RadioBanter - Repeater experts....HELP!

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The Hamtronics manual says you HAVE to use a
duplexer with at least 95 db of isolation (try to find one)
and mine is 77db. I really can't imagine there is not
enough isolation, because I know where there are other
machines running with old duplexers with much less
than 77db of isolation

Rick-

I would guess your duplexer was intended for a commercial repeater that had
greater separation than 600 KHz. You are kidding yourself if you think you can
make it work. Those other repeaters with old duplexers either have desense or
have some kind of super filters in the transmitter and receiver chains.

About the only thing that might help you (after you get that double-shielded
co-ax) would be adding a couple extra cavities. Although that approach will
probably have a higher insertion loss, it may be possible to tune the resulting
set for sufficient isolation.

If you can't fix the cavities, then all you can do is reduce transmit power out
of the repeater. If you reduce from one hundred to one watt, you pick up the
equivalent of 20 dB of isolation.

(A four-cavity duplexer with 95 dB isolation may be possible, but the cavities
will be big ones.)

73, Fred, K4DII

Well you gave the problem in the 1st couple of lines
1) USE Double shielded coax between duplexer and repeater...throw out
the RG 8 foam stuff...NEVER use RG 8 in a rptr install...
2) Hamtronics....enough said
3) Ringo Ranger antenna...if it's loose in any place, it will cause
problems....need to get a real repeater antenna....One without a ring
that depends on a cheap ring connection for matching.

Depending on the cleaness of the RF output, and how good is the rcvr in
overload conditions is what determines the isolation you need in the
duplexer....95db isolation is easy to find...WACOM WP641s, 642, and
other makes!! Get your isolation better than 80db and get rid of the
crap coax...and you'll be a lot better off!

Chris
WB5ITT at arrl . net

me wrote:

Hi guys. Thanks in advance for any help. Please post
responses in NG as my email 'reply' address is fake
since some don't know how to mind their manners.
I recently put back into service a Hamtronics REP100
two meter repeater with a new Telewave Duplexer and
the antenna is a Ringo Ranger II with radials. Coax to
the antenna is RG8 superfoam and jumpers between
repeater and duplexer are RG8 superfoam.
Here is the problem. I am experiencing 'desense' on
the repeater to the point where it takes a signal of S5
or better to get in. A lesser signal just makes the
repeater "chop" (continually opens and closes the
transmit side. The Duplexer was factory tuned
(for what it was worth) and I did 'tweak' it and got a
much noticible improvement. Before tweaking, it took
an S9 or better to get in. I realize I should be running
(supposedly) double shielded jumpers from repeater to
the Duplexer, but I can't imagine they are going to make
that much difference. I am also told to mount the duplexer
in it's own enclosure (it's rack mount so that would be cute)
to keep it away from the repeater.
The Hamtronics manual says you HAVE to use a
duplexer with at least 95 db of isolation (try to find one)
and mine is 77db. I really can't imagine there is not
enough isolation, because I know where there are other
machines running with old duplexers with much less
than 77db of isolation. Just to add to the mix, I sent
the repeater up to Hamtronics and had it tuned and
checked out and it is 100 percent, so I *suspect* it
is not a repeater problem. (Someone suggested to
try killing some of the sensitivity of the reciever).
So....looking for ideas and suggestions on what to try
next (other than double shielded jumpers to the duplexer).
Thanks for any help or ideas...
73's Rick

--
Replace NOSPAM with 1st initial and last name for direct reply!

I agree with Chris, RG8 is mainly good stuff, but it is intended for
more two way radio and not full duplex systems. I also recommend the
best coax to the antenna from duplexer as well, may not affect it
much, but even if it helps the slightest, it helps.

The Hantronics is a good starter repeater to learn with, but you will
notice as you get better equipment, the quality of the system will
greatly improve. Look into a Yeaseu or Kenwood repeater or commercial
repeater. Cheap is good, but like they say, you get what you pay for.
Look inside the case and make sure that the transmitter and receiver
are completely shielded from each other as well. You are getting a RF
leak into the receiver is what is causing the choppy affect if it isnt
shielded.

The duplexer should be at least 80% or better. 80% being bare minimum.
Wacom as recommended below will be the right choices. Some duplexers
are used in different types of systems. The frequency spread
determines the amount of isolation needed in a duplexer. 77% may be
just good enough on a 440 system because of the 5 Mhz spread between
TX and RX frequency. Since 2 meters is 600khz difference, a tighter
duplexer is needed. In most cases, a clean 100 watt repeater will work
great with a 90% duplexer. any more than 100 watts would require a
tighter isolation in my experiences with commercial gear.

Definately a repeater antenna. Depending on the coverage area, A ringo
ranger may be fine, but a repeater antenna is what it is intended for,
a repeater!

Also make sure the repeater case has no exposed openings. Some people
dont realize that when they are tuning the repeater with the lid off
for some reason, that the RF leaks out easily. The better the
shielding on all of your equipment, the better the quality.
Also make sure everything is grounded properly. One case not being
grounded could be severe enough to kill a 4-5 S-Unit signal.

