Hi Ken,
It is always a good practice to use a isolator in com sites. Look at it this way if you loose an antenna you most likley save your amp. Not to mention if your in a site with public safety it is a good idea.
Mike K7PFJ
-- Original message -- At 06:00 AM
I would agree that it's good practice. However in this
situation, the only other equipment at the site is
cellphone stuff. And if they lose an antenna and the
amp goes, they'll just have to get it all fixed. I
don't know how long the repeater would continue to
transmit without an antenna anyway,
Bob, just a suggestion, has he taken the repeater away from the site, hooked it to another antenna to see if he might be riding along a frequency there at the tower site. He could be pulling something in from a second harmonic there. The only reason I mention this, is a friend of mine had a 440
On Tue, 22 Nov 2005, Ken Arck wrote:
I'd like to try a circulator before buying one, since if it doesn't
help the situation, it's a waste of money to have it there.
---Aside from presenting a pretty much constant 50 ohm load to your
xmtr, why do you think a circulator will make a
At 04:27 PM 11/22/2005 +, you wrote:
Well, for one it will limit any locally generated mixing products
resulting from rectification in the PA transistors.
---Yes it will. But that is not the cause of desense, that is one of the
causes of intermodulation products.
Ken
At 08:15 AM 11/22/2005 -0800, you wrote:
I once had an Exec II RFPA that didn't like the duplexer load it was
TXing into. Had massive desense unless there was a circulator between the
TX duplexer.
---Makes sense. I know all about PA's driving a reactive load :-)
Ken
The resistive load isn't an antenna either.
Neil
Ken Arck wrote:
At 08:15 AM 11/22/2005 -0800, you wrote:
I once had an Exec II RFPA that didn't like the duplexer load
it was TXing into. Had massive desense unless there was a
circulator between the TX duplexer.
---Makes
At 09:09 AM 11/22/2005 -0800, you wrote:
The resistive load isn't an antenna either.
---I generally face little resistance when it comes to antennae...
Ken
--
President and CTO - Arcom Communications
Makers of
If anything is coming back down the antennaand through
the duplexer and mixing in the PA, the circulator will
prevent or reduce that effect.
Bob M.
==
--- Ken Arck [EMAIL PROTECTED] wrote:
At 06:00 AM 11/22/2005 -0800, you wrote:
I'd like to try a circulator before buying one,
since
if
I looked at the duplexer with a spectrum analyzer and
a return loss bridge. It's making spec (100dB
rejection) on each side. PB loss is 1.1dB. I did
notice that the return loss indication on the SA
showed a very nice sharp deep null (over 60dB) when
looking into one port, while the other port was
At 10:47 AM 11/22/2005 -0800, you wrote:
If anything is coming back down the antennaand through
the duplexer and mixing in the PA, the circulator will
prevent or reduce that effect.
---Absolutely correct. BUT that is not the same thing as desense nor are
the symptoms the same.
You said the
At 10:54 AM 11/22/2005 -0800, you wrote:
If the PA and duplexer weren't happy together,
wouldn't I also get desense when running on the dummy
load also? Remember it's perfectly happy on a 500w
Bird load.
---You answered your own question. Suspect the antenna, feedline or both.
Ken
The antenna/coax is showing 0.05w reflected (1/2 of
the first minor division) on a 5W element in a Bird 43
with 200 watts feeding the duplexer. From a purely
VSWR standpoint, that's acceptable. Whether or not
it's 50 ohms is something we did not check yet.
Future steps include sweeping the
... only when you hold it out the window ...
Neil
Ken Arck wrote:
At 09:09 AM 11/22/2005 -0800, you wrote:
The resistive load isn't an antenna either.
---I generally face little resistance when it comes to antennae...
Ken
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Just out of curiosity, where did the hardline come from, also, it is not Radian by any chance? I heard of that happening once to a guy who bought some cheap hardline, so he thought. Just kicking idea's around here. Mathew "Bob M." [EMAIL PROTECTED] wrote: I looked at the duplexer with a
(having email issues today, so if this is a dupe, please ignore)
RE: cell mixes and 440 repeater
I had a 440 repeater at a site with no other UHF transmitters for
probably a mile or two. On an adjacent tower was a cell site (this was
back in the early 90's AMPS days). When certain cell
I don't think this is a dupe.
The amp IS a Henry 20in/200out job, brand new. It has
its own switching power supply mounted on the back. I
think they're using 24V MOSFETs now. My 10in/100out
amp uses ordinary 14VDC and bipolar transistors.
I didn't look directly at the PA output. I do remember
Not me, but could have been. I went to buy a piece of 7/8" hardline a few years back, thought the deal was to good to be, then found it was Radian. No the other guy put up 150' of it, only to find it would not work.Mathew Chuck Kelsey [EMAIL PROTECTED] wrote: So how much did you end up
Bob,
Depending upon the frequency band and the modulation being used, it's
possible that the cellular transmitter is radiating a low-level spurious
signal. All cellular telephone sites transmit one or more control
channels continuously, and the associated mobile units home on this
channel to
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