesting guidelines. More for the file.
Regards,
Doug - GM7SVK
On 04/08/2010 11:04 PM, Kevin Custer wrote:
> Doug Hutchison wrote:
>
>> Does the length of coax connecting cable between repeater and filters
>> matter?
>>
>
> Yes - and no.
>
> Please read the note about cabling lengths between the repeater and the
> duplexer in the section on page 4 of the following document:
>
<http://www.repeater-builder.com/wacom/wp6xx-vhf-tuning-instructions-remec.pdf>
>
> Watch for word wrap...
>
> Kevin Custer
>
>
>
> ------------------------------------
>
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>
> Yahoo! Groups Links
>
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