Reducing the sensitivity of the reciever would be pointless. That
would be gaining nothing. If anything, reduce the output power if
necessary. I usually only run my repeater at 75% of what it says for
continuous duty. So if my repeater was 100 watts Continuous Duty, I
would turn it down to 75 watts thus increasing its life, stays cooler
and my receiver isnt affected at all by it, in fact I notice that the
receiver actually doesnt receive as much garbage from the other
systems on the hill while in use and I did notice that distant users
were able to get in the squelch easier this way.

On Tue, 24 Feb 2004 13:39:34 GMT, Chris Boone
wrote:

Well you gave the problem in the 1st couple of lines
1) USE Double shielded coax between duplexer and repeater...throw out
the RG 8 foam stuff...NEVER use RG 8 in a rptr install...
2) Hamtronics....enough said
3) Ringo Ranger antenna...if it's loose in any place, it will cause
problems....need to get a real repeater antenna....One without a ring
that depends on a cheap ring connection for matching.

Depending on the cleaness of the RF output, and how good is the rcvr in
overload conditions is what determines the isolation you need in the
duplexer....95db isolation is easy to find...WACOM WP641s, 642, and
other makes!! Get your isolation better than 80db and get rid of the
crap coax...and you'll be a lot better off!

Chris
WB5ITT at arrl . net

me wrote:

Hi guys. Thanks in advance for any help. Please post
responses in NG as my email 'reply' address is fake
since some don't know how to mind their manners.
I recently put back into service a Hamtronics REP100
two meter repeater with a new Telewave Duplexer and
the antenna is a Ringo Ranger II with radials. Coax to
the antenna is RG8 superfoam and jumpers between
repeater and duplexer are RG8 superfoam.
Here is the problem. I am experiencing 'desense' on
the repeater to the point where it takes a signal of S5
or better to get in. A lesser signal just makes the
repeater "chop" (continually opens and closes the
transmit side. The Duplexer was factory tuned
(for what it was worth) and I did 'tweak' it and got a
much noticible improvement. Before tweaking, it took
an S9 or better to get in. I realize I should be running
(supposedly) double shielded jumpers from repeater to
the Duplexer, but I can't imagine they are going to make
that much difference. I am also told to mount the duplexer
in it's own enclosure (it's rack mount so that would be cute)
to keep it away from the repeater.
The Hamtronics manual says you HAVE to use a
duplexer with at least 95 db of isolation (try to find one)
and mine is 77db. I really can't imagine there is not
enough isolation, because I know where there are other
machines running with old duplexers with much less
than 77db of isolation. Just to add to the mix, I sent
the repeater up to Hamtronics and had it tuned and
checked out and it is 100 percent, so I *suspect* it
is not a repeater problem. (Someone suggested to
try killing some of the sensitivity of the reciever).
So....looking for ideas and suggestions on what to try
next (other than double shielded jumpers to the duplexer).
Thanks for any help or ideas...
73's Rick

The Hantronics is a good starter repeater to learn with, but you will
notice as you get better equipment, the quality of the system will
greatly improve. Look into a Yeaseu or Kenwood repeater or commercial
repeater. Cheap is good, but like they say, you get what you pay for.
Look inside the case and make sure that the transmitter and receiver
are completely shielded from each other as well. You are getting a RF
leak into the receiver is what is causing the choppy affect if it isnt
shielded.

To go cheap and really good quality get a comercial transceiver or two. The
GE Mastr ll is one of the best ways to go. Well shielded and sharp tuning
receiver. They can be had for less than $ 100 and about half that much more
for a set of crystals. Then add a controler such as a Cat 300 and you have
less than $ 500 in the basic unit. Then you add the expensive stuff such as
a duplexer, feedline, and antenna.

Along with the GE Master II check out the Motorola Micor Repeater,
(not the mobiles converted to repeaters, alhough they work too)
They are cheap also and as with the GE, and you can't kill them!!
These are commercial repeaters and built to last almost forever.
Both are excellent!
73

Ralph Mowery wrote:

The Hantronics is a good starter repeater to learn with, but you will
notice as you get better equipment, the quality of the system will
greatly improve. Look into a Yeaseu or Kenwood repeater or commercial
repeater. Cheap is good, but like they say, you get what you pay for.
Look inside the case and make sure that the transmitter and receiver
are completely shielded from each other as well. You are getting a RF
leak into the receiver is what is causing the choppy affect if it isnt
shielded.

To go cheap and really good quality get a comercial transceiver or two. The
GE Mastr ll is one of the best ways to go. Well shielded and sharp tuning
receiver. They can be had for less than $ 100 and about half that much more
for a set of crystals. Then add a controler such as a Cat 300 and you have
less than $ 500 in the basic unit. Then you add the expensive stuff such as
a duplexer, feedline, and antenna.